Evaluation of geochemical behavior and heavy metal

International Journal of Sediment Research 30 (2015) 28-38

Evaluation of geochemical behavior and heavy metal distribution of sediments: The case study of the Tirumalairajan river estuary, southeast coast of India Senapathi VENKATRAMANAN1,2, Sang-yong CHUNG3, Thirunavukkarasu RAMKUMAR4, Gopalakrishnan GNANACHANDRASAMY5, Tae Hyung KIM6

Abstract The purpose of this study was to assess the chemical partitioning of selected heavy metals (Fe, Mn, Cu, Zn, Pb, Cr, Co and Ni) in 10 surface sediments at Tirumalairajan River Estuary in the southeastern coast of India. A five-step sequential extraction technique was used to assess the environmental status of heavy metals. Most of metals were considered to be immobile due to the high availability in the residual fraction of heavy metals. The sediments of Tirumalairajan River estuary had not been polluted by heavy metals, and they didn’t pose any high ecological risk. The seasonal variations of heavy metals were slightly higher in summer than in monsoon season. Factor analysis was also carried out to understand the associations of metals in different fractions with sand, silt, clay, organic matter, pH, salinity and other metals. The relationship between the Q-mode and R-mode cluster analyses was useful for identifying the pollution levels in both seasons. It was proved that the enrichment of heavy metals was related with geogenic and anthropogenic sources. The information on total metal concentrations in sediments was not sufficient for assessing the metal behavior in the environment, but the sequential extraction technique was more effective in estimating the environmental impact of contaminated sediments. Key Words: Five-step sequential extraction, Factor analyses, Q-mode and R-mode cluster analyses, Heavy metals, Tiurmalairajan estuary

1 Introduction Heavy metal speciation using sequential extraction techniques on various types of sediments, i.e., lake, river, coastal, estuarine and marine sediments had been reported by many researchers (Kersten and Forstner, 1991; Fernandes, 1997; Gouws and Coetzee, 1997; Perin et al., 1997; Ngiam and Lim, 2001; Sundaray et al., 2011). Despite the pitfalls and operational character of the sequential extraction techniques pointed out by many researchers (Wallman et al., 1993; Lim and Kiu, 1995), they are one of the most widely used approaches to distinguish between different geochemical associations of many heavy metals and to gain a better insight of geochemical processes occurring in sediments. Estuarine sediments are very important accumulation locations of metals in the coastal areas, and the analysis techniques of these metals are important to assess the degree of pollution in the estuarine environment. Sediment can be considered as a heterogeneous mixture of dissimilar particles. These particles can be considered in turn as a complex assemblage of different organic and inorganic components (Martin et al., 1987). Sediments receive potentially toxic elements from both natural and a wide range of anthropogenic sources, including the vehicle emissions, domestic and industrial discharges, agricultural sources, river inputs and waste disposal (Saeki et al., 1993; Davidson et al., 1992; Langston et al., 1999; Sundaray et al., 2006; Seshan et al., 2010; Anithamary et al., 2012; Guo et al., 2012; Venkatramanan et al., 2013c; Venkatramanan et al., 2014). 1

Research Prof., Dr., Department of Earth & Environmental Sciences, Institute of Environmental Geosciences, Pukyong National University, 599-1 Daeyeon-dong Nam-gu, Busan 608-737, Korea. E-mail: [email protected]. 2 Dr., Department of Earth Sciences, Annamalai University, Annamalai Nagar 608-002, Tamil Nadu, India. E-mail: [email protected]. 3 Prof., Department of Earth & Environmental Sciences, Institute of Environmental Geosciences, Pukyong National University, 599-1 Daeyeon-dong Nam-gu, Busan 608-737, Korea. E-mail: [email protected] (Corresponding author). 4 Prof., Department of Earth Sciences, Annamalai University, Annamalai Nagar 608-002, Tamil Nadu, India. E-mail: [email protected]. 5 Research Scholar., Department of Earth Sciences, Annamalai University, Annamalai Nagar 608-002, Tamil Nadu, India. E-mail: [email protected]. 6 Dr., K-Water Institute, Korea Water Resources Corporation, Daejeon 305-730, Korea. E-mail: [email protected]. Note: The original manuscript of this paper was received in Apr. 2012. The revised version was received in Sept. 2014. Discussion open until Jan. 2016. - 28 International Journal of Sediment Research, Vol. 30, No. 1, 2015, pp. 28–38

