Evaluation of metal contamination in coastal sediments of the Bay of Bengal, India: geochemical and...

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Marine Pollution Bulletin 49 (2004) 174–185

Evaluation of metal contamination in coastal sediments of theBay of Bengal, India: geochemical and statistical approaches

K. Selvaraj a,1, V. Ram Mohan a, Piotr Szefer b,*

a Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, A.C. College Campus,

Chennai 600 025, Indiab Department of Food Sciences, Medical University of Gdansk, al. Gen. J. Hallera 107, PL 80-416 Gdansk, Poland

Abstract

Surface sediment samples collected from the inner shelf region of the Bay of Bengal, were analysed for the major elements and

total and acetic acid available trace elements (Al, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, Si, Zn) to evaluate geochemical

processes influencing their distribution. Major elemental analysis showed that the sediments had high concentrations of Si and

relatively low concentrations of Al and Fe. Both major elemental and trace metal concentrations indicated that the sediments

represent weathered products of granite and charnockite. Normalization of metals to Al indicated relatively high enrichment factors

for Pb, Cd, Zn and Cr. The higher proportions of nondetrital Pb (66%), Cd (41%) and Co (28%) reveal metal contamination due to

anthropogenic inputs. Factor analysis (FA) identified six possible types of sedimentological and geochemical associations. The

dominant factor accounting for 26.9% of the total variance identifies an anthropogenic input and accumulation of nondetrital Cd,

Co, Cr, Ni and Pb. Association of these metals with CaCO3 reveals that shell fragments in the surface sediments are likely act as a

carrier phase for nondetrital metals. The results are discussed in the context of the sources and pathways of elements in the Bay of

Bengal.

� 2004 Elsevier Ltd. All rights reserved.

Keywords: Geochemistry; Enrichment factors; Nondetrital metals; Metal contamination; Surface sediments; Bay of Bengal

1. Introduction

Sediments are important carriers of trace metals in

the hydrological cycle and because metals are parti-tioned with the surrounding waters, they reflecting the

quality of an aquatic system. Coastal and estuarine re-

gions are the important sinks for many persistent pol-

lutants and they accumulate in organisms and bottom

sediments (Szefer et al., 1995). Thus, geochemical

characteristics of the sediments can be used to infer the

weathering trends and the sources of pollution (e.g.,

F€orstner and Salomons, 1980; Fedo et al., 1996; Nesbitt

* Corresponding author. Tel.: +48-58-3493110; fax: +48-58-

3493110.

E-mail addresses: [email protected] (K. Selvaraj), pszef@amg.

gda.pl (P. Szefer).1 Present address: Ocean Science and Technology Cell (Marine

Geology and Geophysics), Mangalore University, Mangalagangothri

574 199, Karnataka, India.

0025-326X/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.doi:10.1016/j.marpolbul.2004.02.006

et al., 1996; Nath et al., 2000). Even though, the total

chemical composition of surficial sediments is a valuable

index of environmental contamination, they are a poor

means of assessing the pathways by which the metalshave accumulated in the bottom sediments. The detrital

(residual) fraction of the total element forms the matrix

of particles and the nondetrital (nonresidual) fraction is

incorporated into the sediments from solution. There-

fore, chemical availability of metals on sediments has

been used to deduce the sources and pathways by which

major and trace elements have entered the marine

environment (Loring and Rantala, 1992).This paper reports the elemental concentrations of

surface sediments from the inner shelf, off Kalpakkam,

Bay of Bengal. The samples were subjected to total and

available (acetic acid-HOAc) geochemical analyses to

evaluate the geochemical processes controlling the ele-

mental concentrations, including possible anthropogenic

influences. The interpretation of the data was achieved

by normalization of all trace elements to Al and the

mail to: [email protected]

K. Selvaraj et al. / Marine Pollution Bulletin 49 (2004) 174–185 175

geochemical associations, including the contents of

sand, mud, CaCO3 and organic matter, were subjected

to R-mode factor analysis.

1.1. Study area

During the last two decades, the coastal environment

of southeast India has experienced intense developments

in industry, urbanization and aquaculture. For example,

a power plant located in the study area, off Kalpakkam

(Fig. 1), utilises a large quantity (35 m3 s�1) of seawateras a coolant and other discharges include wastewater,low-level radioactive effluents, biocides used in the water

treatment and antifouling paints used in the control of

biofouling. The study area has a complex ecosystem,

which is partly influenced by inputs from River Palar

that transports effluents from minor urban settlements

and industries. In addition, the coastal marginal minor

inputs and the Buckingham canal, which runs parallel to

the coast carrying urban sewage, pesticides and fertili-zers derived from agricultural practices and the salt

panning industry.

