ORIGINAL PAPER

Evaluation of heavy metal contamination in groundwatersamples from Kapas Island, Terengganu, Malaysia

Noorain Mohd Isa & Ahmad Zaharin Aris &

Wan Ying Lim & Wan Nor Azmin Wan Sulaiman &

Sarva Mangala Praveena

Received: 11 May 2012 /Accepted: 21 December 2012# Saudi Society for Geosciences 2013

Abstract An attempt has been made to delineate the hydro-chemistry for a small island based on the major ions and heavymetal concentrations. In this investigation, six sampling cam-paigns were conducted to measure the concentrations of majorions (Ca, Mg, Na, K, HCO3, Cl, and SO4) and heavymetals (Zn, Cr, Pb, Mn, As, and Cu) in groundwater samplescollected from seven sampling stations (boreholes) located onKapas Island, Terengganu, Malaysia. The distribution of ma-jor ions is illustrated by a piper plot where Ca–HCO3 is thedominant type. In addition, the concentrations of heavy metalsdemonstrate that Mn shows as being the highest concentratedheavy metal in the groundwater sampled in the samplingcampaigns; the average Mn content in groundwater sampledwas 54.05 μg/L. However, a comparison of the heavy metal(Mn, Cr, Zn, As, Pb, and Cu) concentrations in groundwatersamples with the Drinking Water Quality Standard prescribedby World Health Organization reveals that none of theseheavy metals exceeded the recommended threshold limits.The principal component analyses (PCA) extracted four com-ponents that control the groundwater chemistry. Components1 and 2 from the PCA analyses extracted approximately52.11 % of the total variance, which represent the heavymetals (As and Mn) and physical parameters (pH, redoxpotential, electrical conductivity, temperature, and totaldissolved solids). Based on the output of the PHREEQC

hydrogeochemical software, several species of heavy metalsexist, in which the dominant species found are Mn2+, PbCO3,Cu(OH)2, and Zn+.

Keywords Heavymetals . Groundwater . Kapas Island .

Principle component analyses .WHO guidelines

Introduction

Unconfined aquifers with shallow water tables that are over-lain by permeable soils in small tropical islands are vulner-able to various contaminants. Most of the contaminants,especially heavy metals, penetrate into the soil and eventu-ally pollute the groundwater. Such cases have increasedtremendously and present a serious threat to the world today(Mulligan et al. 2001; Peng et al. 2009). Heavy metals existin their natural forms, as a result of the erosion and weath-ering of parent rocks (Leung and Jiao 2006; Nouri et al.2006), which contribute to the heavy metal concentrations inthe groundwater. An elevated concentration of heavy metalsin the groundwater may derive from fertilizers and pesti-cides or the corrosion of underground pipes (Ledin et al.1989 and Samuding et al. 2009), which may later present amajor issue in the management of small islands. Anothersource of heavy metal contamination in groundwater is fromweak management concerning the disposal of domestic andsolid waste.

Water from disposal sites or surface runoff (containingfertilizers and pesticides) infiltrate as leachates into thegroundwater. Leachates, which are known to contain haz-ardous and deleterious chemicals, might be a contributor tothe dispersion of heavy metals in groundwater (Baumann etal. 2006; Zheng et al. 2008). Groundwater that is used fordrinking purposes is threatened by the heavy metals, whichare nonbiodegradable in composition (Mishra and Tripathi

N. M. Isa :A. Z. Aris (*) :W. Y. Lim :W. N. A. W. SulaimanEnvironmental Forensics Research Centre,Faculty of Environmental Studies, Universiti Putra Malaysia,43400, Serdang, Selangor, Malaysiae-mail: zaharin@env.upm.edu.my

S. M. PraveenaDepartment of Environmental and Occupational Health,Faculty of Medicine and Health Sciences, Universiti PutraMalaysia, 43400, Serdang, Selangor, Malaysia

Arab J GeosciDOI 10.1007/s12517-012-0818-9

2008). Although some trace elements are necessary in smallamounts for normal development of the biological cycle, mostof them become toxic in high concentrations (Herdan et al.1998). Through drinking, these might accumulate in the livingtissue of the consumers, which is linked to various diseasesand disorders, such as Alzheimer's disease and Parkinson'sdisease (Samuding et al. 2009; Katsuro et al. 2004).

Previous studies on heavy metals in groundwater havebeen conducted worldwide in accordance with the use of thegroundwater. Certain areas, such as Korea, India, and theNetherlands, use groundwater as their primary water resourcefor drinking purposes and domestic use. Hence, it is necessaryto conduct groundwater monitoring to maintain the ground-water quality before its composition exceeds the permissiblelimits. Examples of previous studies are shown in Table 1.However, for Malaysia, there is insufficient information re-garding heavy metals in groundwater because, most of thestudies in this country focus on heavy metals in river water,which constitute the primary water resource in Malaysia. Thehydrochemistry field, which describes heavy metals in thegroundwater, especially in remote and isolated areas (smallislands) is still in its infancy and clearly has a long way to go.Consequently, studies on small islands, which represent acomplex geochemical environment, are significant as smallislands have a different chemical mechanism to that of themainland. When the groundwater usage in small islands con-stitutes the only water resource, it is necessary to understandthe conceptual geochemical mechanism that controls thegroundwater composition. It is also important to comprehendthe interaction of this complex geochemical environment withthe surroundings, inasmuch as small islands are completelysurrounded by seawater, and, therefore, susceptible to seawa-ter disturbance. Figure 1 shows the conceptual model of asmall islands geochemistry. The sources of groundwater com-position are contributed by the chemical reaction between theaquifer matrix, dissolution of minerals, and the pollution from

seawater intrusion and infiltration of herbicides. The mineralsthat usually make up the groundwater composition in tropicalregions are calcite and dolomite. The natural metal concen-trations found in the groundwater may come from the precip-itation of secondary minerals, such as granite.