The primary objectives of the present study were: (1) To estimate the speciation concentrations of the heavy metals such as Iron, Manganese, Chromium, Copper, Cobalt, Nickel, Lead and Zinc in surface sediment from Tirumalairajan River Estuary. (2) To evaluate the effects of grain size, physico-chemical parameters and organic matter on metal levels in the sediments. (3) To find out the sources (lithogenic or anthropogenic) of heavy metals in the surface sediments from the Tirumalairajan River Estuary (4) To identify the seasonal variation and geochemical accumulative phase of heavy metals. 2 Environmental settings The Cauvery River originates from the Brahmagiri range of the Western Ghats, and travels 800 km before emptying into the Bay of Bengal. Tirumalairajan River is separated from Cauvery River in Tanjavur district of Tamil Nadu state, and discharges its load into the Bay of Bengal near Tirumalairajapattinam after traversing about 14 km. The influence of tide was noticed upto 8–10 km in the upstream direction. The catchment area comprises of a terrain of granite, charnockite and gneisses. The river then flows through recent alluvium deposits which are composed of clays and silts before it joins into the sea. The mouth of the estuary is always open to the sea. There is not the complete closure of the bar, and regarded as a true bar built estuary with semidiurnal tide nature. The estuary also receives discharges from a number of irrigation channels. The sampling location of the study area is shown in Fig.1a. The average annual rainfall is 43.12 mm in summer season and 451.48 mm in monsoon. The major groups of minerals in the study area were quartz, feldspar, mica, pyroxene and amphibole (Subramanian, 1987; Venkatramanan, 2013a). The geology and geomorphology of the study area are shown in Figs. 1b and c. This area mainly comprises of Quaternary sediments which increases towards the south of Coleroon River. These sediments consist of the alluvial plain deposit of the Cauvery River and its distributaries, narrow fluvio-marine deltaic plain deposits and marine coastal plain deposits (east coast formation). The fluvial deposits comprise of flood plain, flood basin, point bar, channel bar and palaeo-channels with admixtures of sand, silt and clay. The deltaic plain includes paleo-tidal flats with clays and sands and sand ridges or gray brown sand. The marine coastal plains include beach, tidal flats, salt marsh, mangrove swamps, deposits of sand and clay. The Cretaceous formations of the coastal track of the Cauvery basin consist of faunal rich marine sedimentary rocks, namely limestone, sandstone, clay and sandy beds. The mouth of the river contains alluvium deposits of clays and silts.

Fig. 1 Maps showing study area details (a) location (b) geology (c) geomorphology

3 Materials and methods 10 sampling stations of surface sediment were selected considering accessibility to sampling points along the river covering mouth, estuary and freshwater zone, and sampling was carried out during summer (June) and monsoon (December) in the year of 2010. The salinity variations were used to identify the mouth, estuary and freshwater zone of the study area. The sediment samples were collected by using a Van Veen grab sampler on board hired fishing trawler. Sub-sampling of the sediments was done by taking upper 5 cm of the sample from the grab with the help of plastic spatula. Sediment samples were stored at 4oC prior to analyses. Station locations were obtained by the Global International Journal of Sediment Research, Vol. 30, No. 1, 2015, pp. 28–38

