Accumulation of heavy metals by organisms in the Derwent catchment

Abstract

The distribution of Zn, Cd and Pb in water, sediments, plants and animals from the River Derwent and Derwent Reservoir was studied during four periods of intensive survey between October 197 8 and November 1979.Elevated concentrations of Zn, Cd and Pb were found in all components from the river below the entry of a polluted tributary, Bolts Burn. Concentrations of Zn in river sediments from above Bolts Burn and Zn and Cd from below were found to show significant positive correlations with the organic content of sediments. It is suggested that autumn shed leaves may exert considerable influence on the metal composition of river sediments during decomposition and may cause an increase in the amount of metal potentially available to detritivorous invertebrates in their food. Marked variations were observed in concentrations of Zn, Cd and Pb in plants and animals from the river between reaches and surveys. Among the animals, mayflies as a group had especially high concentrations of metals and Zn, Cd and Pb were frequently higher in samples of these from the river above Bolts Burn than in many other animals from below this stream. Metal pollution was shown to extend into the Derwent Reservoir. Elevated concentrations of Zn and Pb evident in water, sediments and submerged plants near the entry of the river were found to decrease on passing towards the dam. Comparisons between metal concentrations in the biota and those in their environment made it possible to assess possible importance of water and sediments as sources from which metals may be accumulated.