Abstract
It has been long discussed that ecological risk varies depending water chemistry because toxicities of metals on biological species vary depending on water chemistry. In this paper we aimed to develop a way to assess such a potentially varying ecological risk with an aid of biotic ligand model（BLM）, which is now recognized as a powerful tool to predict varying toxicity of metals. Copper was used as an example. No-Observed-Effect-Concentrations （NOECs）of copper for various biological species were collected, and BLM corrections were applied for these concentrations. By using the BLM corrected NOECs, species sensitivity distributions（SSD）were estimated. These SSD were compared to the conventional SSD without BLM correction. We found that when the water hardness, pH and dissolved organic carbon were low, 5% hazardous concentration（HC5）with BLM correction could be lower than that without BLM correction. On the other hand, when water hardness, pH and dissolved organic carbon were high, BLM corrected HC5 tended to be higher than that without BLM correction. Among estimated HC5s with BLM corrections, the highest HC5 was about 80 times higher than the lowest HC5 in the range of water chemistry we have investigated. This result suggests that we need to be more careful when we conduct an ecological risk assessment of metals.
