Sediment toxicity and bioaccumulation assessment in abandoned copper and mercury mining areas of the Nalón River basin (Spain).

Sediment toxicity and metal bioaccumulation were assessed at sites affected by historical copper (Cu) and mercury (Hg) mining activities in the Nalón River basin, Asturias, Spain. Toxicity assessment of stream sediments was based on a 28-day oligochaete Tubifex tubifex sediment bioassay, which allowed the classification of sites into three levels of toxicity: 11 sites were classified as nontoxic (including Cu mine sites), three sites as potentially toxic, and seven sites as toxic (all located in Hg mine districts). The greatest levels of arsenic (As), chromium, Hg, lead (Pb), and zinc (Zn) in T. tubifex were measured at sites affected by Hg mining and the highest Cu levels in tissues at Cu mining sites. Chronic toxicity responses were best explained by As and Hg sediment concentrations and by As, Pb, and Zn tissue residues. Residue levels of As, Hg, Zn, and Pb were successfully used to predict sediment chronic toxicity and estimate effective tissue residues.