ORI GIN AL PA PER

Characterization and source of fog water contaminantsin central India

Balram Ambade

Received: 13 June 2013 / Accepted: 29 September 2013 / Published online: 13 October 2013� Springer Science+Business Media Dordrecht 2013

Abstract In the present work, chemical characterization and sources of fog water con-

taminants in the most polluted area of central India, Raipur, and its surroundings are

described. The fog water (n = 22) was collected during 2010–2011 from six sites. The

physical (i.e., pH, fog amount, electrical conductivity and TDS) and chemical (i.e., F-,

Cl-, NO3-, SO4

2-, NH4?, Na?, K?, Mg2?, Ca2?, Al, Mn, Fe, Cu, Zn, Pb and Hg)

parameters of the fog water were investigated. The effect of meteorology, i.e., temperature,

humidity and wind speed, on the precipitation of the fog water contaminants is discussed.

The cluster and factor analysis are used to apportion the sources of the contaminants in the

fog water.

Keywords Fog water � Chemical characterization � Sources � Central

India

1 Introduction

Fogs are composed of fine droplets (&100 times smaller than raindrops) of water and

are highly enriched with the chemicals suspended in the lower troposphere (Krupa

2002). Fog is a natural phenomenon and is formed when condensation of water vapor

triggers aerosol particles as the atmospheric temperature decreases and relative

humidity increases. Fog is thus a multiphase atmospheric system where gaseous spe-

cies, liquid solution (droplet, aerosol) and dry particulate matter coexist and complex

interactions among phases during washout. In India, fog season starts in November and

ends in January, and it becomes moderate during Diwali festival days (Ambade and

Ghosh 2013). These droplets scatter the light and thus reduce the visibility near the

ground, decrease agricultural production and cause a serious health hazard (Biswas

B. Ambade (&)Department of Chemistry, National Institute of Technology, Jamshedpur 831014, Indiae-mail: bambade.chem@nitjsr.ac.in; bambade@gmail.com

123

Nat Hazards (2014) 70:1535–1552DOI 10.1007/s11069-013-0892-7

et al. 2008). A major factor contributing to fog is chemicals and radiative forcing

elements associated with the aerosols and resuspended soil dusts. Investigations into fog

chemistry and physics have become very important as nutrients and pollutants from fog

water exhibit strong influence on the ecosystems (Liu et al. 2005). Ion deposition is an

important source of contaminants in the fog water of the mountain–forest ecosystems

(Holder 2004; Patel et al. 2012). Fog water chemistry plays a very important role as it

may strongly influence atmospheric chemistry and air quality (Ambade 2012). Fog

processes are related regularly to some severe air pollution events, having severe

adverse effects on human health, such as the infamous London smog fog in 1952

(Wilkins 1954). Many studies show close relationships between chemical characteristics

of fog water and atmospheric pollutants. Giri et al. (2013) pointed out that the high

concentrations of sulfate aerosols in the Los Angeles region correlated significantly

with the occurrence of fogs. They analyzed the fog water sampled in Los Angeles and

Bakersfield and stated that the acidity of the fog water and sulfate, nitrate and

ammonium concentrations were very high and also that the interaction between

moisture and aerosol particles and the scavenging of gaseous nitrate were significant

processes distressing the chemical characteristics of fog water (Munger et al. 1983).

However, there are fewer studies on fog than on precipitation. This is because fog

occurs in limited areas and the collection of fog water is time-consuming. Few

investigations into the fog water chemistry in Asian countries have been reported, such

as in India (Ali et al. 2004; Kulshrestha et al. 2005; Lakhani et al. 2007), China (Liu

et al. 2005; Niu et al. 2010 and Japan (Igawa et al. 2002; Watanabe et al. 2006;

Aikawa et al. 2007; Ogawa et al. 2004; Okochi et al. 2007).

In the present work, contamination, variation, enrichment and sources of chemical

species (i.e., F-, Cl-, NO3-, SO4

2-, NH4?, Na?, K?, Mg2?, Ca2?, Al, Mn, Fe, Cu, Zn, Pb

and Hg) in the fog water of the most polluted region, central India (i.e., Raipur region), are

described. A characterization of the fog chemistry of this region is not available yet.

2 Materials and methods

2.1 Study area

Six cities, Raipur, Korba, Bilaspur, Akaltara, Rajnandgaon and Dongargarh, of central

India were selected for the proposed investigation since the geography, pollution source

and pollution-receptor areas of these cities are different (Fig. 1). The geographical

characteristics of the sampling locations are summarized in Table 1. Raipur is the

capital of Chhattisgarh State with a population of &2 million inhabitants. Several steel,

sponge iron and cement industries are situated in Raipur City. The biggest steel plant in

Asia is situated in Bhilai City, close to Raipur, &15 km in the NW direction. Bilaspur

is the second largest city in state with &1 million inhabitants. Rajnandgaon is the

fourth largest city in the state with inhabitants of &0.5 million. Several rice mills are

situated in and around these cities. Dongargarh City, with &0.1 million inhabitants, is

surrounded by hills and is one of the prominent pilgrim and tourist place in this area

mainly due to Bamleshwari temple situated at the top of the mountain &500 m from

the city. Akaltara is a town with &0.1 million inhabitants that lies near Bilaspur and

going to be polluted due to the operation of the Cement Corporation of India Ltd.