The continental shelf of the study area is about 40 km

wide and the shelf break occurs at 135 m depth. The tidal

range is 1.2–1.5 m for spring tides and 0.3–0.6 m for neap

tides. Selvaraj and RamMohan (2003) indicated that the

inner shelf is carpeted with a mosaic of sand and silty

sand with minor amounts of clay (max. 4%). Sedimentsare poorly sorted and depositional environments are

influenced by mixed river/dune/beach conditions. A pa-

leo-shoreline was identified based on the higher sand

(>90%) and CaCO3 (>15%), and very low organic matter

contents (<0.4%) at a depth around 50–53 m.

Fig. 1. Study area and s

2. Materials and methods

2.1. Sampling of coastal sediments

Forty-two surface sediment samples were collected

using a Peterson grab along six traverses approximately

perpendicular to the coastline with an interval of 3 km

during April 1996 (Fig. 1). Special care was taken to

avoid leakage of fine-grained materials during retrie-

val. Sample locations were carefully fixed by digital

KODEN GPS Navigator (Model: KGP-913). All the

collected sediment samples were subjected to bulk (totaldigest) and partition (HOAc extraction) geochemical

investigations after pretreatment.

2.2. Geochemical analyses of sediments

Total digest methods. Major oxides (SiO2, Al2O3,

Fe2O3, P2O5, Na2O, K2O, CaO and MgO) were deter-

mined using the analytical methods described by Shap-iro (1975). The total digestion method of Loring and

Rantala (1992) was adopted for the estimation of total

metals. Briefly, an accurately weighed sediment sample

(�1 g) was placed in a Teflon bomb, 1 ml of aqua regia(AR grade HNO3:HCl; 1:3 v/v) was added, followed by

6 ml HF. The sealed bomb was submerged in boiling

water bath (2 h and 30 min). After the bomb was re-

moved from the water bath, the contents were added to5.6 g of boric acid crystals in a 100 ml polypropylene,

standard flask. The flask was made up to volume (100

ml) with high purity distilled water (HPDW). The

solutions were then analysed for selected trace elements

(Cd, Cr, Co, Cu, Mn, Ni, Pb and Zn) by Flame AAS

ampling stations.

Table 1

Comparison of BCSS-1 values of elements obtained in the present

study with certified values

Element Values obtained in this study Certified values

Cd (lg/g) 0.238 0.25

Cr (lg/g) 118 123

Co (lg/g) 11 11.4

Mn (lg/g) 206 229

Ni (lg/g) 53 55.3

Pb (lg/g) 21.7 22.7

Zn (lg/g) 138 119

176 K. Selvaraj et al. / Marine Pollution Bulletin 49 (2004) 174–185

(Model: Varian SpectrAA 200), which was calibrated

with acidified standards. The accuracies of the analytical

determinations were established using the reference

material BCSS-1. The accuracy of the most determina-

tions was within 5% of the reported values (Table 1),

with the exception of Zn, which was higher by about

16%, and Mn, which was lower by about 10% than thereported values.

2.3. Weak acid extraction

Dilute acetic acid (HOAc; 25% v/v) was preferred

because it is one of the weakest chemical treatments that

can displace elements weakly held in ion exchange sites,

easily soluble amorphous compounds of iron andmanganese, carbonates and those metals weakly held in

organic matter (Loring and Rantala, 1988). The pro-

portion of the total metal concentration removed by the

extraction is operationally defined as nondetrital (acid-

soluble). The extraction method (Loring and Rantala,

1992) utilised two grams of dried sediment sample was

weighed in a polythene centrifuge tube to which 25 ml of

25% v/v HOAc was added. The tubes were shakenmechanically for 6 h, centrifuged for 10 min at 2500 rpm

and the clear supernatant was poured into an acid

cleaned 50 ml volumetric flask. Then 10 ml of HPDW

was added with the solids in the tube, shaken briefly,

centrifuged and the supernatant was added to the flask

and made up to volume (50 ml) with HPDW. The

analysis of nondetrital fraction of Cd, Cr, Co, Fe, Mn,

Ni, Pb and Zn was performed by Flame AAS. Analy-tical blanks and sediment samples were analysed in

triplicate using the same procedures and reagents. The

following coefficients of variation were obtained: Cd,

5.2%; Cr, 6.8%; Co, 2.3%; Fe, 4.6%; Mn, 2.9%; Ni,

3.5%; Pb, 3.5% and Zn, 4.8%.

