Temporal Distribution of Dissolved Trace Metal inthe Coastal Waters

of Southwestern Bay Of Bengal, IndiaR.K. Padhi1*, S. Biswas1, A.K. Mohanty1, R.K. Prabhu2, K.K. Satpathy1, L. Nayak3

ABSTRACT: The objective of the present study was to characterize

the concentrations of selected dissolved trace metals in the coastal

waters (500 m from shore) of Kalpakkam, Tamil Nadu, India. The order

of dissolved concentration of these metals was found to be as follows: Co

(cobalt) , Cd (cadmium) , Cr (chromium) , Mn (manganese) , Cu

(copper) , Ni (nickel) , Pb (lead) , Zn (zinc). The levels of these trace

metals were found to be relatively low as compared to the reported

values for other Indian coastal waters, which indicates negligible

pollution at this location. Cadmium was the only metal found to

increase its concentration during the monsoon period, suggesting its

allochthonous input. Factor analysis indicated that chromium, nickel,

zinc, cobalt, copper, manganese, and lead were of common origin, and

external inputs through land runoff had nominal or little impact,

typifying in-situ regeneration and remineralization linkage with their

temporal variation. However, levels of zinc, cobalt, and copper remained

relatively high during the summer period, and abrupt increases in their

concentration during December (monsoon season) may be due to their

dual (autochthonous as well as allochthonous) input. Water Environ.

Res., 85, 696 (2013).

KEYWORDS: trace metals, coastal water, factor analysis, east coast of

India, nuclear power plant.

doi:10.2175/106143012X13560205144975

IntroductionCoastal environments receive numerous contaminants, ema-

nating both from nearby anthropogenic activities and from more

distant points of origin. Coastal zones support large-scale

fisheries, serve as important avenues for transportation, and

host a range of commercial/industrial enterprises; these

activities can deposit a variety of pollutants (Liang et al.,

2010). Among the various contaminants in coastal zones, trace

metals pose the most serious concerns for marine systems due to

their toxicity, tenacity, biogeochemical cycling, and ecological

risks. Numerous biogeochemical and sedimentological processes

that occur in coastal zones cause them to act both as sink and

source for trace metals’ transport into sea water. Many trace

metals, once entered into water systems, are accumulated by

marine invertebrates, associated with particulates, and removed

to a great extent by adsorption onto sediments. A small

proportion is left in water as suspended or soluble complexes.

These accumulated trace metals subsequently get released into

the overlying water column even long after the cessation of

direct discharges, either as a result of physical disturbance or

sediment digenesis (Rainbow, 2007). Various effects of pollution

on marine organisms have been reviewed by Reish et al. (2005).

Trace metals in coastal waters display a sharp decline in their

concentration within a short distance from shore, due to the

physical mixing/advective processes, along with particle scav-

enging, in the dynamic coastal water. Their enrichment in

coastal water appears to be greatly influenced by the local

hydrography and external inputs (terrestrial, anthropogenic, and

sedimentary) and do not tend to correlate well with nutrients

(Gavriil and Angelidis, 2005). The extremely dynamic and

complex nature of these elements in the coastal zone, and the

fact that both natural and anthropogenic sources have similar

biogeochemical pathways, complicate the understanding of their

spatial distribution patterns (Chester and Murphy, 1990).

Relatively high concentrations and extremely variable composi-

tions of organic matter in coastal waters further obscure the

partitioning processes of trace metals between their dissolved

and particulate phases, thereby affecting their transport,

behavior, and bioavailability (Chester and Murphy, 1990). An

intensive study on the temporal and spatial distribution of trace

metals, on both a local and regional scale and with the highest

level of analytical precision, is a vital need, in order to accurately

decipher the effects of local hydrology on trace metals’ fate,

transport, and bioavailability in marine systems.

