Effects of pH on the toxicity of cadmium, copper, lead and zinc to Folsomia candida Willem, 1902 (Collembola) in a standard laboratory test system.

EC50s for cadmium, copper, lead and zinc were determined for juvenile production of Folsomia candida at pH6.0, 5.0 and 4.5 in a standard laboratory test system. In contrast to most previous studies where metal toxicity was increased at low pHs, in our experiments there was no clear relationship between soil acidity and EC50-reproduction in this species. The EC50-reproduction values (microgram g-1) for cadmium and zinc were similar at all three pHs (pH6.0: Cd 590, Zn 900; pH5.0: Cd 780, Zn 600; pH4.5: Cd 480, Zn 590). In contaminated field sites adjacent to primary zinc smelters, zinc is invariably present in soils at concentrations of at least 50 times that of cadmium. Thus deleterious effects of mixtures of these metals on populations of Collembola in such sites can be attributed to zinc rather than cadmium.