(CCI) cement plant of capacity 4 MT/year.

1536 Nat Hazards (2014) 70:1535–1552

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2.2 Collection of fog water

A passive collector that consists of a 2.5-m-tall PVC pipe of two horizontal disks 20 cm in

diameter framed vertically at a distance of 40 cm from each other and stretched into two

rows with nylon strings of 0.2 mm diameter was used for fog sampling (Skar _zynska et al.

2006). After collection, the water was filtered, and physical parameters, i.e., pH, electrical

Fig. 1 Geographical representation of sampling sites (scale in kilometers)

Table 1 Geographical information of study area

Sampling location Site Longitude and latitude Altitude (m) Environment

Raipur RSU campus 21�1304800N, 81�3704800E 298 I and U

Rajnandgaon Nandai Chowk 21�60000N, 81�104800E 307 U

Dongargarh Kankali Para 21�1018.300N, 80�4031.500E 355 SU

Bilaspur Telipara 22�502400N, 82�90000E 346 U

Akaltara Jawahar Nagar 22�101200N, 82�2504800E 283 SU

Korba Kusmunda 22�210000N, 82�4004800E 252 I

RSU Ravishankar Shukla University, I industrial, U urban, SU semi-urban

Nat Hazards (2014) 70:1535–1552 1537

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conductivity and TDS values, were measured. The sample was divided into two portions.

The first portion was used for the analysis of anions and cations, and the second was

acidified with a few drops of ultrapure nitric acid (E. Merck) for further analysis of the

metals. In total, 22 fog water samples from six locations, Raipur, Bilaspur, Korba, Ak-

altara, Rajnandgaon and Dongargarh, were collected during the year 2010–2011. Among

them, Raipur lies close (&15 km) to the industrial area and Bhilai steel plant.

The samples were kept in airtight 250-ml polyethylene bottles and refrigerated at 4 �C

for the further analysis.

Fog thickness (h) was calculated using the following equation:

h ¼ v=pr2

where, v and r represent the volume of fog water and radius of passive fog sampler,

respectively.

2.3 Analysis

pH and electrical conductivity values were measured using the Checkmate Analyzer.

Fluoride content was monitored with Metrohm ion meter-781 equipped with a fluoride ion

selective electrode and calomel electrode. The ion meter was calibrated with a standard F-

solution over a range of 2.0–25.0 mg/l containing acetate buffer in a 1:1 ratio (58 g NaCl

and 57 ml acetic acid with deionized water and neutralized with 5 M NaOH solution to pH

5.5 into final dilution of l l). Similarly, 10 ml of the sample solution was mixed with 10 ml

of buffer in a 50-ml plastic beaker in a 1:1 ratio, and F- content was measured.

The Dionex DX-120 Ion Chromatograph (Dionex Corporation, Sunnyvale, CA, USA)

equipped with an anion separation column (AS9-HC, 250 9 4 mm), cation separation

column (CS12A, 250 9 4 mm) and conductivity detector was used for the analysis of ions.

The Varian Liberty AX Sequential ICP-AES and Varian AA280FS Atomic Absorption

spectrophotometer equipped with VGA-77 (plasma flow 15 l/min, auxiliary flow 1.5 l/min,

power 1 kW, PMT voltage 650 V) were used for the analysis of metals. The GBC AAS-

935 equipped with HG-3000 was used for the analysis of Hg. E. Merck multi-element

standard solutions were used for the preparation of calibration curves.

Multivariate statistical analyses such as factor analysis (FA) and cluster analysis (CA)

were used to simplify and organize large data sets to provide meaningful insights (La-

aksoharju et al. (1999); Shresta and Kazama 2007). The statistical software STATISTICA

7.1 for Windows was used for multivariate statistical calculations.

3 Results and discussion

3.1 Physical characteristics of fog and meteorology

In the central India (Chhattisgarh), a thin layer of fog (&0.06 to 0.36 mm) precipitated in

the night (1800–0600 hours, 12 h/day) during the winter season in late November to early

March. It wetted the vegetation and ground beneath the canopy. The color of fog water was

generally yellowish, maybe due to the presence of high amounts of iron, manganese,

organic compounds, etc.