3. Results and discussion

3.1. Geochemistry of major elements

The mean concentrations of major elements ðN ¼ 42Þin the study area are compared with concentrations of

major elements from other regions of the Bay, Upper

Crust (UC) and Post-Archean Australian Shale (PAAS)

(Taylor and McLennan, 1985) and the North American

Shale Composite (NASC) (Gromet et al., 1984) (Table2). It is apparent that the higher mean concentration of

Si in our sediments, when compared to the shelf and

intertidal sediments of East Coast of India, suggests the

presence of quartz (±feldspar) dominated terrigenous

sands. Also, the mean concentrations of Al and Fe are

much lower than the values of Al and Fe for the Bay

sediments (Sarin et al., 1979) as well as the shelf and

intertidal sediments of East Coast of India (Table 2). Astudy of Indian river basins (Subramanian et al., 1985)

found a lower mean concentration of Fe compared to

the mean concentration reported for Indian subconti-

nent (i.e. 2.9%). Similarly, the mean concentrations of

Na, K and Mg are also lower than those in creek sedi-

ments of SE coast of India. All major elements show

lower concentrations compared to UC, PAAS and

NASC (see Table 2) further substantiates the coarse-grained, detrital nature of the sediments. This is sup-

ported by Rao and Sarma (1993) who concluded that

the geochemistry of sediments in the Bay of Bengal is

dominated by their texture and irrespective of their

origin, which are mostly detrital in nature.

Chemical weathering alters the composition of sili-

clastic sediments where larger cations (e.g., Ba, Cs,

Al2O3) remain fixed in the weathered residue whencompared to smaller cations (e.g., Na, Ca, Sr), which are

selectively leached (Nesbitt et al., 1980; Fedo et al.,

1996). These chemical changes may be recorded in the

sediments (e.g., McLennan et al., 1993), which can

provide indicators of source area weathering conditions.

The intensity of chemical alteration/weathering of

source area can be quantified by Chemical Index of

Alteration (CIA¼ [Al2O3/(Al2O3 +CaO+Na2O+K2O)]·100; Nesbitt and Young, 1982) and Chemical Index of

Weathering (CIW¼ [Al2O3/(Al2O3 + CaO +Na2O)] ·100; Harnois, 1988). CIA values for average shales range

from 70 to 75, and 100 for residual clays with high

kaolinite and chlorite or gibbsite contents (Nesbitt and

Young, 1982), whereas Taylor and McLennan (1985)

quoted a CIA value of 85–100 for residual clays. Condie

(1993) reported that most post-Archean shales showmoderate losses of Ca, Na and Sr from source weath-

ering with CIW values of 85–95. In contrast, most Ar-

chean shales show greater losses of these three elements

with CIW of 90–98. The mean value of CIA (44) for the

sediments of the present study is close to unweathered

igneous rocks (50 or below; Nesbitt and Young, 1982),

in particular, granites and charnockites. The mean value

of CIW (48) is also low; moreover, it is evident fromTable 2 that the mean values of both CIA and CIW are

lower than those of UC, PAAS and NASC suggesting

low to moderate source area weathering. Further, the

calculated CIA and CIW values in the sediments reflect

Table 2

Mean concentrations of major elements in surface sediments, off Kalpakkam, the Bay of Bengal, compared with concentrations of major elements from other areas of the Bay, UC, PAAS and

NASC

Concentrations in wt.% CIA CIW

Si Al FeT Na K Ca Mg P

This study

Min. conc. 29.80 0.73 0.18 0.44 0.25 0.12 0.28 0.018 16.30 17.80

Max. conc. 40.10 4.13 2.69 2.78 0.79 2.21 5.43 0.142 65.70 73.30

Mean conc. 34.20 2.07 1.50 1.18 0.49 0.91 1.72 0.066 43.79 48.47

Std. dev. 2.30 1.02 0.67 0.64 0.13 0.60 0.98 0.030 12.82 13.76

(N ¼ 42)Shallow cores sediment, the Bay of Bengala – 7.60 3.90 – – – – – – –

Shelf sediments, Visakhapatnam––Kakinadab – 6.09 4.60 – – – – – – –

Shelf sediments, Visakhapatnam––Narasapuramb – 6.27 7.16 – – – – – – –

Shelf sediments, Visakhapatnamc – 4.72 – – – – – – – –

Intertidal sediments, SE coast of Indiad 7.31 – 2.89 – – 0.98 0.67 – – –

Shelf sediments, Bhimunipatnam-Amalapurame 20.85 8.52 5.94 – – – – – – –

Core sediment, 0–2.5 cm interval, Ennore Creek, SE

Coast of India

17.53 6.42 4.24 2.23 1.41 0.49 2.23 – 69.27 –

UCf 66.00 15.20 5.00 3.90 3.40 4.20 2.20 – 56.92 65.24

PAASf 62.80 18.90 7.22 1.20 3.70 1.30 2.20 0.16 75.30 88.32

NASCg 64.80 16.90 5.65 1.14 3.97 3.63 2.86 0.13 65.91 77.99

CIA ¼ [Al2O3/(Al2O3 +CaO+Na2O+K2O)] · 100 and CIW ¼ [Al2O3/(Al2O3 +CaO+Na2O)]· 100.a Sarin et al. (1979).bMascarenhas et al. (1985).c Satyanarayana et al. (1985).dMohanachandran and Subramanian (1990).eRao and Sarma (1993).f The Upper Crust (UC) and Average Post-Archean Australian Shale (PAAS), from Taylor and McLennan (1985).gAverage North American Shale Composite (NASC), from Gromet et al. (1984). UC, PAAS and NASC values are in the form of oxides. Total Fe (FeT) as Fe2O3.