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positioning system (GPS). Sediment Salinity was determined by the method described by Jackson (1973), and was measured by Refractometer. Sediment samples were then oven dried at 60◦C for further analysis. Sieving was carried out in ASTM sieve at 1/4 φ intervals for about 20 minute in Digital sieve shaker (Retsch AS 200). Pipette analysis was carried out to compute sand, silt and clay fractions. Organic matter in sediments was determined by loss on ignition method (Fishmen and Friedman, 1985). A sequential extraction procedure developed by Tessier et al. (1979) was applied in this study to extract the metals in sediments. In this study, the sequential extraction procedure includes five phases: exchangeable, bound to carbonate, bound to Fe–Mn oxide, bound to organic matter and residual (Fig. 4). This method used various chemicals to decrease pH and increase oxidizing strength, and to remove the operationally-defined host fractions corresponding to the exchangeable, carbonate, reducible, organic matter and residual fractions. The concentrations of selected metals (Fe, Mn, Zn, Pb, Co, Cr, Cu and Ni) in sediments were very high (Ramanathan et al., 1993). The heavy metals were analyzed by inductively coupled plasma optical emission spectrometer (ICP-OES, Perkin Elmer optima 5300 DV). The detection limits of heavy metals were Fe-0.004 μg g-1, Mn-0.001μg g-1, Zn-0.005 μg g-1, Pb-0.042 μg g-1, Cu-0.009 μg g-1, Cr-0.007 μg g-1, Co-0.007 μg g-1 and Ni-0.015 μg g-1. The accuracy of the analytical method was examined by the standard reference material MAG-1 (marine mud from the United States Geological Survey). Multivariate Statistical analyses were carried out by SPSS 10.0 statistical software. The detail of the different steps and reagents used in this sequential experiment are shown in flow chart (Fig. 2).

Fig. 2 Flow charts for sequential extraction scheme of sediments (Tessier et al. 1979)

4 Results and discussion 4.1 Physico-chemical characteristics of sediments The physico-chemical characteristics (Table 1a and b) of surface sediments were related with the mobility of heavy metals. pH of the sediments was about 7.2–8.3 (monsoon) and 7.3–7.8 (summer), indicating that the sediments were - 30 -

International Journal of Sediment Research, Vol. 30, No. 1, 2015, pp. 28–38

alkaline and decreasing from estuary to upstream. The level of pH in both seasons was not showed much difference. The higher level of pH was observed during summer season, it may be due to the removal of CO2 by primary producers. The salinity was ranged between 3-25‰ in monsoon and 4–29‰ in summer, higher in the estuary and lower in the upstream. This may be attributed to high temperature and less amount of rainfall in summer. The salinity was lower during monsoon; this may be due to higher rainfall and the incoming of fresh water from the river and its tributaries. During monsoon, sand content for the studied samples varies from 68.85–97.46%, whereas silt and clay content varies from 0.86–23.09% and 0.29–8.06%, respectively. Sand shows increasing trend from stations 6 to 10, but decreasing trend from stations 2 to 5. Silt and clay show increasing trend up to station 2, 3 and 4, and they decrease towards the upstream. In case of summer, sand, silt and clay varies from 64.2–98.26%, 1.06–25.76% and 0.44–10.04%, respectively. Sand decreases at station 2 and increases at the mouth and freshwater region. Silt increases at the station 2 and 3 with lower value, and decreases at station 10 and furthers upstream. In general, clay shows increasing trend from station 1 to 4, and it increase even at further upstream. This fact indicates the sediments are relatively coarse and represent bed load derived from the Cauvery river basin. Due to selective deposition, silt and clay particles are transported into the mouth bar area and outer estuary, while the sand particle is deposited in the fresh water zone. So, this may be due to the nonlinear sand-mud mixing under complex hydrodynamic condition (Venkatramanan et al., 2011). During monsoon and summer, organic matter varies from 2.05–3.44% and 2.57–5.03%, respectively. It indicates the estuary is possibly accomplished by the high productivity of the region besides the huge population of biota died and increase the concentration of organic matter. The deposition rates of the organic matters and inorganic constituents are larger in this environment, and results in the retarded decomposition of organic matters and its better retainment (Yamamuro, 2000; Carrie et al., 2009). The fine texture of the sediments in this environment also represent the accumulation of organic matters. Stations 1 2 3 4 5 6 7 8 9 10

Table 1a pH 7.3 8.5 7.2 8.5 7.4 7.4 7.6 7.4 8.3 7.8

Physico-chemical parameters of the Tirumalairajan estuary sediments (monsoon) Salinity ‰ Sand % Silt % Clay % Organic matter % 24 93.86 5.04 1.10 2.423 22 78.01 19.10 2.89 3.011 19 68.85 23.09 8.06 3.435 18 78.35 18.54 3.11 3.266 18 96.55 2.43 1.02 2.045 7 95.35 4.25 0.4 2.045 5 96.05 3.66 0.29 3.435 2 93.73 5.69 0.58 2.809 2 94.82 3.5 1.68 2.045 1 97.46 0.86 1.68 3.435

