Abstract
The water chemistry dependency of toxicities of metals has long been recognized as a large uncertainty in the ecological risk assessment and management. To incorporate the water chemistry dependency, a couple of methodologies have been developed. These methodologies were developed almost independently without close link each other. Each method persisted on one aspect of the water chemistry dependency（e.g., dependency on water hardness）, and ignored the others. Recently, a model which unites and compiles existing methodologies were developed. The model is Biotic Ligand Model（BLM）. The BLM first developed as a model for predicting acute toxicities of metals, and then it evolved to predict the chronic toxicity of metals. The BLM is now recognized as the powerful tool for the site-specific ecological risk assessment. In this article, an evolutionary history and a theoretical framework of the BLM are overviewed, and then some examples for the ecological risk assessment are shown. The BLM is still under a development, and therefore there are a lot of limitations and problems to be solved. Such future tasks will be discussed at end.
