Chapter 4 Result and Discussion of Area 1

Chapter 4: Result and Discussion of Area 1

73

Chapter 4

Result and Discussion of Area 1

4.1. Introduction

As described in chapter 2, the area of this study is divided into three areas named

Area 1, Area 2, and Area 3. The division is based on the geological conditions and the

hydrological problems existing in the area. In each area, all research data will be shown

and discussed simultaneously. The discussion procedure will be started from data

presentation, analysis, interpretation and discussion and followed by conclusion. The

discussions include various aspects of the groundwater problem in each area.

The map of Area 1 and its land uses are given in Figure 4.1. Area 1 covers

approximately 98 km² extending from Kampung Tok Bok in the south to Kampung

Ketereh at northern part. The western and eastern part of the study area are bounded by

Kelantan River and Boundary Range, respectively. The land use within Area 1 is mainly

for agriculture such as palm oil plantation (kelapa sawit), paddy planting and rubber

trees plantation. The palm oil plantation covers approximately 20 km² of the southern

part of Area 1. Paddy planting is found at the lower land elevation especially in the

northern part, whilst rubber trees plantation is at the higher land elevation.


74

Figure 4.1. The land use and topography map of Area 1. Palm oil plantation is a

dominant farming plantation at the southern part which has relatively higher elevation.

200000 300000 400000 500000 600000 700000

200000

300000

400000

500000

600000

700000

Sumatra Island - Indonesia

Kuala Lumpur

N


75

In this chapter, the results and the associated discussion are divided into the

following three main parts:

1. The first part of the discussions focuses on the study of geoelectrical resistivity

and hydrogeochemical correlation in specific soil characters. The result can be

used as calibration and standardization for the subsequence investigation.

2. The second part concerns on the study of Area 1 groundwater character. This

includes the description of all groundwater-related problems within Area 1, the

pollutants involved, its sources, and the possible subsurface groundwater

movement patterns in Area 1, and,

3. The third part focuses on the detection and monitoring of chemical fertilizer

(especially nitrate) concentration within the soil water. Emphasize is on the

source of the nitrates and the specific mechanism of nitrate infiltration through

the soil for specific soil property characteristics.

In many part of the world, chemical fertilizers (Yang et al, 2006; Anayah &

Almasri, 2009) are rigorously used to enhance the agricultural establishment. It includes

palm oil plantation establishment. In the study area (palm oil plantation), fertilization is

carried out every two months using fertilizers of different chemical content. At the

beginning of the year, 400 kilograms of Urea with 60% nitrogen is used for every two

hectares palm plantation. Two months after that, a different fertilizer with 15%

Nitrogen, 30% Phosphorus, and 55% Potassium (NPK) is applied to further improve the

production of palm. This process is repeated in the middle of the same year and

continues until the end of the year. In total, at least 800 kilograms of urea are used to

fertilize the palm trees in a two hectare area per year.


76

Sometimes organic fertilizers from farm animals are used. This includes

farmyard manure from farmed cows and goats. It is believed to be good for the

improvement of palms oil fruits production. At least 2600 kilograms of manure are

required to fertilize two hectares of palm oil trees.

The other agricultural activities, paddy plant and rubber tree plantation within

Area 1 require less fertilization intensity than that of palm oil plantation. Generally, the

farmers in Area 1 plant paddy only once a year, although some planted up to twice a

year in some areas. Paddy plants consume 100 kilograms of urea per two hectare a year,

while, rubber plantation need 200 kilograms of urea every two hectare a year.

4.2. Geoelectrical Resistivity and Hydrogeochemical Correlation in Specific Soil

Characters

This study was conducted in different selected sites with different soil characters

and different environment (Figure 4.2.A). The first study (Test-site 1 and Test-site 2)

was to investigate the geoelectrical resistivity and hydrogeochemical contrast that exists

between regularly fertilized soil and the non-fertilized ones. Regularly fertilized areas is

defined as those areas that have been recurrently fertilized over a period of more than 25

years. The objective is to characterize the geoelectrical resistivity and the

hydrogeochemical property for the site which has been treated by natural and chemical

fertilizer for a long period. The subsequence study (Test-site 3) was performed in the

site which has different soil characters and different environment. In this site, the

studies focus on the geoelectrical resistivity characters in respect to soil grain size and

soil chemical content.


77

4.2.1. Geoelectrical Resistivity and Hydrogeochemical Contrast between

Fertilization and Non-Fertilization

This study is carried out at Kampung Tok Bok, Machang. A detailed map and

the photographs of the investigated site are given in Figure 4.2 and Figure 4.3,

respectively.

In this study, two Test-sites were used: Test-site 1 is the non-fertilized zone, and

Test-site 2 is the regularly-fertilized zone. Test-site 1 is a grass field which is sometimes

used by the local people for celebration grounds and by their farm animals for grazing.

This represents the unfertilized zone. Test-site 2 consists of an old palm oil plantation.

The field had been farmed recurrently for over 25 years. The palm oil plantation in Test-

site 2 has not been fertilized for ten months (from Aug 2007) before the survey was

done. The fertilization scheme for the palm oil plantation for trees more than 12 years

old is shown in Table 4.1.

For both sites the investigation methods are: soil property analysis, water

chemical analysis and a 2-dimensional (2D) geoelectrical resistivity imaging survey.

Grain size distribution, moisture content and hydraulic conductivity for both

sites were measured to distinguish the different soil properties. For the grain size

distribution and moisture content, soil samples were collected randomly from four point

location at each site (Figure 4.2). Each location was taken from a depth of 0 to 1 m, at

every 25 cm interval. Inverse auger methods were used to measure hydraulic

conductivity at shallow depths above water level (vadose zone).


78

Figure 4.2. (A) Location of Test-Site 1,2 and 3. (B) Survey lines, soil and water

sampling location in Test-site 1 and 2.

465000 470000 475000

645000

650000

655000

660000

Kelantan River

N

Boundary Range

B

200 meter

N

40 m

A

B TB01

TB02

TB03

TB04

TB05

C

D

TB06

TB07

TB08

TB09

TB10

F

G

H

Test-Site 2

Test-Site 1

E

Highway

Grass Field

Old Palm Field

Resistivity Lines

Soil Sample

Borehole

Legend

A

Test-Site 1 and 2

Test-Site 3


79

Figure 4.3. Photograph; (A) grass field, (B and C) old palm oil plantation in Kampung

Tok Bok, Machang.

(A)

(B)

(C)


80

Table 4.1. Fertilization scheme of palm oil plantation in the Test-site 2 Kampung Tok

Bok. The data was obtained from the palm oil plantation office (Personal conversation

with a field supervisor of the company).

No Month Fertilizer Types Content Amount per 2 ha

Ha

ha

1 February Urea Nitrogen (60%) 600 kg

2 April NPK N(15%), P, K 600 kg

3 August Urea Nitrogen (60%) 600 kg

4 October NPK N(15%), P, K 600 kg

5 December Dolomite Dolomite 300 kg

6 When needed KCl KCl 300 kg

7 Anytime Farmyard manure Mixture As available

To analyze chemical content in water from the vadose zone, soil water was

collected at depths of 0.25 m, 0.50 m, 0.75 m and 1 m (four samples at each depth) from

four random locations (Figure 4.2) using a 1900 Soil Water Samplers (manufactured by

Soilmoisture Equipment Corp, USA). Four soil-water samples of around 5 ml were

obtained in each depth sampling. The sampled water were mixed and diluted with pure

water (1:1). The samples were kept in plastic bottles of 40 ml at 40C and one day later

were analyzed using Ion Chromatography (IC) and Inductively Coupled Plasma (ICP).

The 2D geoelectrical resistivity imaging surveys were performed at both sites.

The Wenner arrays were used on five lines within each Test-site with 1 m electrode

spacing. The total profile length is 40 m. The purpose of the investigation is to compare

the geoelectrical resistivity imaging results with the soil properties and the soil-water

chemical content.


81

4.2.1.1 Soil Properties Results

4.2.1.1.1 Grain Size Distribution

The results of soil analysis (grain size and moisture content) on Test-site 1 and

Test-site 2 are given in Figure 4.4. The detailed are shown in Table 4.2. In both sites,

medium sand-sized grain dominates in all locations with average 50.43-51.33%. The

highest medium sand-sized grain content is observed on the surface ranging from 60.39

to 62.02% and decrease with depth. Coarse sand-sized grain has average ranging from

27.94 to 28.59%. The lowest percentage of coarse sand-sized grain occur on the surface

and increase drastically with depth. The fine sand-sized grain has average ranging from

17.56 to 18.17% and the highest percentage (25.25 to 26.49%) occurs at a depth of 25

cm and decrease with depth. The percentage sand-sized grain (except coarse sand-sized

grain) has the same trend which the highest percentage occurs near surface (0 to 25cm)

and decrease gradually with depth.

All soil samples in Test-site 1 and Test-site 2 show a lower percentage for silt

and clay content ranging from 0.32 to 1.60%. Average silt and clay content for all

locations in Test-site 1 and Test-site 2 is less than 1 %. However, with increasing depth,

silt and clay content notably generally decreases from a depth of 25 cm.

Gravel-sized grain is less than 1% at the surface and 0% at a depth of 25 cm and

50 cm in several sampling locations for both sites. The percentage of gravel-sized grain

then increase with depth. Generally, grain-size distribution is similar for both site (Test-

site 1 and Test-site 2). It can be concluded that Test-site 1 and Test-site 2 have the same

soil and geologic conditions. This conclusion is based on the same grain-size

distribution and both sites are only 200 m apart.


82

Figure 4.4. Grain size distribution in each sampling locations for Test-site 1 (A,B,C,D)

and Test-site 2 (E,F,G,H). The graph show similarity of grain size distribution for both

sites.

0

25

50

75

100

0 20 40 60 80 100

Sam

plin

g D

epth

(cm

)

Percentage (%) A

0

25

50

75

100

0 20 40 60 80 100

Sam

plin

g D

epth

(cm

)

Percentage (%) E

0

25

50

75

100

0 20 40 60 80 100

Sam

plin

g D

epth

(cm

)

Percentage (%) B 0

25

50

75

100

0 20 40 60 80 100

Sam

plin

g D

epth

(cm

)

Percentage (%) F

0

25

50

75

100

0 20 40 60 80 100

Sam

plin

g D

epth

(cm

)

Percentage (%) C

0

25

50

75

100

0 20 40 60 80 100

Sam

plin

g D

epth

(cm

)

Percentage (%) G

0

25

50

75

100

0 20 40 60 80

Sam

plin

g D

epth

(cm

)

Percentage (%) D

Gravel Coarse Sand Med Sand

Fine Sand Silt & Clay

0

25

50

75

100

0 50 100

Sam

plin

g D

epth

(cm

)

Percentage (%) H

Gravel Coarse Sand Med Sand

Fine Sand Silt & Clay


83

Table 4.2. Soil properties result of Test-site 1 and Test-site 2.

S ID Gravel Coarse Sand

Med Sand

Fine Sand

Silt & Clay Moisture

S ID Gravel

Coarse Sand

Med Sand

Fine Sand

Silt & Clay Moisture

(%) (%) (%) (%) (%) (%)

(%) (%) (%) (%) (%) (%)

A-0 0.76 18.50 60.39 19.40 0.95 16.53

E-0 0.91 16.18 62.02 19.95 0.94 15.76

A-25 0.00 22.56 50.67 25.25 1.52 11.54

E-25 0.00 22.48 50.66 25.30 1.56 10.87

A-50 0.47 22.99 54.86 21.28 0.86 9.75

E-50 0.00 22.59 55.10 21.47 0.85 9.23

A-75 1.53 33.03 49.68 15.10 0.66 10.33

E-75 1.22 31.90 50.49 15.65 0.74 10.15

A-100 7.05 48.38 37.01 7.25 0.32 10.31

E-100 6.56 47.19 38.38 7.53 0.34 10.37

Mean 1.96 29.09 50.52 17.66 0.86 11.69

Mean 1.74 28.07 51.33 17.98 0.88 11.28

B-0 0.86 17.63 60.48 20.03 1.00 15.98

F-0 0.85 17.91 60.77 19.52 0.95 15.93

B-25 0.00 21.33 51.42 25.68 1.56 10.44

F-25 0.00 22.14 50.89 25.42 1.55 10.92

B-50 0.00 22.01 55.76 21.31 0.92 9.97

F-50 0.00 22.71 55.67 20.73 0.88 9.72

B-75 1.44 31.87 50.44 15.52 0.74 10.56

F-75 1.54 32.47 50.09 15.17 0.73 10.17

B-100 7.22 46.88 38.13 7.43 0.34 9.99

F-100 7.23 46.86 38.12 7.44 0.34 10.03

Mean 1.91 27.94 51.25 17.99 0.91 11.39

Mean 1.92 28.42 51.11 17.66 0.89 11.35

C-0 0.82 17.24 61.24 19.73 0.97 16.29

G-0 0.85 18.12 61.68 18.40 0.96 15.78

C-25 0.00 22.80 50.96 24.64 1.59 11.23

G-25 0.00 22.55 50.01 25.90 1.55 10.79

C-50 0.59 22.54 55.19 21.39 0.88 10.01

G-50 0.00 21.55 56.51 21.03 0.91 9.65

C-75 1.55 32.53 50.00 15.26 0.67 10.51

G-75 1.56 32.46 50.14 15.11 0.73 10.12

C-100 7.24 46.83 38.11 7.47 0.36 10.23

G-100 7.86 46.53 37.89 7.35 0.37 10.09

Mean 2.04 28.39 51.10 17.70 0.89 11.65

Mean 2.05 28.24 51.24 17.56 0.90 11.29

D-0 0.81 17.41 60.96 19.84 0.97 16.16

H-0 0.85 18.02 61.12 19.06 0.95 15.69

D-25 0.00 23.10 48.81 26.49 1.60 11.08

H-25 0.00 22.01 50.59 25.87 1.53 10.48

D-50 0.00 22.67 54.92 21.55 0.86 9.86

H-50 0.00 22.26 55.23 21.66 0.86 9.53

D-75 1.54 32.97 49.30 15.52 0.66 10.52

H-75 1.52 33.30 49.47 14.99 0.72 10.15

D-100 7.27 46.79 38.14 7.46 0.34 10.18

H-100 7.77 46.60 37.90 7.39 0.34 10.06

Mean 1.93 28.59 50.43 18.17 0.89 11.56

Mean 2.03 28.44 50.86 17.79 0.88 11.18


84

4.2.1.1.2. Moisture Content

At Test-Site 1, the average moisture content ranges from 11.39% to 11.69%

(Figure 4.5 and Table 4.2). The highest percentage value was obtained at location A. At

each location, maximum values of moisture content are obtained at the surface. Though

moisture content increases slightly in the near subsurface for location A, the moisture

content does not show a similar general trend.

At Test-site 2, the highest moisture content is also at the surface level and

decrease at a depth of 25 cm and deeper. The same decreasing trend of moisture content

is observed at this site.

The two Test-sites differ in average moisture content percentages. Test-Site 1

has an average of 11.57% with 2.44% standard deviation and Test-Site 2 averages

11.27% with 2.35% standard deviation. Differences in moisture content are attributed to

the different time data acquisition and the different rate of evaporation. Data for Test-

Site 1 was acquired one day prior to data for Test-Site 2. However the weather

conditions of the two days of data acquisition were nearly the same (cloudy), thus

resulting in a small difference of the moisture content in both sites.

4.2.1.1.3. Hydraulic Conductivity

The rate of decrease in water level versus time for both Test-site 1 and Test-site

2 is given in Figure 4.6. The hydraulic conductivity value for Test-site 1 and Test-site 2

were recorded to be 0.001079 cm/s and 0.001096 cm/s respectively. The difference

between the measured values is negligible and therefore it can be concluded that the

porosity and permeability of both test-sites is similar. Based on soil grain size


85

distribution and hydraulic conductivity data, the soil condition is semi-pervious

characters (Bear, 1972).

Figure 4.5. Moisture content for Test-site 1 and Test-site 2. Relatively higher moisture

content in Test-site 1 near surface due to the data for Test-site 1 collected 1 day after

collecting data for Test-site 1.

Figure 4.6. (A) Result of hydraulic conductivity test for Test-site 1 and (B) Test-site 2.

