TRACE-ELEMENT GEOCHEMISTRY OF RIVER SEDIMENT, ORISSA STATE, INDIA

Geochemical analyses of bottom sediment from rivers flowing through Or issa State, India indicated that trace element concentrations were ext remely variable, and commonly higher than crustal abundance. The highe st elemental concentrations were associated with the Brahmani River, f ollowed by the Baitarani and Mahanadi Rivers. Although ail three river s drain similar geology, the Brahmani River catchment is heavily indus trialized, and sediment collected downstream from industry confirms th at anthropogenic activity influenced its chemical composition. A simil ar pattern was observed in sediments collected downstream from towns i n the Mahanadi and Baitarani catchments. Ln both examples, the clay si ze fraction was shown to be the most highly reactive component of the sediments. Comparisons between metal concentrations from the upper to lower stretches of the three river systems indicated no net accumulati on downstream. Apparently, trace elements discharged into the river sy stem tend to be short-lived in the water column, rapidly settling out or becoming adsorbed into the bottom sediment. Although for much of th e year, the trace metals may remain locally incorporated as bottom sed iment, during monsoonal episodes, where bedload transport can be signi ficant, the effects of pollution may expand over regional distances. ( C) 1997 Elsevier Science B.V.