Small islands are generally formed with highly perme-able soil, which, with sufficient recharge water, easily trans-ports the heavy metals at the surface area into thegroundwater (Nouri et al. 2006; Shokrzadeh and Saravi2009). Due to their isolated nature, to which Kapas Islandis no exception, small islands are dependent on groundwateras their primary water resource. Kapas Island has beendeveloped for ecotourism activities, which provide the pri-mary income of its population. As this island receives atremendously high number of tourists in a concentrated area,a large volume of groundwater is needed to meet thedemands for drinking water purposes and domestic use.Hence, it is a priority to make sure that the groundwater inKapas Island is of suitable quality for the purpose of islandmanagement.

Kapas Island consists of ephemeral streams that are onlyfound during the transition of the monsoon when KapasIsland experiences heavy rainfall. Such a condition doesnot permit the streams to be considered as potential waterresources as they only exist for a limited duration andexperience a small and low flow rate. The current watersupply for domestic use on Kapas Island depends solely onthe groundwater, which receives recharge from the infiltra-tion of water (rainfall) for its aquifer. Currently, at least fivedug wells of different depths in various locations are usedfor freshwater extraction with only one water cistern beingfound. The groundwater is pumped out automatically usinga water pump that has been installed with a water-levelmeter, the operation of which is controlled by the resortsoperator. Groundwater from the water tank is usually con-sumed by the tourists and for domestic use in the resorts,

Table 1 List of examples ofprevious studies on heavy metalin groundwater—worldwide

Article Study location Heavy metal Study on

Chowdhury et al. (2012) Bangladesh As General study

Christodoulidou et al. (2012) Cyprus As General study

Haloi and Sarma (2012) India Cd, Fe, Mn, Pb, and Zn General study

Kargar et al. (2012) Iran Al, Cd, Cu, Fe, Mo, Ni, and Pb General study

Norrström and Knutsson (2012) Sweden Pb General study

Subyani and Ahmadi (2010) Saudi Arabia Ba, Cu, Mn, Pb, and Zn General study

Sang et al. (2008) China Cu, Pb, and Cd Water treatment

Aris et al. (2007) Malaysia Se, Mn, Ba, Fe, Ag, Al, Cr, and Ni General study

Lee et al. (2007) Korea As, Zn, Ni, and Cd Water treatment

Parga et al. (2005) Mexico As Water treatment

Rattan et al. (2005) India Zn, Cu Fe, Mn, Ni, Pb, and Cd General study

Critto et al. (2003) Italy As, Cr, Ni, Pb, Cu, and Zn General study

Ahmed and Sulaiman (2001) Malaysia Cd, Cu, Zn, Cr, Pb, and Ni General study

Arab J Geosci

with the water from the dug wells used directly for theresorts surrounding maintenance, such as watering plantsand pool cleaning.

This study was conducted to investigate the heavymetal concentrations in the groundwater of KapasIsland, Terengganu, Malaysia. Groundwater samples fromseven constructed boreholes were analyzed based on theirheavy metal concentrations of Mn, Cr, Zn, As, Pb, andCu, and, subsequently, statistical methods were employed toidentify the controlling factors affecting the heavy metal con-stituents of the groundwater. Finally, the results were com-pared with the Drinking Water Quality Standard of the WorldHealth Organization (WHO 2011) to ascertain its suitabilityfor drinking purposes since the groundwater usage in KapasIsland is mainly for drinking purposes.

Study area

Kapas Island covers an area of approximately 2 km2. It islocated at 5°13.140′ N, 103°15.894′ E. The local economy isheavily dependent upon ecotourism activities. The annualminimum and maximum precipitation for the study area,which was based on the average for 2000–2009, is approx-imately 1,500 and 2,800 mm, respectively (Fig. 2). Morethan 80 % of the total precipitation occurs during the mon-soon period from November to January every year. KapasIsland experiences a constant temperature varying from 28to 31 °C and has a warm and humid climate of around 70–80 % annually.

Approximately 90 % of the topography of Kapas Island ishilly while the rest is heavy populated. The population of localresidents mostly practices tourism activities and Kapas Islandreceives thousands of tourists every year. Geologically, KapasIsland is underlain by sedimentary rock with a conglomeratesequence overlay. The sedimentary rocks represent the sand-stone, mudstone, shale and siltstones sequence (Ali et al.2001) while the lithology formation of Kapas Island is alluvial(Abdullah 1981).

The sampling locations for groundwater collection werechosen in the vicinity of highly residential areas, which areflat and low lying areas due to the simultaneous occurrenceof pumping activities. The sampling campaigns were con-ducted bimonthly from February to April 2011. Seven bore-holes were constructed perpendicular to the coastal areawith a maximum distance of approximately 150 m fromthe coastline (Fig. 3). Borehole installations were done withdifferent depths, as stated in Table 2 and Fig. 3.