Hydraulic conductivity measurements indicate both sites have similar permeability.

0

25

50

75

100

6 8 10 12 14 16 18 20

Sam

plin

g D

epth

(cm

)

Percentage of moisture content (%) Test Site 1

A B C D

0

25

50

75

100

6 8 10 12 14 16 18 20

Sam

plin

g D

epth

(cm

)

Percentage of moisture content (%) Test Site 2

E F G H

0

10

20

30

40

50

60

70

0 100 200 300 400 500 600 700

ht

+ r/

2 (c

m)

Time (s)

0

10

20

30

40

50

60

70

0 100 200 300 400 500 600 700

ht

+ r/

2 (c

m)

Time (s)

A B


86

4.2.1.2. Water Chemical Result

The chemical composition of extracted water at Test-site 1 and Test-site 2 are

given in Table 4.3 and Figure 4.7. In both Test-sites, among the detected cations, the

content of K, Ca, and Na shows the highest range of concentration from 2.04 to 13.58

mg/L. The content of other cations is lower than 1 mg/L. The results indicate that there

is no significant difference in the cation content of the soil water extracted from both

sites.

The nitrate concentration ranges from 2.72 to 5.50 mg/L and 10.28 to 18.23

mg/L in the Test-Site 1 and Test-Site 2, respectively. The highest nitrate concentration

is found at the surface level and decreasing with depth. The same trend is also

recognized for chloride concentration. The sulphate and fluoride concentration range

from 0 to 8.02 mg/L and 0.28 to 1.04 mg/L respectively. Thus, the results (Table 4.3)

show that the concentration of nitrates and chlorides in Test-Site 2 are significantly

higher than in Test-Site 1 (Figure 4.8).


87

Table 4.3. Water extraction analysis result of Test-site 1 and Test-site 2.

No Sample ID Chloride Nitrate Sulphate Fluoride K Ca Mg Na Pb Cd Se Al Mn Cu Zn Fe As

mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L

1 TB001-25 20.524 5.504 0.982 0.304 3.906 5.946 1.142 9.912 0.000 0.002 0.004 0.392 0.018 0.022 0.202 0.074 0.000

2 TB001-50 17.152 4.902 6.716 0.274 2.462 5.134 1.426 8.060 0.000 0.000 0.000 0.194 0.022 0.016 0.160 0.064 0.000

3 TB001-75 15.550 5.158 8.016 0.746 3.116 4.376 1.076 7.840 0.010 0.000 0.010 0.136 0.016 0.012 0.066 0.024 0.000

4 TB001-100 11.870 2.714 0.000 0.310 2.040 2.558 0.790 5.588 0.002 0.000 0.002 0.086 0.012 0.014 0.056 0.016 0.006

Average 16.274 4.570 3.929 0.409 2.881 4.504 1.109 7.850 0.003 0.001 0.004 0.202 0.017 0.016 0.121 0.045 0.002

1 TB006-25 41.004 18.232 0.000 0.864 5.090 7.914 0.576 8.680 0.000 0.002 0.002 1.200 0.036 0.040 0.202 0.548 0.002

2 TB006-50 26.206 13.554 6.062 0.796 4.958 7.882 0.666 9.222 0.002 0.004 0.010 0.812 0.036 0.042 0.198 0.112 0.000

3 TB006-75 20.518 12.208 0.000 1.046 3.858 6.278 0.528 13.538 0.010 0.004 0.004 1.482 0.038 0.026 0.128 0.174 0.000

4 TB006-100 19.638 10.272 3.288 0.088 2.324 2.878 0.300 4.414 0.000 0.002 0.008 0.166 0.022 0.008 0.068 0.022 0.000

Average 26.842 13.567 2.338 0.699 4.058 6.238 0.518 8.964 0.003 0.003 0.006 0.915 0.033 0.029 0.149 0.214 0.001


88

Figure 4.7. Cations concentration in Test-site 1 and Test-site 2. A relatively higher K,

Ca and Na concentration can be found in Test-site 2. The other cations content show

that Test-site 1 and Test-site 2 is more or less the same of their concentration.

0

25

50

75

100

0 3 6 9 12 15 D

epth

(cm

) Concentration (mg/L)

Cations Test Site 1

K Ca Mg Na Pb Cd Se

Al Mn Cu Zn Fe As

0

25

50

75

100

0 3 6 9 12 15

Dep

th (

cm)

Concentration (mg/L) Cations Test Site 2

K Ca Mg Na Pb Cd Se

Al Mn Cu Zn Fe As


89

Figure 4.8. Graph of nitrate (A) and chloride (B) concentration in Test-site 1 and Test-

site 2. Relatively higher nitrate and chloride are obtained in Test-site 2.

4.2.1.3. Geoelectrical Resistivity Model

The geoelectrical model of Test-site 1 and Test-site 2 are shown in Figure 4.9.

The same scale is used for all geoelectrical models. In the geoelectrical model along line

TB01, a high-resistivity value ranging between 2000-5000 ohm.m is obtained from the

surface level to a depth of around 1.5 m, corresponding to the present of compact sand

with low moisture content (see moisture content in Table 4.2). The geoelectrical model

0

25

50

75

100

0 5 10 15 20 D

epth

(cm

)

Nitrate (mg/L) A

Nitrate Site 1 Nitrate Site 2

0

25

50

75

100

0 10 20 30 40 50

Dep

th (

cm)

Chloride (mg/L) B

Chloride Site 1 Chloride Site 2


90

is supported by ten folds random direct resistivity measurement at the surface with

average of 2804.3 ohm.m and standard deviation of 205.7 ohm.m. The same feature is

also observed in other geoelectrical models (TB02-TB05).

A borehole was drilled at the 19 m mark of line TB03. The measured water table

was 3.60 m below the ground surface (see table 4.2 (B) for the soil characters). In line

TB003, the resistivity values of approximately 500 ohm.m corresponded to a unit of

compact fully saturated sand.

At a depth of more than 4 m, zones that are probably more porous and more

permeable can be seen in the section with resistivity values of around 150 ohm.m. This

value corresponds to the fully saturated zone.

The line TB03 crosses the lines TB01 and TB02, and the line TB04 crosses

TB05. The intersection point is marked with an arrow in Figure 4.9. The geoelectrical

model show consistency feature at every line crossing. It is indicated from the same

resistivity value found at the same depth at the crossing position.

Test-site 2 is located northwest of Test-site 1 in an old palm oil plantation. The

geoelectrical surveys were conducted along five lines at this site. In the geoelectrical

model of all the lines (TB06-TB10), the resistivity values is relatively lower (1800

ohm.m) from the near surface to 1 m depth compared to the geoelectrical model in Test-

site 1. This low resistivity value (coloured yellow) does not appear in geoelectrical

model of the Test-site 1. The geoelectrical model is also supported by ten folds direct

surface resistivity measurement with average of 1963.6 ohm.m and standard deviation

of 93.7 ohm.m.


91

Figure 4.9. Geoelectrical resistivity model of Test-site 1 (TB01-05) and Test-site 2

(TB06-10). All the geoelectrical model in Test-site 1 show relatively higher resistivity

value near surface compare to the geoelectrical model of Test-site 2.

TB02 TB01

TB03

TB03

TB05

TB04

TB01

TB02

TB03

TB04

TB05

WT

PA

PA

PA

CSL = Compacted soil with low moisture content; WT = Water table,

PA = Potential aquifer (More porous saturated soil); GBl = Granite boulder

CSL

CSL

CSL

CSL

CSL

Borehole


92

Figure 4.9. Continued

TB09

TB09

TB06 TB07 TB08

TB09

TB06

TB07

TB08

TB09

TB10

CSL

CSL = Compacted soil with low moisture content

WT = Water table

PA = Potential aquifer (More porous saturated soil)

GBl = Granite boulder

WT

PA

PA

PA

PA

GBl

PA

CSL

CSL

CSL

CSL

Borehole


93

Zones with fairly high resistivity values (more than 4000 ohm.m) in sections

TB06, TB07, and TB08 correspond to features with the presence of compact material.

These features (high resistivity values) are also due to weathered granite boulders, as

proved by drilling with a hand auger. The water table was found at a depth of 3.48 m in

a borehole that was drilled using a hand auger at 20 m mark line of TB009. In the

geoelectrical model along line TB009, resistivity values of around 500 ohm.m

correspond to the fully saturated compact sand unit.

4.2.1.4. Soil Parameters, Water Chemical Content, and Geophysical Parameters

Contrast

Table 4.4 shows the statistical summary of the extracted resistivity value for

both sites (left-hand side) and average of selected soil properties (right-hand side). The

maximum average resistivity values from the surface to a 75 cm depth for both sites is

4950.52 ohm.m (TB002) and 3027.63 ohm.m (TB010). All the resistivity values in

Test-Site 1 are higher than in Test-Site 2 (Figure 4.9). The similarity composition of

gravel, sand, silt and clay (soil grain size) indicates similar geological conditions at both

sites. Furthermore, based on the hydraulic conductivity data, the porosity and

permeability values of Test-Site 1 are approximately equal to Test-Site 2. Although the

moisture content at Test-Site 2 is lower than Test-Site 1, but the resistivity value in

Test-Site 1 is higher than in Test-Site 2. The lower average resistivity of Test-Site 2 is

believed to be caused by the higher nitrate and chloride concentrations in the near

subsurface. Even if fertilizing activities had been stopped since last year, residual

chloride and nitrate still remain in the soil. The negative charges of nitrate and chloride

ions caused a decrease of the medium’s resistivity. This is the reason why there is a 36.6

% decrease in average resistivity from the surface to depths of 75 cm for Test-Site 2.


94

Table 4.4. Statistical values of Geoelectrical resistivity extraction derived from surface to 75 cm depth. At the right side, soil properties

value within the Test-site 1 and Test-site 2 exhibits their mean and standard deviation (in bracket).

Inverse geoelectrical model (ohm.m) Soil properties

Line Name Mean resist Stdev Max Min Gravel

(%)

Sand

(%)

Silt &

Clay (%)

Moisture

(%) K (cm/s)

TB001 4042.62 1245.367 8021 2084.3

1.95

(2.74)

97.20

(2.47)

0.88

(0.41)

11.5975

(2.45) 0.001079

TB002 4950.52 1275.909 8496.8 2873.5

Test TB003 4303.951 1358.411 9065 1932.4

Site 1 TB004 3995.408 1201.233 6783.1 1466

TB005 4003.477 1328.22 8940.9 1980.5

TB006 2597.096 1300.075 7825.7 290.5

1.93

(2.84)

97.17

(2.55)

0.89

(0.39)

11.2745

(2.35) 0.001096

TB007 2270.121 1127.833 6605 944.42

Test TB008 2718.001 1326.222 7173 933.97

Site 2 TB009 2872.892 719.566 4636.3 885.07

TB010 3027.621 936.733 5881.7 1375.9


95

Finally, based on the soil properties, hydrogeochemical, geoelectrical model and

direct resistivity measurement as discussed above, the summary of geoelectrical

characters in this site study can be concluded as given in Table 4.5. In the table,

generally, increases of soil size cause decrease resistivity value because porosity and

permeability will increase, so that electrical current more easily to flow.

Table 4.5. Summary of soil resistivity characters in Test-site 1 and Test-site 2.

No Dominant

Medium

Moisture Polluted/

Unpolluted

Relative

permeability

Resistivity

(ohm.m)

1 Medium and

coarse sand

Low (8-15%) Unpolluted Semi previous 2000-3000

2 Fine sand Fully Saturated Unpolluted Semi previous 400-600

3 Medium and

coarse sand

Fully Saturated Unpolluted Semi previous 90-150

4 Shallow granite

boulder

Bounded by

saturated semi

previous soil

Unpolluted - >4000

5 No 1,2 and 3 Polluted by

chloride and

nitrate (low)

Semi previous Reduce around

36%

4.2.2. Relationship of Soil Properties and Geoelectrical Resistivity in Test-Site 3

The Test-site 3 is located in the west side of Kampung Pulai Condong. This site

is elevated 14 m above mean sea level which is the beginning of Kelantan River flooded

zone. The study here includes soil chemical analysis, soil properties analysis, water

chemical analysis, direct resistivity measurement and geoelectrical resistivity survey.

A well WA1 was drilled to obtain subsurface data. The drilling was stopped

immediately after the bedrock was encountered at a depth of 24.10 m. Gravel was found


96

at about 50 cm before bedrock. The well was cased with a 3 inch in diameter of a PVC

pipe. The screen of the well was at 19 m depth where coarse sand grain was found.

During the boring processes, the disturbed soil samples of 500 gr were collected at

every 3 m interval. The soil samples were kept at around 4° C in plastic bags prior to

laboratory analysis. In the hydrogeochemical laboratory, each soil sample was divided

into two parts. The first part was used to obtain soil grain size distribution. Whilst, the

second part was used for soil chemical analysis. This soil was digested and processed by

Multiwave 3000 (microwave sample preparation, manufacturing by Anton Pear,

Austria). Water sample was collected one day after the drilling completion. 2D

geoelectrical resistivity survey was performed one day after drilling completion. At the

beginning of survey line there was minor farming of corn and other vegetables. The

geoelectrical resistivity survey line was aligned in a east-west direction.

4.2.2.1. The Borehole WA1 Soil Grain Size Distribution

The grain size distribution of borehole WA1 at each sample location is given in

Table 4.6. Figure 4.10 shows a plot of the data. Fine sand consisting of 78.34 % is

dominant at depth of 2 m and followed by silt and clay (12.85%), medium sand (8.15

%) coarse sand (0.66), while gravel is absent. Fine sand decreases with depth until 8 m

depth and increase again until 14 m depth. Fine sand has the same trend with silt and

clay.

The highest percentage of medium sand (42.13%) is observed at depth of 5 m

and decrease gradually (28.23 %) to until depth of 14 m. It increases again at 17 m

depth (40.86%) and decreases at 20 m depth (33.71%). Generally, medium sand has a

relatively lower fluctuation compared to fine sand.


97

The lowest value of coarse sand is observed at depth of 2 m. It increases until

reaching the highest value (47.03%) at a depth of 8 m. It decreases again until 14 m

depth and increases drastically to 36.14% at a depth of 17 m. Occurrence of coarse grain

at depth from 6 m to 11 m and at depth around 17 m indicate the presence of higher

permeability aquifer within the depth interval.

Gravel is not present at depths of 2 m, 5 m, 11 m and 14 m. However, it is found

at depth of 8, 17 and 20 m (1.2%, 2.64% and 25.13%).

Table 4.6. Grain size distribution within WA1

Sample_ID Depth

(m)

Gravel

(%)

Coarse

Sand (%)

Med Sand

(%)

Fine Sand

(%)

Silt &

Clay (%)

WA1-02 2 0 0.66 8.15 78.34 12.85

WA1-05 5 0 2.84 42.13 51.45 3.58

WA1-08 8 1.2 47.03 33.12 17.25 1.4

WA1-11 11 0 16.64 32.78 48.17 2.41

WA1-14 14 0 7.14 28.23 59.27 5.36

WA1-17 17 2.64 36.14 40.86 18.37 1.99

WA1-20 20 25.13 9.54 33.71 28.14 3.48


98

Figure 4.10. Grain size distribution (left) and lithology log (right) of borehole WA1.

Generally, the fine sand dominates soil grain size in the WA1. More porous formation

can be found at depth of around 8 m and 17 m.

4.2.2.2. The WA1 Soil and Water Chemistry Content

The soil and water chemical result is given in Table 4.7. Figure 4.11 is a plot of

soil chemical concentration value versus sampling depth.

The Al is a dominant chemical content ranging from 37326.5 mg/Kg to 60414.2

mg/Kg. The lowest Al concentration (37326.5 mg/Kg) is represented by near surface

0

2

4

6

8

10

12

14

16

18

20

0 50 100

Dep

th (

m)

Weigh Percentage (%)

Gravel Coarse Sand

Med sand Fine Sand

Silt & Clay


99

soil sample whilst the highest Al concentration (60414.2 mg/Kg) is in soil sample at 11

m depth. Al concentration increases with depth until 11 m depth and decreases until 20

m depth. At the deepest depth (24 m), Al concentration increases drastically to about

60367 mg/Kg.

