COPPER TOXICITY TO PARATYA-AUSTRALIENSIS .3. INFLUENCE OF DISSOLVED ORGANIC-MATTER

The influence of dissolved organic matter on the toxicity of copper to the Australian freshwater shrimp, Paratya australiensis, was measured using water collected from three sites in Victoria, Australia. A two‐ligand model was used to describe copper complexation in these test waters. The binding characteristics of the ligands (i.e., total ligand concentrations and conditional stability constants) were determined using a method combining ion selective electrode and anodic stripping voltammetry. Ion selective electrode measurements and the two‐ligand model were each used to estimate the concentration of copper(II) (the major toxic species) at the LC50 values. Both methods overestimated by a factor of approximately 1.5 to 3 the expected copper(II) concentration at the LC50 values, based on earlier experiments in Melbourne tap water. The agreement seems remarkably good given the many assumptions used in making the comparison and the difficulties encountered with the use of ion selective electrodes in natural waters. Copyright © 1990 SETAC