The physical characteristics of fog are presented in Table 2. Fog amount ranged from

0.06 to 0.36 mm with a mean value of 0.13 ± 0.03 mm. The highest fog amount

(&0.36 mm/day) was observed at Dongargarh. The values of pH, electrical conductivity

1538 Nat Hazards (2014) 70:1535–1552

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and TDS ranged from 5.00 to 7.51, 165 to 332 lS/cm and 87 to 183 mg/l, with a mean

value of 7.07 ± 0.40, 180 ± 22 lS/cm and 96 ± 14 mg/l, respectively. The volume-

weighted mean value of pH, electrical conductivity and TDS ranged from 6.08 to 7.51, 190

to 308 lS/cm and 102 to 183 mg/l, with a mean value of 6.90, 234 lS/cm and 133 mg/l,

respectively. Among them, the lowest pH value was observed in Korba due to the burning

of a huge amount of coal (&30 MT/year) for generating 38,000 MW electricity. The

highest values of conductivity and TDS were observed in Dongargarh due to the presence

of higher amount of ions.

In Raipur, temperature, humidity and wind speed during the study period ranged from 8

to 12 �C, 83 to 95 % and 2.0 to 4.0 km/h, with mean values of 10.0 ± 0.5 �C, 89 ± 2 %

and 2.5 ± 0.4 km/h, respectively. pH value of the fog has a significant correlation with

some anions, Cl- or SO42- (r = 0.34–0.41), and some metals, Al, Fe, Zn and Hg (r = -

0.33 to 0.49). It suggests that the acidity of the fog is mainly due to HCl and H2SO4, which

increase the metal content in the fog. Ambient temperature showed a significant correlation

with some species, e.g., Cl-, NO3-, SO4

2- and Al (r = 0.21–0.53). However, it exhibits a

significant negative correlation with some species, e.g., F-, NH4?, Fe and Hg (r = -0.35

to 0.41). Increasing the temperature increases the formation of the acids and decreases the

decomposition or hydrolysis of fluoride, ammonium and iron compounds. Humidity

showed a positive correlation (r = 0.09–0.47) with most of the species (except F-, NH4?,

Al and Fe) maybe due to their higher scavenging ability. Wind speed has a significant

Table 2 Physical characteristics of fog water

S. no. Date Location Fog amount (mm) pH Conductivity (lS/cm) TDS (mg/l)

1 28/29-11-2010 Raipur 0.07 6.43 165 87

2 06/07-12-2010 Raipur 0.08 7.16 210 105

3 07/08-12-2010 Raipur 0.09 7.42 183 97

4 10/11-12-2010 Raipur 0.09 6.31 178 89

5 11/12-12-2010 Raipur 0.12 6.97 180 91

6 18/19-12-2010 Raipur 0.14 6.93 193 123

7 19/20-12-2010 Raipur 0.15 6.71 196 92

8 22/23-12-2010 Raipur 0.17 7.36 322 178

9 30/31-12-2010 Raipur 0.13 6.72 239 158

10 01/02-01-2011 Raipur 0.11 7.29 238 173

11 08/09-01-2011 Raipur 0.09 7.34 254 152

12 15/16-01-2011 Raipur 0.08 6.87 261 148

13 28/29-01-2011 Raipur 0.07 6.76 201 120

14 02/03-02-2011 Raipur 0.06 6.52 261 140

15 01/02-02-2011 Rajnandgaon 0.15 7.26 219 111

16 03/04-02-2011 Dongargarh 0.36 7.51 308 183

17 02/03-02-2011 Bilaspur 0.13 7.17 250 135

18 14/15-02-2011 Akaltara 0.22 7.45 300 164

19 15/16-02-2011 Korba 0.10 5.00 190 101

20 01/02-01-2011 Korba 0.15 6.10 183 99

21 30/31-01-2011 Korba 0.18 6.41 172 87

22 15/16-02-2011 Korba 0.14 6.42 222 157

Nat Hazards (2014) 70:1535–1552 1539

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negative correlation (r = -0.26 to 0.60) with some species, e.g., Cl-, NO3-, SO4

2-,

NH4?, Mg2? and Mn. These species are emitted probably by local sources, and their

concentrations are diluted by an increase in air mass speed.