Methods

In this study of Kapas Island, a total of 126 groundwatersamples were sampled from 7 boreholes for the determinationof major ions (Ca, Mg, Na, K, bicarbonate (HCO3), chloride(Cl), and SO4) and heavy metals (Mn, Cr, Zn, As, Pb, and Cu).The sampling standard methods prescribed by APHA (2005)were followed carefully for the groundwater collection andanalytical techniques. The groundwater was pumped out forabout 10 to 15 min using a set of purging pumps prior togroundwater sampling, to evade nonrepresentative samples of

Seawater

Transition zone

SMALL TROPICAL ISLAND

Groundwater level

Freshwater

OceanOcean

Intruding of seawater

Bedrock

23 4

1

Precipitation

Evapo-transpiration

Mixing zone

1 Oxidation/Reduction

2 Cation exchange

3 Dissolution of minerals

4 Precipitation of secondary minerals

5 Leaching of herbicide

6 Simple mixing of freshwater and seawater

5

6

Fig. 1 The complex geochemical model of small islands (modified from Appelo and Postma 2005)

0

100

200

300

400

500

600

700

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Perc

ipit

atio

n (m

m)

Month '2011

Fig. 2 Rainfall data of year 2011 for Marang district of Terengganu

Arab J Geosci

stagnant or polluted water (Appelo and Postma 2005).Groundwater samples at each site were measured for in situparameters—temperature, dissolved oxygen (DO; YSI 52Dissolved Oxygen Meter), electrical conductivity (EC), totaldissolved solids (TDS), redox potential (Eh), pH, and salinity(Mettler Toledo, Columbus). For analyses of major anions,HCO3, Cl, and SO4 were measured immediately after the col-lection of samples. HCO3 andClwere determined using titrationmethods of 0.02 N HCl and 0.0141 N AgNO3, respectively,while SO4 was determined using a HACH (DR/2000) meter(HACH, Loveland, CO). Groundwater samples for the mea-surement of cations were filtered using 0.45 μm cellulose ace-tate membrane filter and acidified to pH<2 using ultrapure nitric

acid. Next, the filtered samples were kept in a cooler box fortransportation to the laboratory for further analyses. Major cat-ions were measured using a flame atomic absorption spectro-photometer (FAAS; PerkinElmer, Waltham, MA) while heavymetals were measured using inductive couple plasma massspectrometry (ICP-MS: PerkinElmer ELAN DRC-e).

Quality control and analysis procedures for obtaining ac-curate data were performed including the calibration of theprobe for the in situ parameters, standard deviation of tripli-cate data, and analyses of blanks as well as laboratory standardaddition methods to obtain the calibration curve while usingthe FAAS and ICP-MS. The annual preventive maintenancefor the FAAS and ICP-MS was done to receive accreditation

KW 1KW 2KW 3KW 4

KW 5KW 6

KW 7

5.1297

5.1298

5.1299

5.1300

5.1301

5.1302

5.1303

5.1304

5.1305

5.1306

5.1307

5.1308

103.1575 103.1576 103.1577 103.1578 103.1579 103.1580 103.1581

A

A’

B

B’

MALAYSIA

Terengganu

Terengganu

Kapas Island

(m)

Fig. 3 The overview of the location of Kapas Island, which is situated in the district of Marang, Terengganu, Malaysia, and the location of theconstructed boreholes in Kapas Island in the low-lying area

Table 2 The coordinates, dis-tances, and depths of boreholesat Kapas Island

Station Station coordinates Distance fromthe coastline (m)

Depth of boreholes fromsurface level (m)

KW1 05°12.999 N 103°15.799 E 119 11.5

KW2 05°12.996 N 103°15.787 E 98 9.1

KW3 05°12.992 N 103°15.778 E 83 3.5

KW4 05°12.989 N 103°15.771 E 68 3.0

KW5 05°12.985 N 103°15.762 E 48 2.9

KW6 05°12.982 N 103°15.754 E 31 2.5

KW7 05°13.069 N 103°15.774 E 150 4.4

Arab J Geosci

of the systems and approval of the laboratories by govern-mental bodies.

Major concentrations of ions in the groundwater werereported as mg/L while heavy metal concentrations were inμg/L. Statistical Package, PASW 18 (formerly SPSS Statistics)was applied for descriptive statistics, correlation coefficientand principal component analysis. The PHREEQC softwarewas used in order to estimate the heavy metal speciations,which are dominant in the groundwater samples. PHREEQCperforms speciation calculations based on the law of massaction, which states that for a reaction of the generalized type(Eq. 1):

aAþ bB $ cC þ dD ð1Þ

Whereas, the distribution at thermodynamic equilibriumof the species at the left and right side of the reaction isgiven by (Eq. 2):

K ¼ C½ �c � D½ �dA½ �a � B½ �b ð2Þ

where, K is the equilibrium constant and the bracketedquantities denote activities or effective concentrations.Specifically, a, b, c, and d are the number of moles of thereactants A and B and the end products C and D, respective-ly for the given reaction of the mass-action law. In particu-lar, the term K is defined as solubility product of dissolution/precipitation of minerals. Several databases that are avail-able in PHREEQC software with constants for the variousreactions were selected for the speciation calculations. Theaqueous concentrations in a solution are defined withSOLUTION in the input file for the speciation calculationsin this study and the symbols for the elements for example,Ca, Mg, Na, and K are listed in the first column ofSOLUTION_MASTER_SPECIES in the database.

Finally, the studied variables were compared with themaximum permissible limits for drinking water by WHO(2011). These methods act as an accurate tool to fullyintegrate a better explanation of the origin of groundwatercontamination. The identification of groundwater quality isimportant to understand the groundwater chemistry processinvolved in the aquifer. This information is very useful,especially in a small tropical island environment.

Principal component analysis (PCA) was used in this studyto detect the similarities among the variables or the samples byinterpreting the structure within the variance–covariance ma-trix and extraction of eigenvalues from the matrix of correla-tions. This technique helps to simplify, organize and presentlarge data sets that can provide a good explanation concerningwhat really happens in the study area. The results of theinterrelationships of a small number of components given willusually provide the same amount of information as the largerset of original observations. The interpretation of the

component is based on high (≥0.7), moderate (0.69–0.3),and weak (≤0.29) component loading. Each component load-ing of ≥0.7 is taken into consideration during interpretation forthe explanation of factors that control the groundwater com-position. Moderate to zero component loading indicates thatthe areas are affected to an average degree or are unaffected bythe hydrochemistry processes in the study area.