Stations 1 2 3 4 5 6 7 8 9 10

Table 1b Physico-chemical parameters of the Tirumalairajan estuary sediments (summer) pH Salinity ‰ Sand % Silt % Clay % Organic matter % 7.4 28 90.54 7.03 2.43 3.114 7.9 27 75.65 20.65 3.70 4.345 7.4 25 64.20 25.76 10.04 5.034 8.1 21 74.65 20.13 5.22 4.221 7.2 19 96.65 2.07 1.28 2.567 7.3 10 94.73 4.82 0.45 2.567 7.4 8 93.12 2.36 4.52 5.034 7.2 6 94.46 4.78 0.76 3.840 8.2 3 96.23 3.33 0.44 2.567 7.5 2 98.26 1.06 0.68 5.034

4.2 Heavy metals in different geochemical fractions The metal speciation of Fe, Mn, Zn, Pb, Co, Cr, Cu and Ni in Tirumalairajan river estuary is summarized in Table 2a and b. Figure 3 (a to h) displays the speciation of metals in estuary sediments. In both seasons, all metals except Pb in estuarine sediments are characterized by the phase order: V > III > IV > II > I Phase. The phase order of Pb is IV > V > III > II > I Phase. The speciation pattern of metals was mainly found in phase 3, 4 and 5. Phase 5 (residual phase) is the predominant phase incorporated into the mineral phase, and is related with natural geochemical origin in addition to agricultural sources. The association of Zn and Pb in this residual phase may be attributed to alumino-silicate minerals holding metals within the crystal structure. Cr, Co, and Ni association is higher in residual phase than other phases. These metals were mainly derived from natural origin (Rath et al., 2009). Pardo et al. (1990) also explained that the higher level of Cr, Co and Ni associated with residual phase was due to association with crystalline matrix. Very small amounts of the metals were found in the exchangeable fraction, and the metals were originated from natural sources. Metals are loosely International Journal of Sediment Research, Vol. 30, No. 1, 2015, pp. 28–38

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Fig. 3 Geochemical fractionation of heavy metals in sediments

adsorbed into sediment surfaces, and flowing through polluted areas, metals released in the first phase could probably be introduced by pollution and informal settlements (Gouws and Coetzee, 1997). It is anticipated that samples collected under low anthropogenic pressure will show the dominance of the residual phase content relative to the mobile phases. The exchangeable phase carries very small concentration of metals which can be attributed to high pH. Higher - 32 -


availability of Fe compared to Mn in this phase can be explained by the non-redox condition of sediment. Under low redox condition, Mn is controlled by pH. Fe-compound formed by weathering is readily soluble and less stable compared to Mn (Schoer et al., 1983; Rankama and Sahama, 1964). The case of very low concentration of heavy metals in this phase suggests the absence of adverse impact from aquatic biota. Table 2a Metals (μg g-1) Fe Mn Cu Zn Pb Cr Co Ni

Results of sequential extraction for metals in sediments from Tirumalairajan river estuary in monsoon Phase-I Phase-II Phase-III Phase-IV Phase-V 0.009–0.022 0.004–2.894 11.03–29.16 0.08–11.85 634.5–1674 0.020–0.075 0.032–0.432 0.081–1.344 0.036–0.321 3.094–11.09 BDL–0.024 BDL–0.044 BDL–0.058 BDL–0.051 5.08–19.08 0.012–0.020 0.006–0.092 0.011–0.095 0.011–0.048 7.063–14.43 BDL–0.043 BDL–0.044 BDL–0.098 0.907–1.96 0.042–0.245 BDL–0.015 BDL–0.054 BDL–0.189 0.043–0.374 0.022–0.331 BDL–0.015 BDL–0.022 0.007–0.024 BDL–0.020 0.012–0.068 BDL–0.022 BDL–0.084 BDL–0.064 BDL–0.143 0.078–0.945

