Biotic Ligand model A tool for risk assessment of metals in Scandinavian fresh waters?

Abstract: Products from iron and copper mining are among Sweden’s top exports. However, as the metals are excavated, they often end up in the aquatic environment where they can cause toxicity. To implement the Water Framework Directive (WFD) within the European Union, all member states must classify their waters and set local environmental quality standards (EQS). These EQS are used to set the maximum concentration of a metal allowed in water and can be set both by the Swedish EPA and EU. The WFD EQS are to be based on the bioavailable metal fraction, as compared to the total metal concentration as have been used previously. As a tool in setting EQS, bioavailability models, like the biotic ligand model (BLM), have been proposed. BLMs can calculate toxicity endpoints based on water chemistry and organismal response and these predictions can be used for regional EQS values.However, BLMs are often calibrated toward hard waters with neutral or high pH, containing low concentrations of natural organic material (NOM), a water chemistry most commonly found in the central and southern parts of Europe. The overarching aim of this doctoral thesis was, therefore, to assess the regulatory applicability of Cu BLMs for Swedish conditions.Results from Paper I and II show that for at least 50% of Fennoscandinavian (Sweden, Finland and Norway) freshwater bodies, the models are not fully applicable. This due to crucial model input parameters being outside of the current calibration range of the Cu BLM. Papers II and III further showed that BLM calculated results differed from measured Cu toxicity to daphnids and algae, indicating that model-based EQS will not be protective for these organisms. Moreover, Paper III showed that Al had an impact on Cu speciation and, hence, toxicity. In conclusion, the present thesis shows that several available Cu BLMs are not yet fully applicable for Swedish or Scandinavian freshwater bodies due to incomplete parameterisation of the models.  To improve the applicability of the models, there is a need to calibrate the models for soft freshwater bodies and include Al and NOM properties as input parameters.