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Authors
Affiliations
1 Climate Change Research Unit, Department of Applied Geology University of Madras, Guindy Campus, Chennai 600 025, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 55, No 4 (2000), Pagination: 387-394
Abstract
Fourteen sediment samples collected from Pichavararn mangrove were analysed for grain size, organic carbon, sedimentary sulphur, calcium carbonate, Fe, Mn, Al, Cu, and Hg. Factor analysis was carried out to infer the mechanisms controlling the behaviour of metals. Four factors accounted for around 75% variance. Fe, Mn, and Hg are associated with organic carbon and fine fraction content of the sediments and loaded onto factor I whlch accounted for 33.6% variance. This is due to the complexation of Fe, Mn, and Hg with organic matter and the adsorption of these organo-metallic compounds onto the finer sediments due to their high surface/volume ratio and presence of surface charge. Factor 2 accounted for 18.6% variance and is loaded with CaCO3, finer fraction, Al and Cu, implying contribution of Al and Cu from detritai clay minerals. The association of CaCO3, with this factor is not clearly understood. Factor 3 is loaded with organic carbon and coarse fraction of the sediments and it accounted for 13.3% variance. The association of organic carbon with coarse fraction of the sediments could be either due to the Ca2+ and Mg2+ ions induced adsorption of organic matter onto mineral grains, or due to the presence of coarse vegetal debris. The fourth factor accounted for 9.8% variance and is loaded with sedimentary sulphur; no metal is associated with this factor. This explains that though sulphate reduction occurs in the surface sediments, it could not result in the burial of Fe, Cu, and Hg as their respective sulphides. This could be due to their back oxidation by Mn oxides present in the sediments where upon FeS is converted to Fe hydrous oxide, and Cu and Hg are released to the water column.
Keywords
Geochemistry, Sediments, Pichavaram Mangroves, Trace Metals, East Coast of India.
