Biotic Ligand Models : availability, performance and applicability for water quality assessment

Biotic ligand models (BLMs) for heavy metals were developed in past years as tools for water qualityassessment, following the Water Framework Directive (WFD). The essence of BLMs is that chemicalspeciation is incorporated in the assessment of ecotoxicological risks for aquatic species. For WFD purposes,BLMs are recognized as useful concepts to determine site-specific risks, and are allowed as second-tierassessment method. Concepts have been made operational, resulting in tools that make the approachavailable to a larger audience. As a consequence, these tools are in general simplifications of the original,validated concept.