TRACE-METAL LEVELS IN CHIRONOMID LARVAE AND SEDIMENTS FROM A BOLIVIANRIVER - IMPACT OF MINING ACTIVITIES

The effect of mining activity on metal accumulation in sediments and C hironomidae in a river in Bolivia was assessed. Surficial sediments an d midge larvae (Chironomidae, Diptera) were collected at five sampling sites. Concentrations of the trace metals Cd, Cu, Cr, Ni, Pb, and Zn were measured in organisms and sediments by inductively coupled plasma atomic emission spectrometry. Sediments were subjected to two differe nt extraction procedures to identify total trace metals and reducible trace metals. Geochemical characteristics of the sediment were analyze d: total organic carbon (TOC), Fe and Mn oxides, and particle size dis tribution. To determine the relative importance of the different sedim ent factors contributing to the variation in metal accumulation by the chironomid larvae, nonlinear regression models were constructed. No i ncrease in metal concentration in sediment could be measured downstrea m of the mining activity. Larval concentrations, however, increased ma rkedly. Only for zinc and chromium was a significant amount of variati on (48 and 73%, respectively) found. The lack of relationship for the other metals probably was due to a unmeasured exposure route, the over lying water. (C) 1998 Academic Press.