K.Selva

rajet

al./Marin

ePollu

tionBulletin

49(2004)174–185

177


the absence of clay minerals, which is highly correlated

with extremely low clay contents (max. 4%; Selvaraj and

Ram Mohan, 2003).

Nesbitt and Young (1982) and Nesbitt et al. (1996,and related references therein) used the ternary dia-

grams, the A–CN–K, i.e. Al2O3–(CaO+Na2O)–K2O

diagram and the A–CNK–FM, i.e. Al2O3–(CaO+

Na2O+K2O)–Fe2O3 +MgO diagram, to deduce wea-

thering trends. The ternary plot of Al2O3–CaO+Na2O–

K2O [Fig. 2; compared to data of UC and PAAS and

NASC] shows that all the sediments fall on a trend

parallel to the Al2O3–CaO+Na2O join. This impliesthat the sediments represent weathered products from

granite and charnockite sources (Fedo et al., 1996; Nath

et al., 2000). When the present sediments are plotted in

Al2O3–CaO+Na2O+K2O–Fe2O3 +MgO ternary dia-

gram (Fig. 3), all the sediments fall in the proximity of

Fe2O3 +MgO suggesting the presence of ferromagne-

sian minerals (likely to be pyroxene) in our sediments.

3.2. Geochemistry of total metals

Table 3 compares the mean concentrations of total

trace metals for our sediments with those obtained from

other areas of the Bay including estuarine and tidal

zones of SE coast of India, the Gulf of Mannar, crustal

average (Taylor, 1964) and the upper crust (Taylor and

McLennan, 1985). In general, the mean concentrationsof total Mn, Cr, Cu, Ni and Zn are lower than the

concentrations of these metals in sediments of the Bay,

River Palar and, creek and tidal zones of SE coast of

Fig. 2. A–CN–K plot of sediment samples compared to data of Upper C

Composite.

India. The lower concentrations of these metals are

probably attributed to sandy, detrital nature of our

sediments. The negative correlations of Si with Al and

Fe and almost all of the other metals (Table 4) suggestsdilution of particulate trace metals by sandy, detrital

sediments (Buckley and Winters, 1992). Lead has a

higher mean concentration than sediments from estu-

aries and coastal zones of SE Coast of India (Hema

Achyuthan et al., 2002) and the crustal average, sug-

gesting Pb contamination. However, when compared to

bed sediments of River Palar and intertidal sediments of

SE coast of India, it is clear (Table 3) that the concen-tration of Pb is relatively low. The mean concentration

of Cd is consistent with reported concentrations of this

metal in sediments of the Gulf of Mannar, one of the

heavily industrialized areas of the SE Coast of India

(Jonathan and Ram Mohan, 2003). The measured metal

concentrations decrease in the following order in

accordance with reported concentrations of these metals

in crustal average (Taylor, 1964): Mn>Zn>Cr>Ni>Cu>Pb>Co>Cd. Thus, the total trace metals in these

sediments originate from crystalline materials from the

adjoining landmass to the coastal zone. The country

rocks of the adjacent landmass are collectively known as

the granulites of South India dominated by charnockites

of acid to intermediate composition associated with

granites (Chattopadhyay and Sarkar, 1999). Table 4

demonstrates a strong association between total Ni andtotal Co, Pb and Cd. The non-association of these

metals with mineral concentrating phases such as mud,

aluminosilicates and organic matter (Table 4) indicates

rust and Post-Archean Australian Shale and North-American Shale

Fig. 3. Ternary A–CNK–FM plot of sediment samples in comparison with Upper Crust and Post-Archean Australian Shale and North-American

Shale Composite.

Table 3

Mean concentrations of total trace metals in surface sediments, off Kalpakkam, the Bay of Bengal, compared with concentrations of total metals

from other areas of SE Coast of India, the Gulf of Mannar, crustal average and the upper crust