Kalium is the second dominant cation content of the soil samples. The lowest

(12482 mg/Kg) and highest (21311 mg/Kg) K concentration is at depth of 8 m and 17

m, respectively. The third highest chemical dominant is Fe that has concentration from

10510 mg/Kg to 17403.1 mg/Kg. Lowest Fe concentration is observed near the surface

and increases until 8 m depth, and decreases until a depth of 14 m. It fluctuated until the

deepest depth. Generally, trend of the Fe concentration is increasing with depth.

Na concentration varies from 2575.9 mg/Kg to 5093.7 mg/Kg and has no

specific trend from the surface to the deepest depth. The Ca and Mg concentration

varies from 584.9 mg/Kg to 1406.3 mg/Kg and 936.3 mg/Kg to 2713.3 mg/Kg

respectively. Mn concentration range from 162 mg/Kg to 298.7 mg/Kg. Pb, Cu, Zn and

As concentration is less than 100 mg/Kg. Cd and Se are not detected in the soil samples.


100

Table 4.7. Soil (top) and water (bottom) chemical content within WA1

Sampling ID K Ca Mg Pb Cd Se Al Mn Cu Zn Fe As Na

mg/Kg mg/Kg mg/Kg mg/Kg mg/Kg mg/Kg mg/Kg mg/Kg mg/Kg mg/Kg mg/Kg mg/Kg mg/Kg

WA1-02 20210.2 1251.1 2631.9 72.2 0.0 0.0 37326.5 298.7 41.1 89.6 10811.2 34.3 Sat

WA1-05 20514.4 1406.3 2713.3 59.8 0.0 0.0 40550.2 266.1 39.1 61.8 12701.4 36.5 5077.8

WA1-08 12482.0 862.3 2526.0 65.9 0.0 0.0 58053.6 209.6 43.4 52.8 12554.0 56.4 2575.9

WA1-11 13821.2 908.4 936.3 67.5 0.0 0.0 60414.2 285.9 40.8 60.3 10810.4 31.3 3701.7

WA1-14 20298.8 584.9 1154.8 42.2 0.0 0.0 57928.3 162.0 20.1 29.3 10510.0 25.3 3468.1

WA1-17 21311.8 857.9 2234.8 68.6 0.0 0.0 53907.5 261.4 36.7 60.8 15412.7 36.3 5093.7

WA1-20 17176.8 813.0 2128.9 64.6 0.0 0.0 45171.6 212.7 35.7 59.5 13822.8 35.9 4068.2

WA1-24 20775.1 604.5 1155.8 68.7 0.0 0.0 60367.6 230.9 34.6 55.3 17403.1 37.4 4832.2

Sampling ID K Ca Mg Pb Cd Se Al Mn Cu Zn Fe As Na

mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L

WA1-Water 2.984 6.017 1.61 0 0 0.009 0.012 0.325 0.016 0 0.098 0 7.905


101

Figure 4.11. Soil chemical content in borehole WA1. Al is a dominant chemical

concentration, followed by K and Fe.

The water chemistry result is given in Table 4.7. Na and Ca dominate among the

other cations in the water sample which has concentration of 7.90 mg/L and 6.02 mg/L

respectively. Whilst K and Mg concentration is 2.98 mg/L and 1.61 mg/L. Other

elements are less than 0.4 mg/L. All cations content fall in the acceptable limit for

human consumption.

0

2

4

6

8

10

12

14

16

18

20

22

24

0 10000 20000 30000 40000 50000 60000 70000

Dep

th (

m)

Concentration (mg/Kg)

K Ca Mg Na Pb Cd Se

Al Mn Cu Zn Fe As


102

4.2.2.3. Geoelectrical Resistivity and Its Correlation to the Other Parameters in

Test-site 3

The geoelectrical model for this site study is given in Figure 4.12. Relatively

lower resistivity value of around 14 ohm.m is observed near the surface between 30 - 60

m marks. The geoelectrical model is supported by ten random direct surface resistivity

measurements at this zone. The direct average resistivity was 24.32 ohm.m with

standard deviation of 6.57 ohm.m. This corresponds to the medium sand with higher

moisture content. The low resistivity value is probably due to a direct impact of

farmyard manure activities found around the zone. At this site, the farmers do not use

chemical fertilizers to improve yield. Manure gathered from their farm animals is used

instead for fertilization. Nitrate concentration of 22.6 mg/L is observed in well WA114

where location of the well is about 20 m away from the survey line and crossing

perpendicular at 40 m mark.

Compacted sandy clay soil was observed on the surface along the profile from

100 m mark to the end of the survey line. Average resistivity value of 398.65 ohm.m

with standard deviation of 56.23 ohm.m was obtained from direct surface resistivity

measurement at 10 point location.

A relatively higher resistivity value of around 280 ohm.m is observed at 3 - 5 m

depth from 100 m mark to the end of geoelectrical model. This corresponds to the fully

saturated fine sand clayey soil. This interpretation is also supported by grain size soil

data within this depth interval (Table 4.6). The well WA1 is drilled 10 m away from the

survey line and perpendicular at 340 m mark.

A potential aquifer is clearly seen at a depth ranging from 5 - 12 m below the

100 m mark with resistivity value of around 60 ohm.m. The aquifer gently dips to the


103

east which has depth from 7 m to around 22 m at the end of survey line. Medium to fine

sand is dominant at the depth interval. However at the depth of 8 m and 17 m, coarse to

medium sand is dominant.

A relatively higher resistivity value (more than 400 ohm.m) can be seen dipping

from the west to the east which corresponds to the basement of the area. The granite

basement was encountered at a depth of 24.10 m with resistivity value of around 400

ohm.m.

Figure 4.12. Geoelectrical model of Test-site 3.

The summary of geoelectrical resistivity interpretation based on soil properties

and direct resistivity measurement is given in Table 4.8.

Table 4.8. Summary of geoelectrical resistivity interpretation in Test-Site 3.

No Dominant

Medium

Location Moisture Polluted /

Unpolluted

Resistivity

(ohm.m)

1 Clay to Fine sand Near surface Low (8-10%) Unpolluted 350-450

2 Clay to Fine sand B water table Fully saturated Unpolluted 150-250

3 Medium sand Near surface High (>20%) Unpolluted 60-120

4 Medium, coarse sand B water table Fully Saturated Unpolluted 50-100 ohm.m

5 Granite basement B water table Bounded by

saturated soil

>400 ohm.m

East

Aquifer (medium to coarse sand)

Clay to fine sand (low moisture)

24.1 m

WA1

Clay to fine sand (saturated)

GB

GB PA

Medium sand (high moisture)

GB = Granite bedrock; PA = Potential aquifer


104

4.3. Groundwater Investigation for Area 1

A combination of hydrogeochemical, geoelectrical resistivity and soil properties

analysis were used to study the groundwater characteristic in this area. In this study,

special emphasis was given to the shallow aquifer because it is the main source of the

water supply for domestic uses and because there is no existing well with depth more

than 15 m in Area 1.

Samples of groundwater were collected from the existing wells. The in-situ

parameters, well location, well depth, water level, total dissolved solid, pH,

conductivity, salinity and temperature were measured. Chemical analyses in the

laboratory were conducted to determine their major ion contents. The hydrogeochemical

data obtained from this study were used in the interpretation of the overall data. Major

ion concentration, electrical conductivity, and total dissolved solids were the

hydrogeochemical parameters used in the characterization of the groundwater.

Soil sampling using conventional auger was done in certain location. The grain

size distribution is needed in order to obtain soil distribution for Area 1.

In addition to hydrogeochemical investigation, geoelectrical resistivity survey

was conducted to determine the characteristics of the subsurface and the groundwater

within the aquifers. 2D geoelectrical resistivity imaging surveys were performed at

nineteen sites with 61 electrodes configuration. The maximum line spread was 400m in

length, and the minimum spread was 80m in length, each line spread location depended

on the available space in the field. The location of geoelectrical resistivity survey,

groundwater and soil sample is given in Figure 4.13.


105

Figure 4.13. Map of survey location for geoelectrical resistivity, groundwater and soil

sample.

465000 470000 475000

645000

650000

655000

660000

Kelantan River

N

Boundary Range

Exposed Granite

Legend

. Soil Sample

_Geoelect. Surv.

o Well Location

4 Km

Meters

Mete

rs

Kampung Ketereh

Kampung Tok Bok


106

4.3.1. Water Chemistry and Its Environmental Impact

The hydrogeochemical content and well physical parameters are given in Table

4.9. Figure 4.14 shows the water chemical plotted in the base map. Ninety percent of the

groundwater in the shallow aquifer possesses hydrogen ion concentration (pH) that is

moderately acidic (4 - 6.5). The remaining five percent has pH value of 6.5-7.8

indicative of neutral environment (Hounslow 1995). Lower pH value of less than 6 is

observed in the zone of where either granite bedrock found around the well or the well

depth reach the basement bedrock. The pH of groundwater will vary depending on the

composition of the rocks and sediments that surround the travel pathway of the recharge

water infiltrating to the groundwater. The chemical composition of the bedrock tends to

stabilize (buffer) the pH of the groundwater (Hounslow 1995). In this area, granite

bedrock and so many boulders are found so that the ground water tend to be acidic.

The sodium (Na) and potassium (K) contents in the water samples are

remarkably low. The concentration of Na and K range from 0 to 13.19 mg/l and 1.17 to

7.58 mg/l, respectively. The contributing factor is possibly of the weathering feldspars

and leaching of clay minerals (Egbunike, 2007; Hounslow, 1995). Potassium, an

important fertilizer component, is strongly held by clay particles in the soil. Therefore,

leaching of potassium through the soil profile and into ground water is important only in

coarse-grained soils. Potassium is common in many rocks. Most of the potassium in the

rocks is relatively soluble and thus its concentrations in ground water increase with

time. Important sources of sodium include fertilizing activities and animal waste. In

Figure 4.14, potassium is observed in the area of relatively higher fertilization activities

and the area in which clay is dominant. Sodium is also a common chemical in minerals.

Like potassium, sodium is gradually released from the rocks. Its concentrations thus

increase with time.


107

Magnesium ion (Mg2+

) concentration is generally low (0.26-2.42 mg/l). The

availability of magnesium ions in the groundwater can be explained by the occurrence

of ferromagnetic minerals such as goethite and limonite in the alluvium.

Aluminium ion (Al) and Iron (Fe) concentration are generally low ranging from

0.00 to 1.51 mg/L and 0 to 1.99 mg/L respectively. However, Al and Fe concentration

vary for different location. The discussion on Al and Fe concentrations in groundwater

will be presented in Chapter 5.

Concentration of bicarbonate (HCO3) is low in all water samples with value less

than 90 mg/L except for WA115 sample which has bicarbonate concentration of 195.2

mg/L. There are only two groundwater samples (WA120 and WA101) in which

bicarbonate are absent. The presence of bicarbonates in the shallow aquifer within study

area is probably due to agricultural activities that utilize carbonate powder (neutralising

agent) for various purposes such as for normalizing land pH level.

The chloride (Cl) concentration is also relatively low (less than 12.5 mg/L),

because chloride does not show any correlation with the components of pore water

derived from mineral dissolution. The chloride in rain water and subsequently by

evaporation may be an important source of chloride concentration in the area. Another

common source of chloride in groundwater is the leaching of chloride in fertilizer over

long period of time. Higher chloride concentration is observed in the area with higher

fertilization activities. Sulphate (SO4) concentration ranges from 0 - 12.34 mg/L which

is considered low.


108

Table 4.9. In-situ parameters and results of groundwater samples analysis of Area 1. Limit concentration for domestic use by WHO (1992)

and U.S.EPA (2002) is displayed In the bottom row of the table.

No

Sample Location X

Location Y

Well Depth

Ground Depth to

Water L (msl) TDS Conductivity Salinity T pH

Level Water

ID (m) (m) (m) (m) (m) (m) mg/L S/cm 0/00 0C

1 WA101 467159 646187 5 24 1.43 22.57 370 751 0 28.3 6.88

2 WA102 467455 645676 5 26 1.92 24.08 247 501 0 28.3 5.98

3 WA103 469175 646657 3 28 2.38 25.62 49 98 0 30.5 5.09

4 WA104 469982 645778 7 38 2.46 35.54 60 121 0 28.1 4.49

5 WA105 470622 646025 5 29 1.22 27.78 35 70 0 28.5 6.19

6 WA106 470630 645415 <7 33 2.96 30.04 48 97 0 30.1 6.42

7 WA107 471343 646277 <7 28 2.56 25.44 76 159 0 27.8 4.77

8 WA108 470511 646770 <7 24 2.1 21.9 323 654 0.1 30.5 5.98

9 WA109 468507 648571 5 22 1.96 20.04 407 830 0 29.4 4.93

10 WA110 466884 648964 <7 21 0.86 20.14 76 159 0 29.2 4.63

11 WA111 467562 650522 <7 22 0.98 21.02 78 163 0 29.1 5.72

12 WA112 470178 649987 <7 18 0.67 17.33 151 313 0 27.4 5.75

13 WA113 471890 651687 <15 40 10.62 29.38 57 120 0 28.5 6.14

14 WA114 471962 653352 <7 24 1.35 22.65 83 173 0 31.7 4.86

15 WA115 468452 650985 <7 20 0.91 19.09 50 104 0 34.4 5.72

16 WA116 473804 654980 <7 19 1.02 17.98 183 381 0 42.2 4.77

17 WA117 473733 656574 <7 14 0.23 13.77 84 170 0 31.1 6.4

18 WA118 470689 656930 5 17 0.65 16.35 89 180 0 25.7 6.42

19 WA119 470404 658785 6 28 2.11 25.89 64 130 0 28.7 6.22

20 WA120 470475 654957 <7 17 0.61 16.39 106 217 0 27.2 4.11

6-8


109

Table 4.9. (Continued)

No Sample Chloride Nitrate Sulfate Fluoride K Ca Mg Na Al Fe CO3 HCO3

ID mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L

1 WA101 12.28 24.18 0.318 0 2.534 6.025 1.558 7.835 0 0.032 0 0

2 WA102 8.18 18.93 5.571 0 5.044 22.25 2.418 13.19 0.034 0.146 4.8 80.6

3 WA103 5.23 6.83 1.605 0 1.457 6.211 0.433 8.004 0.304 0.029 0 4.2

4 WA104 8.15 6.06 12.339 0 4.343 6.238 1.048 10.35 0.266 0.001 0 7.3

5 WA105 3.65 9.72 1.394 0 2.064 3.917 0.666 4.831 0.144 0.004 0 4.5

6 WA106 2.11 0.34 0.237 0 4.616 4.146 0.575 3.949 0.082 0.122 0 12

7 WA107 5.86 2.77 5.915 0 1.309 4.782 0.304 7.912 0.045 0.054 0 85.32

8 WA108 11.66 22.28 1.716 0.058 1.693 24.79 0.588 5.124 0.015 0.006 0 47.16

9 WA109 6.63 143.8 0.304 0 2.181 19.54 1.887 10.01 0 0.22 0 52.56

10 WA110 6.75 12.9 0.622 0 1.785 3.295 0.447 6.057 0.331 0.023 0 62.23

11 WA111 4.11 3.84 3.544 0.049 2.505 8.306 0.622 3.581 0.122 0.058 0 12.51

12 WA112 12.1 4.46 4.154 0 3.228 12.21 0.536 10.55 0.072 0.055 1.76 73.34

13 WA113 2.14 0 1.213 0 1.329 2.469 0.327 3.059 0.025 0.54 0 2.7

14 WA114 3.51 2.18 1.443 0 1.172 3.681 0.258 3.078 0.059 0.021 0 1.3

15 WA115 7.21 22.58 0 0.22 1.487 3.628 0.698 11.24 0.13 0.025 1.6 23.8

16 WA116 11.16 0 7.953 5.643 2.303 2.972 0.326 0 0.072 0 0 195.2

17 WA117 2.43 0 0.263 0.032 4.151 3.048 0.888 3.227 0.13 1.993 0 7

18 WA118 4.36 0 0.212 0 7.581 2.739 1.094 1.715 1.505 0.541 0 10.1

19 WA119 1.83 0 0 0.073 3.797 3.34 0.915 1.183 0.448 0.164 0 13.2

20 WA120 9.9 0 0.663 0.052 5.547 3.309 1.127 3.609 1.338 0.28 0 0

250 45 400 1.5 150 200 0.2 0.3


110

Figure 4.14. pH, K, Ca, Mg, Na, Al, Fe, HCO3, SO4, Cl, and NO3 distribution in

groundwater sample.