The present study is focused on the Kalpakkam coast of Tamil

Nadu, India, which has become an intense hub of industrial

activities and witnessed a substantial increase in mechanized

fishing boats, coupled with a phenomenal increase in motorized

vehicles, in the last decade. The study site is influenced by the

polluted freshwater input from the historic Buckingham canal

through two backwater channels. Trace metal contamination of

this canal has been assessed by Jayprakash et al. (2012). A study

on the various physicochemical and biological aspects of

Kalpakkam coastal waters has been carried out by Satpathy et

al. (2010a). Trace metal concentrations in the edible fish from

the same location have been investigated in a recent work

(Biswas et al., 2012). In this paper, the authors’ goal was to study

1 Environment & Safety Division, Radiological Safety & EnvironmentalGroup, IGCAR, Kalpakkam, Tamil Nadu, India-6031022 MPCS, Material Chemistry Division, Chemistry Group, IGCAR,Kalpakkam, Tamil Nadu, India-6031023 P.G. Dept. of Marine Sciences, Berhampur University, Berhampur,Odisha, India-760007

* Tel.: þ91-4427480500 (Ext. 23483); Fax: þ91-4427480235; email:ranjib@igcar.gov.in.

696 Water Environment Research, Volume 85, Number 8

the distribution and seasonal variation pattern of the trace

metals in order to understand their source, enrichment patterns,

and localized influence. In addition to the pollution introduced

by the canal, the sampling site is also the cooling water intake

point for a nuclear power plant, which draws in copious amount

of seawater daily for the heat transfer process, and discharges it

again into the sea. Furthermore, another nuclear power plant

will be operational at this location in the near future; this study

will therefore provide benchmark data for future impact

assessment. This study will further help to shed light on the

public perception of contamination from the nuclear power

plant, due to the treated cooling water discharge into the coastal

waters.

Materials and MethodsDescription of Study Area. The study site (120330N, 800110E) is

located on the southeast coast of India, and is in close proximity

to a nuclear power plant (the Madras Atomic Power station,

known as MAPS), as well as a desalination plant at Kalpakkam,

situated about 80 km south of Chennai (Figure 1). The sampling

site is influenced by both the cooling water discharge from the

atomic power plant and discharge effluents from the desalina-

tion plant. Moreover, the polluted Buckingham canal, which

carries domestic, industrial, and agricultural runoff along with

untreated municipal waste water from the Chennai metropolitan

area and adjacent small coastal towns, runs parallel to this coast.

The coastal water receives these polluted effluents at both side of

sampling site through two backwater channels. Of the two

backwaters, one (Sadras) is open to the coast only during the

monsoon period, while the other (Edaiyur) remains connected to

the sea throughout the year, due to dredging activities. The

Sadras backwater channel receives the domestic discharge of the

Kalpakkam township, which is a clear source of its pollution

content. The township of Kalpakkam has a population of about

50,000. Two villages inhabited by fishermen are located on

adjoining sides of the township, both having a sizable

Figure 1—Map of study area showing sampling location.

Padhi et al.

August 2013 697

population. The Edaiyur backwater channel, however, does not

have any clear point source anthropogenic influences. However,

a large number of aquaculture farms have been established along

the Buckingham canal, and thus have affected the water quality

significantly. Moreover, a large number of small industries have

developed in the entire belt; because of this increase in industrial

activity, associated anthropogenic input into this body of water

has also increased. Regarding the region’s climatology, this area

experiences three seasons: (1) the post-monsoon/summer

season (February–May), (2) the pre-monsoon or southwest

monsoon season (June–September), and (3) the northeast

monsoon season (October–January). The northeast monsoon

is active in this part of the peninsular India contributing ~ 65%

of the yearly rainfall. During this season, the freshwater input to

the coastal water, through many intermittent streams, is

significant. The wind pattern that prevails in the area is seaward

during the post-monsoon/summer season and landward during

the northeast monsoon season. Atmospheric transport thus

delivers a wide range of contaminants to this coastal area during

the post-monsoon/summer season.

Sample Collection and Preservation. The sampling of surface

seawater was carried out monthly (February 2010 to January

2011) at a fixed location at the MAPS jetty (the cooling water

intake point for MAPS) (Figure 1). The samples were collected in

polyethylene bottles previously cleaned with ultrapure nitric acid

(2 N) and Milli-Q water. Shortly after collection, samples were

filtered through pre-cleaned and pre-weighed 0.45lm cellulose

nitrate membrane filter paper, and then analyzed for various

physicochemical parameters. The filtered samples were acidified

with ultrapure nitric acid to a pH of about 2, and stored in acid-

cleaned polyethylene bottles for dissolved trace metal analysis.