Concentrations in lg/g

Mn Cr Cu Ni Co Pb Zn Cd

This study

Min. conc. 179 24 7 22 6 9 44 0.12

Max. conc. 638 111 44 44 14 28 163 0.31

Mean conc. 356 57 20 30 9 16 71 0.21

Std. dev. 117.8 21.91 7.36 5.80 1.92 4.75 21.39 0.04

(N ¼ 42)Shallow cores sediment, the Bay of Bengala 529 84 26 64 – – – –

Bed sediments, River Palarb 1131 338 64 – – 45 – –

Intertidal sediments, SE Coast of Indiac 51–2005 11–394 0–105 – – 5–130 13–144 –

Core sediments, 0–10.5 cm interval, 345 318 – 426 10 2 168 –

Adyar Estuary, SE Coast of Indiad

Core sediments, Tidal zones, SE Coast of Indiad

1. 0–5 interval, Muttukadu 409 48 – 49 8 1 68 –

2. 0–1 cm interval, Mamallapuram 777 87 – 53 9 13 106 –

3. 0–1 cm interval, Marakkanam 442 58 – 12 7 11 87 –

Surface sediments, the Gulf of Mannare 296 167 – 24 7 16 73 0.20

Core sediments, 0–2.5 cm interval, 391 643 – 49 11 17 105 0.108

Ennore Creek, SE Coast of India

Crustal averagef 950 100 55 75 25 12.5 70 0.20

Upper crustg 600 35 25 20 10 20 71 –

a Sarin et al. (1979).bMohanachandran, 1988.c Subramanian and Mohanachandran (1990).dHema Achyuthan et al. (2002).e Jonathan and Ram Mohan (2003).f Taylor (1964).g Taylor and McLennan (1985).


Table 4

Correlation coefficients ðrÞ at 95% confidence level (level of significance at p ¼ 0:05) between different pairs of sedimentological and geochemicalparameters ðN ¼ 42Þ

Si Al Mn(t) Cr(n) Ni(t) Ni(n) Co(t) Co(n) Pb(t) Pb(n) Cd(n) Sand Mud

Al )0.82Fe(t) )0.57Cr(t) 0.56 0.64

Ni(n) 0.80

Co(t) 0.80

Co(n) 0.78 0.94

Pb(t) 0.76 0.85

Pb(n) 0.80 0.92 0.92

Cd(t) 0.65 0.74 0.77

Cd(n) 0.63 0.83 0.81 0.78

Sand 0.77 )0.92Mud )0.77 0.92

OM 0.69 )0.71 0.71

CaCO3 )0.56 0.57 0.79 0.71 0.75 0.72 0.59 )0.59

OM––organic matter; CaCO3––calcium carbonate; t––total; n––nondetrital; Critical r value at p ¼ 0:05 is 0.56.


that the land derived total metals in the sediments are

concentrated in oxides and other accessory non-alumi-

nous silicate minerals. Table 4 also demonstrates the

positive correlation of Al with mud, organic matter and

total Cr would imply that the fine particle fraction en-

riched in Al adsorb more organic matter, which scav-enge the Cr. The association among mud, organic

matter and Al is not unusual (Rao and Murty, 1990;

Buckley and Winters, 1992; Ravichandran et al., 1995).

Total Cr also shows positive covariance with Mn, and

implies that Mn-oxides in the surface sediments may

partly control the Cr levels. Sand exhibits moderate

positive covariance with CaCO3 indicating that the shell

materials present in the sand dominated sedimentswhich are source for carbonates in the study area. This

was also evidenced by higher concentrations of CaCO3observed in the sand-rich (80% and above) sediments of

these samples (Selvaraj and Ram Mohan, 2003).

3.3. Enrichment factors

Differentiating the metals originating from humanactivity and those from natural weathering is an essential

part of geochemical studies. One such technique largely

applied is ‘normalization’ where metal concentrations

were normalized to a textural or compositional charac-

teristic of sediments. Normalizing elements relative to Al

is widely used to compensate for variations in both grain

size and composition, since it represents the quantity of

aluminosilicates which is the predominant carrier phasefor adsorbed metals in coastal sediments (Alexander

et al., 1993). According to Nolting et al. (1999), this

method is also a powerful tool for the regional com-

parison of trace metals content in sediments and can also

be applied to determine enrichment factors (EFs).

Table 5 presents the mean values of calculated EFs

for the studied metals with respect to crustal average

(Taylor, 1964), employing the equation EF¼ (metal/Al)sediment/(metal/Al)crust. EFs close to unity point to

crustal origin while those greater than 10 are considered

to be non-crustal source (Nolting et al., 1999). The

minimum EFs obtained for many metals (Co, Cr, Cu,

Mn and Ni; Table 5) are less than unity implying thatthese elements are depleted in some of the phases rela-

tive to crustal abundance in the study area. However, it

is evident that all elements with a mean EF value greater

than unity reveal sediment contamination, for example

the higher mean EF values for Pb, Cd, Zn, and less so

Cr. In addition, the maximum EF values for Pb, Cd and

Zn suggest the presence of contaminated sediments, with

metals derived from various activities of power plantoperation, atmospheric input, inputs from the River

Palar and domestic sewage contribution and the Buck-

ingham canal. Table 5 also demonstrates that sediments

from along this coast (Hema Achyuthan et al., 2002)

have higher EFs for Ni and Cr in contrast to Pb and Cd

in this study.