3.2 Chemical characteristics of fog

Chemical characteristics of the fog are summarized in Table 3. The sum of total con-

centration of 15 species (i.e., F-, Cl-, NO3-, SO4

2-, NH4?, Na?, K?, Mg2?, Ca2?, Al,

Mn, Fe, Zn, Pb and Hg), RS15, in 22 fog water samples from six sites ranged from 82 to

189 mg/l, with a mean value of 130 ± 13 mg/l. The highest concentration of the RS15 is

seen in Raipur in December 2010, which may be due to the accumulation of local pol-

lutants. The concentration (n = 22) of individual species, i.e., F-, Cl-, NO3-, SO4

2-,

NH4?, Na?, K?, Mg2?, Ca2?, Al, Mn, Fe, Zn, Pb and Hg, ranged from 1.1–2.9, 12.4–40.6,

10.5–26.4, 21.7–52.5, 1.9–8.7, 4.6–18.6, 1.8–23.3, 2.6–7.6, 8.5–25.5, 0.05–1.85,

0.15–3.06, 0.18–1.60, 0.05–0.16, 0.07–0.97 and 0.01–0.02 mg/l, with mean values of

1.9 ± 0.6, 25.7 ± 0.3, 14.9 ± 2.1, 39.0 ± 3.1, 4.7 ± 1.5, 9.8 ± 2.7, 10.8 ± 2.7,

5.1 ± 1.1, 14.6 ± 2.2, 0.83 ± 0.12, 1.43 ± 0.14, 0.91 ± 0.16, 0.09 ± 0.01, 0.19 ± 0.01

and 0.010 ± 0.002 mg/l, respectively. The volume weighted mean (VWM) concentration

of F-, Cl-, NO3-, SO4

2-, NH4?, Na?, K?, Mg2?, Ca2? Al, Mn, Fe, Zn, Pb and Hg ranged

from 1.4–2.4, 12.4–33.1, 10.5–23.8, 21.7–116, 2.8–8.2, 4.6–33.7, 4.8–22.4, 2.6–6.7,

8.5–18.5, 0.57–1.03, 1.04–2.33, 0.56–1.56, 0.05–0.12, 0.07–0.97 and 0.004–0.013 mg/l,

with mean values of 2.0 ± 0.2, 23.3 ± 7.0, 16.3 ± 4.6,45.9 ± 28.2, 4.8 ± 1.4,

11.8 ± 8.7, 11.1 ± 4.8, 4.6 ± 1.3, 14.0 ± 3.4, 1.01 ± 0.12, 1.37 ± 0.14, 0.94 ± 0.15,

0.09 ± 0.01, 0.44 ± 0.01 and 0.010 ± 0.002 mg/l, respectively.

The ratios of the sum of total equivalent concentrations of anions to cations [Ranion/

Rcation] at the six sites were found to be 0.91, 0.95, 0.80, 0.94, 0.78 and 1.03, respectively,

suggesting that all fog waters are being alkaline in nature due to the presence of higher

Ca2? content.

3.3 Variations

The monthly variations of chemical species in the fog at Raipur and Korba are given in

Figs. 2a, 3a. The highest concentration of all ions was observed in the months of December

and January, mainly due to the lowest wind speed, &2 km/h. The lowest concentration of

the ions was observed in the month of February 2011 due to twofold increase in the wind

speed, &4 km/h. This suggests that the ions are mainly contributed by the local sources.

However, in the case of metals, a relatively higher concentration was observed in the

month of February, mainly due to the blown soil dusts (Figs. 2b, 3b).

The spatial variation of ions and metals in the fog is shown in Fig. 4. The highest

content of the sum of 9 ions was observed in Raipur and Dongargarh, maybe due to a larger

number of emission sources and higher fog precipitation, respectively (Fig. 4a). In turn,

higher metal content was observed in Akaltara, which may be due to the cement plant

(Fig. 4b). Among them, SO42- showed the highest content in all six sites, which may be

due to the huge amount of coal burnt in these regions. The common distribution pattern of

ions is in the following order: SO42- [ Cl- [ NO3

- [ Ca2? [ K? [ Na? [ Mg2?

[ NH4?. A higher content of Cl-, Na? and K? are expected due to the burning of a huge

amount of solid fuel (i.e., coal and biomass) in these regions. Similarly, a large number of

thermal processes (fuel burning, combustion, smelting, roasting, etc.) occurring in these

regions are responsible for the higher nitrate content. Several cement and steel plants

1540 Nat Hazards (2014) 70:1535–1552

123

Ta

ble

3C

hem

ical

char

acte

rist

ics

(mg/l

)o

ffo

gw

ater

S.

no

.F

-C

l-N

O3

-S

O4

2-

NH

4?

Na?

K?

Mg

2?

