ELEMENTAL COMPOSITION AND PARTICULATE METAL FLUXES FROM NETRAVATI AND GURPUR RIVERS TO THE COASTAL ARABIAN SEA

Physico-chemical parameters of water (pH, dissolved oxygen, salinity and suspended particulate concentration) and geochemistry (Cu, Pb, Zn, Ni, Co, Mn, Fe, Al, Ca and organic matter) and magnetic susceptibility of suspended particulates have been measured, incidentally for the first time, in two west-flowing rivers - Netravati and Gurpur - of southwestern India in order to understand weathering processes, to determine gross particulate metal fluxes to the coastal Arabian Sea and to decipher anthropogenic influences, if any. Physico-chemical parameters do not show significant variations because of the heavy fresh water discharge during southwest monsoon. The composition of Netravati and Gurpur rivers SPM (suspended particulate matter) are similar and characterized by enrichment of Al, Fe, Ni and Co but strong depletion of Ca in comparison with temperate and major rivers of the world. This is an imprint of the intense chemical weathering in the study area. Copper, Pb, Zn and Mn contents in Netravati and Gurpur R. SPM are lower than world river SPM, implying that there may not be significant anthropogenic input of these metals. The gross particulate metal fluxes from the Netravati R. are considerably higher than those in Gurpur R, because of the former's high sediment discharge. However, the fluxes are significantly lower than those of Narbada and Tapti rivers. Magnetic susceptibility of Netrdvati and Gurpur SPM is nearly the same, but substantially low (by a factor of three) when compared to the silt+clay fraction of river-bed sediments, indicating that dense magnetic minerals are not transported in suspension but as bed-load.