Table 2b Results of sequential extraction for metals in sediments from Tirumalairajan river estuary in summer Metals (μg g-1) Phase-I Phase-II Phase-III Phase-IV Phase-V Fe BDL–21.67 BDL–17.45 23.07–58.5 5.32–45.7 843.9–1810 Mn 0.041–0.395 0.018–0.421 0.015–7.654 0.012–2.55 16.04–32.29 Cu BDL–0.039 BDL–0.062 BDL–0.453 BDL–0.204 11.72–26.84 Zn 0.005–0.153 0.006–0.137 0.008–0.342 0.007–0.113 14.52–24.42 Pb BDL–0.085 BDL–0.104 BDL–0.455 1.706–4.061 0.042–3.77 Cr BDL–0.155 BDL–0.095 BDL–0.567 BDL–0.254 0.034–3.896 Co BDL–0.027 BDL–0.042 BDL–0.072 BDL–0.054 0.018–0.124 Ni BDL––0.072 BDL–0.113 BDL–0.130 BDL–0.276 0.031–0.705

The speciation pattern of metals indicated that the second higher concentration of metals was associated with the Fe–Mn phases. These results show that known ability of Fe–Mn oxides are good scavenger of heavy metals by the processes of adsorption and co-precipitation (Lim and Kiu, 1995). Not only Mn (similar to Fe) acts as adsorbed during the oxide/hydroxide co-precipitation, but the metal itself could react with Fe or itself to form stable and solid compounds (Perin et al., 1997). However, since the Fe–Mn oxides and organic phases carry significant amount of metals, there exist potential danger of substantial amount of metals becoming chemically mobile with the environmental changes (Papadopoulos et al., 1997; Wang et al., 2010; Davutluoglu et al., 2011). The proportion of heavy metals bound to Fe–Mn oxides is highly variable and depends on environmental changes as depth of water and redox reactions with the sediments. The slightly higher concentrations of all metals were observed during summer rather than monsoon season. It indicates the oxidation–reduction cycle is important in controlling the fate of Fe and Mn in most aquatic system. This cycle varies especially in summer, when oxygen concentrations often decrease at the interface between water and sediment. This causes the reduction of Mn4+ and Fe3+ to soluble Mn2+ and Fe2+ which is then transported upward in water column where the oxygenated water results in re-oxidation to insoluble metals settling to the bottom sediment to repeat the cycle (Moore et al., 1979). So, Fe-Mn phase plays an important role in determining the fate of heavy metals in estuarine environment. There are other factors controlling the mobilization of metals in the environment, which are the redistribution of anoxic, sulfidic sediments during dredging; as well as de-stratification of water system which enhances oxygenation of water column. The significant agitation and mixing with oxygenated water occurred during the study period as the sediments were dredged during the construction of railway line in this River (Srividya, 2009; Venkatramanan et al., 2013b). This causes the oxidative, degradation of organic matter, and the enhanced metals could be mobilized to greater extent. The low association of Mn to this organic fraction is due to weak affinity of Mn for organics (Bendell-Young and Harvey, 1992; Dessai and Nayak, 2009). Slightly higher concentration of Pb in this phase may be derived from the coating paints of fishing boats. The organic matter of sediments may be the scavenger for Pb, Zn and Ni in this study. The metals of this phase were slightly higher compared to the phase I and II. Hseu (2006) also stated that metals associated with the two phases such as exchangeable and carbonate bound were more labile and readily leachable or bioavailability. Perin et al. (1997) indicated that the grain size and organic matter were most important devices in regulating the amount of free or bioavailable metals in the sediment. The high proportion of metals in the residual phase related with low levels of extractable metals indicated that the sediments of Tirumalairajan River Estuary environments were relatively unpolluted. 4.3 Factor analyses (FA) In order to establish the natural and geochemical processes responsible for enrichment of heavy metal ions in different geochemical speciation phases with respect to textural parameters, organic matter content of the sediments, pH and International Journal of Sediment Research, Vol. 30, No. 1, 2015, pp. 28–38