Ca2

?A

lM

nF

eZ

nP

bH

g

11

.40

25

.41

2.0

42

.93

.21

3.6

12

.86

.21

8.4

0.8

10

.85

0.5

60

.08

0.0

90

.01

22

.20

28

.81

4.4

43

.34

.81

2.5

11

.45

.81

4.6

0.3

60

.15

0.3

80

.08

0.1

00

.01

31

.20

22

.41

1.8

42

.72

.76

.31

2.4

4.7

8.8

0.6

00

.59

0.1

90

.07

0.0

90

.01

42

.30

40

.62

6.4

51

.35

.81

4.3

23

.35

.81

6.8

0.1

81

.30

0.5

80

.10

0.1

20

.02

51

.60

31

.12

1.7

52

.51

.97

.21

0.9

7.6

17

.50

.30

3.0

61

.08

0.0

60

.07

0.0

0

62

.20

39

.41

4.8

52

.18

.71

8.6

6.4

6.3

17

.50

.50

2.6

41

.12

0.0

70

.09

0.0

1

71

.80

23

.71

3.7

39

.66

.91

7.1

11

.54

.51

5.4

1.8

51

.20

0.3

10

.08

0.0

80

.01

81

.50

31

.61

5.8

47

.26

.25

.41

1.1

5.4

17

.80

.70

0.2

30

.42

0.0

90

.08

0.0

1

92

.60

34

.31

8.7

49

.35

.81

3.4

19

.06

.22

5.5

1.1

71

.71

1.3

50

.11

0.1

20

.01

10

1.8

02

6.3

13

.04

1.6

4.2

7.0

1.8

4.5

8.8

0.0

52

.45

1.6

00

.06

0.0

70

.01

11

2.2

02

9.4

16

.74

4.7

5.2

10

.61

2.8

5.2

10

.70

.22

1.3

20

.18

0.1

20

.13

0.0

1

12

2.9

02

6.0

13

.94

1.5

5.6

8.3

13

.65

.61

9.1

0.7

41

.86

1.4

50

.08

0.1

00

.01

13

2.8

02

4.9

15

.73

9.9

4.4

8.5

10

.16

.71

3.7

0.6

51

.64

1.4

10

.06

0.0

90

.02

14

2.3

02

9.3

14

.63

7.7

6.5

14

.69

.54

.71

6.3

0.8

90

.90

0.7

20

.13

0.1

40

.02

15

1.3

71

2.4

10

.52

6.0

3.3

5.0

7.2

3.1

13

.40

.76

1.0

41

.31

0.0

50

.68

0.0

1

16

1.9

72

4.5

12

.74

2.6

4.0

15

.51

4.8

5.6

19

.31

.53

1.1

30

.71

0.1

10

.97

0.0

1

17

1.1

16

.61

1.6

21

.94

.65

.26

.33

.09

.00

.97

1.1

70

.67

0.1

20

.11

0.0

1

18

1.7

31

8.8

11

.42

1.7

2.8

4.6

8.2

3.7

8.5

1.2

72

.33

1.5

60

.08

0.7

60

.01

19

1.6

71

4.2

11

.53

2.0

4.4

7.0

9.4

4.4

14

.70

.96

1.2

41

.51

0.1

30

.08

0.0

2

20

2.2

73

3.1

23

.24

3.8

5.2

10

.41

2.5

5.9

18

.00

.97

1.1

70

.67

0.1

00

.12

0.0

1

21

1.9

71

4.5

12

.72

2.6

4.0

5.5

4.8

2.6

9.3

1.5

31

.13

0.7

10

.09

0.1

10

.01

22

1.7

31

8.8

11

.42

1.7

2.8

4.6

8.2

3.7

8.5

1.2

72

.33

1.5

60

.16

0.0

80

.01

Nat Hazards (2014) 70:1535–1552 1541

123

operating in these regions are responsible for the higher alkaline earth metal content in the

fog water.

3.4 Correlation and enrichment

The correlation matrix of ions and metals is presented in Table 4. All anions and cations

among themselves have significant-to-excellent correlation (r = C0.36), suggesting their

common origin in fog water. The Al and Fe content has a significant positive correlation

with Cl- and Mn (r = 0.54 and r = 0.67, respectively). Zn, Pb and Hg content has partial-

to-good correlation with almost all ions and metals (except Al, Mn and Fe).

Calcium and aluminum are used as reference elements for the evaluation of enrichment

factors (EFs) in order to evaluate enrichment or depletion of the crustal sources (Larssen and

Carmichael 2000). The average composition of upper crust was used as crustal reference

material (Larssen et al. 2006). The enrichment is defined using the following equations:

EFca ¼ ½x�=½Ca2þ�� �

fog= ½x�=½Ca2þ�� �

crust

EFcrust ¼ ½x�=½Al�ð Þfog= ½x�=½Al�ð Þcrust

where x denotes the concentration of the species of interest in the fog and crustal material,

respectively.

Fig. 2 Monthly variation of ions and metals in Raipur

1542 Nat Hazards (2014) 70:1535–1552

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EFcrust values for the ions and metals are presented in Table 5, which are grouped into

three categories: non-enriched, moderately enriched and highly enriched, as follows:

1. All ions are moderately enriched with respect to Ca2?.

2. Fe, and Zn, Pb and Mn are poorly and moderately enriched with respect to Al,

respectively.

