Heavy metals in water,sediments and invertebrates from a metal-contaminated river free of organic pollution

A study was made of water, sediments and invertebrates in the R. Derwent, North-East England, at one site above and three sites below a stream bringing in high concentrations of Zn, Cd and Pb derived from an active fluorspar mine. The mean concentrations of these metals in filtrable water at the unpolluted site were 0.020, <0.0003, 0.005 mg l^-1, respectively, while those at the first polluted site were 0.29, 0.0006, 0.016 mg l^-1. The benthic macroinvertebrate fauna was dominated by insects; all taxa present at the unpolluted site were represented at one or more of the polluted sites. In almost all cases the elevated concentrations of metals in water and sediments at polluted sites were paralleled by higher concentrations in animals. Significant positive correlations were demonstrated between metal concentrations in certain taxa and those in their environment e.g. Ecdyonurus venosus and aqueous Pb. Mayflies tended to concentrate Zn, Cd and Pb to higher levels than other groups. Comparison of carnivorous species with other taxa revealed no indication of increased metal concentrations at higher trophic levels.