In order to know the discrepancy in EFs between

earlier studies and the current one, the total metals dataare also subjected to EFs calculation employing the

concentration of metals in the upper crust (Taylor and

McLennan, 1985). The calculated result also given in

Table 5 demonstrates the higher mean EFs for Cr (7.35)

and Ni (7.25), well consistent with previous studies

(Hema Achyuthan et al., 2002). The upper crustal metal

concentrations for the calculation of EFs have been

applied and Hema Achyuthan et al. (2002) concludedthat wastewater discharge from electroplating industries

has been responsible for the enhanced concentrations of

Cr and Ni in estuary and tidal zones sediments. How-

ever, it is quite clear from Table 5 that the calculation of

EFs with respect to the upper crust invariably shows

higher mean EFs for all the studied metals, when com-

pared to calculated EFs with respect to crustal average.

Table 5

Summary statistics of enrichment factors (EFs) with respect to crustal average and the upper crust in surface sediments, off Kalpakkam, the Bay of

Bengal, compared with EFs from other areas of SE Coast of India

Mn Cr Cu Ni Co Pb Zn Cd

This study––EFs with respect to crustal averagea

Min. value 0.68 0.80 0.27 0.72 0.69 1.93 1.69 1.86

Max. value 3.47 8.65 4.57 5.91 5.06 23.64 12.36 13.72

Mean value 1.75 2.63 1.91 1.98 1.84 6.70 4.94 5.34

Std. dev. 0.74 1.37 1.16 1.12 1.08 4.46 2.52 3.25

EFs with respect to the upper crustb

Min. value 1.06 2.22 0.59 2.62 1.68 1.17 1.63 –

Max. value 5.36 24.17 9.82 21.62 12.41 14.42 11.91 –

Mean value 2.71 7.35 4.10 7.25 4.51 4.09 4.76 –

Std. dev. 1.14 3.83 2.49 4.12 2.64 2.72 2.43 –

Core Sediments, 0–10.5 cm interval, 0.57 8.99 – 21.12 0.99 0.10 2.35 –

Adyar Estuary, SE Coast of Indiac

Core Sediments, Tidal zones, SE Coast of Indiac

1. 0–5 cm interval, Muttukadu 0.78 1.57 – 2.81 0.92 0.06 1.10 –

2. 0–1 cm interval, Mamallapuram 1.39 2.67 – 2.84 0.97 0.69 1.60 –

3. 0–1 cm interval, Marakkanam 0.75 1.69 – 0.61 0.61 0.56 1.25 –

Core sediments, Ennore Creek, SE Coast of India

0–2.5 cm interval

0.53 8.24 – 0.84 0.55 1.75 1.92 0.70

a Taylor (1964).b Taylor and McLennan (1985).cHema Achyuthan et al. (2002).


Moreover, the maximum EFs for Cr and Ni are elevated

and this anomalous condition, in general, does not exist

in normal coastal environment and would imply the

very low concentrations of metals such as Cr, Co, Cu,

Mn and Ni recommended for the upper crust. Espe-

cially, the concentrations of Cr and Ni in the upper crust

are too small, i.e. 65% and 73%, respectively than those

in crustal average (Table 3). Therefore it appears that tocalculate EFs for metals in sediments of SE coast of

India, crustal average (Taylor, 1964) is better material

for the purpose of normalization than the upper crust. It

is supported by the partition geochemical data of the

sediments studied here being in accordance with the

Table 6

Mean concentrations (lg/g) of nondetrital trace metals and their percent contother similar studies of SE Coast of India

Fe Mn

This study

Min. conc. 318 44.2

Max. conc. 1115 192

Mean conc. 702 86

Std. dev., N ¼ 42 188 34.92

Mean % contribution 6 25

Core sediments, 0–2.5 cm interval,

Ennore Creek, SE Coast of Indiaa1673 108

% contribution 4 28

Surface sediments, the Gulf of Mannarb 255 82

% contribution 2 28

a Selvaraj et al. (2003).b Jonathan and Ram Mohan (2003).

result of EFs related to crustal average. Moreover, the

higher EF values for Pb and Cd in the studied sediments

are consistent with the geoaccumulation index of inter-

tidal sediments of SE coast of India, indicating higher

index for Cd and Pb (Subramanian and Mohanachan-

dran, 1990).

3.4. Geochemistry of available metals

The mean concentrations of metals extracted by

HOAc and the mean proportion of the total metals

content are shown in Table 6 and are compared with

earlier studies of coastal and creek areas of SE coast of

ribution to the total metal content in surface sediments, compared with

Cr Ni Co Pb Zn Cd

1.4 1.2 1.9 4.3 4.5 0.05

4.0 4.1 5.3 14.5 9.5 0.16

2.60 2.49 3.46 9.96 5.92 0.08

0.61 0.68 0.74 2.03 0.95 0.02

5 9 28 66 9 41

54 3.1 3.0 6.3 16.6 0.108

8 6 28 37 16 36

4.25 5.91 5.04 3.06 3.60 0.15

3 25 72 19 5 75


India. It is apparent from Table 6 that the higher mean

concentrations of available Fe and Mn reflect the pres-

ence of Fe hydroxides and Mn oxides (Rao and Murty,

1990). Earlier studies (Lyle et al., 1984; Selvaraj et al.,2003) have demonstrated that the acetic acid leach not

only dissolves carbonates but also desorbs metals from

the surface of clays, organic matter and Fe–Mn oxy-

hydroxides.