Results and discussion

Descriptive analyses and correlation coefficient

Table 3 shows some basic physicochemical characteristicsof groundwater. The pH values of groundwater varied be-tween 7.04 and 7.41. Generally, groundwater samples fallwithin a pH range of 6 to 9 in natural conditions (Stummand Morgan 1996). This is because natural water normallycontains dissolved carbon dioxide and hydrogen carbonateions (Mokhtar et al. 2009) (Eqs. 3 and 4), which form abuffer system. The Eh ranged from −13.20 to 9.90 mV,where a negative value indicates reducing conditions, whichprevails in the shallow aquifers. Both the pH and Eh valuesshow a strong negative correlation (r=−0.991; p<0.01;Table 4), suggesting that the redox potential is stronglydependent on the changes in pH.

H2Oþ CO2 ! H2CO3 ð3Þ

H2CO3 ! 2Hþ þ CO�3 ð4Þ

Table 3 Descriptive analysis for in situ and major ions during the sixsampling campaigns (n=126)

Units Mean SD Min Max

Temperature °C 29.30 0.90 27.70 32.20

pH 7.21 0.09 7.04 7.41

EC mS/cm 0.42 0.09 0.32 0.68

DO mg/L 3.82 2.47 1.23 11.08

TDS mg/L 209.31 47.23 158.80 342.00

Eh mV −0.91 5.44 −13.20 9.90

Salinity ppt 0.20 0.05 0.15 0.33

Ca mg/L 86.24 14.08 53.62 117.02

Mg mg/L 7.15 3.41 3.53 16.10

Na mg/L 10.08 7.53 1.84 35.47

K mg/L 0.48 0.45 0.05 2.48

HCO3 mg/L 284.61 45.73 229.36 505.08

Cl mg/L 24.68 15.76 10.00 75.98

SO4 mg/L 9.83 5.10 1.00 25.00

SD standard deviation, Min minimum, Max maximum

Arab J Geosci

Tab

le4

Correlatio

ncoefficientof

major

ions,selected

heavymetals,andin

situ

parametersin

Kapas

Island

,Terengg

anu

Tem

ppH

EC

Salinity

DO

TDS

Eh

Ca

Mg

Na

Tem

perature

1−0.52

9**

0.14

80.15

4−0.33

5**

0.14

80.50

2**

−0.02

80.07

8−0.17

1pH

1−0.68

6**

−0.68

3**

0.46

8**

−0.68

4**

−0.99

1**

0.05

1−0.07

0−0.02

4EC

10.99

8**

−0.26

6**

0.99

9**

0.71

5**

0.07

6−0.03

90.14

1Salinity

1−0.25

4**

0.99

8**

0.711*

*0.06

1−0.05

70.12

1DO

1−0.26

4**

−0.46

5**

−0.19

4*−0.15

4−0.00

3TDS

10.71

3**

0.07

6−0.03

90.14

1Eh

1−0.05

90.05

50.02

3Ca

10.77

4**

0.64

6**

Mg

10.71

2**

Na

1K HCO3

Cl

SO4

Zn

Pb

Mn

Cu

Cr

As

KHCO3

Cl

SO4

Zn

Pb

Mn

Cu

Cr

As

Tem

perature

0.10

0−0.10

5−0.05

9−0.16

90.19

1*−0.17

7*−0.07

10.24

4**

0.31

5**

0.43

5**

pH−0.02

90.13

00.03

10.00

0−0.05

90.03

2−0.45

9**

−0.47

1**

−0.16

0−0.50

5**

EC

0.00

5−0.00

9−0.06

20.28

0**

−0.07

4−0.27

4**

0.86

2**

0.46

1**

0.011

0.41

3**

Salinity

0.00

4−0.01

2−0.07

50.26

5**

−0.08

1−0.28

7**

0.86

1**

0.45

9**

0.02

60.41

0**

DO

0.07

30.12

60.03

7−0.01

7−0.02

70.07

7−0.08

4−0.28

9**

0.43

5**

−0.23

5**

TDS

0.00

6−0.00

9−0.06

20.28

3**

−0.07

3−0.27

6**

0.86

3**

0.46

0**

0.01

40.41

4**

Eh

0.03

6−0.13

8−0.03

30.02

10.06

5−0.03

00.50

0**

0.49

2**

0.14

50.50

0**

Ca

−0.03

10.45

9**

0.48

6**

−0.07

3−0.01

4−0.24

8**

0.011

−0.05

9−0.20

4*0.29

3**

Mg

0.34

4**

0.57

9**

0.70

5**

−0.16

00.03

0−0.13

1−0.16

3−0.00

4−0.19

3*0.26

8**

Na

0.38

4**

0.56

7**

0.79

7**

0.09

2−0.01

6−0.16

60.14

2−0.05

3−0.05

40.12

9

K1

0.39

1**

0.49

1**

−0.116

−0.00

50.02

0−0.02

20.16

80.12

5−0.011

HCO3

10.611*

*−0.05

8−0.15

2−0.15

3−0.00

1−0.06

80.09

9−0.13

2

Cl

1−0.20

0*−0.07

9−0.12

0−0.06

5−0.04

80.02

7−0.08

1

SO4

10.02

2−0.111

0.43

2**

−0.06

3−0.01

6−0.10

5

Zn

1−0.02

9−0.02

7−0.03

20.02

50.18

7*

Pb

1−0.28

7**

0.12

00.02

0−0.17

9*

Mn

10.21

9*0.00

30.20

6*

Arab J Geosci

The TDS values of groundwater varied between 158.8 to342.0 mg/L. The groundwater in the study area can be classi-fied as freshwater as the TDS values were below the limitstipulated by WHO (2011) (1,000 mg/L), during the samplingperiods (February to April 2011). The groundwater of KapasIsland encapsulates a range from 0.32 to 0.68 mS/cm in whichthe measured EC value is lower than the 1.50 mS/cm recom-mended by WHO (2011) and correlated well with TDS (r=0.999; p<0.01). The EC measurement indicates the ability ofthe water sample to allow an electric current to flow, which isrelated to the concentration of ionized substances in the water(Radojevic and Bashkin 2006). Thus, a lower value of ECindicates