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

4.11 to 4.77

4.77 to 5.09

5.09 to 5.75

5.75 to 6.14

6.14 to 6.4

6.4 to 6.881

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

1.172 to 1.457

1.457 to 1.785

1.785 to 2.303

2.303 to 3.228

3.228 to 4.616

4.616 to 7.582

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

2.469 to 3.048

3.048 to 3.34

3.34 to 3.917

3.917 to 6.025

6.025 to 12.21

12.21 to 24.8

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

0.258 to 0.327

0.327 to 0.536

0.536 to 0.622

0.622 to 0.888

0.888 to 1.127

1.127 to 2.419

pH K

Ca Mg


111

Figure 4.14. Continued.

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

0 to 3.059

3.059 to 3.581

3.581 to 4.831

4.831 to 7.835

7.835 to 10.35

10.35 to 13.2

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

0 to 0.025

0.025 to 0.059

0.059 to 0.082

0.082 to 0.144

0.144 to 0.331

0.331 to 1.506

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

0 to 0.006

0.006 to 0.025

0.025 to 0.054

0.054 to 0.122

0.122 to 0.28

0.28 to 1.994

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

0 to 2.7

2.7 to 7

7 to 12

12 to 23.8

23.8 to 73.34

73.34 to 195.3

Na Al

Fe HCO3


112

Figure 4.14. Continued.

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

0 to 0.237

0.237 to 0.318

0.318 to 1.213

1.213 to 1.605

1.605 to 5.571

5.571 to 12.34

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

1.83 to 2.43

2.43 to 4.11

4.11 to 5.86

5.86 to 7.21

7.21 to 11.16

11.16 to 12.29

465000 470000 475000

645000

650000

655000

660000

WA101

WA102

WA103

WA104WA105

WA106

WA107

WA108

WA109

WA110

WA111

WA112

WA113

WA114

WA115

WA116

WA117

WA118

WA119

WA120

WA1

Kelantan River

N

Boundary Range

Exposed Granite

0 to 0.34

0.34 to 2.77

2.77 to 6.06

6.06 to 12.58

12.58 to 22.28

22.28 to 143.9

SO4 Cl

NO3


113

The concentration of nitrate (NO3-) in the northern part of the study area is

generally low (0 - 5 mg/L). In the southern part (palm oil plantation area), especially

where the surface water flow ends (around WA108, WA109, WA109, WA101 and

WA102), the nitrate concentration is relative higher (more than 20 mg/L). The highest

nitrate concentration is found in WA109 (143 mg/L) where the well is located at lower

elevation. The nitrate concentration in water is safe for drinking if less than 45 mg/L

(U.S. EPA, 1980). The potential source of nitrate in the area may come from fertilizing

activities and animal excrement.

In term of environmental impact, thirty percent of the water sample has pH value

of 5 and is considered not suitable for human consumption if untreated (Hounslow

1995). K, Ca, Mg and Na cations content in all groundwater samples lies within the

accepted limit for human consumption. Two wells (WA116 and WA117) have Fe

content more than 0.3 mg/L and five wells (WA103, WA109, WA117, WA118 and

WA120) have Al content above the boundary of accepted limit for human consumption.

All water samples have Cl and SO4 anions content that are safe for human

consumption. One well (WA115) is not suitable for human consumption due to fluoride

content more than 1.5 mg/L. In particular, nitrate concentration tend to be higher in the

area of relatively higher fertilization activities (farm of palm oil) and exceed for human

consumption (> 45 mg/L) in the lower topography zone (WA109, 143 mg/L) where the

fertilization is still going on.

4.3.2. Conductivity and Anion Content

In the zone with relatively higher fertilization activities, the anion content in

groundwater is relatively higher (Figure 4.14). For water sample with higher anion


114

concentration, water conductivity tends to be higher. Correlation between conductivity

and anion water chemical content can be calculated statistically using the Pearson

product-moment correlation (Till 1974). Based on data in Table 4.9, correlation

coefficient between conductivity and chloride is 0.82, conductivity and nitrate is 0.80,

and conductivity and sulphate is 0.04 and finally the correlation coefficient between

conductivity and TDS is 0.99. Low correlation between conductivity and sulphate is due

to higher local variation sulphate concentration which was found in the groundwater.

Finally, it is concluded that the amount of nitrate and chloride in the

groundwater has a role in influencing the total conductivity readings. High nitrate and

chloride concentration can increase the conductivity reading. Different of water

conductivity in subsurface is one of other parameters that influence geoelectrical

resistivity reading. High soil and groundwater conductivity will cause lower resistivity

in the surface resistivity measurement.

4.3.3. Nitrate Distribution and Groundwater Flow Pattern

The map in Figure 4.15 shows the nitrate concentration of samples collected at

the well location and the land use. Relative high nitrate concentration ranging from 5

mg/L to 30 mg/L can be found in wells located at the palm oil plantation zone. Except

for well WA109 has nitrate concentration of 143 mg/L. The higher nitrate in this well is

due to the location of this well in the catchment area within palm oil plantation. In the

rubber and paddy fields plantation, groundwater sample has lower nitrate concentrations

of less than 5 mg/L. However, in sample of well WA114, nitrate concentration tend to

be high (12.58 mg/L) although no palm oil plantation exist around the well. It could

possibly cause by minor agricultural activities, including corn cultivation. For these

activities, chemical fertilizer was not utilized. Only organic fertilizers like cow manure


115

were used. The trend of higher nitrate concentration was found in the zone with

relatively higher fertilization activity.

Figure 4.15. Land uses and nitrate concentration map within the shallow aquifer (less

than 11 m depth). Nitrate concentration tends to be higher in the palm oil plantation and

almost absent in the area of paddy planting and rubber tree plantation.

465000 470000 475000

645000

650000

655000

660000

Area 1 Rubber Plantation Palm Plantation Paddy Area

Kelantan River

N

Boundary Range

4 Km

Meters

Mete

rs

0 to 0.99

1 to 4.99

5 to 9.99

10 to 19.99

20 to 29.99

100 to 150


116

A map of well groundwater level relative to mean sea level and vector direction

of groundwater movement is given in Figure 4.16. The area is defined into three zones

based on its topography. Zone 1 represents highest topography area bounded by X;Y

coordinates from 465000;645000 to 473000;650000. Zone 2 is a middle topography

area which is bounded by coordinates of 465000;650000 to 655000;475000. Whilst,

Zone 3 is the lowest topography area with coordinates ranging from 468000;655000 to

660000;478000.

The groundwater in the southeastern part of Zone 1 flows from Boundary Range

Hill to northwest in Kampung Tok Bok. Boundary Range Hill is at more than 250 m

elevation whereas Kampung Tok Bok is at elevation around 35 m above mean sea level.

In the southwestern part of Zone 1, the groundwater around the wells WA101 and

WA102 flows toward the Kelantan River. Generally, groundwater movement within

Zone 1 is from southeast to northwest.

In Zone 2, groundwater flow originates from Boundary Range Hill towards

Kampong Merbau Condong. As in Zone 1 the groundwater flow is from elevation 250

m at the Boundary Range Hill to about 30 m above mean sea level at the Kampong

Merbau Condong. In Kampung Merbau Condong, the groundwater flows in three

directions; southeast-northwest, east-west and northeast-southwest. The general

groundwater flow direction is however from the southeast to the northwest, towards the

Kelantan River which is elevated at 15 m above mean sea level.


117

Figure 4.16. Groundwater level (solid colour) and vector direction of groundwater

movement (black arrow). Vector direction of groundwater movement is commonly from

the southeast to the northwest.

465000 470000 475000

645000

650000

655000

660000

12

14

16

18

20

22

24

26

28

30

32

34

Kelantan River

N

Boundary Range

Exposed Granite

Meter

Vector direction of

4 Km

Mete

rs

Legend

Groundwater movement


118

The north-eastern part of Zone 3 has the lowest groundwater level of the study

area. It is at a lower elevation than the Kelantan River. Thus, in this zone the

groundwater does not flow toward the Kelantan River. Instead, the groundwater flows

downward into the lower aquifer.

Generally, the direction of groundwater movement is influenced by elevation,

moving from high land to lowland areas. This factor may affect the potential

distribution of nitrate concentration within an area. Groundwater in lower elevation

which is covered by palm oil plantation tends to have higher nitrate concentrations

(WA101, WA102, WA108, WA109, and WA109) whereas groundwater in higher

elevation areas (WA103 and WA104) have lower nitrate concentration.

4.3.4. Geoelectrical Resistivity Model

The geoelectrical resistivity surveys had been carried out along 19 survey lines.

These lines are additional to the survey conducted for the previous study discussed in

subchapters 4.2 and for nitrate monitoring in next subchapter (4.4). The coordinate

central point of the survey lines are plotted in Figure 4.17. The geoelectrical resistivity

interpretation will be based on standardized and calibrated results obtained in the

previous study (subchapter 4.2). In the discussions of all the geoelectrical models, the

analysis are divided into three zones; shallow, intermediate and deep depth. The

discussion starts from near surface and subsequently to the lowest depth.

The following terms will be used as labels of all the geoelectrical models: CSL =

Compacted soil with low moisture content; SA = Shallow aquifer; PA = Potential

aquifer; GB = Granite basement; GBl = Granite boulder.


119

Figure 4.17. Location of geoelectrical resistivity survey lines in Area 1

465000 470000 475000

645000

650000

655000

660000

A101

A102

A103

A104

A105

A106

A107 A108

Test Site 3 A109

A110

A111

A112 A113

A114A115A116

A117A118

Test Site 1Test Site 2

Kelantan River

N

Boundary Range

Exposed Granite

Legend

Geoelect. Surv.

4 Km

Meters

Mete

rs

Kampung Ketereh

Kampung Tok Bok

Kampung Pulai Condong

A101

Hill Boundary

Test-site 1, 2, A104


120

Line A101

The first survey line A101 was conducted at a palm oil plantation on a small

valley with elevation of 24 m above mean sea level. The aim of this survey was to

define the water table in the site and to observe the possibility of its correlation to water

chemical content. The survey line was in an east - west direction.

Figure 4.18 shows the geoelectrical inversed model of line A101. An average

resistivity value of about 1200 ohm.m is observed near the surface, which corresponds

to the soil with low moisture content. At depth of around 22.5 m, the resistivity value

coloured dark green (about 150 ohm.m) forms an almost horizontal line. This value

corresponds to the water table at the site. Observation at wells WA101 and WA102,

situated roughly 40 m from the line survey, indicate the water table was at 1.4 m below

the ground surface when the measurement was carried out. Water chemical analysis

results from the wells show a relatively higher nitrate concentration (24 mg/L) in the

groundwater (Table 4.9). The geoelectrical model shows comparatively low resistivity

value (around 15 ohm.m) in zones of around 19 m and 13 m deep. This zone is

interpreted as potential aquifer.

Figure 4.18. Geoelectrical model of line A101.

West

Aquifer (medium to coarse sand)

Water table

WA101

PA GBl

CSL

PA = Potential aquifer; GBl = Granite boulder;



121

There are two anomalies with high resistivity values (more than 2000 ohm.m)

within the section. These anomalies are believed to be due to weathered granite boulder.

This interpretation is based on some core boulders found in this area with diameters of

around 1.5 m (see description of Area 1 in Chapter II).

Line A102

Line A102 was located at the end northeast part of palm oil plantation. The site

has an elevation of 24 m above mean sea level as in the north but, comparatively lower

than the surrounding areas. Some zones around this site were puddled by water. The

aim of survey here is to define the water table and to observe the possibility of its

correlation with water chemical content. The survey line direction was from south to

north.


An average resistivity value of about 90 ohm.m is observed near surface. It

corresponds to the soil with relatively higher moisture content (Figure 4.19). The

feature coloured light green at a depth of around 21.7 m form an almost horizontal line.

This probably corresponds to the water table. The well WA108 located approximately

North

PA

PA = Potential aquifer


122

30 m from this survey line, the water table was 2.1 m below the ground surface. The

water chemical result indicates relatively higher nitrate concentration (28 mg/L) in the

groundwater (Table 4.9). The geoelectrical model show relatively low resistivity value

(around 13 ohm.m) in a zone of about 19 m deep. This correlates to potential aquifer.

Line A103

The line A103 was located at a site with elevation of 38 m above mean sea level.

The site was on a small hill and was slight undulating topography. The land surface is

dipping gently to the west. The aim of this survey is similar with the other two previous

surveys, A101 and A102.

An average resistivity value of about 1300 ohm.m is observed near surface to

about 36 m depth (Figure 4.20). This corresponds to the soil with low moisture content

and low porosity. This model is also supported by five direct surface resistivity

measurements with an average value of around 1350 ohm.m.


East PA

CSL

PA = Potential aquifer; CSL = Compacted soil with low moisture content


123

Water chemical results from well WA104 (water table = 2.46 m, 50 m away

from the survey line) show a relatively low nitrate concentration (6 mg/L) in

groundwater. The lowest resistivity value in the geoelectrical model is around 60

ohm.m. However, on the geoelectrical model, resistivity value of around 180 ohm.m is

interpreted as representing saturated zone (potential aquifer).

Line A104

The survey line A104 was located at a site with an elevation of 27 m above

mean sea level. The survey line direction was laid in a west to east.

In the geoelectrical model along line A104 (Figure 4.21), an average resistivity

value of around 1000 ohm.m is observed at near surface. It corresponds to the coarse

soil with low moisture content. The direct surface resistivity measurement also supports

this value with an average of 1079.65 ohm.m and standard deviation of 96.27 ohm.m.


The groundwater table is interpreted at a depth of around 20 m with resistivity

value of 350 ohm.m. Unfortunately, there is no existing well in the site. A relatively

lower resistivity value (100.39 ohm.m, minimum values in the section) is observed at a

East PA

CSL

PA = Potential aquifer; CSL = Compacted soil with low moisture content


124

depth of around 17 m down. This correlates to the groundwater accumulation in the

relatively porous medium (potential aquifer).

Line A105

Line A105 was located on a small hill with an elevation of 37 m above mean sea

level. The line was laid beside a small road in a west-east direction. Exposed massive

granite of Boundary Range of Machang Batholith was found about 4 km to the east of

the survey line.

In the geoelectrical model (Figure 4.22), an average resistivity value of about

300 ohm.m is observed near surface. It corresponds to the soil with moderate moisture

content. This value was also supported by five direct surface resistivity measurements

which has an average resistivity of 320 ohm.m. There is however no well available in

the study area.


A relatively lower resistivity value (200 ohm.m) is observed at depth of 33 m to

27 m. This is probably due to porous sand with very low moisture content. A relatively

East GB

GB = Granite bedrock


125

higher resistivity value (more than 1000 ohm.m) is observed at a depth of around 10 m

down, which correspond to the basement. The basement dips towards the west.

Line A106

Line A106 was located at an elevation of 23 m above the mean sea level. The

survey was exactly in the border area of a palm oil plantation. The line was laid in a

south-north direction.

Figure 4.23 shows the geoelectrical model of line A106. An average resistivity

values of about 400 ohm.m is obtained near surface. It corresponds to sandy soil with

moderate moisture content. The direct surface resistivity measurements were again

supporting the values with an average of 482.12 ohm.m.

A relatively lower resistivity value of about 40 ohm.m is encountered at a depth

of around 21.5 m to 19 m, corresponded to the possibility of shallow aquifer.

Unfortunately, there is no existing well in the surrounding site. The nearest well WA109

was found at about 1.5 km to the northeast with nitrate concentration of 143 mg/L.


North

SA

GB

GB = Granite bedrock; SA = Shallow aquifer


126

Line A107

The line A107 was located at a site outside of the palm oil plantation to the

northern part of the study area. The site has elevation of 18 m above mean sea level.

The site was surrounded by paddy fields with very wet soil condition. The survey line

was in a west-east direction. Exposed massive granite of Boundary Range of Machang

Batholith can be found around 4 km to the east of the survey line.

In the geoelectrical model (Figure 4.24), an average resistivity value of about 90

ohm.m is observed near surface. This correlates to the fully saturated soil with fresh

water content. An aquifer which is indicated by lower resistivity values (35-80 ohm.m)

can be found within a depth ranging from around 12 - 3 m below the 80 - 200 m mark.