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salinity variations, the R-mode varimax factor analysis was applied by taking 54 variables from geochemical speciation data collected in monsoon and summer, respectively (Table 3). The variance/covariance and factor loadings of the variables with eigenvalues were computed. FA with varimax rotation of standardized component loadings were conducted for extracting and deriving factors, respectively, and principal components (PC) with eigenvalue greater than 1 were retained (Bengraine and Marhaba, 2003; Singh et al., 1999; Chen et al., 2007; Sundaray et al., 2011). The factor analysis of the present data set was sorted by the contribution of less significant variables (factor loading < 0.5). During the study period, there are four factors or PCs, explaining 100% of the total variance for monsoon season. Factor 1 represents 43.48 % of total variance and has more number of significant variables than the others during the monsoon season. This factor is positively loaded with silt, clay and organic matter along with all fractions of Fe and Cu, exchangeable Co, Pb, Cr, Ni, carbonate Pb, reducible Co, Pb, Zn, organic Ni, residual fraction of Pb, Mn and Zn, respectively. Sand is negatively loaded in this factor. Fe and Mn oxides/hydroxides singly or in combination seem to play important role in scavenging heavy metals (Tessier et al., 1979). The present study reveals that all heavy metals are scavenged by Fe oxy-hydroxide colloids, but to different degrees. Textural parameters of silt and clay along with organic matter also play an important role for the fixation of heavy metals. The significant loading on clay content demonstrates that the deposition of fine grained materials is the most important physical control on the abundance and distribution of most non-residual metal concentrations (Loring, 1984; Francois, 1988). Further the association of non-bioavailable fraction of Mn and Zn with total metals reveals that most of metals were derived from lithogenic source. It indicates that the reason for slightly high Mn and Zn in residual phase was due to the association with the crystalline matrix of minerals. Considering the above observations, Factor 1 may be termed as “Fe-Mn oxy-hydroxide or Textural Factor”. Factor 2 is accounting for 27.97% of the total variance in monsoon, and characterized by negative loadings of salinity along with Ni, Fe, Mn, and Zn in carbonate, Ni in reducible, Pb in organic fractions. Ni and Mn in exchangeable, Cr in carbonate, Cr in organic, Ni, Cr, and Co in residual fraction along with Ni, Cr, and Co in total are positively loaded in this factor. This factor suggests that salinity is an important factor for metal distributions in the respective fractions. The inverse relationship might be due to the different contributing sources. Besides, the association between residual fractions of Ni, Cr and Co with total metals reveals that most of metals are contributed from lithogenic source. In case of summer season, Factor 1 exhibits 66.83% of the total variance, where salinity entails Mn, Fe, and Co in exchangeable, Mn, Ni, Cr, Zn, and Co in carbonate, Ni, Cr, Zn, Pb, and Co in reducible, Zn and Fe in organic, Fe and Cu in residual fractions respectively. The fine grain sediments of silt and clay act as a sink for these metals, derived from terrigenous source, and also control the levels of metals in the sediment–water system due to the great cation capacity promoting the adsorption of positively charged metal ions with help of salinity levels (Sahu and Mukherjee, 1983). Thus, this factor may be termed as “Salinity Factor” in both seasons. In Factor 3 of monsoon season, Mn, Cr, and Cr in reducible, Cu, Co, and Cr in exchangeable, Co, in carbonate, Cr and Mn in organic, Cr in residual fractions along with organic matter are positively loaded. Fe-Mn oxy-hydroxide plays a major role for controlling the dynamics of these metals. In summer season, Factor 2 exhibits the variance of about 18.58%, where Fe-Mn oxy-hydroxide, silt and organic matter play major roles in controlling the reducible phase of Cr, Co and Cu, exchangeable phase of Fe, carbonate phase of Cu, organic phase of Cr, Fe, Mn, Pb and residual phase of Cr, Co, Fe, Pb, Zn, Cu metals. Fe and Mn oxides/hydroxides singly or in combination seem to play an important role in scavenging heavy metals (Tessier et al., 1979). This study reveals that all heavy metals are scavenged by Fe-Mn oxy-hydroxide. Thus, this factor may be termed as “Fe-Mn oxy-hydroxide factor in both seasons. Major portions of Co are contributed from geogenic origin in addition to anthropogenic sources. It might be controlled by hydrous oxides of Fe-Mn. Generally Fe-Mn oxide phase contain the substantial concentrations of these metals, the role of adsorption on Fe-Mn phase control the metal behavior under oxidizing conditions of an estuarine region (Arakel and Hongjan, 1992). Factor 3 of summer season, loaded 8.02 % of the total variance, which is strongly associated with clay, Cr, Mn, Pb, Ni, Cu, Zn exchangeable, Pb and Cu in carbonate, Cu in reducible, Mn, Pb, Ni, Cu, Co in organic, Mn, Ni, Fe, Zn in residual fractions, Mn, Ni, Fe, Zn total along with organic matter, respectively. Textural parameters like sand and clay are inversely related to each other. Clay plays an important role for fixation of heavy metals. The significant loading on clay content demonstrates that the deposition of fine grained materials is the most important physical control on the abundance and distribution of metal concentration. This factor may be termed as “Clay Factor”. Factor 4 of monsoon season represents 13.57 % of the total variance, which is found to be strongly associated with pH, Zn in all fractions except reducible fraction, Co consist in organic bound fraction, whereas Pb loaded in reducible fractions. In case of summer season, Factor 4 suggests that pH is strongly associated with Cu and Co in exchangeable, Ni in organic, Ni and Pb in residual fractions and Ni and Pb, respectively. This factor contributes 6.57% of the total variance in summer season. This factor demonstrates that pH is an important factor for distribution of these metals. The low concentration of these metals ions suggests that poor availability of the metals in the sediments can be attributed to high pH. This factor may be termed as “pH Factor” in both seasons. Thus, this study suggests that the major portion of all metals is contributed from geogenic sources associated with textural parameters, Fe-Mn oxy-hydroxide, and salinity variation in both seasons. - 34 -