the presence of a low concentration of dissolved ions,such as inorganic salt and organic matter in water (WHO 2011;Radojevic and Bashkin 2006). The salinity of the groundwateris in the range 0.15 to 0.33 ppt with an average of 0.20 ppt. TheDO concentration in the groundwater of Kapas Island rangesfrom 1.23 to 11.08 mg/L. These wide variations in DO con-centration are due to the different hydrogeochemical processesoccurring at different sampling locations as well as the distinctclimatic conditions that exist during the different samplingcampaigns. The low DO concentration is caused by thegroundwater being beneath the ground surface in a closedsystem.

The order of major ion concentrations was Ca>Na>Mg>Kand HCO3>Cl>SO4 (Table 3; Fig. 4). The distribution of themajor ion concentrations is shown in the piper plot; thesamples have been identified as Ca-HCO3 water type(Fig. 5). The dominant ions in the groundwater are Ca andHCO3, with average values of 86.24 and 284.61 mg/L, re-spectively, while the elements include Na, Mg, K, Cl, andSO4, for which the concentrations are 10.08, 7.15, 0.48, 24.68,and 9.83 mg/L, respectively. The Ca and HCO3 concentra-tions are high due to the wide and long contact with thecrystallized carbonate minerals, which cause the carbonatedissolution process (Eq. 5). Statistical analyses show that theCa and HCO3 are correlated with r=0.459 (p<0.01). KapasIsland also consists of dolomite minerals (Ali et al. 2001),which explain the concentration ofMg (Eq. 6), and show goodcorrelation with Ca (r=0.774; p<0.01). The HCO3 and Mgrelationship also shows significant correlation (r=0.579; p<0.01). Na and Cl are the seawater component, which arebelieved to come from the dissolution of crystalline halite,which evaporates during inundation at the soil surface. Theanalysis shows a positive correlation between Na and Cl withr=0.797 (p<0.01).

CO2 þ H2Oþ CaCO3 ! Ca2þ þ 2HCO�3 ð5Þ

2CO2 þ 2H2Oþ CaMg CO3ð Þ2 ! Ca2þ þMg2þ þ 4HCO�3

ð6ÞTab

le4

(con

tinued)

KHCO3

Cl

SO4

Zn

Pb

Mn

Cu

Cr

As

Cu

10.011

0.311*

*

Cr

10.113

As

1

p<0.05

*;p<0.01

**—

sign

ificantvalues

Arab J Geosci

Groundwater environments are often characterized byhigh bicarbonate ion concentrations since carbonates are

present in many different types of rocks including mostsedimentary rocks and even some igneous and metamorphic

(a) (b)

(c) (d)

(e) (f)

(g)

Fig. 4 The distribution ofmajor ion concentrations in thegroundwater samples: a Ca, bMg, c Na, d K, e HCO3, f Cl,and g SO4

Arab J Geosci

rocks (Kim et al. 2000). These carbonate minerals reactreadily with groundwater, unlike other minerals, such assilicate minerals, which do not react readily with groundwa-ter. As already noted, the interaction of water and rocksplays an important role in the evolution of groundwater. Itbecomes an issue when the pH is not correlated with HCO3

since HCO3 is affected by the buffer system. Referring toEqs. 4 and 5, the reaction of water with CO2 resulted in H+

ions, which explain the acidic condition (low pH). From thelast reaction (Eqs. 6 and 7) the solubility of the minerals isalso controlled by the pH, inasmuch as a low pH dissolvesmore minerals.

The pH values in this study have no distinct group thatwould make it possible to make a change according to thegroundwater composition (p>0.05). The explanation ofHCO3 concentrations can be proven by the reaction of (1)CO2 with groundwater, and the reaction of (2) aquifer ma-trix with groundwater (Isa et al. 2012). These reactions (1)and (2) were induced to carbonate concentration yet pro-duced H+ and OH− ions. The combination of H+ and OH−

ions is considered to be neutral when the activity of theseions is equal. Considering the total pressure is 1 atm, theequilibrium pH in relation to calcium and HCO3 activitiesfor this study would probably give an approximate pH rangeof 6.5 to 7.5 (Hem 1985). This is in the agreement with thepresent study where the mean of pH value in this study is7.21±.21 t suggesting the direct interaction between Ca andHCO3.

Apart from the elaboration of in situ and major ions,Table 5 shows the descriptive concentration of heavy metalsin the groundwater samples, which are compared with thedrinking water guidelines recommended by WHO (2011).

