Pollution Research Paper

SIGNIFICANCE OF GEOCHEMICAL PROXIES IN ASSESSING THE QUALITY OF MARINE SEDIMENTS OFF GULF OF MANNAR

JUDITH D. SILVA, S. SRINIVASALIP AND P. SARAVANAIV

Abstract

The Environmental conditions of Gulf of Mannar are unique, mainly because of the coral reefs, sea grass beds and mangroves, which act as spawning and feeding grounds and shelters for many species of economically important finfish and shellfish. The islands in the Gulf of Mannar are formed of calcareous substratum with dense coral growth around them. The Gulf of Mannar is influenced by both southwest and northeast monsoons and hence the physical, chemical and biological characteristics are different from other areas. The important major industries contributing to pollution are Starlit., SP1C, Tuticorin Alkali Chemicals, Dharangadhra chemicals work, Madura coats, Kilbum chemicals industries. The public sector undertakings are the Thermal power unit (620mm), Heavy water plant, and port trust. Metal accumulation on sediment particles mainly depends on the adsorptive bonding on fine-grained materials, precipitation of the element in discrete compounds, co-precipitation of the element with hydrous Fe and Mn-oxides and carbonates, association with organic compounds and incorporation in crystalline material and moreover the enrichments of metal is mainly due to the surface adsorption and ionic attraction in clay/silt fractions. This study mainly focuses on the impact on marine sediments and its role in pollution studies. The sediment can be considered as a heterogeneous mixture of dissimilar particles due to these processes and also as a complex assemblage of different organic and inorganic components. The quantification of such processes is important for geochemical studies and prediction of the fate of environmental contaminants. This study concentrates on understandingthegeoMemical behaviour of the coastal surface sediments and its performance and relation with the pollution indices and statistical analysis. GeoMemical proxy is used in this study to predict the fate of the naturally enriched environment. The gcochemical proxies used for the current study are textural analysis, organic matter, calcium carbonate, major elements and trace metals. The pollution indices used for analysing the pollution load are Enrichment Factor, Contamination Factor and Igeo index. Al Is used as a nonnalher to calculate the enrichment of trace metals and are in the following order Cr > Cu > Pb > Sr >Zr > Zn > Co > Da > Ni > Cd > Ti > Mn > V> Rb (Wedepohl Shale value) indicating that the high values (EF>I.5) are due to the anthropogenic addition of metals to the system. EF values greater than I can be well thought out to be attributed to long transportation phenomenon from natural or manmade sources and not from crustal background (Notting et at, 1999). The EF for Cr, Cu, Pb, Sr and flare more than & The contamination factor values are in the range of Cr > Cu > Pb >Sr > Zr > Zn > Ba > Co > Ni > Cd > Ti >Mn > V > Rb. The CF values fora Cu, Pb, Sr and Zr are greater than 2.The Geoaccumulation index (I) based on shale values (Wedepohl 1995) showed values less than one for all the trace metals except Cr, Cu, Pb, Sr and Zr. of which Cr showed a I.* val ue of 113, Cu with a lgeo value of 27, Pb with a lasvalue of 10, Sr with a Isavalue of 3 and Zr with a I...value of 2. All these indices strongly indicate that this area is highly polluted due to the anthropogenic influence and these prevailing conditions should be controlled or should be reduced to certain extent to protect the Mother Nature with all her inborn beauties.