Variables Fe5 FeT CuT Cu5 Co3 Fe1 Pb2 Sand Fe4 Fe3 Cu2 Silt Clay Ni4 Cu3 Pb1 Pb5 MnT Cu4 Mn5 Pb3 Co1 OM Cr1 Ni1 Cu1 Ni3 Ni2 NiT Ni5 Fe2 Salinity ppt Cr2 PbT Co5 Mn1 Pb4 Cr5 Mn2 Mn3 Cr3 Co2 Mn4 CrT CoT Cr4 Zn3 Zn4 Zn1 pH Co4 Zn5 ZnT Zn2 Eigenvalue Percent of Variance Cumulative %

Table 3 Factor analyses results for sediment data of Tiurmalairajan estuary Monsoon Summer F1 F2 F3 F4 Variables F1 F2 0.957 Salinity ppt 0.981 0.956 Mn2 0.98 0.955 Ni2 0.946 0.954 Cr2 0.913 0.944 Ni3 0.900 0.942 Zn3 0.882 0.918 Pb3 0.875 -0.915 Zn4 0.863 0.903 Zn2 0.851 0.903 Fe1 0.818 0.526 0.889 Fe2 0.719 0.887 Cu5 0.717 0.601 0.872 Co2 0.716 0.87 CuT 0.708 0.606 0.849 Co1 0.626 0.845 0.514 Fe5 0.607 0.541 0.839 FeT 0.604 0.563 0.834 Co3 0.598 0.574 0.821 Cr4 0.978 0.821 Cr5 0.905 0.818 -0.511 CrT 0.887 0.789 0.569 Co5 0.821 0.788 0.53 Fe3 0.81 0.739 0.501 Fe4 0.53 0.791 0.728 0.622 Mn3 0.788 0.709 0.705 Mn4 0.734 -0.972 PbT 0.728 -0.948 Zn1 0.713 0.933 Pb5 0.697 0.925 Pb4 0.694 -0.922 Cr3 0.661 0.68 -0.91 CoT 0.665 0.897 Silt 0.608 -0.893 OM 0.559 0.844 Cr1 0.813 Mn5 -0.782 Pb1 0.768 0.572 Pb2 -0.657 -0.648 Ni1 0.999 Cu4 0.954 Clay 0.862 Co4 0.855 MnT 0.561 0.618 0.766 Mn1 0.587 0.571 0.754 Cu1 0.566 0.732 Cu3 0.622 0.592 -0.66 Cu2 0.585 0.992 Sand -0.525 0.937 Zn5 0.524 -0.913 ZnT 0.527 0.529 -0.894 pH 0.599 0.782 Ni4 0.603 0.780 NiT -0.575 -0.747 Ni5 23.482 15.102 8.09 7.326 Eigenvalue 36.088 10.036 Percent of 43.485 27.967 14.981 13.567 Variance 66.83 18.584 43.485 71.452 86.433 100 Cumulative % 66.83 85.414