A lower resistivity value is obtained (about 40 ohm.m) near surface at the zone between

210-220 m marks. At this zone, the aquifer is probably connected directly to the surface,

so that surface water is more easily infiltrating through the aquifer. There is no

groundwater sample obtained from this site due to the site being around a paddy

plantation. At a depth of around -15 m, relatively higher resistivity values (more than

4000 ohm.m) were observed corresponding to the compacted basement which is

dipping to the west.


East GB

PA



127

Line A108

Line A108 is located almost northeast to the line A107. The survey was

conducted beside a small road shoulder in an east-west direction. The site (24 m above

mean sea level) was surrounded by paddy fields with moderately wet conditions.

Around this site, exposed massive granite of Boundary Range Machang Batholith can

be found less than 2 km east of the survey line.

In the geoelectrical model along line A108 (Figure 4.25), resistivity values of

around 300 ohm.m dominate near surface which correlates to the soil with relatively

low moisture content. More porous material occurs at zone with resistivity value

coloured light green (70-80 m mark and 220-240 m mark). At this zone surface water is

possible to infiltrate into shallow aquifer directly.

A lower resistivity value (65 ohm.m) is observed at depth ranging from 20 - 12

m, which corresponds to the potential aquifer. The aquifer dips and thicken to the west.

The highest resistivity value of more than 1300 ohm.m is found at a depth of around -6

m. This feature is the granite basement. It dips gently from the east to the west.


West GB

PA



128

Line A109

Line A109 is located at a site of 33 m above mean sea level with in a west-east

direction. The line was located about 2 km to the west of Machang Batholith Boundary

Range. The site was located in the preparation area for housing development.

The geoelectrical model along line A109 (Figure 4.26) shows an average

resistivity value of around 1300 ohm.m near the surface. The values correspond to the

compacted material with low moisture content. However at interval of 360 - 400 m

mark, more porous material is observed with resistivity value of 100 ohm.m. The

surface water is almost possible to infiltrate along the zone. A resistivity value of

around 80 ohm.m is observed at a zone ranging from 21 - 8 m depth. It correlates to the

potential aquifer. The aquifer dips to the Kelantan River ward. There was no well drilled

in this site.

A zone with high resistivity value of more than 400 ohm.m can be recognized at

a depth of -7 m down. The value corresponds to the basement which dips to the west.


East GB

PA



129

Line A110

Line A110 is located at a site of 18 m above mean sea level. The line direction

was from the east to the west. The site was very wet due to surrounded by puddle of

water within paddy field. Water table was around 30 cm below the ground surface.

The geoelectrical model (Figure 4.27) shows relatively higher resistivity value

(around 250 ohm.m) near the surface ranging from 31 m to 38 m mark. The values

correspond to the more compacted material with high clay content. The minimum value

is 48.7 ohm.m located at about 32 m mark with depth of 15.5 m. It corresponds to fully

saturated porous zone of fresh water.


Line A111

Line A111 was located at a site with elevation of 24 m above mean sea level.

The site was located adjacent to a site office for developing houses. The ground surface

inclined to the west around 2/400 of its gradient.

Along geoelectrical model (Figure 4.28), average resistivity value of around 600

ohm.m is obtained near surface, corresponding to the coarse soil of weathered materials

West

PA

SA = Shallow aquifer


130

with low moisture content. It dominated the whole site surface. Direct surface resistivity

measurements gave an average 613.84 ohm.m with 38.65 ohm.m of standard deviation.

Fresh groundwater can be found from well WA113 with a water table of 1.35 m

(Table 4.9). It is located around 150 m from the 50 m mark of line A111 to the west.

Resistivity value in the geoelectrical model show around 120 ohm.m for the fully

saturated zone (potential aquifer). Relatively higher resistivity value of more than 1500

ohm.m is observed at depth below than 4 m from the middle of profile to the east

corresponding to the granite basement.


Line A112

Line A112 was placed at a site 20 m above mean sea level. The line was laid

between a road shoulder and an artificial drainage system aligned in northeast-

southwest direction. Compacted clay material dominated the surface of site area. Water

level in artificial drainage system was almost equal to ground surface.

Well WA116 can be found at 30 m away from line A112 with fresh water

indication. Connected with the groundwater character, in the geoelectrical model

(Figure 4.29), the minimum resistivity value of 69.8 ohm.m to around 150 ohm.m

East

GB PA

CSL

GB = Granite bedrock; PA = Potential aquifer;



131

(coloured by dark green) correspond to the fully fresh water saturated soil. Low

resistivity value is observed at the end of profile and at the 140-190 m mark. This

indicates the surface water has direct contact with shallow aquifer.

The high resistivity value (more than 400 ohm.m) as indicator of very

compacted material is found at depth below than -5 m. This zone corresponds to the

granite basement which dips to the northeast.


Line A113

The next geoelectrical resistivity survey (line A113) was conducted at a site near

to the Machang Batholith Boundary Range (around 1 km to the east). It was done on a

grass field surrounding a rubber tree plantation in a northeast-southwest direction. The

site survey has an elevation of 28 m above mean sea level and relatively higher about 3

m above the surrounding area.

In the geoelectrical model (Figure 4.30), relatively higher resistivity value (about

1200 ohm.m) can be observed near the surface. This corresponds to the soil with a low

moisture content. In the deeper part, the yellow-coloured value is interpreted as the

maximum value for fully saturated zone. It almost makes a horizontally feature,

Southwest

GB

PA PA



132

correlated with the water table. This interpretation was supported by well WA115 with

water level of 2.11 m. The well was located around 120 m to the west of the survey line.

The minimum value of resistivity in the geoelectrical model is 63.76 ohm.m.

Hydrogeochemical result indicates that the groundwater type is fresh except containing

high Fluoride content (5.6 mg/L) which lay above the WHO limit. However, the

potential aquifer is indicated with resistivity value of about 120 ohm.m. The highest

resistivity value (>1000 ohm.m) is observed at a depth of around 13 m, which

corresponds to the compact material probably Batholith basement.


Line A114

Survey line A114 was located in a paddy field with an elevation of 13 m above

the mean sea level. It was conducted on a small road shoulder in a south-north direction.

At this site, all the survey line was wet with paddy field water. In the

geoelectrical model (Figure 4.31), average resistivity value of around 30 ohm.m occur

at the surface zone until 3 m depth from 160 m mark to the end of line. This correlates

to the shallow aquifer that has direct connection to the surface. At the 160 mark to the

Southwest GB

PA

PA

CSL




133

south ward, resistivity value increase to relatively higher (180 ohm.m) corresponding to

zone of low moisture content. In this profile, the aquifer dips to south ward from below

160 m mark to the beginning of survey line. Unfortunately, there was no existing well

for ground water sampling near this line. Relatively higher resistivity values (more than

400 ohm.m) is observed from depth below than -12 m, correlate to the basement.


Line A115

Line A115 was located in between a paddy field and a small rubber tree

plantation. The site is located 14 m above mean sea level. The geoelectrical resistivity

survey was performed on the small road shoulder in an east-west direction. A puddle of

water in the paddy field was around 1 m from the ground surface.

Along the geoelectrical model (Figure 4.32), an average resistivity value of

about 130 ohm.m occurs near the surface. It corresponds to the clayey sand soil with

high moisture content. A possibility of a shallow aquifer can be observed from the

surface level reaching a depth of 10 m. This is indicated with occurrences of relatively

lower resistivity value coloured green. At depth of around 9 to 2 m, the zone of

resistivity value ranging from 300 - 500 ohm.m can be correlated to confined material.

North

GB PA

GB = Granite bedrock; PA = Potential aquifer; SA = Shallow aquifer


134

The zone of potential aquifer is observed at depth from 2 to -14 m. The relatively higher

resistivity values (more than 400 ohm.m) appear at a depth of -38 m corresponding to

the basement.


Line A116

A site with elevation of 18 m above mean sea level was chosen for laying line

A116. The survey line was conducted on a minor road around a paddy field in a west-

east direction. A puddle of water in the paddy field was around 1 m from the ground

surface.

Along the geoelectrical model (Figure 4.33), an average resistivity value of

about 150 ohm.m appears near surface. It corresponds to the clayey soil filled by water.

A shallow aquifer appears almost along the survey line reaching a depth of 16.5 m. The

granite basement cannot be found in the section.

West GB

PA

SA

GB = Granite bedrock; PA = Potential aquifer; SA = Shallow aquifer


135


Line A117

Line A117 was located between a minor road shoulder and an artificial drainage

system with elevation of 17 m above mean sea level. The geoelectrical resistivity survey

was in a north-south direction.

In the Figure 4.34, along geoelectrical model, relatively lower resistivity value

of around 130 ohm.m is obtained near surface after the 300 m mark. It corresponds to

the more porous material with high moisture content (shallow aquifer). Although the

water table was around 30 cm below ground surface along the survey line, a relatively

higher average resistivity value (around 350 ohm.m) appears along the zone up to 300

m mark. This corresponds to more compacted material (less porous material, see Table

4.5). Relatively higher resistivity value of more than 400 ohm.m is obtained starting

from a depth of around 0 m. This correlates to the granite basement.

East

SA

SA = Shallow aquifer


136


Line A118

Line A118 was located around a paddy field with elevation of 17 m above mean

sea level. The survey line was conducted on a small road shoulder in a north – south

direction. The site was puddle by paddy field water about 20 cm below the ground

surface.

Figure 4.35 shows the geoelectrical model of line A118. A relatively lower

resistivity value (around 65 ohm.m) occurs after 60 m mark near the surface. It

corresponds to the more porous material. Although the water table was around 20 cm

below the surface along the survey line, relatively higher average resistivity value

(around 180 ohm.m) is observed along the zone from 22 m to 45 m mark representing

more compacted material. A higher resistivity of more than 350 ohm.m at depth below

the 6 m is possibly representing weathered granite bedrock.

South GB

SA



137


4.3.5. Correlation between Geoelectrical Resistivity and Hydrogeochemical Result

All resistivity lines A101, A102, A103, A104, A105 and A106 were located

within the palm oil plantation. Lines A109 and A113 were located on the proposed

housing site and the grass field. Lines A107, A108, A109, A110, A111, A112, A114,

A115, A116, A117 and Test-site 3 were located within the site around paddy field and

rubber trees plantation area. Figure 4.36 shows geoelectrical survey location and the

distribution of percentage weight of sand and gravel obtained from the surface to a

depth of 1 m using hand auger. The grain size distribution in palm oil plantation,

propose housing and grass field is similar for all survey locations.

A lower subsurface resistivity value of around 18 ohm.m can be observed at a

depth of about 3 m, in the geoelectrical model along lines A101 and line A102 (Figure

4.18 and 4.20), although these profiles were conducted on relatively lower porosity and

permeability zone (see subchapter 4.2.). A relatively higher nitrate concentration of 24

mg/L and 23 mg/L in the groundwater was found (WA101 and WA108 in Table 4.9)

near these survey lines.

South

SA

GB



138

Figure 4.36. Percentage weight map of gravel and sand. Gravel and sand increase to

direction of the Boundary Range.

465000 470000 475000

645000

650000

655000

660000

A1S01

A1S02A1S03

A1S04

A1S05A1S06

A1S07

A1S08

A1S09

A1S10

A1S11 A1S12

A101

A102

A103

A104

A105

A106

A107 A108

Test Site 3 A109

A110

A111

A112 A113

A114A115A116

A117A118

Test Site 1Test Site 2

Kelantan River

N

Boundary Range

Exposed Granite

A1S01 Soil Sample

A101 G.elect. Surv.

4 Km

Mete

rs

Kampung Ketereh

Kampung Tok Bok


Legend

- - - - Gravel & Sand.


139

Line A103, A104, A105 and A106 were also conducted in the palm oil

plantation. In the geoelectrical model of line A103, possible groundwater accumulation

is indicated at a depth of around 3 m with resistivity value about 60 ohm.m (52.39

ohm.m is minimum values in the section). The nitrate concentration found at this site is

less than 5 mg/L (wells WA105). A104 survey line was conducted around 50 m from

the nearest well (WA106) and about 250 m from line A105 due to the lack space in the

surrounding well. Nitrate concentration in the well is almost absent (0.34 mg/L). Line

A106 is the last resistivity survey line conducted in the palm oil plantation.

Unfortunately, there is no existing well surrounding the survey site. However, the

lowest resistivity value of around 80 ohm.m is found in this line section. It probably the

results of lower nitrate concentration in groundwater. This interpretation is supported by

the condition of the ground surface around line A106 which dips to the north-west

direction with a small river at the end of the palm oil plantation. In this situation, the

fertilizer is transported directly into the small river by surface run off.

In geoelectrical model of lines A109 (Figure 4.26) and A113 (Figure 4.30),

minimum resistivity values of about 35 ohm.m and 60 ohm.m respectively are observed

at depth of about 6-12 m. It is only a well WA116 around 20 m from the line A113,

however shows no nitrate concentration in the groundwater.

The survey line Test-site 3 was conducted beside a corn farm which farmyard

manure is used for fertilizing. In geoelectrical model along Test-site 3 (Figure 4.12 and

Table 4.8), although the resistivity survey used 5 m electrodes spacing, the geoelectrical

model can still show lower resistivity value (less than 15 ohm.m) in the zone with high

farmyard manure. Around 50 m away from the location, the well with ID WA115

shows the presence of high nitrate concentration of 22 mg/L.


140

Generally, in the palm oil plantation, the lowest subsurface resistivity value of

around 80 ohm.m is normal in the old palm oil plantation area and resistivity around 40

ohm.m is normally observed in the area with active fertilizing activities. In the zone

where the surface water ends, subsurface and surface resistivity has been found

relatively lower (around 15 ohm.m) than other places within the palm oil plantation.

This fact exhibiting that presence of nitrate in the groundwater reduces medium

resistivity value.

Figure 4.37 shows the graph of nitrate concentration found in the groundwater

versus minimum resistivity value of the geoelectrical model around the well. The nitrate

values in the graph were derived from the nearest existing well from the survey line.

Obviously, the plotted nitrate data is not giving the real condition of nitrate in the zone

where the model section been surveyed. This is due to the line surveys were not

conducted crossing with well where water sample was collected. Figure 4.37 show that

the presence of nitrate in groundwater reduces the resistivity of soil medium.

Figure 4.37. Nitrate concentrations versus lowest resistivity. The nitrate values were

derived from the nearest existing well from the survey line. Resistivity value decreases

with increasing nitrate concentration.

0

5

10

15

20

25

30

0 20 40 60 80 100 120

Nit

rate

(m

g/l)

Resistivity (ohm.m)


141

4.3.6. The Near Surface Resistivity Distribution and Basement Geometry

The map of near surface resistivity distribution within Area 1 is given in Figure

4.38. The near surface resistivity map was derived from interpolated resistivity value

using Kriging method. In Figure 4.38, higher surface resistivity values exist near the

Machang Batholith Boundary Range. In very wet conditions such as the paddy field, the

surface resistivity values tend to be lower (40-200 ohm.m). However, resistivity values

of not less than 15 ohm.m are observed in areas with aquifer filled by unpolluted

freshwater.

Figure 4.39 shows the basement depth relative to the mean sea level derived

from the resistivity model of each survey lines where the resistivity value of basement

relatively high (more than 400 ohm.m). Figure 4.40 show the basement depth relative to

mean sea level in 3D shape. The green coloured indicates the basement with depth of 40

m above mean sea level. The lower zone is represented by the blue. The shallow

basement is much closer to the Machang Batholith Boundary Range. The southern half

of the area is shown as light blue coloured area with a depth ranging between -20 to -25

m. The groundwater flow in the southern part cannot reach the area in the north because

they are separated by pre-Quaternary bedrock in the middle area. Any pollutants in the

groundwater from the southern part cannot enter the northern part although the area in

the northern part is generally lower than the area in the southern part.


142

Figure 4.38. Surface resistivity distribution. The resistivity map is derived from

dominant resistivity of the geoelectrical model and direct surface resistivity

measurements from the site.

465000 470000 475000

645000

650000

655000

660000

Kelantan River

N

Boundary Range

0

200

400

600

800

1000

1200

1400

1600

1800

2000

4 Km

Meters

Mete

rs

Ohm.m


143

Figure 4.39. Basement map relative to mean sea level derived from interpreted geoelectrical model. Relatively higher basement occur at Kampung Pulai Condong and

Kampung Tok Bok. In Kampung Pulai Concong, basement steeply dip to northwest.