Samples were treated for the elimination of salt matrixes and put

through a trace metal pre-concentration process; the final acid

extracts were analyzed for trace metals by Inductively Coupled

Plasma Mass Spectrometry (ICP-MS; Perkin-Elmer model,

Sciex, Elan 250) within a month of sample collection. The

measurements were carried out both in medium- and high-

resolution mode to avoid spectral interference. Gallium and

rhodium were used as internal standards, for low- and high-

mass elements, respectively, to correct instrumental drift during

analytical runs. Along with each set of samples, Milli-Q water

treated in the same way was analyzed in order to manage

method blank. The quality assurance of the analytical results was

controlled with the use of the following reference materials:

CASS-5 (Coastal Seawater for Dissolved Metals) and NASS-6

(Seawater for Dissolved Metals) obtained from the National

Research Council, Canada. The observed percentages of

recovery for different metals were as follows: chromium: 78.4

6 3.2, manganese: 88.7 6 3.5, cobalt: 78.2 6 3.6, nickel: 80.9

6 4.8, copper: 84.3 6 1.2, zinc: 104.5 6 2.7, cadmium: 79.1 6

2.7, and lead: 85.8 6 4.6 (Table 1). All the samples were analyzed

twice, and the average values are represented in the manuscript.

Matrix Elimination and Trace Metal Pre-Concentration.

Seawater and other high-ionic-strength matrices pose numerous

analytical challenges, which are attributed to variety of causes,

including low trace element concentrations combined with

contamination issues and a plethora of matrix interferences. A

number of methods have been developed to address this

problem. In this study, the sodium form of chelex-100 resin

(analytical grade, 200–400 mesh, Bio-Rad Laboratories, Rich-

mond, California) was used for the trace metals pre-concentra-

tion and seawater matrix cleaning (Censi et al., 2006; Gavriil and

Angelidis, 2005). Prior to use, the resin was equilibrated with

Milli-Q water for 24 hours and cleaned with ultrapure 2N nitric

acid. A 10% suspension reagent of chelex-100 was prepared with

Milli-Q water, and a pH of 5.5 to 6.0 was maintained with 1 M

ammonium acetate buffer. The pH of the acidified sea water

sample was adjusted to 5.5 to 6.0 with 1 M ammonium acetate

buffer just before the pre-concentration process. 200ll of

chelex-100 suspension was added to 50 ml of each sample in a

centrifuge tube. The mixture was shaken vigorously, followed by

continuous moderate circular shaking (50 rpm) for three hours

by a mechanical shaker. The resultant solution was centrifuged

at 5000 rpm for 15 minutes, to cause the chelex-metal complex

to form a compact bead at the bottom of the centrifuge tube.

The supernatant was carefully discarded and the chelex bead

was sequentially washed with 5 ml of 1 M ammonium acetate

and 10 ml of Milli-Q water. Each wash was followed by

centrifugation and removal of the supernatant liquid, without

disturbing the chelex-metal complex bead at the bottom of

centrifuge tube. Then trace metals were extracted from the

complex bead with 5 ml of 2N nitric acid and analyzed by ICP-

MS.

Statistical Analysis. Correlation analysis was performed to

evaluate the relationships between all measured parameters.

Factor analysis was carried out, applying the varimax rotation

technique, to facilitate easier interpretation. The above statistical

analyses were carried out by using XLStat Pro.

Results and DiscussionPhysico-Chemical Properties of Water. Data on the physico-

chemical character of the studied coastal water are presented in

Figure 2. The pH values varied from 7.9 to 8.3, with the lowest

value measured in January 2011. The variation in pH values,

Table 1—Analytical results for heavy metals in seawater CRMs.

Metal

Certified values (lg/l) Observed values (lg/l)

Recovery (%)CASS-5 NASS-6 CASS-5 NASS-6

Cr 0.106 6 0.013 0.118 6 0.008 0.086 6 0.010 0.089 6 0.009 78.4 6 3.2Mn 2.62 6 0.20 0.530 6 0.050 2.416 6 0.217 0.452 6 0.036 88.7 6 3.5Co 0.095 0.015 0.078 6 0.005 0.011 6 0.001 78.2 6 3.6Ni 0.330 6 0.023 0.301 6 0.025 0.283 6 0.025 0.229 6 0.025 80.9 6 4.8Cu 0.380 6 0.028 0.248 6 0.025 0.325 6 0.023 0.206 6 0.016 84.3 6 1.2Zn 0.719 6 0.068 0.257 6 0.020 0.0771 6 0.092 0.262 6 0.029 104.5 6 2.7Cd 0.0215 6 0.0018 0.0311 6 0.0019 0.018 6 0.002 0.024 6 0.002 79.1 6 2.7Pb 0.011 6 0.002 0.006 6 0.002 0.010 6 0.001 0.005 6 0.001 85.8 6 4.6

Padhi et al.