Nondetrital metal concentrations (Table 6) show

lower mean proportions for Cr, Fe, Ni and Zn indicating

similarity in their inputs. The nondetrital fraction of Fe

shows positive correlation with nondetrital Cr (Table 4)suggesting the input of these metals from iron and steel

industries located in the coastal zone. According to Rao

et al. (1993), iron bacteria cause Fe precipitation in the

cooling waters of power plants and to control the

corrosion of iron and steel materials, chrome salts are

frequently added to cooling water systems. Also,

cupronickel has been widely used as an alloy in heat

exchangers of power plant (Ford andMitchell, 1990) andto avoid the general problem of biofouling (Rajagopal

et al., 1991; Rao et al., 1993), antifouling paints, which

contain considerable amounts of Zn oxides (Danielsson,

1980), are commonly used by many coastal industries.

Relatively high proportions of Pb, Cd and Co imply

(Table 6) that the sediments are contaminated by these

metals, as supported by the calculated EFs, especially Pb

and Cd. Similar proportions were obtained for Pb, Cdand Co in the sediments of Ennore Creek, SE coast of

India (Selvaraj et al., 2003). The higher proportions of

nondetrital Cd and Co in surface sediments of the Gulf

of Mannar (Table 6) support the above inference (Jon-

athan and Ram Mohan, 2003). These facts suggest that

these metals are sourced from anthropogenic inputs, in

particular, discharge of fly ash in the coastal zone as well

as atmospheric deposition of Pb and domestic effluentdischarge and the Buckingham canal (Cd and Co). A

previous study (Selvaraj et al., 2003) related to nonde-

trital metals indicated that fly ash (containing around 70

lg/g of Pb) produced by combustion of coal from powerplant is a prime source of Pb to the estuarine sediment of

SE coast of India. Likewise, Abu-Hilal and Badran

(1990) attributed unusually high levels of Cd in sedi-

ments of the Gulf of Aqaba to combined inputs fromsewage effluent and phosphate dust particles.

A striking feature is the presence of higher nonde-

trital concentrations of Cd, Co, Cr, Ni and Pb associ-

ated with sediments of higher carbonate values (>15%).

This inference was substantiated by the correlation

coefficients data (Table 4), which exhibit significant

positive relationships between CaCO3 and nondetrital

Cd, Co, Cr, Ni and Pb (0.70, except Cr). This authen-ticates the role of carbonates in the incorporation of

nondetrital trace metals present in the HOAc soluble

fraction of the sediments.

3.5. Factor analysis (FA)

Geochemical factor analyses aid the identification of

parameters controlling trace metal distributions (Lor-ing, 1991; Winters and Buckley, 1992). A varimax

rotated factor matrix showed that six common fac-

tors described 75.2% of the total data variability in 42

surface sediments (Table 7). Factor 1, accounted for

26.9% of the total variance, portrays the anthropogenic

input and accumulation of nondetrital Cd, Co, Cr, Ni

and Pb. A large portion of these metals has a strong

association with CaCO3 indicating incorporation ofHOAc extractable fractions of metals into carbonate

debris present in the sediments. Calcium carbonate-

metal associations have been previously reported in

sediments from northern Euboekos Bay, Greece, by

Voutsinou-Taliadouri and Varnavas (1993) and from

Miramichi Estuary, New Brunswick (Willey and Fitz-

gerald, 1980), suggesting that variable amounts of shell/

skeletal fragments act as scavengers for Cd, Co, Cr, Niand Pb.

Factor 2 accounting for 18.5% of the total vari-

ance, contains a high loading of Al, mud and organic

matter. The concentration of Si has a strong nega-

tive relationship with mud, which correlates with high

sand/quartz content. The geochemical and sedimen-

tological characteristics of this group are related to

composition of mud sized (fine-grained) and phyl-losilicate rich sediments. Generally, the fine texture

of the samples is associated with a relatively high

loading of adsorbed organic matter on the detrital

components of these sediments (Buckley and Winters,

1992).

Factor 3 accounted for 10.5% of total variance is

characterised by high loading of total trace metals Cd,

Co, Ni and Pb. This factor, without significant positiveemphasis on metal variables such as mud, organic

matter, Al, Fe or Mn, strongly suggests the common

source is natural materials from the adjoining landmass.