The mean concentration of heavy metals in the groundwatersamples follows the order: Mn>Cr>Zn>As>Pb>Cu. Thedissolved concentrations of Mn, Cr, Zn, Pb, As, and Cu ingroundwater were determined, with a mean value of54.05 μg/L for Mn, 23.81 μg/L for Cr, 5.51 μg/L for Zn,0.84 μg/L for Pb, 1.96 μg/L for As, and 0.49 μg/L for Cu.All the heavy metals studied (Mn, Cr, Zn, Pb, As, and Cu)are likely to be derived from the natural water-rock reactionprocesses in the aquifers since none of these metalsexhibited concentration values outside the WHO (2011)limits (Table 5).

The potential sources of these metals are related tonatural processes or man-made influences. Under naturalconditions, the dissolved ions in the water are attributedto the mineral assemblages in the rocks near the landsurface (Hem 1989). Rock composition, nature of miner-als, texture, porosity, and regional structure also affectthe composition of heavy metals in the groundwater(Hem 1989). Meanwhile, anthropogenic inputs, such aspiping services and dumping sites are other potentialsources attributed to these variations. There is an inap-propriate dumping site in the study area, which, directlyor indirectly, allows leakage during the transportation ofwaste along the pathways. Therefore, these contaminantscan easily infiltrate the soil and pollute the groundwater.This includes metals, especially Mn, which is used as anadditive in steel production. In addition, metals are usedabundantly in offshore construction and the waste fromwhite goods and the corrosion from the undergroundsteel pipelines also delivers these elements into the aqui-fer. Likewise, heavy rainfall also plays an essential rolein controlling the mobility of trace elements in the va-dose zone (Leung and Jiao 2006). Heavy rainfall leads tofarm draining as large amounts of pesticides are appliedto control the grass growth. Pesticides containing metalcompounds are brought via surface runoff then infiltrateinto the groundwater, which contributes to the high agri-cultural pollution (Yi et al. 2008). The distribution ofthese contaminants is limited to a small area once theyinfiltrate into the aquifer. Consequently, it will be con-fined within the dumping area and is not diffused ordispersed over a wide area.

The correlation of TDS values with Mn Cu and As(p<0.01) indicates the presence of these metals in thegroundwater as free ions (Table 4). Meanwhile, the ac-tivity of pH/Eh significantly controls the Mn, Cu and Asmobilization in the groundwater. The relationship of thesemetals with pH and Eh can be seen in the correlationtable with p value of <0.01 (Table 4) where these metalshave a positive relationship with Eh (Mn=0.500; Cu=0.492; and As=0.500) and vice versa with the pH, whichhas a negative relationship (Mn=−0.459; Cu=−0.471;and As=−0.505). Usually, groundwater is in the reducing

Ca2+

CATIONS

Mg

2+ Na +

+K + C

O 32-+

HC

O 3-

SO4 2-

Cl-

ANIONS

SO4

2- +C

l- C

a 2++

Mg 2+

EXPLANATIONKW1KW2KW3KW4KW5KW6KW7

Fig. 5 The distribution of major ions using a piper plot and thedetermination of water type (n=126)

Arab J Geosci

condition (Eh value is negative), which triggers the mol-ecules in the groundwater to oxidize to form mobilizedions. The degradation of the organic waste matrix,changes in pH, Eh, or soil solution composition, due tovarious remediation schemes or to natural weatheringprocesses, may also enhance metal mobility.

Mn shows the high correlation with TDS (r=0.863;p<0.01), which indicates that the abundant ions aremostly from Mn. The Mn concentrations in the ground-water may originate from the primary minerals or sec-ondary oxides and oxy-hydroxides present in most rocktypes. The possible sources of Mn in this study includethe anaerobic environment in groundwater where partic-ulate Mn oxides are reduced, direct reduction of partic-ulate Mn oxides in aerobic environments by organicmatters, the natural weathering of Mn(II)-containingminerals and acidic environments (Hem 1989; WHO2011) (Eq. 7).

Mn2þ þ 2HCO�3 þ H2Oþ 1

2O2

! Mn OHð Þ4 þ 2CO2 ð7ÞSeawater contains trace amounts of Pb at about 2–30 ppt.

Ocean deposition may evaporate and leave Pb as a precip-itate. As Kapas Island receives heavy rainfall, Pb will betransported into the groundwater system (Eq. 8). The exis-tence of Pb in the bedrock occurs in a sporadic or patchynature and is influenced by tidal fluctuations. The amount oflead dissolved from the plumbing system depends on sev-eral factors, including the presence of chloride and dissolvedoxygen, pH, temperature, water softness, and the acidity ofthe water.