F3

F4

0.555 0.534 0.511

0.544 0.575 0.639 0.674 0.52

0.523 0.548 0.972 0.951 0.887 0.86 0.858 0.851 0.832 0.797 0.789 0.766 0.739 0.697 0.614 -0.584 0.582 0.57

0.55

-0.521

0.509 0.551 0.604 4.329

-0.966 0.838 0.79 0.744 3.547

8.018 93.432

6.568 100 - 35 -

4.4 Cluster analyses (CA) This analysis for metal concentrations in all fractions is rendered as dendrogram (Fig 4a and b), the relationship among stations and parameters obtained through cluster analysis synthesized by the dendogram plots. This gives indication to assess the level of heavy metals pollution. The dendograms illustrate a sequence in the association, displaying the information as degree of contamination of heavy metals between stations and group of parameters. The R-mode CA produced three clusters in both seasons. During the monsoon season, CA 1 consists of pH, Mn, Zn, clay, OM, Pb, Cr and Ni; and CA 2 entails of Co, Cu, silt and salinity. CA 3 contains sand and Fe. Mn in cluster 1 is associated with the Mn oxides rather than Fe. The dendrogram patterns for summer season indicate a slightly different patterns with three different type of clustering. CA 1 includes pH, clay, OM, Pb, Cr, Co, Ni and silt, and CA 2 consists of salinity, Mn, Zn and Cu. CA 3 contains sand and Fe. These metals are the clustering of metals with grain size and OM of a similar linkage pattern suggesting that the excess metals is mainly controlled by geogenic mechanism, grain size and organic matter apart from the anthropogenic sources (Forstner et al., 1982).

Fig. 4a Dendrograms showing relationship among the parameters (R mode) and stations (Q mode) in monsoon

Fig. 4b Dendrograms showing relationship among the parameters (R mode) and stations (Q mode) in summer

Q-mode CAs for 10 sampling stations of Coleroon River Estuary form three major clusters for monsoon and summer seasons. Cluster 1 consists of sampling points of 1, 9, 5, and 6 in monsoon season, and stations 1 and 4 at a slightly lower significance level in summer season. It may be regarded as less contaminated due to the geogenic origin. Cluster 2 consists of sampling points of 4, 7 and 10 in monsoon, and 2, 8, 7 and 3 in summer, respectively. This indicates the accumulation of metal loads from agricultural runoff. Cluster 3 consists of station 2, 8, and 3 in monsoon, and 5, 9, 6 and 10 in summer. Organic matter and grain size were more effective scavengers for the metals. This indicates that these sites may be contributing sources for the slightly higher concentration of metals in the present study. 5 Conclusions According to the sequential extraction method, heavy metals can be considered to be immobile because of their high concentrations in the residual fraction. It suggests that they are strongly bound to minerals and resistant components. This fact shows that textural parameters, Fe-Mn phase and organic matter can be more effective scavengers for these selected heavy metals. Factor analysis revealed the contribution of heavy metals in the sediment with four different - 36 -


factors, which exhibited that the enrichment of heavy metals was derived mainly from geogenic origin in addition to anthropogenic sources. Besides, cluster analysis clearly elucidated that the grain size and organic matter acted as efficient scavengers for metals. On the whole, all heavy metals in the sediments generally pose no risks even to a low impact on the environment. In the future, this kind of harmonizing approaches for heavy metals in the sediments would be important to evaluate the potential risks towards the estuarine ecology. Acknowledgement The authors would like to thank the results generated by ICP-OES, IIT Madras, Chennai, Tamil Nadu, India. This research was supported by a grant (code 13AWMP-B066761–02) from AWMP Program funded by Ministry of Land, Infrastructure and Transport of Korean government. The authors are also grateful to editor and reviewers for their constructive comments and suggestions which led to significant improvements to the manuscript. 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