Sediments characterised by Factor 4, which accounts for

7.1% of the total variance, have high loading of total Cr,

Mn and Zn with nondetrital Fe. This association indi-

cates that metals such as Zn and Cr are associated with

Fe–Mn oxides, which also act as concentrators fornondetrital Fe.

Factor 5 explains 6.7% of the total variance and is

characterised by high loading of total Fe and moderate

loading of Na indicating that the association is likely

due to garnet minerals in the sediments. Factor 6 ac-

counted for only 5.5% of the total data variability, with

positive loading on total and nondetrital Mn, suggests

rare presence of Mn-oxides. This factor also showsstrong negative loading on Cu (less so, Ni and Zn)

indicating that Mn-oxides in the study area are not a

metal associate phase.

Table 7

Varimax rotated factor matrix (N ¼ 42)Variable F1 F2 F3 F4 F5 F6

Si 0.07 )0.77 )0.03 )0.08 )0.33 )0.23Al )0.22 0.89 0.00 0.15 0.08 0.18

FeT )0.17 0.19 0.07 0.22 0.72 0.28

Fe(n) 0.33 0.14 0.05 0.51 0.41 0.22

Na 0.15 0.11 0.30 0.01 0.60 )0.39K )0.16 0.20 0.15 0.33 0.09 0.26

Ca )0.06 )0.03 )0.27 )0.03 )0.83 0.06

Mg )0.01 )0.02 )0.12 )0.02 )0.11 0.04

P )0.79 0.08 )0.02 )0.29 0.23 0.01

Mn(t) )0.15 0.29 0.02 0.56 )0.02 0.62

Mn(n) 0.22 0.42 0.14 0.08 0.02 0.65

Cr(t) )0.04 0.50 0.14 0.64 0.12 0.20

Cr(n) 0.87 0.01 0.07 0.21 0.12 )0.02Cu(t) 0.13 0.04 0.00 0.06 )0.11 )0.85Ni(t) 0.18 0.24 0.83 0.29 0.17 )0.16Ni(n) 0.96 )0.11 0.09 )0.05 0.02 )0.11Co(t) 0.09 0.07 0.89 0.06 0.22 0.17

Co(n) 0.94 )0.14 0.07 )0.04 0.11 0.06

Pb(t) 0.02 0.05 0.92 )0.02 0.06 0.00

Pb(n) 0.93 )0.06 0.00 )0.04 0.00 )0.06Zn(t) 0.09 0.17 0.09 0.77 0.00 )0.20Zn(n) )0.18 )0.06 )0.04 0.70 0.12 0.11

Cd(t) )0.08 )0.07 0.90 )0.07 0.08 0.07

Cd(n) 0.86 )0.22 0.06 0.09 0.13 0.13

Sand 0.26 )0.92 0.03 )0.13 )0.06 0.01

Mud )0.26 0.92 )0.03 0.13 0.06 )0.01OM )0.08 0.84 0.18 )0.05 )0.04 0.02

CaCO3 0.75 0.41 0.01 0.21 0.19 )0.19Total variance 26.9 18.5 10.5 7.1 6.7 5.5

FeT––total Fe; OM––organic matter; t––total; n––nondetrital.


4. Conclusions

The results of the major elemental analyses show the

coarse-grained, detrital nature of sediments with high

values of Si and lower values of Al and Fe. The mean

CIA and CIW values (44 and 48) reflect that sedi-

ments are highly immature and mostly derived from

adjoining landmass consisting of charnockitic and gra-nitic rocks. Normalization of total trace metals to Al

and their ratios with crustal average demonstrate the

higher mean EF for Pb, Cd, Zn and Cr revealing con-

tamination of sediments by these metals from external

sources such as industrial and modern population

activities. The sediments analysed have higher percent

contributions of acetic acid soluble Pb, Cd and Co

possibly due to discharge of fly ash and atmosphericemissions as well as domestic waste discharge. Factor

analysis reveals three dominant geochemical associa-

tions: (i) association of nondetrital forms of Cd, Co, Cr,

Ni and Pb with carbonates; (ii) fine-grain size with

phyllosilicates and (iii) association of total content of

metals such as Cd, Co, Ni and Pb with crystalline

materials. The data presented here confirm that metal

contamination, at least by Pb and Cd, is a significantfactor in the coastal and estuarine sediments of SE coast

of India and justifies the need for continuous monitoring

of sediment contamination.

Acknowledgements

The authors thank Prof. S.P. Mohan, Head, Depart-

ment of Geology, University of Madras, for providinglaboratory facilities. We are very grateful to Dr. Mark

M. Baskaran, Wayne State University, for providing

SRM BCSS-1. We are very grateful to anonymous ref-

erees for their valuable and constructive comments. A

Ph.D. scholarship from the UGC, New Delhi, to the

first author is gratefully acknowledged. The work is also

partly supported by financial assistance of the UGC-

SAP Phase II programme.

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