PbCl2 $ Pb2þ þ 2Cl� ð8ÞMost Zn found naturally in the environment is in the

form of zinc sulfide. These compounds are used to make

Table 5 The concentration ofheavy metals in the groundwatersamples

SD standard deviation, Minminimum, Max maximum, DLdetection limit

μg/L Zn Pb Mn Cu Cr As

KW1 Mean 3.21 0.42 25.93 0.84 26.28 5.10

SD 2.02 0.45 18.81 0.65 14.20 2.93

Min 1.39 <DL 0.36 0.26 5.56 0.92

Max 7.63 1.34 47.17 2.22 44.36 8.82

KW2 Mean 21.93 0.92 20.64 0.38 20.23 4.80

SD 44.68 0.52 21.65 0.20 10.06 1.24

Min 0.61 0.16 2.31 0.11 6.38 3.47

Max 118.97 1.75 65.06 0.69 33.12 7.29

KW3 Mean 1.41 0.71 0.53 0.39 23.14 0.36

SD 1.17 0.47 0.53 0.26 12.57 0.26

Min 0.38 0.17 0.08 0.13 6.81 0.18

Max 3.62 1.52 1.26 0.76 40.36 1.01

KW4 Mean 3.56 2.17 0.53 0.39 25.06 0.29

SD 3.47 1.09 0.32 0.29 12.81 0.22

Min 0.77 1.21 0.14 0.08 7.39 0.15

Max 10.29 4.35 0.90 0.93 41.09 0.84

KW5 Mean 4.10 0.40 0.72 0.42 24.60 0.39

SD 5.59 0.39 0.59 0.22 12.41 0.20

Min <DL 0.03 0.05 0.07 7.61 0.20

Max 16.59 1.17 1.82 0.67 39.19 0.74

KW6 Mean 1.34 1.05 0.91 0.34 22.32 0.32

SD 0.83 1.43 1.03 0.21 13.78 0.18

Min 0.17 0.16 0.01 0.09 0.16 0.18

Max 2.52 4.28 2.80 0.73 35.68 0.72

KW7 Mean 3.02 0.17 311.27 0.63 25.01 2.47

SD 4.16 0.16 43.90 0.24 15.47 0.32

Min 0.23 <DL 251.36 0.35 0.12 2.14

Max 11.97 0.43 370.18 1.06 41.33 3.07

WHO (2011) Mean 50 10 400 2000 50 10

Arab J Geosci

white paints, ceramics, and several other products. Zn canbe enriched in the groundwater as zinc sulfide reacts withthe Mg in the groundwater (Eq. 9).

Mg þ ZnSO4 ! MgSO4 þ Zn ð9ÞThe existence of As and Cu in groundwater is largely as a

result of minerals dissolving naturally from weathered rocksand soils (Parga et al. 2005). As(III) is mostly found in theenvironment, which generally to be catalyst from Mn oxidein the groundwater. As Kapas Island has Mn as the domi-nant heavy metal, it is significantly with elevation of Asconcentrations (r=0.206; p<0.05) are from Mn oxide in thegroundwater. However, other researchers state that As bindsto the colloidal matter present in the leachates and is trans-ported into the groundwater (Baumann et al. 2006).

Principal component analysis

PCA analyses only measure the physical parameters withheavy metals to review the hydrochemistry changes in thegroundwater. In this case, most of the major ions do notcontribute significantly to the heavy metal concentrations atp>0.05.

The PCA of the physicochemical parameters reveals that75.29 % of the total variance is explained by four compo-nents (Table 6), with more than half (52.11 %) of the datavariance explained by the first two components (Fig. 6).

Component 1 (C1) accounts for 26.42 % of the totalvariance and is characterized by the association of tem-perature, EC, and As. The source of As in the ground-water is the weathering process of minerals. In the

natural environment, As occurs in different forms andis usually found as As(III) or As(V) in groundwater(Hem 1989). Due to the anoxic condition presented inan aquifer, most of the As is usually assumed to be inthe As(III) form. EC correlated with the As concentra-tions (r=0.278; p<0.01) and similar results have beenfound by other researchers, such as Frost et al. (1993)and Zandsalimi et al. (2011).

Component 2 (C2) includes TDS, Mn, Eh, and pHand explains 20.69 % of the total variance. TDS corre-lates with Mn with r=0.863 (p<0.01), which representsthe dissolved ions in water that might be dominated byMn. As described elsewhere, the Mn concentration isalready known to be higher than the other heavy metals.Thus, the Mn ion may be abundant as dissolved ions.The sources of Mn occurrence could be from the weath-ering process (Aris et al. 2007). Mn is very soluble inlow pH or within oxygen depleted (reducing condition)groundwater (Mn and pH—r=−0.459 (p<0.01); Mn andEh—r=0.500 (p<0.01)). In other words, groundwaterthat is relatively more reducing conditions are exhibitsgreater concentrations of Mn.

Component 3 explains 12.87 % to the total variance andis characterized by a high loading of Cr and DO. Theoxygen concentration against heavy metal toxicity influen-ces a change in the physiological characteristics of heavymetals where the oxygen concentrations influence the intakeof heavy metals.

Component 4 (C4) contributes 10.32 % of the total var-iance and is only associated with Pb. Common sources oflead are manure and sewage sludge. As Kapas Island is adeveloping area, it is believed that the small amount of Pbwas originally from the leachate that infiltrated into theaquifer from the dumping site or herbicide used for control-ling the growth of the grass.

Temp

EC

As

TDSMn

Eh

pH

-1.0

-0.5

0.0

0.5

1.0

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

C2

(26.

42 %

)

C1 (25.69 %)

Fig. 6 Variables of components 1 and 2

Table 6 Rotated component matrix of groundwater samples at KapasIsland using Varimax rotation

Variables Component

1 2 3 4

Temperature 0.909 −0.006 −0.015 −0.067

EC 0.848 0.144 0.192 0.025

As 0.529 0.348 −0.140 −0.141

TDS 0.155 0.956 −0.072 −0.027

Mn −0.097 0.915 0.048 −0.170

Eh 0.604 0.674 −0.164 0.228

pH −0.629 −0.642 0.160 −0.225

Cr 0.418 0.025 0.853 0.076

DO −0.374 −0.161 0.806 −0.073

Pb −0.087 −0.283 0.020 0.830

Cu 0.309 0.423 −0.194 0.498

Zn 0.364 −0.196 −0.110 −0.366

% total variance 26.42 25.69 12.87 10.32

Arab J Geosci

Heavy metals speciation

The heavy metal speciations were calculated usingPHREEQC software. The speciation of heavy metals wasintroduced to improve the understanding of the speciesdistribution of heavy metals in the study area. It is essentialto obtain the toxicity and biotransformation of heavy metalsby quantifying the individual species of elements (Jain andAli 2000). The different species of the same elements wouldhave different chemical and toxicology properties, whichlikely occur in the different oxidation states in the environ-ment to form various species. As the heavy metal speciationis affected by the oxidation and reduction process, it isimportant to understand the pH/Eh activity (described else-where) in the groundwater. Occurrences of heavy metalspecies are summarized on a pH/Eh graph and discussedbased on a previous study by Hem (1963) and Hitchon(2006).