698 Water Environment Research, Volume 85, Number 8

limited to the short monsoon season, is attributed to the

freshwater input into the coastal zone (Hatje et al., 2003). The

neutral-subalkaline environment at this pH substantially limits

trace metal mobility in marine water (Manta et al., 2002). No

significant correlation between pH levels and heavy metal

concentrations could be observed (Table 3). Owing to the

narrow variation, it has little importance on the seasonality of

dissolved trace metal distributions. The dissolved oxygen

content varied between 5.25 and 8.41 mg l�1. An increase in

the dissolved oxygen content was observed in August, during the

pre-monsoon period, which could be due to its photosynthetic

release coinciding with a relatively high phytoplankton growth

as reflected in Chl-a values (Satpathy et al., 2010a). Salinity

values ranged from 27.50 to 34.78 psu, the lowest and the

Figure 2—Variations in pH, salinity, dissolved oxygen, and chlorophyll-a concentrations in the coastal waters from February 2010 toJanuary 2011.

Table 2—Comparison of dissolved metal concentration s (lg l�1) from different coastal regions of India.

Location & study period Cu Zn Mn Pb Co Ni Cr Cd References

Inshore waters of westernBay of Bengal

5.37 25.4 3.57 - 6.19 - - Rajendran et al.,1982

Coastal waters,Visakhapatnam, 1982–1984

0.5-2.9 2.9–22 2.8-7.7 6.5–12 ND 0.8-1.8 - 0.5-1.2 Satyanarayana etal., 1985

Saurashtra Coast, 1986 5.73-8.00 10.54-11.89 8.83-10.41 - 0.78-0.83 2.63-3.05 - - Rao &Indusekhar,1986

Coastal waters of northernBay of Bengal

2.3 25.3 3.50 6.7 - 2.0 - 1.0 Satyanarayana etal., 1987

Cochin Estuary, 1985-86 2.2–22.2 105–385 - 8–14 - 0.3-0.6 - 1.8-4.2 Ouseph, 1992Coastal waters, Gulf of

Mannar- 15.28 9.21 8.96 - 3.12 2.84 1.82 Jonathan, 1995

Kalpakkam coastal waters,Bay of Bengal

- 53.07 5.84 56.91 - 22.67 4.97 2.93 Selvaraj, 1999

Palk Bay & Gulf of Mannar,2003–2004

6.78 119.8 - - - - - 259 Sulochanan et al.,2007

Coastal waters off Cuddalore,2001

4.80 14.39 22.27 12.53 0.83 4.32 1.67 0.46 Jonathan et al.,2008

Mullipalam Creek ofMuthupettai Mangroves

161.43 22.77 19.42 - - - - 3.02 Ashokkumar etal., 2009

Pondicherry, 2010 1.25-10.75 6.13–80.13 2.38–51.38 1.25–47.5 - - 0.5–10.5 0.2–5.38 Solai et al., 2010Kalpakkam Coast, 2010–2011 3.5-4.95 26.55-44.26 1.34-4.11 1.2–8.1 0.04-0.15 2.8-5.35 0.15-0.55 0.24-0.52 Present study

ND¼ Not Detected.

Padhi et al.

August 2013 699

highest levels being observed in December 2010 and June 2010,

respectively. Decreases in the salinity values were observed

during the monsoon period. Relatively low salinity values

coincided with the monsoonal precipitation period. The above

salinity variations were corroborated with earlier observations

from the Kalpakkam coast as well as from other coastal waters of

India (Satpathy et al., 2010a). Relatively high values of Chl–a

were observed during the pre-monsoon period. Positive

correlations between Chl–a and chromium (r ¼ 0.626), nickel

(r ¼ 0.656), and cobalt (r ¼ 0.682) were found (Table 3).

Trace MetalsChromium. Chromium does not occur freely in nature and

chromium compounds are only found in trace amounts in water.

