Algal bioassays for metal mining wastes

The project is a Danish contribution to a larger Canadian project funded by Environment Canada. The overall objective is to develop scientifically based algal bioassays that can reveal the presence and toxicity of bioavailable metal forms in complex wastewaters from the Canadian metal mining industry and in leachates from Danish deposits of combustion residues. The main effort has been the optimization and interpretation of algal toxicity tests of heavy metals which are complicated by interactions between algal growth and medium factors on the one hand and by the influence of these factors on metal speciation. The main emphasis of the TUD project part has been to study iron-chelator interactions and to develop an optimized medium for heavy metal toxicity testing. It has further been found that the commonly used chelator EDTA photodecomposes under the test conditions and therefore an alternative chelator should be selected, for instance citrate. The work has been considered (and used in part) by the ISO.