3. K?, Mg2? and Ca2? are highly enriched with respect to Al.

F-, Cl-, NO3-, SO4

2-, NH4?, Na?, K?, Mg2? and Ca2? are highly enriched, which

may be largely due to anthropogenic sources, i.e., coal burning, mineral roasting, industrial

emissions,. while other elements, i.e., Mn, Fe, Cu, Zn, Pb and Hg, are poorly to moderately

enriched, more or less due to dusts.

3.5 Statistical analysis

Cluster analysis was applied to find out the similarity in groups between the sampling

stations. The spatial variability of fog water quality in the whole study area was determined

from CA, using the linkage distance, reported as Dlink/Dmax, which represents the quotient

between the linkage distances for a particular case divided by the maximal linkage dis-

tance. The quotient is then multiplied by 100 as a way to standardize the linkage distance

Fig. 3 Monthly variation of ions and metals in Korba

Nat Hazards (2014) 70:1535–1552 1543

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represented on the y-axis (Wunderlin et al. 2001; Simeonova et al. 2003; Singh et al. 2004,

2005). It resulted in a dendrogram that groups the twenty-two sampling stations into two

statistically meaningful clusters at (Dlink/Dmax) 9 100 = 30 (Fig. 5). Cluster 1 contains (9

observations) the sampling sites numbered 8, 9, 10, 11, 12 and 14, which are located in

Raipur (industrial zone), and the sampling sites numbered 16, 17 and 18, which are located

in urban areas. Cluster 2 contains the sampling sites numbered 1–7, 13, 15 and 19–22 (13

observations), of which some are located in industrial zones (1–7 and 13 in Raipur, and

19–22 in Korba), and the sampling site numbered 15, which is located in urban areas. In

cluster 2 (right side), the sampling stations join together in a cluster at a smaller distance

than those in cluster 1 (left side), indicating that the stations in cluster 2 are more similar to

each other than those in cluster 1. At (Dlink/Dmax) 9 100 = 12, cluster 1 and cluster 2 each

are divided into two subgroups forming a total of four groups. Table 6 shows the summary

statistics of clusters 1 and 2. CA revealed three groups of variables (Fig. 6). Group I

contained TDS and EC, which correspond to the mineralization of fog water. Group II has

major cations (i.e., Ca2?, Na? and K?) and anions (i.e., Cl- and SO42-). Group II reflects

the atmospheric deposition of evaporated compounds. Group III contains metals (i.e., Pb,

Hg, Zn, Al, Fe, Mn and Mg2?), NH4? and pH. Group III probably characterizes an

atmospheric pollution due to industrial activities. In group III, pH is a controlling factor of

Mg 2? and NH4? concentrations in fog water. A high fog amount would correspond to high

metal concentrations in fog water samples (Figs. 7, 8).

Fig. 4 Spatial variations of fog water constituents

1544 Nat Hazards (2014) 70:1535–1552

123

Tab

le4

Corr

elat

ion

mat

rix

of

fog

wat

erel

emen

ts

F-

Cl-

NO

3-

SO

42

-N

H4

?N

a?K

?M

g2?

Ca2

?A

lM

nF

eZ

nP

bH

g

F-

1.0

0

Cl-

0.6

61

.00

NO

3-

0.9

10

.79

1.0

0

SO

42

-0

.60

0.3

90

.59

1.0

0

NH

4?

0.6

80

.45

0.6

70

.92

1.0

0

Na?

0.6

00

.36

0.5

71

.00

0.9

11

.00

K?

0.5

50

.52

0.6

50

.94

0.8

50

.91

1.0

0

Mg

2?

0.4

90

.79

0.7

00

.62

0.6

70

.57

0.8

01

.00

Ca2

?0

.47

0.6

10

.67

0.5

00

.67

0.4

40

.62

0.8

61

.00

Al

0.0

00

.30

-0

.03

-0

.03

-0

.08

-0

.02

-0

.08

-0

.35

-0

.31

1.0

0

Mn

-0

.08

0.0

0-

0.0

60

.00

-0

.08

0.0

0-

0.0

20

.00

-0

.18

0.0

11

.00

Fe

-0

.23

0.1

6-

0.1

40

.00

-0

.01

0.0

00

.02

0.0

0-

0.0

40

.03

0.4

11

.00

Zn

0.9

10

.45

0.7

80

.38

0.5

20

.38

0.3

10

.28

0.3

60

.01

-0

.24

-0

.41

1.0

0

Pb

0.7

40

.32

0.5

90

.17

0.2

00

.18

0.1

30

.09

0.0

90

.09

-0

.06

-0

.35

0.8

31

.00

Hg

0.5

40

.28

0.3

40

.69

0.6

30

.72

0.5

20

.25

0.1

4-

0.0

2-

0.0

2-

0.0

20

.37

0.2

11

.00

Nat Hazards (2014) 70:1535–1552 1545

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Factor analysis was applied in the matrix of 22 9 19 variables and 22 observations

(sampling sites) using the varimax rotation. Data were autoscaled, and each column

(parameter) has zero mean and unit variance. Six factors were extracted, which account for

83.05 % of the cumulative variance. Factor loadings are thus classified as ‘‘strong,’’

‘‘moderate’’ and ‘‘weak,’’ corresponding to absolute loading values of [0.75, 0.75–0.50

and 0.50–0.30, respectively.