The concentration of chromium at the study site ranged from

0.15 to 0.55 lg l�1 (the annual average was 0.38 lg l�1).

Chromium and its compounds are discharged into coastal

waters predominately through various anthropogenic sources.

The sparingly soluble nature of chromium (III) oxide limits its

level in the dissolved phase; thus, chromium largely exists as

adsorbed floating particles in seawater. A comparative account

of dissolved metals from other coastal regions of India is given in

Table 2. Chromium levels were found to increase during the pre-

monsoon season and decrease to minimum levels during the

monsoon season (Figure 3). Chromium is best correlated with

nickel, manganese, cobalt, and lead, which indicates common

sources of origin for these metals. The decrease in the chromium

content during the monsoon season could be due its adsorption

into sedimentary particles and organic particulate matter at

lower levels of salinity (Mayer and Schick, 1981). The monsoon

period is from November to January, during which salinity dips

and the concentration of suspended particulate matter increases

(Satpathy et al., 2010b). The above fact is supported by the

strong positive correlation of chromium with salinity (Table 3).

Microbial activity is higher during the monsoon season, and

microbial activity reduces aqueous metal concentrations

through the metal precipitation selectivity of chromium

(Darnault, 2004)

Manganese. Concentration of dissolved manganese ranged

from 1.34 to 4.11 lg l�1 (annual average: 3.07 lg l�1). It showed a

similar seasonal trend to that of chromium (Figure 3). The

present observed values are significantly lower than the reported

values from other coastal waters of India (Table 2). In general,

enrichment of this metal in coastal water takes place mainly

through the process of external input (Kremling, 1985) and

continental weathering (Schenau et al., 2002); localized enrich-

ment of manganese also takes place through the redox process.

Organic matter produced during the summer and the pre-

monsoon season, levels of which are relatively high at this

location as compared to other periods of the year (Satpathy et

al., 2010a), reaches the bottom and undergoes rapid microbial

degradation. This microbial degradation of organic matter

possibly leads to an oxygen-deficient environment in the bottom

sediment which transforms the solid manganese oxides into

soluble forms. The soluble manganese enters into the water

column through the process of diffusion and turbulent mixing,

which may leads to its increase in concentration during this

period. A similar trend has been reported in other coastal waters

(Burton et al., 1993; Tappin et al., 1993). Concentrations of

manganese registered at maximum levels at this location during

the summer; this may be due to the transport of soluble

manganese by atmospheric dust, through the seaward wind.

Cobalt. Cobalt is an important micronutrient for marine

phytoplankton (Morel et al. 1994), in particular for photosyn-

thetic Cyanobacteria (Sunda and Huntsman, 1995), yet its

surface-water concentrations are very low. The factors control-

ling the distribution of cobalt in seawater are not well

understood. Furthermore, the potential effect of these low

concentrations of cobalt on species composition in the oceans is

also unknown. An understanding of the processes that control

the temporal and spatial variability of cobalt in the ocean surface

waters is paramount to surmising its biological importance.

Concentrations of cobalt at this location range from 0.04 to 0.15

lg l�1 (annual average: 0.11 lg l�1) showing maximum levels in

summer. It showed a similar trend to those of nickel, manganese,

zinc, copper, and chromium, and was strongly correlated with all

these elements. The behavior of cobalt in estuarine and coastal

waters is influenced by particle–solution interactions, such as

scavenging, and benthic processes, including remobilization

during reduction of manganese oxy-hydroxides and particle

resuspension (Sanudo-Wilhelmy and Flegal, 1996). Consequent-

ly, enhanced levels of cobalt in coastal waters have been related

to the following factors: the resuspension of bottom sediments

with subsequent desorption (Sanudo-Wilhelmy and Flegal,

1996); cobalt-enriched pore water infusions (Tappin et al.,

1995); and atmospheric inputs, particularly of anthropogenic

origin (Guieu et al., 1991; Nimmo and Chester, 1993). The

redox-sensitive nature of cobalt is exemplified by its close

Table 3—Pearson correlation matrix for dissolved metals.