Table 7 shows the percentage of each species calculatedfrom PHREEQC. The lack of thermodynamic data preclud-ed the calculation of the distribution of Cr and As. Asdiscussed above, the activity of pH/Eh affects the solubility

and mobility of heavy metals. The ranges of pH (7.04 to7.41) in this study are mostly found in a neutral to slightlyalkaline conditions. From previous studies, species that existin neutral condition include MnHCO3+ (Hem 1963),ZnCO3, and PbCO3 (Hitchon 2006). The dominant speciesof Mn, Pb and Zn are Mn2+, PbCO3, and Zn2+ where thepercentages are 59.96, 90.64, and 48.28 %, respectively.Other complexes, especially the carbonate, are also signifi-cant species in the groundwater (Fig. 7).

Based on PCA analyses, Mn, pH, and Eh are in the sameC2, which explains the mechanism controlling the ground-water composition. As discussed previously in respect ofpH/Eh activity, Mn mobility is extremely sensitive to thesurrounding conditions, such as acidity and the biologicalactivities. Thus, the solubility of Mn is controlled by the pH/Eh activities in which a low pH results in elevated Mn in thegroundwater. Decomposition of organic materials usuallyoccurs in low pH, which may contribute to the concentrationof Mn.

According to Hitchon (2006), species PbCO3 and ZnCO3

may derive from the aged rocks of Cretaceous aquifers orCarboniferous-Jurassic. The formation of Kapas Island

Table 7 Range of highest per-centages of heavy metal species(n=126)

Element Percentage range (%) Species

Cu 77.73 Cu(OH)219.67 Cu2+

2.45 CuOH+

<0.1 CuSO4 Cu(OH)3− Cu(OH)42−

Mn 59.96 Mn2+

23.62 MnHCO3+

15.83 MnCO3

0.35 MnSO4

<0.2 MnCl+ MnOH+ MnCl2 MnCl3−

Pb 90.64 PbCO3

5.52 PbHCO3+

2.03 Pb(CO3)22−

1.28 Pb2+

0.45 PbOH+

0.05 PbSO4

<0.01 PbCl+ Pb(OH)2 Pb(SO4)22− PbCl2 Pb(OH)3−

PbCl3− Pb2OH3+ Pb(OH)4

2− PbCl42−

Zn 48.28 Zn2+

25.55 ZnHCO3+

21.56 ZnCO3

3.08 Zn(CO3)22−

0.88 ZnOH+

0.48 ZnSO4

0.11 ZnCl+

<0.01 Zn(OH)2 Zn(SO4)22− ZnCl2 Zn(OH)3−

ZnCl3− ZnCl42− Zn(OH)4

2−

Arab J Geosci

aquifer is known to be from the Late Permian to Triassic ageor Jurassic–Cretaceous age (Shuib 2003), which explainsthe existing species. While, in a natural condition, As maynot be found in high abundance in the Earth’s continentalcrust, it may be found in small amounts in the sedimentaryrocks of sandstone and limestone (Bissen and Frimmel2003). The deposition of these minerals can cause the in-crement of As concentration in the groundwater. In addition,Malaysia is under the Franciscan deposition type where thespecies MnHCO3 may deposit as reported by Mosier andPage (1988).

Conclusions

Kapas Island is a suitable area for the investigation of someof the natural processes that control the variations in themajor ions and trace elements. The groundwater type fromthe samples collection is identified as Ca–HCO3. The orderof the heavy metal concentrations in the groundwater sam-ples is Mn>Cr>Zn>As>Pb>Cu. Nevertheless, the averagevalues of these metals did not exceed the maximum permis-sible concentrations specified by the WHO StandardGuidelines for Drinking Water.

PCA extracted four components that were classified un-der the first major factor having high factor loading. Thisreveals that about 52.11 % of total variance representing C1(as, temperature, and EC) and C2 (Mn, Eh, pH, and TDS)control the groundwater hydrochemistry of Kapas Island.Furthermore, the pH/Eh activities show the abundant spe-cies of heavy metals in the groundwater. The dominantspecies in the groundwater samples are Mn+, PbCO3, andZn+, which comprise more than 50 % of the total. Other thanthat, these elements show a normal range of values that are

usually found in groundwater. This implies that the geo-graphical location and the natural processes, such as weath-ering and mineralization, play an important role incontrolling the variation in trace elements along with thedifferent species of heavy metals that are used to delineateits origin. Hence, it can be presumed that the heavy metals inKapas Island will not present a serious problem in the futureunless intense human intervention takes place. Nevertheless,the common practice of using an open area as a wastedisposal site (dumping area) could cause deterioration ofgroundwater quality by the infiltration of leachates.Assessing the potential impacts, concerns, together withthe possible mitigation measures and monitoring are crucialsteps for continuous protection of the groundwater in KapasIsland.

Acknowledgments This study was funded by the Ministry of HigherEducation, Vot No. 07/11/09/696FR. The provision of allowance Grad-uate Research Funding (GRF) by Universiti Putra Malaysia andMOHE Budget Mini Scholarship is gratefully acknowledged, as isthe valuable help from the Faculty of Environmental Studies andFaculty of Engineering, Universiti Putra Malaysia, in preparing bore-holes for this research and also for the lab analyses. Special thanks tothe Minerals and Geoscience Department Malaysia, Terengganu, forproviding helpful information about the geology of the study area.

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