Factor 1 accounts for 29.58 % of the total variance, and it is strongly and positively

loaded with acid anions and alkaline cations and moderately loaded with a positive value

for K?. Factor 1 indicates the source of major ions that could be evaporated such as NaCl,

KCl, CaSO4, MgSO4 and (NH4)2SO4 (Table 7).

Table 5 Enrichment factor of metals and ions

Species EfAl EfCa

Raipur Korba Raipur Korba

Na 1.5 4.4

K 870 1,600 4.3 6.7

Mg 2,970 3,380 3.5 4.5

Ca 2,200 2,430 1.5 4.4

Mn 150 160

Fe 2 3

Zn 11 12

Pb 35 50

NH4? 16.5 44

F- 6.1 4.3

Cl- 11.1 9.2

NO3- 3.5 3.2

SO42- 6.1 4.3

Fig. 5 Dendrogram of CA for fog water samples

1546 Nat Hazards (2014) 70:1535–1552

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Table 6 Summary of the cluster statistical descriptive

Parameter Cluster 1 (n = 9) Cluster 2 (n = 13)

Median Min Max SD_median Median Min Max SD_median

Fa 0.13 0.06 0.36 0.09 0.10 0.07 0.15 0.03

pH 7.29 6.52 7.51 0.35 6.71 5.00 7.42 0.78

EC 261.00 238.00 322.00 31.32 190.00 165.00 219.00 14.21

TDS 158.00 135.00 183.00 16.83 99.00 87.00 123.00 11.20

F- 1.97 1.10 2.90 0.56 1.80 1.20 2.80 0.46

Cl- 26.30 16.60 34.30 5.75 24.90 12.40 40.60 9.13

NO3- 13.90 11.40 18.70 2.44 13.70 10.50 26.40 5.11

SO42- 41.60 21.70 49.30 10.15 42.70 21.70 52.50 10.65

NH4? 5.20 2.80 6.50 1.19 4.40 1.90 8.70 1.87

Na? 8.30 4.60 15.50 4.26 8.50 4.60 18.60 4.74

K? 11.10 1.80 19.00 5.06 10.90 4.80 23.30 4.51

Mg2? 5.20 3.00 6.20 1.02 5.80 2.60 7.60 1.48

Ca2? 16.30 8.50 25.50 6.02 14.70 8.50 18.40 3.52

Al 0.89 0.05 1.53 0.48 0.76 0.18 1.85 0.49

Mn 1.32 0.23 2.45 0.71 1.20 0.15 3.06 0.82

Fe 0.72 0.18 1.60 0.53 0.71 0.19 1.56 0.48

Zn 0.11 0.06 0.13 0.02 0.08 0.05 0.16 0.03

Pb 0.12 0.07 0.97 0.34 0.09 0.07 0.68 0.16

Hg 0.01 0.01 0.02 0.00 0.01 0.00 0.02 0.01

Fa Fog amount

Dendrogram of 19 Variables Ward's method

Euclidian distances

TDSEC

K+

Na+Ca2+

NO3-SO4

2-

Cl-Mg2+

NH4+pH

FeAl

MnF-

PbHg

ZnF. a.

0

20

40

60

80

100

120

(Dlie

n/D

max

)*10

0

Group IGroup II Group III

Fig. 6 Dendrogram of CA for variables

Nat Hazards (2014) 70:1535–1552 1547

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Factor 2 accounts for 17.27 % of the total variance. EC and TDS recorded strong

positive loadings of 0.93 and 0.94 for factor 2, respectively, and they are identified as the

mineralization of fog water.

Factor 3 accounts for 12.48 % of the total variance. Metals such as Zn and Hg recorded

moderate and strong positive loadings of 0.72 and 0.77, respectively. Factor 3 characterizes

the impact of industrial activities related to the burning process.

Factor 4 accounts for 9.94 % of the total variance. Metals such as Fe and Mn recorded

strong negative loadings of -0.87 and -0.91, respectively. Factor 4 characterizes the

impact of another type of industrial activity related to atmospheric emissions. Thus, Fe and

Mn are not emitted from the same source as Zn, Al and Hg.

Factor 5 accounts for 8.12 % of the total variance and is strongly and positively cor-

related with Al and fog amount, for which the loading values are the same (0.81). Factor 5

is identified also as the impact of industrial activity of atmospheric emissions. The thicker

the fog, the higher will be the Al content in the fog water. This can suppose a primordial

role of aerosol in the transport of Al.