465000 470000 475000

645000

650000

655000

660000

Kelantan River

N

Boundary Range

Meter

4 Km

Meters

Mete

rs

Kampung Ketereh

Kampung Tok Bok


-40

-35

-30

-25

-20

-15

-10

-5

0

5

10

15

20

25

30

35

40


144

Figure 4.40. Basement map relative to mean sea level in 3D shape. The basement dips

to the north and it rises in the middle so that can resist the polluted groundwater to move

from the south.


145

4.3.7. Depth Slice Resistivity Distribution

The relatively high resistivity contrast between the Quaternary basinal clastic

sediments and the pre-Quaternary bedrock opened the way to extract geological

information from geoelectrical resistivity explorations. All the high-resolution electrical

images show a remarkable resistivity contrast between relatively low resistivity values

in the shallow layers and relatively high resistivity in the deep zones. The shallow

conductive layers can be associated to the presence of fluvial deposits such as gravel,

sand and clay. The resistivity zone at the surface, instead, could represent weathered

slope deposits that form along the sides of the fluvial basin. The geoelectrical resistivity

survey carried out in this area is able to trace the geometry of the pre-Quaternary bed-

rock and hence the aquifer geometry. The thickness of fluvial deposit inferred from

geoelectrical resistivity survey is about 0-5 m at the southern region, 10 m at the middle

and 20-35 m at the northern region. All the geoelectrical model for deeper zone indicate

the pattern of the high resistivity values clearly defines the shape of the pre-Quaternary

bedrock having a depth around 5-30 m.

A simplified depth slice resistivity distribution has been developed to better

show the shape and distribution of the potential aquifer. Figure 4.41 and 4.42 shows a

depth slice resistivity distribution image for particular depth obtained from the sequence

of 2D sections. The depth slice resistivity distribution in Figure 4.41 and 4.42 has been

generated using a Kriging interpolating technique. It may be emphasized that the

electrical images are the result of a tomographic 3D data inversion. Furthermore, the

resolution of the depth slice resistivity distribution is limited by the low number of the

geoelectrical model profiles compared with the surveyed area of 98 km2, but it

represents a simple tool to estimate the shape of aquifer.


146

Figure 4.41. Resistivity distribution relative to mean sea level derived from 20

geoelectrical models. Low resistivity value indicates the possibility of potential aquifer.

-40 m

-30 m

-20 m

-10 m

0 m

10 m

Ohm.m

0

200

400

600

800

1000

1200

1400

1600

1800

2000


147

Figure 4.42. Resistivity distribution from surface to a depth of 12.5 m. Potential aquifer

is separated by granite bedrock in the middle.

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Surface

2.5 m

5.0 m

7.5 m

10.0 m

12.5 m

Ohm.m


148

At depth of up to 5 m, a good correspondence between the magnitude of the

resistivity image to the higher surface topography has been observed (Figure 4.38). At

the hill peak, the resistivity values are relatively higher because the moisture content is

lower and dense material dominates the area. A potential aquifer is found at about 10 m

depth above the mean sea level (Figure 4.39, 4.40, 4.41). This is inferred by the

relatively lower resistivity values that appear at depth until 10 m. Up to depth of -10 m,

the resistivity slices show a regular and closed geometry of the basin floor along the

southeastern part; instead, it has an irregular shape of the basin along the northwestern

part.

Figure 4.42 shows a geoelectrical resistivity image obtained from the near

surface level to a depth of 12.5 m. In this figure, the distribution of shallow groundwater

potential is more easily be traced. At the surface level, the resistivity distribution is in

good deal with the elevation and grain size distribution of the area. Higher resistivity

values appear at site with relatively elevated area. At a depth of 2.5 m, some areas

exhibit relatively lower resistivity value of around 250 ohm.m. In the site with denser

(more compact) soil material, water table was found at this depth. At a slice depth of 5

m and 7.5 m, two lower anomalies appear at the sites which are conducted in palm oil

plantation. These sites are the end area of surface water (catchment area). These

anomalies are due to a relatively higher nitrate concentration in the groundwater.


149

4.3.8. Subsurface Geological Model

Figure 4.43 shows the base map of the Area 1. Six lines have been constructed

on the map and they are crossing each other. Each line in the Figure 4.43 is cultivated

through the survey line so that the subsurface geological model can be developed. Then,

the geological model was developed based on the geoelectrical resistivity interpretation

in previous subchapter (4.3.5). Figure 4.44, Figure 4.45, Figure 4.46 and Figure 4.47 are

the geological subsurface model below the lines given in Figure 4.43. Figure 4.48 is the

stack of all subsurface geological models displayed in one figure.

The zones of potential aquifer, shallow aquifer and granite bedrock have been

discussed in previous subchapter (4.3.5) trough the geoelectrical interpretation.

Subsequently, each zone is drawn regarding to their location in the map (Figure 4.43).

An example of a procedure to develop geological model derived from geoelectrical

interpretation is shown in Figure 4.44. Here, two geoelectrical models are selected.

These geoelectrical models are cropped and displayed at survey position where the lines

(geoelectrical model) which intersect line A1B1.


150

Figure 4.43. Base map and cross line section. Geological model was developed along

these lines as given in the Figure 4.44 – 4.47.

A1

A2

B1

B2

C1

C2

C3

C4

D1

D2

D3

D4


151

Figure 4.44. Cross section of line A1B1.

West East A109 A115

A109 A115

Seaward


152

Figure 4.45. Cross section of line A2B2.

Seaward


153

Figure 4.46. Cross section of line C1D1 and C2D2.


154

Figure 4.47. Cross section of line C3D3 and C4D4.


155

Figure 4.48. Stacked geological model.

N


156

In the section of A1B1 (Figure 4.44), it can be clearly seen that the sediment at

the northern side is thicker than the sediment at the southern. The thickness of the

aquifer ranges from 5 to 15 m and 25 to 40 m in the southern and northern, respectively.

The south shallow aquifer is possibly contaminated by the agriculture activities

especially in the palm oil plantation area (southern area). Shallow aquifer coloured as

pink is the zone with relatively higher nitrate concentration (more than 20 mg/L) has

been found (A1B1, A2B2 and C4D4). In the south, a lot of boulder was found in the

shallow aquifer. The shallow aquifer was possibly contaminated by surface water at

some location and coloured as purple (Figure 4.44). In the middle of the section

(A1B1), the pre-Quaternary bedrock blocked the groundwater flow from the southern

area to the northern area despite northern area has lower elevation. The bedrock

however situated to the northwest (Figure 4.44).

The pre-Quaternary bedrock rises towards Kelantan River as seen along C1D1,

C3D3 and C4D4 (Figure 4.46 and Figure 4.47). As the result, the sediment is thinner in

these areas. Generally, the northern area has a good groundwater potential due to no

possibility of groundwater contamination by agriculture (especially palm oil plantation)

activities. Moreover, in this area, the shallow aquifer is confined by material with lower

porosity and permeability.


157

4.4. Time Lapse Nitrate Evaluation and Monitoring in Palm Oil Plantation

Groundwater pollution in areas of intensive agricultural activity is a

consequence of farming practices in using large quantities of fertilizers. Contaminant

leaching (especially nitrate) in agricultural soils has been widely studied (Almasri et al.

2004; Saadi et al. 2003).

In this study, chemical fertilizer especially nitrate concentration was evaluated

and monitored at different time survey periods under a “natural schema condition”,

which means that, all the processes were conditioned by natural processes including

watering process by rainfall, undisturbed biological habitat and chemical fertiliser

application by recurrent schema (Table 4.1).

An unproductive site of an old palm oil plantation in Kampung Tok Bok,

Machang, was chosen for the investigation. This is because the area no chemical

fertiliser was introduced in this area for around 10 months before the survey was done.

If the survey was conducted in the productive palm oil plantation, it would be very

difficult to control and monitor the type of fertiliser during the fertilising activities.

The survey specification setup for nitrate monitoring is given in Figure 4.49. The

chemical monitoring was performed within three months from 3 May to 3 August,

2009. This time frame was chosen based on rainfall distribution in the area (Figure

4.50). Rainfall distribution data collected from a station located 8 km away from the site

survey show that rainfall occurs at an average amount within this period every year. It is

a representative of the average water input in this area. The maximum and minimum

rainfall happens around November–December and February–March, respectively. The

first, second, third, fourth, and fifth surveys then refer to monitoring-1, monitoring-2,

monitoring-3, monitoring-4, and monitoring-5, respectively. The first survey


158

(monitoring-1) was done before the chemical fertiliser was introduced to the land. After

the data set was completed in monitoring-1, the chemical fertiliser (urea) was

distributed. Urea has the highest nitrogen content among the fertilisers. Thirteen

kilograms of urea was distributed over the whole fertiliser zone (Figure 4.49). The total

of its weight was equal to 600 kg per 2 ha. The distribution of chemical fertiliser used

was by the “natural schema condition”. It was distributed by hand and approximately

covered all the area with equal intensity.


159

Borehole and Monitoring 1 = (17 ; 20.5)

Monitoring 2

Monitoring 3

Monitoring 4

Monitoring 5

TBMXX Location of resistivity survey

Fertilizer used: 13.2 kg of Urea (600 kg/2 ha)

Borehole Diameter = 11.5 cm

Borehole Depth = 4.5 m

Crossing of line 1 and line 2 is at 16 m mark of line 1 and 20 m mark of line 2.

Figure 4.49. Field set up for nitrate monitoring in Kampong Tok Bok.

(Arrow shows the study site)

465000 470000 475000

645000

650000

655000

660000

Kelantan River

N

Boundary Range

Rubber Plantation Palm Plantation Paddy Area

N

5 m

TBM11 +

TBM12 +

(6,10) (27,10)

(6,31) (27,31)

M1

M1

M1

M2

M2

M2

M3

M3

M4

M4

M4

M5

M5

M5

M3


160

Figure 4.50. Average amount and number of rainfall within 2004-2008 (source: MMD

Malaysia)

Several methods of investigation were used to analyze the chemical content

including soil properties analysis, hydrogeochemical analysis, and 2D geoelectrical

resistivity imaging survey.

In each survey, soil samples were collected for measuring the moisture content.

Soil samples were taken from three holes (Figure 4.49). In each hole, soil was sampled

from a depth of 0 - 1 m at 25 cm intervals.

To analyze the chemical content of the soil water in the vadose zone, the

samples have to be extracted directly from the soil. Soil water was sampled at 0m, 0.25

m, 0.50 m, 0.75 m and 1 m depths for three random locations (Figure 4.49) using a 1900

Soil Water Samplers (manufactured by Soilmoisture Equipment Corp, USA). Three soil

water samples were merged into a plastic bottle of 40 ml for each depth and labelled

according to depth level. Because the quantity of water sample was less than 25 ml for

each sampling depth, the water sample was diluted with pure water to become 50:50 in

0.0

100.0

200.0

300.0

400.0

500.0

600.0

1 2 3 4 5 6 7 8 9 10 11 12

Am

ou

nt

of

Rai

nfa

ll (m

m)

Month

Amount of rainfall Number of rainfall x 10


161

their composition. Subsequently, the soil’s water samples were kept in plastic bottles

and maintained at a temperature of 40C. The samples were analysed in the

hydrogeochemical lab using Ion Chromatography (IC) and Inductively Coupled Plasma

(ICP) two days after the samples were collected.

The 2D geoelectrical resistivity imaging surveys were also performed at the site

using ABEM Terrameter SAS4000 resistivity meter. The Wenner arrays were used on

two lines within each survey with 1 m electrode spacing. The total profile length was 40

m. It was very difficult to carry out survey with gridded lines due to the undulating field

condition. Furthermore, there were palm oil trees at every 6 m and also the presence of

swales (0.3 m depth, 1.5 m wide and around 7 m long) at every seven rows of palm oil

tree intervals.

4.4.1. Soil Moisture and Extracted Soil Water Chemical Content

4.4.1.1. Moisture Content

Figure 4.51 shows a profile of the moisture content for different monitoring

periods with different sampling depths. The highest amount of moisture content can be

found on the surface level. This is due to the relatively higher silt and clay content near

the surface (see Table 4.2). The moisture content in monitoring-1 decreases with depth.

A similar decreasing trend was also observed in monitoring-2, monitoring-3,

monitoring-4 and monitoring-5. Soil moisture content was influenced by the amount of

rainfall and interval time before the soil was taken. The soil samples for monitoring-5

were taken after several hours of rainfall. Decreasing of moisture content with depth is

due to the increase of gravel and sand-sized grains content with depth. Generally, the

moisture content decreases with depth for all monitoring.


162

Figure 4.51. Moisture content versus depth sampling for each time lapse monitoring.

4.4.1.2. Extracted Soil Water Chemical Content

Table 4.10 shows the chemical results of the extracted soil water contents for all

monitoring. In monitoring-1, cation content ranges from 0 to 10.78 mg/l. The highest

cations content is Ca (10.78 mg/l) at 50 cm of sampling depth. K, Ca and Na are the

dominant cations contents which have an average of 4.58 mg/l, 7.42 mg/l and 6.40 mg/l,

respectively, while Mg, Pb, Cd se Mn, Cu, Zn, Fe, As concentrations have the average

concentration less than 2 mg/l. The cations concentrations do not show any specific

trend from the surface level to a depth of 100 cm. Almost the maximum cation

concentration appears near the surface level to a depth of 25 cm. This is due to the

source of cation and anion concentration is mainly from the fertilisation activities.

0

20

40

60

80

100

120

0 5 10 15 20

De

pth

(cm

)

Moisture Content (%)

M1 M2 M3 M4 M5


163

However, all cation contents lie within the accepted limits for human consumption

(WHO 1984).

For anion content, chloride and nitrate concentrations are highest near the

surface level. Other researchers also found higher nitrate concentration near surface

(Kaushal et al., 2005; Oelmann et al. 2007; Mirjat et al., 2008). Nitrate concentration

decreases with depth, except at depth of 25 cm. Meanwhile, the chloride concentration

decreases with depth until a depth of 100 cm. Average chloride and nitrate

concentrations from the surface level until a depth of 100 cm are 13.9 mg/l and 10.74

mg/l, respectively. The highest sulphate concentration (5.56 mg/l) is observed near the

surface level. There is almost no fluoride concentration except at the surface and 25 cm

depth (0.06 mg/l and 0.12 mg/l). In the drilled well, with 3.42 m depth of water table

and the well depth of 4.5 m, chloride concentration is 15.52 mg/l whilst nitrate

concentration is zero.

.


