Development of a methodology to investigate the importance of chemical speciation on the bioavailability of contaminants to Eisenia andrei

The uptake of metals by earthworms occurs predominantly via the soil pore water, or via an uptake route which is related to the soil pore water metal concentration. However, it has been suggested that the speciation of the metal is also important. A novel technique is described which exposes Eisenia andrei Bouché to contaminant bearing solutions in which the chemical factors affecting its speciation may be individually and systematically manipulated. In a preliminary experiment, the LC50 for copper nitrate was 0.046 mg l –1 (95% confidence intervals: 0.03 and 0.07 mg l –1). There was a significant positive correlation between earthworm mortality and bulk copper concentration in solution (R 2 = 0.88, P ≤ 0.001), and a significant positive increase in earthworm tissue copper concentration with increasing copper concentration in solution (R 2 = 0.97, P ≤ 0.001). It is anticipated that quantifying the effect of soil solution chemical speciation on copper bioavailability will provide an excellent aid to understanding the importance of chemical composition and the speciation of metals, in the calculation of toxicological parameters.