Variables Cd Cr Ni Zn Co Cu Mn Pb pH Salinity DO Chlorophylla

Cd 1Cr �0.273 1Ni �0.151 0.826a 1Zn 0.317 0.372 0.384 1Co �0.042 0.586b 0.724a 0.817a 1Cu 0.181 0.233 0.452 0.669b 0.740a 1Mn 0.002 0.771a 0.886a 0.478 0.720a 0.597b 1Pb �0.249 0.569c 0.823a 0.040 0.439 0.446 0.681b 1pH 0.325 0.007 0.081 �0.341 �0.373 �0.048 0.161 0.343 1Salinity �0.613b 0.745a 0.632b �0.112 0.240 0.136 0.562c 0.743a 0.221 1DO �0.119 0.250 �0.071 0.214 0.090 �0.300 �0.206 �0.455 �0.549c �0.090 1Chlorophyll a �0.352 0.626b 0.656b 0.469 0.682b 0.155 0.378 0.383 �0.359 0.317 0.347 1

a p � 0.01; b: p � 0.05; c: p � 0.1.

Padhi et al.

700 Water Environment Research, Volume 85, Number 8

coupling with dissolved manganese; similar observations were

reported in the North Sea (Kremling and Hydes, 1988).

Furthermore, simultaneous high concentrations of manganese

and cobalt during summer can be explained by the diagenetic

benthic fluxes, initiated by a process of organic matter

decomposition at or close to the sediment interface (Tappin et

al., 1995); this explanation could also be true for the coastal

waters at this location.

Nickel. Relatively high dissolved concentrations of nickel were

observed during the post-monsoon/summer season, with lower

concentrations encountered during the monsoon season. Nickel

concentrations ranged from 2.8 to 5.35 lg l�1 (annual average:

4.33 lg l�1). The present observed values are comparable with

the reported values from other coastal waters of India (Table 2).

Generally, slate, sandstone, clay minerals, and basalt rocks act as

the source of nickel, and the element gets accumulated in

sediments passing through various biological cycles. In the

present study, nickel concentrations were found to be relatively

high during the dry post-monsoon/summer season, with

negligible freshwater input. This indicates the non-point source

of origin of this metal at this location. Furthermore, its strong

positive correlation with salinity and other metals (cobalt,

manganese, lead, and chromium) (Table 3) suggests its marine

origin at this location. In marine environments, the behavior of

nickel is generally linked with manganese. During formation, the

manganese oxides/hydroxides act as excellent scavengers of

trace metals. In this process, nickel gets trapped with manganese

oxides in the surface oxic layer (Glasby, 1984; Klinkhammer et

al., 1982), and then released in constant atomic ratios. During

the process of anoxic reduction of manganese oxides, as

explained earlier, the nickel gets released into the water column,

which could be the reason for the enrichment of nickel in coastal

waters during the post-monsoon/summer season.

Copper. Copper showed the lowest annual variation of all

elements studied, and its concentration ranged from 3.5 to 4.95

lg l�1 (annual average: 4.06 lg l�1). The highest and the lowest

values were observed during the post-monsoon and monsoon

periods, respectively. These findings show that copper concen-

trations in the Kalpakkam coastal waters are not influenced

significantly by any external input through the backwater

channels or other fresh water sources. The negligible decrease

in its concentration during the monsoon season, except during

December, could be due to its dilution by the freshwater input

during this period. Moreover, the organic ligands– originating

from humic and fulvic substances present in the sewage and

backwater discharges during the monsoon season– could have

led to formation of organic copper complexes, leading to a

decrease in the dissolved copper content in the coastal waters. It

was previously proposed that multiple metals were competing

for binding sites in algae, and copper was suggested to be in

competitive equilibria with various other ligands in seawater

(Pascucci et al., 1999). The present observed values of copper are

comparable with that of the other coastal waters of India (Table

2). However, copper values reported in the same area by Selvaraj

Figure 3—Variations in trace metal concentrations (lg l�1) in the coastal waters from February 2010 to January 2011.

Padhi et al.

August 2013 701

(1999) were significantly higher (72 to 2565 lg l�1) which has

been countered by Satpathy et al. (2006). The present copper

concentrations are in close agreement with another recent

report from the Kalpakkam coast (Rajamohan et al., 2010).