164

Table 4.10. Time lapse extracted water chemical content in palm oil plantation

Date No Sample ID Sampling Chloride Nitrate Sulphate Fluoride K Ca Mg Pb Cd Se Al Mn Cu Zn Fe As Na

Depth

(cm) mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L

M-1 1 TBM1-0 0 21.310 12.926 5.560 0.060 9.888 8.472 1.028 0.032 0.000 0.000 3.242 0.014 0.124 0.088 0.128 0.000 6.612 3-May 2 TBM1-25 25 12.988 9.970 1.550 0.122 4.470 6.352 0.744 0.000 0.000 0.000 0.000 0.006 0.032 0.314 0.000 0.000 7.530 2009 3 TBM1-50 50 12.310 10.460 2.704 0.000 2.846 10.788 0.782 0.026 0.000 0.006 0.202 0.026 0.000 0.148 0.000 0.000 6.194

4 TBM1-75 75 12.148 10.380 2.230 0.000 2.702 6.260 0.660 0.000 0.000 0.002 0.000 0.020 0.036 0.226 0.000 0.000 5.942

5 TBM1-100 100 10.748 9.948 2.114 0.000 3.014 5.242 0.618 0.000 0.000 0.010 0.002 0.008 0.050 0.128 0.000 0.000 5.702

6 TBW 4.5 450 15.518 0.000 1.854 0.000 2.084 2.906 0.834 0.000 0.000 0.000 0.024 0.012 0.012 0.054 0.008 0.000 5.910

Mean(1-5)

14.170 8.947 2.669 0.030 4.167 6.670 0.778 0.010 0.000 0.003 0.578 0.014 0.042 0.160 0.023 0.000 6.315

M-2 1 TBM2-0 0 320.000 106.722 207.576 0.000 7.504 8.536 1.048 0.000 0.000 0.006 5.482 0.044 0.036 0.036 0.908 0.000 8.340

31-May 2 TBM2-25 25 278.400 50.838 24.864 0.000 6.084 5.706 0.116 0.000 0.002 0.024 0.032 0.014 0.026 0.000 0.000 0.000 4.002 2009 3 TBM2-50 50 65.718 10.334 2.534 0.068 2.126 7.028 1.706 0.014 0.006 0.010 3.944 0.190 0.034 0.350 0.134 0.000 7.248

4 TBM2-75 75 13.914 10.242 7.966 0.000 5.662 5.756 0.806 0.010 0.000 0.018 1.028 0.060 0.030 0.070 0.104 0.000 6.936

5 TBM2-100 100 16.020 10.136 6.074 0.000 2.500 8.264 0.912 0.010 0.000 0.010 0.618 0.054 0.038 0.082 0.044 0.000 5.962

6 TBW-450 450 11.134 9.942 2.002 0.000 14.396 9.308 1.750 0.000 0.000 0.020 0.046 0.126 0.034 0.030 0.000 0.000 7.952

Mean(1-5)

138.810 37.654 49.803 0.014 4.775 7.058 0.918 0.007 0.002 0.014 2.221 0.072 0.033 0.108 0.238 0.000 6.498

M-3 1 TBM3-0 0 92.000 122.482 71.548 0.080 7.828 8.292 0.994 0.018 0.000 0.000 3.156 0.054 0.114 0.102 0.084 0.000 6.424

16-Jun 2 TBM3-25 25 160.000 23.228 16.864 1.530 5.220 6.522 0.782 0.000 0.000 0.002 0.002 0.006 0.042 0.144 0.002 0.000 7.208 2009 3 TBM3-50 50 94.330 15.086 4.214 0.192 5.002 7.496 0.750 0.020 0.000 0.006 0.042 0.020 0.002 0.180 0.000 0.000 6.344

4 TBM3-75 75 37.142 11.042 5.078 0.000 2.964 7.260 0.642 0.000 0.000 0.002 0.000 0.034 0.012 0.324 0.000 0.000 8.140

5 TBM3-100 100 21.580 10.712 0.000 0.000 2.228 5.150 0.634 0.000 0.002 0.008 1.144 0.006 0.038 0.162 0.254 0.000 5.102

Mean

81.010 36.510 19.541 0.360 4.648 6.944 0.760 0.008 0.000 0.004 0.869 0.024 0.042 0.182 0.068 0.000 6.644

M-4 1 TBM4-0 0 26.480 26.642 12.330 0.090 7.198 9.250 1.478 0.002 0.000 0.002 4.410 0.062 0.100 0.232 1.764 0.000 6.786

6-Jul-09 2 TBM4-25 25 16.918 20.080 2.290 0.100 5.484 6.114 3.810 0.000 0.000 0.000 0.000 0.084 0.106 0.204 0.000 0.000 6.886 2009 3 TBM4-50 50 16.162 20.158 3.790 0.000 2.618 6.470 1.000 0.000 0.000 0.006 1.092 0.044 0.052 0.104 0.616 0.000 6.516

4 TBM4-75 75 19.130 21.310 4.234 0.038 3.796 6.728 1.064 0.008 0.000 0.006 1.146 0.050 0.046 0.074 0.630 0.000 8.706

5 TBM4-100 100 17.218 20.882 3.346 0.054 3.930 7.018 0.866 0.026 0.000 0.004 0.000 0.014 0.064 0.142 0.000 0.000 7.626

Mean

19.182 21.814 5.198 0.056 4.605 7.116 1.644 0.007 0.000 0.004 1.330 0.051 0.074 0.151 0.602 0.000 7.304

M-5 1 TBM5-0 0 22.760 15.498 5.492 0.330 7.026 8.154 1.010 0.036 0.000 0.002 2.820 0.014 0.110 0.102 0.048 0.000 8.110

3-Aug-09 2 TBM5-25 25 14.474 13.868 1.848 0.132 4.718 6.320 0.712 0.032 0.000 0.016 0.000 0.006 0.064 0.068 0.000 0.000 7.778 2009 3 TBM5-50 50 12.164 12.754 2.576 0.000 3.442 5.990 0.632 0.038 0.000 0.008 0.270 0.006 0.092 0.066 0.000 0.000 6.406

4 TBM5-75 75 13.914 14.110 2.358 0.000 2.828 5.744 0.696 0.012 0.000 0.006 0.000 0.030 0.028 0.222 0.062 0.000 6.932

5 TBM5-100 100 11.764 10.710 2.292 0.074 3.362 6.316 0.724 0.034 0.000 0.000 0.020 0.038 0.066 0.252 0.000 0.000 6.348

6 TBM5-150 150 9.730 6.094 2.244 0.000 2.074 4.832 0.528 0.044 0.000 0.002 0.000 0.002 0.050 0.114 0.000 0.000 3.994

7 TBM5-200 200 6.214 5.464 1.420 0.358 3.872 4.744 0.398 0.032 0.000 0.000 0.000 0.000 0.078 0.084 0.000 0.000 3.380

8 TBK 75 18.030 107.806 34.368 0.088 5.058 5.960 3.268 0.008 0.000 0.002 2.912 0.812 0.126 1.144 0.000 0.000 9.186

Mean (1-5)

15.015 13.388 2.913 0.107 4.275 6.505 0.755 0.030 0.000 0.006 0.622 0.019 0.072 0.142 0.022 0.000 7.115


165

In monitoring-2 (28 days after chemical fertilizer has introduced to the land), the

highest level of chloride and nitrate concentration (320.00 mg/l and 106.72 mg/l,

respectively) could be found at the surface. However, nitrate concentration of below 45

mg/l in water is safe for human consumption (U.S.EPA 1980). The impact of fertiliser

after monitoring-1 is observed in the extracted water content. The sulphate

concentration is also increased drastically due to the fertiliser (207.58 mg/l). The level

of nitrate concentration decreases with depth. Meanwhile, the chloride concentration

decreases from shallow to a depth of 75 cm and increases slightly at a depth of 100 cm.

Average chloride and nitrate concentrations from the surface to a depth of 100 cm are

138.82 mg/l and 37.66 mg/l, respectively. The values are completely different from the

results of monitoring-1. Average values for both chloride and nitrate from surface to a

depth of 100 cm are increased around 9.98 and 3.50 times larger than monitoring-1,

respectively. Meanwhile, in the drilled well (TBW 4.5), nitrate concentration is also

observed to be increase drastically. This result is believed to be due to direct pollution

on the surface. This was because the surface water was seeping into the water table

through a gap between the well and the casing, although the gap had earlier been filled

with soil. This is supported by the situation whereby there was no existence of any soil

between the well wall and the well casing when monitoring-2 was done. For the next

monitoring, no water was sampled from the well. However, cations content is relatively

similar compared to monitoring-1, as no significant changes are found in monitoring-2.

In monitoring-3, the nitrate concentration level is still at the highest level

(122.48 mg/l) at the surface and even larger than the concentration in monitoring-2. The

nitrate concentration is gradually reduced with depth. Meanwhile, the highest level of

chloride (160.00 mg/l) is observed at depth of 25 cm and decreases gradually with

increasing depth. The sulphate concentration level is highest (71.54 mg/l) on the


166

surface. The average chloride and nitrate content are 81.02 mg/l and 36.52 mg/l, which

are around 0.58 and 0.97 times less than monitoring-2, respectively, whilst the cations

content is still relatively similar as compared to the previous two surveys.

In monitoring-4, chloride and nitrate concentrations observed are still the highest

at the surface and reduced gradually with depth. Meanwhile the sulphate concentration

shows no significant value anymore. The average chloride concentration is 19.20 mg/L

which is around 1.37 times higher than that for monitoring-1. Meanwhile average

nitrate concentration is 21.82 mg/L which is around 2.03 times higher than that of

monitoring-1.

In the last Monitoring-5, besides extracting water for analysis from surface to

depth of 100 cm, water was also extracted for depths of 150 cm and 200 cm. The two

highest nitrate concentrations (15.5 mg/l) were found at the surface level and at the

fourth sampling depth (14.12 mg/l). Meanwhile the highest concentration of chloride

(22.76 mg/l) exists at the surface level and decreases gradually with depth. The sulphate

concentration level is not significant for all samples except for sample TBK, which the

soil water sample at the anomaly zone observed after the geoelectrical survey. Average

chloride and nitrate concentrations from the surface sample to a depth of 100 cm are

15.02 mg/l and 13.38 mg/l, respectively. These values are more or less equal to

monitoring-1. In general, the cations content are relatively similar for every time lapse

measurement. Figure 4.52 shows the average concentration of anion content ranging

from 0 cm to 100 cm depth and ranging from 0 cm to 25 cm for each monitoring. In

these figures, nitrate has a different trend with chloride and sulphate.


167

Figure 4.52. Average concentration of anion for different depth range content (A) 0 -

100 cm depth and (B) 0 - 25 cm depth versus time lapse monitoring. Nitrate has

different trend with chloride and sulphate.

4.4.2. Time Lapse Geoelectrical Resistivity Model in Palm Oil Plantation

The geoelectrical model of all monitoring survey is given in Figure 4.53. In

monitoring-1, visually, an average resistivity value of around 1900 ohm.m is observed

at the surface corresponding to the compacted soil with low moisture content. This

0

20

40

60

80

100

120

140

160

M-1 M-2 M-3 M-4 M-5

Co

nce

ntr

atio

n (

mg/

l)

Monitoring

Chloride

Nitrate

Sulphate

0

50

100

150

200

250

300

350

M-1 M-2 M-3 M-4 M-5

Co

nce

ntr

atio

n (

mg/

l)

Monitoring

Chloride

Nitrate

Sulphate

A

B


168

value is also supported by direct surface resistivity measurement of 10 random point

locations which have an average of 2100.03 ohm.m with standard deviation of 245.84

ohm.m. In both geoelectrical models (TMB11 and TBM12), no significantly lower

resistivity values appear from the surface level to a depth of 1 m. The measured water

table was 3.60 m below the ground surface in the borehole which was drilled at the 19

m mark of line TBM11. In the geoelectrical model along line TBM11, resistivity values

of approximately 400 ohm.m corresponded to a unit of fully saturated compact sand. A

lower resistivity value of 120 ohm.m below than 5 m depth correlates with potential

aquifer.

Due to equipment technical problem, only one line (TBM21) was conducted in

monitoring-2. The geoelectrical model of line TBM21 shows significantly low

resistivity values on the surface within the fertilised zone (6–27 m mark) compared to

the non-fertilised zone. The average surface resistivity value is about 400 ohm.m within

the fertilised zone. The values are also equivalent to values of direct surface resistivity

measurement in the fertilised zone, with average of 437.00 ohm.m and standard

deviation of 78.72 ohm.m. Below the 17–19 m mark from 2.5 m depth, it can be noticed

that resistivity values are relatively higher than in the surrounding area. Other features

are still relatively similar to the previous survey (monitoring-1).

In the geoelectrical model of line TBM31 and line TMB32 (monitoring-3),

relatively lower resistivity values still can be observed on the surface within the

fertilised area (6–27 m mark). The value is around 0.4 times lesser than in the non-

fertilised zone. Below the 17 m mark starting from 2.5 m depth, it can be seen that

resistivity values are relatively higher than the surrounding area.


169

Figure 4.53. Geoelectrical models for Monitoring-1 to Monitoring-5

TBM11

TBM21

TBM12

Monitoring-1

Monitoring-2

Low resistivity zone

CSL

PA

PA

CSL


170

Figure 4.53. Geoelectrical result for Monitoring-1 to Monitoring-5 (Continued).

TBM31

TBM32

Monitoring-3

TBM41

TBM42

Monitoring-4






171

Figure 4.53. Geoelectrical result for Monitoring-1 to Monitoring-5 (Continued).

In monitoring-4, relatively lower resistivity value in geoelectrical model of lines

TBM41 and TBM42 still exist in the fertilized zone, as in monitoring-3. The existence

of relatively higher resistivity values remain in the same position as in previous

monitoring.

In the last survey (monitoring-5), resistivity values representing the fertilised

zone are not significantly different compared to the resistivity of non-fertilised zone

(TBM51 and TBM52). However in some places, the lower resistivity still persists on the

TBM51

TBM52

Monitoring-5

TBK, Nitrate = 107

mg/L, Cl = 18 mg/L


172

surface of the fertilised zone. In both geoelectrical models TBM51 and TBM52, the

relatively lower resistivity value (coloured yellow) can be seen clearly at the deeper

depth (75 cm), at the zone where the previous survey was not found. Two other

interesting features are appeared in the geoelectrical model TBM51. The zone with

relatively lower resistivity value is observed in the section at around 75 cm depth below

10 and 15 m marks. This corresponds to the more porous and more permeable zone

filled by pore water, with some anions concentration. Chemical analysis on the

extracted water of 7s cm depth indicates the presence of higher nitrate concentration

(see TBK in Table 4.10)

In monitoring-2 to monitoring-5, a new feature can be found below the 20 m

mark of TBM_2 and below the 17.5 m mark of TBM_1. The relatively higher resistivity

value is seen at the position in each geoelectrical model. This feature is believed to be

an effect of the existing vertical borehole with 4.5 m depth. The borehole position is

around 20 cm from the TBM_2 at 20 m mark, and 40 cm away from the TBM_1 at 17.5

m mark.

Overall, for the entire survey from monitoring-2 to monitoring-5, lower

resistivity values appear on the surface within the fertilised zone. Increasing resistivity

values near the surface were obtained for third, fourth and fifth measurements compared

to the second measurements. In the last survey (monitoring-5), although the resistivity

value in the fertilised zone is lower than in the non-fertilised zone, the difference is not

too big. The decreasing resistivity value at the near surface within the fertilised zone is

due to the effect of nitrate and chloride concentration. The negative charges of anions

caused a decrease in the resistivity of the medium. Similar results were also reported on

the decrease of resistivity caused by only a small amount of chloride due to salt water


173

intrusion. (Abdul Nassir et al., 2000; Leroux et al., 2006; Samsudin et al., 2007).

Conductivity is inversely proportional to resistivity.

4.4.3. The Correlation of Extracted Water Chemical Content, Soil Properties and

Geoelectrical Model

Table 4.11 shows statistical values of the extracted geoelectrical model for both

monitoring lines and the chemical content of soil water at the surface level. In the table,

the left side consists of extracted geoelectrical model within fertilized zone whereas the

middle side consists of the non-fertilized zone. Whilst, at the right side is the soil

moisture content and chemical soil water.

The highest average resistivity value is observed in monitoring-1, in which

TBM11 and TBM12 have 2040.23 ohm.m and 2026.74 ohm.m, respectively. Moisture

content is lowest (13.04%) in monitoring-1 among the rest of all monitoring, while total

anion is found to be 39.80 mg/l. In monitoring-2, average resistivity of TBM21

decreases 78.28% compared to monitoring-1 in the fertilised zone, while in the non-

fertilised zone, resistivity values decrease 42.00%. The decreasing resistivity value in

the non-fertilised zone is due to a 38.57% increase of moisture content. The bigger

resistivity decrease in the fertiliser zone (78.28%), besides the impact of increasing

moisture content, also is because of the increase in total anion in soil water (1493.87%).

Thus, the increase in total anion around 1493% has decreased the soil resistivity of

around 36%.


174

Table 4.11. Statistical values of extracted geoelectrical model (surface) for all monitoring and chemical pore water. The left side shows the

fertilized zone, in the middle shows the unfertilized zone and the right side shows moisture and chemical pore water. At the bottom shows the

correlation of extracted geolectrical model and soil properties.