Fig. 7 Loading plots of factors 1–3

1548 Nat Hazards (2014) 70:1535–1552

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Factor 6 accounts for 5.64 % of the total variance and is loaded strongly with NH4?

(positive loading, 0.88) and moderately Na? (positive loading, 0.72). Factor 6 character-

izes ammonia emissions possibly in the neighboring areas and the same source for Na? and

NH4? (see Table 7) with the correlation coefficient of 0.56 and 0.63 between NH4

?–Cl-

and Na?–Cl-, respectively.

3.6 Comparison of fog composition

Comparison of composition of ions in the fog water at Agra, Delhi, Chile, Milesovka and

Ecuador is presented in Table 8. Fog composition is an indicator of lower tropospheric dust

pollution. The higher load of ions, i.e., Cl-, NO3-, SO4

2-, NH4?, Na?, K?, Mg2? and

Ca2?, in the fog water in the central India is observed largely due to higher particulate

matter content in the air.

Fig. 8 Loading plots of factors 4–6

Nat Hazards (2014) 70:1535–1552 1549

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Table 7 Factor loading values and explained variance of fog water quality parameters

Parameter Factor 1 Factor 2 Factor 3 Factor 4 Factor 5 Factor 6

Fa 0.02 0.44 -0.15 -0.04 0.81 -0.07

pH 0.12 0.70 -0.56 0.17 -0.04 -0.06

EC -0.09 0.93 0.09 0.05 0.21 0.04

TDS -0.03 0.94 0.04 -0.16 0.09 0.12

F- 0.49 0.11 0.38 -0.39 -0.15 0.40

Cl- 0.81 0.10 -0.11 0.02 -0.26 0.37

NO3- 0.83 -0.15 0.08 -0.02 -0.20 -0.04

SO42- 0.83 0.04 -0.29 0.10 -0.25 0.30

NH4? 0.20 0.13 0.19 0.09 -0.14 0.88

Na? 0.51 -0.10 -0.03 0.17 0.19 0.72

K? 0.83 -0.02 0.29 0.29 0.16 -0.09

Mg2? 0.85 -0.04 -0.26 -0.12 -0.16 0.14

Ca2? 0.74 0.01 0.05 -0.04 0.26 0.36

Al -0.32 -0.15 0.25 0.03 0.81 0.18

Mn 0.08 -0.06 -0.27 20.87 0.01 -0.04

Fe -0.17 0.08 0.13 20.91 0.04 -0.13

Zn -0.05 -0.01 0.72 0.09 0.21 -0.03

Pb -0.09 0.49 -0.08 -0.04 0.68 -0.23

Hg 0.00 0.00 0.77 0.05 -0.24 0.20

Eigenvalue 5.62 3.28 2.37 1.89 1.54 1.07

% Variance 29.58 17.27 12.48 9.94 8.12 5.64

% Cumulative variance 29.58 46.85 59.33 69.28 77.40 83.05

Bold values represent high value either it may high positive or high negetive, both values were highlighted

Fa Fog amount

Table 8 Comparison of fog water ion concentration (leq/l) at various locations

Species Present work Agra (14) Delhi (6) Chile (24) Milesovka (10) Ecuador (7)

Raipur Korba

pH 6.95 6.08 7.2 6.61 4.73 3.2 4.42

F- 117 140 74.1 – 20 – –

Cl- 845 879 382 50 69.9 810 9.2

NO3- 259 383 494 11.6 522.6 390 40.1

SO42- 946 2,411 691 16.3 545.6 1,200 42.6

NH4? 296 457 1,700 307 732.8 100 64.2

Na? 490 1,465 175 50 70.9 880 19.8

K? 301 576 235 7 54.6 35 12.5

Mg2? 471 558 146 20 51.7 220 6.0

Ca2? 805 925 338 120 158.5 150 13.6

1550 Nat Hazards (2014) 70:1535–1552

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4 Conclusion

The fog leaches out the particulate matters from the lower troposphere. The increasing

urbanization and industrialization remarkably enhances the fog contamination. The content

of ions is decreased as the air mass speed is increased, while the reverse trend is observed

for the metals. Six sources for the fog contamination are identified. Contamination of ions

Na?, K?, Mg2?, Ca2?, NH4?, Cl- and SO4

2- is due to evaporation of NaCl, KCl, CaSO4,

MgSO4, and (NH4)2SO4. EC and TDS are computed due to mineralization of fog water.

The sources of the metals Fe, Mn, Zn, Pb and Hg are different industrial activities, i.e., coal

burning, steel and sponge iron production. Ammonia contamination is mainly due to the

natural emissions. Al contamination is related to the fog amount and due to the weathering

of the soil dust Al.

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