Zinc. Zinc enters the marine aquatic environment from a

number of natural and anthropogenic sources, including

industrial discharges, sewage effluent, and runoff (Boxall et al.,

2000). A change in the water environment, such as seasonal tidal

fluctuations, could result in a release of zinc from suspended

particles or sediments (Yang et al., 2009). Zinc values at the

study site ranges from 26.55 to 44.26 lg l�1 (annual average:

35.14 lg l�1), the highest and the lowest being observed during

the monsoon season and the post-monsoon/summer season,

respectively. Its level during the summer and pre-monsoon

seasons remained relatively high; however, the highest value was

encountered in the month of December. This could be attributed

to the fact that rainfall during this month was the highest of any

month during the study period (Figure 2), which might have

brought zinc associated with land runoff. However, due to the

non-soluble nature of zinc, it might have been adsorbed into the

particulate matter (Benoit et al., 1994), leading to its abrupt

decrease during the subsequent months. The strong association

of zinc with cobalt and copper, and a similar trend of summer

enrichment, suggests remineralization of these metals during

particulate organic matter degradation within the thin oxic layer

of the superficial sediment (Campbell et al., 1988).

Cadmium. Among all trace metals measured in this study,

cadmium exhibited the second-lowest concentration. Its con-

centrations varied from 0.24 lg l�1 (January) to 0.52 lg l�1

(December) with an annual average of 0.35 lg l�1. Month-scale

concentrations of cadmium show maximum concentrations in

April and December, with a distinct minimum in the month of

August. Cadmium is mostly present as an organic complex in

surface waters; complexation with inorganic chloride, and its

high mobility in intermediate and deep waters, distribute it

homogeneously in the dissolved phase (Campbell et al., 1988;

Pempkowiak et al., 2000). Cadmium is a nutrient-like metal, its

concentration in surface waters deeply regulated by marine

biogeochemical processes such as phytoplankton uptake (Abe,

2001; Delgadillo-Hinojosa et al., 2001). Rapid utilization by the

photosynthetic community is the primary reason for its short

residence time and depleted values in surface waters (Calvert

and Pedersen, 1993; Morford and Emerson, 1999). Increased

utilization by the photosynthetic community, due to their

favorable growth during the post-monsoon/summer season

and pre-monsoon period, led to a decrease in cadmium

concentrations from April to August in this study. There is no

important source of cadmium in this area, and the wind pattern

is landward during the monsoon season, so rain-driven input

from surrounding lands and atmospheric deposition might play

a minor role in the concentration increase during the monsoon

period. However, agricultural runoff input through backwater

channels, particularly containing phosphate fertilizer, may

provide a significant contribution. In addition, the reduction in

uptake by the phytoplankton community during the monsoon

season, a period unfavorable for their growth, and diagenic

remobilization of cadmium from bottom sediments explain the

relatively higher concentration observed during this period.

Lead. In the present study, concentrations of dissolved lead

demonstrated a similar seasonal trend as that of chromium,

nickel, and manganese, with relatively high values during the

post-monsoon/summer season. Lead concentrations ranged

from 1.28 to 8.15 lg l�1 (annual average: 5.03 lg l�1). The

association of dissolved lead with other trace metals (chromium,

nickel, and manganese) indicated that at higher levels of salinity,

it mixed and behaved conservatively with seawater, which is

further supported by its strong positive correlation with salinity

(Table 3). The present observed values of lead were relatively low

as compared to the values reported from other Indian coastal

waters (Table 2). The gradual decrease in concentrations of lead

during the monsoon season is assumed to be due to minimal

contributions by surface runoff, dilution by rain water inputs,

and exclusion by other prevailing physico-chemical process.

Suspended particulate matters are relatively high in these coastal

waters during the monsoon season. Particle-reactive lead

removal through scavenging (Phol et al., 2010) may be the main

reason for its falling trend in the dissolved phase. Atmospheric

wet and dry particle deposition are the major pathways by which

lead is delivered to ocean surfaces (Duce et al., 1991). It has been

reported that the atmospheric input of lead is about two orders

of magnitude higher than the fluvial input in some coastal

environments (Martin et al., 1989) and often exceeds the riverine

input (Guieu et al., 1997; Schneider et al., 2000). It is worthwhile

to mention here that the southeastern coast of India experiences

northeasterly winds during the post-monsoon/summer season.

The data reported in this study reflects the atmospheric

enrichment of lead– mainly emitted from the combustion of

automobile fuels– by the seaward wind, further facilitated by

high temperatures during summer. However, a similar phenom-

enon during the monsoon season is ruled out, as a southwesterly

wind flows landward during this period.