Line Fertilizer Zone Non-Fertilizer Zone Moisture Chloride Nitrate Sulphate Total Anion

ID Mean Stdev Max Min Mean Stdev Max Min (%) mg/L mg/L mg/L mg/L

TBM11 2040.23 582.44 2835.5 1129.5 2160.73 986.98 5276.8 1494.7 13.04 21.31 12.926 5.56 39.796

TBM21 443.18 256.6 1131.2 253.44 1253.14 475.39 2074.8 592.02 18.07 320 106.722 207.576 634.298

TBM31 515.85 160.35 814.01 222.7 1232.33 473.42 1992 514.78 18.85 92 122.482 71.548 286.03

TBM41 786.76 244.9 1337.1 344.16 1505.25 476.2 2312 748.99 16.99 26.48 26.642 12.33 65.452

TBM51 1093.48 336.76 1647.2 623.69 1509 442.51 2201.9 768.87 15.12 22.76 15.498 5.492 43.75

Line Fertilizer Zone Non-Fertilizer Zone Moisture Chloride Nitrate Sulphate Total Anion

ID Mean Stdev Max Min Mean Stdev Max Min (%) mg/L mg/L mg/L mg/L

TBM12 2026.74 535.25 3175.8 866.13 2268.61 427.1 2769.6 1539.2 13.04 21.31 12.926 5.56 39.796

TBM22 No Data No Data 18.07 160.00 53.36 103.79 317.15

TBM32 509.02 253.01 1112.1 207.47 1318.27 1079.67 3875.3 819.86 18.85 92 122.482 71.548 286.03

TBM42 810.16 298.33 1446.4 382.08 1487.3 698.96 3008.8 1060.7 16.99 26.48 26.642 12.33 65.452

TBM52 1016.82 624.41 2224.7 350.81 1502.13 395.94 1864.4 577.38 15.12 22.76 15.498 5.492 43.75


175

In monitoring-3, average resistivity values within the fertilised zone increase to

about 16.40% compared to monitoring-2; however there still are decreases of 74.71%

and 74.88% compared to monitoring-1 for TBM31 and TBM32, respectively. Total

anion in soil water increases to about 618.74% (compared 1493.87% in monitoring-2)

and moisture content in monitoring-3 increases 4.31% more than monitoring-2. This

means that the resistivity value in monitoring-3 is not too big as its decrease. The

average resistivity value in the area unfertilised zone decreases 42.96% and 41.89% for

TBM31 and TBM32, respectively. These decreasing values in monitoring-3 for the non-

fertilised zone are similar to the decrease in monitoring-2.

Moisture content decreases from 18.85% in monitoring-3 to 16.99% in

monitoring-4. This causes the resistivity values in the non-fertilised zone to increase

from 1232.33 ohm.m (TBM31) to 1505.25 ohm.m (TBM41) and 1318.27 (TBM32)

ohm.m to 1487.30 ohm.m (TBM42), respectively. In the fertilised zone, resistivity

values increase from 515.85 ohm.m to 786.76 ohm.m and 509.02 ohm.m to 810.16

ohm.m for TBM31 and TBM32, respectively. Again, anion content causes a 61.39%

decrease of resistivity value in the fertilised zone.

In the last survey, average resistivity values within the fertilised zone decrease

46.40% and 49.82% for TBM51 and TBM52, respectively, compared to TBM11 and

TBM12. Moisture content increases 15.95% and total anion increases 9.93%. In the

non-fertilised zone, the resistivity value only increased around 32%. Generally, the

occurrence of increasing anions content in pore soil water ranging from 10–1500% has

decreased soil resistivity value from 50% to 80%.

Finally, measurements of geoelectrical resistivity correlate significantly with soil

properties with respect to the measured soil moisture content and chemical pore soil

water (Table 4.12). Interpretations were given only for the comparable depth intervals


176

of soil sampling and geoelectrical resistivities. The correlation of resistivity and

moisture content within fertilised zone using Pearson product-moment correlation (Till,

1974) is -0.95. The highest negative correlation implies higher moisture content,

resulting in lower soil resistivity value. Resistivity and total anion content has a

negative correlation of -0.61, of which resistivity and sulphate, resistivity and chloride

and resistivity and nitrate correlate -0.61, -0.52 and -0.71, respectively. Moreover,

within the non-fertilised zone, the correlation coefficient between resistivity and soil

moisture content is -0.91. However, a value of correlation coefficient of more than 0.7

indicates a high probability of correlation (Taylor, 1997). Relatively lower correlation

coefficient between resistivity value within the fertilised zone and total anion content is

due to an increase in total anion content with a power trend of soil resistivity value

(Figure 4.54). This result is also supported by result found in subchapter 6.2.

Meanwhile soil moisture content has a linear trend with resistivity value (Figure 4.55).

Moreover, it can be seen that anion content in pore soil water has increased correlation

coefficient significantly between resistivity in the fertilised zone and moisture content,

from -0.91 to -0.95. This means that the anion content in pore soil water decreases the

soil resistivity significantly. Figure 4.56 shows the increasing percentage of anion

content versus percentage differences between soil resistivity in non-fertilised and

fertilised zones. In Figure 4.56, a power trend has been observed when the pore soil

water increased its anion content range from 10–1500% so that the resulting lower

resistivity value differs from 16–36%.

Table 4.12. Correlation of modelled geoelectrical resistivity with soil properties.

Fertilized Zone

Non Fertilized

Zone

Resist and

Moisture

Resist and

Total Anion

Resist and

Nitrate

Resist and

Chloride

Resist and

Sulphate

Resist and

Moisture

Correlation -0.95 -0.61 -0.71 -0.52 -0.61 -0.91


177

Figure 4.54. Trend of total anion content versus soil resistivity within fertilized zone.

Figure 4.55. Variation of moisture content versus soil resistivity.

0

100

200

300

400

500

600

700

0 500 1000 1500 2000 2500

To

tal A

nio

n (

mg/

l)

Resistivity (Ohm.m)

y = -0.0035x + 19.852 y = -0.0055x + 24.9

10

11

12

13

14

15

16

17

18

19

20

0 500 1000 1500 2000 2500

Mo

istu

re C

on

ten

t (%

)

Soil Resistivity (ohm.m)

Soil Resistivity (Fertilized zone) Soil Resistivity (Non Fertilized Zone)

Linear (Soil Resistivity (Fertilized zone)) Linear (Soil Resistivity (Non Fertilized Zone))


178

Figure 4.56. The trend of anion content against percentage differences between soil

resistivity in non-fertilized and fertilized zone.

4.4.4. Fate of Nitrate

Figure 4.57 shows a graph of nitrate concentration levels for each depth of

sampling versus time lapse monitoring (survey days). The maximum nitrate

concentration on the surface happens in 44 days (monitoring-3) after the introduction of

the chemical fertiliser to the site. The maximum nitrate concentration at depth of 25 cm

happens after 28 days (monitoring-2), as shown in Figure 4.57. The nitrate

concentration increases significantly in monitoring-2 compared to monitoring-1 (before

fertiliser introduction). Then, it decreases almost linearly with increase in sampling

depth. Other researchers (Oelmann et al., 2007; Mirjat et al., 2008; Kaushal et al., 2005)

also found highest nitrate concentration near surface. Meanwhile, for a depth of 50 cm,

75 cm and 100 cm, the maximum nitrate concentration values occur 64 days after the

fertiliser was introduced (Figure 4.57.C.D. & E).

y = 0.1764e0.2402x

1

10

100

1000

10000

0 5 10 15 20 25 30 35 40

Per

cen

tage

Incr

ease

s A

nio

n C

on

ten

t (%

)

Percentage Differences Resistivity (%)


179

Figure 4.58 shows the nitrate concentration level versus depth of sampling for

each monitoring survey. In monitoring-1, nitrate concentration hardly fluctuates, whilst

in monitoring-2, nitrate concentration increases significantly on the surface and

decreases linearly with depth until a depth of 50 cm. In monitoring-3, a nitrate

concentration has its highest level on the surface but decreases significantly with

increasing depth. In monitoring-4, higher nitrate concentration values are still

maintained on the surface. For the last survey (monitoring-5), the nitrate concentration

levels are not as high as monitoring-1. Silva et al. (2005) reported that soil hydrological

properties (e.g., water flux, moisture content) were found more important to explain

different magnitudes of nitrate leaching losses.

The total amount of water inputs (rainfall) during the monitoring survey are

shown in Figure 4.59. Rainfall data were obtained from the nearest rainfall monitoring

station (Pejabat Haiwan Jajahan Machang, around 8 km inland from the site). Total

water inputs at the site between intervals of monitoring-1 and monitoring-2, monitoring-

2 and monitoring-3, monitoring-3 and monitoring-4, and monitoring-4 and monitoring-5

are 92.5 mm, 75.9 mm, 127.7 mm and 212.4 mm of rainfall, respectively. Spray

irrigation is not a common farming practice in the region. The amount of rainfall

occurred during the monitoring period interval did not create much water in the pore

soil. Soil moisture contents at a depth up to 100 cm showed temporal variations within

few days of rainfall.


180

Figure 4.57. Nitrate concentration versus time (survey days) for each sampling depth

(A) surface, (B) 25 cm, (C) 50 cm, (D) 75 cm, (E) 100 cm.

0

20

40

60

80

100

120

140

0 28 44 64 92

Nit

rate

(m

g/l)

Days Nitrate-0

0

20

40

60

80

100

120

140

0 28 44 64 92

Nit

rate

(m

g/l)

Days Nitrate-25

0

20

40

60

80

100

120

140

0 28 44 64 92

Nit

rate

(m

g/l)

Days Nitrate-50

0

20

40

60

80

100

120

140

0 28 44 64 92

Nit

rate

(m

g/l)

Days Nitrate-75

0

20

40

60

80

100

120

140

0 28 44 64 92

Nit

rate

(m

g/l)

Days Nitrate-100

A

C

B

D

E


181

Figure 4.58. Nitrate concentration versus sampling depth (cm) for each monitoring, (A)

Monitoring-1, (B) Monitoring-2, (C) Monitoring-3, (D) Monitoring-4, (E) Monitoring-

5.

0

25

50

75

100

0 30 60 90 120 150

Dep

th (

cm)

Nitrate (mg/l)

0

25

50

75

100

0 30 60 90 120 150

Dep

th (

cm)

Nitrate (mg/l)

0

25

50

75

100

0 30 60 90 120 150

Dep

th (

cm)

Nitrate (mg/l)

0

25

50

75

100

0 30 60 90 120 150

Dep

th (

cm)

Nitrate (mg/l)

0

25

50

75

100

125

150

175

200

0 30 60 90 120 150

Dep

th (

cm)

Nitrate (mg/l)

A B

C D

E


182

Based on Figure 4.57, Figure 4.58 and Figure 4.59, there was no significant

correlation between the amounts of nitrate concentration with rainfall and with apparent

water content in the pore soil (moisture content). The highest moisture content on the

surface can be found in monitoring-2, whereas the highest nitrate concentration

observed in monitoring-3 at the same location. Furthermore, in Figure 4.59, it is noted

that there are high rates of rainfall between monitoring-3 and monitoring-4 and also

between monitoring-4 and monitoring-5 that cause the nitrate concentration for a depth

of 100 cm to decrease significantly. The result in this research supports the study that

was done by Silva et al. (2005). He said that the water flux is more important for nitrate

leaching.

Figure 4.59. Amount of rainfall during the monitoring survey.

0

10

20

30

40

50

60

-5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Am

ou

nt

of

Rai

nfa

ll (m

m)

Days Monitoring Days Rainfall


183

In conjunction with the nitrate concentration in pore soil, the ammonia and

nitrite-oxidising bacteria need to be considered. According to Lee et al. (2006), the

presence of oxygen by the autotrophic ammonia-oxidising bacteria (the major genera is

Nitrosomonas) can cause ammonia to be oxidised to nitrite (NO2-

) much faster. In the

next step, due to the nitrite being a rather unstable nitrogen species, the autotrophic

nitrite-oxidising bacteria (the true nitrifying bacteria with major genera is Nitrobacter)

oxidise nitrite to nitrate (NO3-

). However, in this study, the amount of these bacteria is

not determined and not questioned.

The distribution pattern of nitrate on the surface as given in Figure 4.44.A, is

similar to nonmonotonic function (Andrews 1986). Using Wolfram Mathematica 7

software, the predicted equation for nitrate concentration (Nc with mg/L) at the surface

is developed as the following equation:

Where is initial nitrate concentration before fertilizer application (mg/L), β is constant

(0.264494), D is days monitoring, γ is constant (0.0541654) and δ is constant

(0.00077287).

In order to see the correlation between the developed equation above (predicted

nitrate concentration on the surface) with measured nitrate concentration data, the

equation was plotted together with measured nitrate concentration in the same graph

(Figure 4.60). Visually, in Figure 4.60, correlation between predicted and measured

nitrate concentration on the surface is very good. It is supported by calculating their

correlation coefficient to be 0.98. It takes 36 days after fertilization for the nitrate to

become maximum in concentration. Moreover, the nitrate concentration will be at the

initial concentration 100 days after fertilization. Regarding this finding, it can be


184

concluded that the nitrate concentration will be laid above accepted limits for human

consumption at a depth up to 1 m. This happened starting from around 17 to 60 days

after fertilization.

Figure 4.60. The fate of nitrate in palm oil plantation area.

0

20

40

60

80

100

120

140

160

180

0 20 40 60 80 100 120

Nit

rate

Co

nce

ntr

atio

n (

mg/

l)

Days

Equation Measured


185

4.5. Summary

The lower average geoelectrical resistivity values from the surface to depths of

75 cm were obtained from surveys in the regularly fertilized site which has not been

fertilized for the last ten months prior to the survey. The average resistivity values were

around 0.4 times less compared to resistivity measured in unfertilized sites. Residual

nitrate and chloride measured in the regularly chemically fertilized sites were still

present. At sites with no chemical fertilizer, nitrate and chloride concentration were

found to be lower but still present due to the faces excretion of the grazing farm

animals. The nitrate and chloride content in pore soil water reduced the resistivity

values, despite low moisture content. Normally, resistivity values are inversely

proportional to moisture content for area with similar soil condition.

In the whole of Area 1, nitrate concentration in shallow aquifer is higher in the

southern part compared to the northern part which is absent instead. In the southern

part, the soil properties are all similar. However, the geoelectrical model shows lower

resistivity values (around 15 ohm.m) at sites with relatively higher nitrate content in the

groundwater (more than 20 mg/L). Conversely, relatively higher resistivity value (more

than 30 ohm.m) is found in the sites with low (0-6 mg/L) nitrate concentration in

groundwater. Furthermore, the trend of higher nitrate concentration was found in

catchment area.

The 3D basement map of the area is generated from the interpolation of an

interpreted geoelectrical model. The areas that possibly possess nitrate-contaminated

groundwater have been mapped along with groundwater flow patterns. The southern

part of the study area has an east to west groundwater flow pattern, making it

impossible for contaminated water from the southern area to reach into the northern


186

area, despite having lower elevation. Furthermore, pre-Quaternary bedrock located in

the middle of Area 1 blocks the groundwater to flow from the southern area into the

northern area. The possibility of good potential aquifer which has thickness vary from

25 to 40 m can be found in the northern area. The aquifer is probably of freshwater type

as indicated compare higher resistivity. Meanwhile, in the southern area, the aquifer

thickness varies from 5 to 15 m with high nitrate contamination. In some palaces,

surface water has direct connection with the top / shallow aquifer.

Nitrate concentration of the study area has been successfully evaluated by the

time lapse monitoring survey of geoelectrical resistivity, hydrogeochemical and soil

properties analysis. The hydrogeochemical measurements indicate that the cations

content are relatively similar for every time lapse measurement. However, relatively

higher changes of anions content occur on the surface to a depth of 1 meter. Of

particular interest, nitrate concentration lies above the limit for safe human

consumption. The geoelectrical model prior to fertilization showed similar resistivity

values near the surface to a depth of about 75 centimetres with no significant

occurrences of low resistivity values. Lower resistivity values were obtained during the

second, third, fourth and fifth measurement within the chemically fertilized zone. In the

last measurement, the resistivity values in the fertilized zone are almost similar to the

non-fertilized zone. This indicates that the contaminant has been dissolved into the

surrounding area within this time of period.

An equation for nitrate concentration around the surface was derived. The

equation can be used to predict the growth of nitrate after the application of fertilizer

(urea) in palm oil plantation of the semi-pervious soil. The maximum nitrate

concentration is predicted 36 days after fertilization and will be at the original

concentration around 100 days after fertilization. It also can be concluded that the


187

nitrate concentration will be laid above accepted limit for human consumption at a

depth up to 1 m starting from around 17 to 60 days after fertilization.

Documents

Chapter 4 Result and Discussion of Area 1