TRANSPORT AND DISTRIBUTION OF HEAVY-METALS IN CAUVERY RIVER

Heavy metal transport in Cauvery river chiefly takes place in the part iculate form. Tributaries Hemevathi and Kabini draining highly mineral ized areas contribute significantly to the heavy metal load of the Cau very river. Particulate metal transport is influenced by the presence of major dams built across the river. Factor analysis of the elemental data identifies two major group of heavy metals, (a) Fe, Mn, Cr, V an d Ti and (b) Cu, Pb and Zn in the suspended sediments of Cauvery river . Heavy metals in surface sediments show wide variations in their conc entrations due to the non-uniform grain size distribution of the sedim ents. The elements Fe, Mn, Pb, Cu, Zn, Ni, Co and As are dominantly pr esent in the < 20 mum fraction of the river sediments. Speciation stud ies show that Fe-Mn oxide phase held the largest share of heavy metals in the sediments. The depth variation of heavy metals in the core sed iments suggest their similar mobility during diagenesis. Geoaccumulati on indices calculated suggest that Cd, Zn, Cr, Pb, Cu and Ni are enric hed in sediments several times over background values.