Factor AnalysisIn the factor plane distribution, all months are grouped into

three different combinations (Figure 4). May to August formed

one group, indicating similar environmental conditions (e.g.,

high salinity and chl-a) in the coastal waters during these

months. September to January, during which the monsoon

season is experienced at this location, formed another group.

Figure 4—Factor plane distribution of various months, showingthree possible states of coastal waters.

Padhi et al.

702 Water Environment Research, Volume 85, Number 8

The third assemblage was made up of February, March, and

April, representing the post-monsoon period with minimal

rainfall.

Three factors were obtained (F1, F2, and F3) from factor

analysis (Figures 5a and 5b), and together they describe 77.06%

of cumulative variations. F1 accounts for 43.46% of total

variance, with positive loadings of salinity, chlorophyll, and

dissolved trace metals (except cadmium). During summer, when

the coastal water salinity increases and phytoplankton growth is

relatively high, concentrations of the above metals are relatively

high as compared to other periods. The strong positive

correlations of chromium, nickel, manganese, and lead with

salinity, and chromium, nickel, and cobalt with chlorophyll

(Table 3), further support the above observation. This factor

represents the state of coastal waters during summer, when the

relatively high organic matter that is produced reaches the

bottom, and possibly causes an oxygen deficient environment,

leading to remineralization of these elements from their oxides

and hydroxide forms.

Factor 2 accounts for 18.91% of the total variance, with

positive loading of lead and pH, and negative loading of

dissolved oxygen. It shows that in alkaline conditions, when

the dissolved oxygen content is relatively low, enrichment of lead

takes place in the coastal waters, indicating the release of lead to

the water column from the oxidative degradation of organic

matter (Aruga et al., 1993). Atmospheric transportation of lead

by a seaward wind contributed significantly to its concentrations

in these coastal waters, which might have caused the lead to

form an independent factor.

Factor 3 accounts for 14.68% of the variance and is

characterized by negative loading of cadmium, copper, and pH.

Dissolved oxygen was found to be positively loaded in this factor.

This factor represents the state of coastal waters for the

monsoon period, during which dissolved oxygen increases with

a decrease in pH. The nearby metallurgical industries and local

combustion of fossil fuels are the main sources of these metals in

coastal waters. Substantial amounts of these elements also enter

with municipal wastewater. During the monsoon season, the

terrestrial runoff brings these metals into the coastal waters,

causing an increase in their concentration and a decrease in

salinity (Vasantha, 2010). However, the negative loading of

copper in this factor indicated that external input of this metal

due to surface runoff is minimal, and dilution may be the

primary reason for the decrease in its concentration. Though

cadmium content was observed to be high during the monsoon

period, negative loading in this factor could be attributed to a

sharp decrease in its concentration at the end of the monsoon

period. Insignificant external inputs (due to very low rainfall as

compared to earlier parts of the monsoon), the short-lived

nutrient-like nature of cadmium, and phytoplankton uptake

could be the cause of the above observation.

ConclusionsDistributions of dissolved heavy metals in the coastal waters at

Kalpakkam are in the following order: cobalt , cadmium ,

chromium , manganese , copper , nickel , lead , zinc.

They are primarily regulated by in-situ regeneration and

remineralization. The results will serve as the benchmark data

for future assessment. The observed trace metals concentrations

are relatively low as compared to the reported values from other

Indian coastal waters, which indicates the unpolluted nature of

this location. The observed lower levels of trace metals in this

location contradict the theory of trace metals contamination of

these coastal waters through cooling-water discharge from the

existing nuclear power plant. Salvito et al. (2001) also observed

no measurable difference between intake and discharge samples

from a cooling water system. Concentrations of cadmium were

found to be elevated during the monsoon period, indicating its

external input at this location. Chromium, nickel, manganese,

and lead were found to be of common origin, most likely

through in situ regeneration/ remineralization. Zinc, cobalt, and

copper concentrations remained relatively high during the

summer period; however, an abrupt increase of these metals

during the monsoon season, followed by a sharp decrease,

indicates their dual origin.

AcknowledgementsThe authors are grateful to the director of IGCAR and the

director of Chemistry Group, IGCAR for their encouragement

and providing all the facilities involved in carrying out this work.

Submitted for publication September 6, 2012; accepted for

publication November 19, 2012.

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