Ghent University. Laboratory of Environmental Toxicology and Chemistry
Abstract
The accurate prediction of Ni ecotoxicity in natural surface water with bioavailability models such as the biotic ligand model (BLM) depends on how well these models can predict both the speciation of Ni (i.e. Ni2+ concentration), the toxicity of Ni2+ ions to an organism, and the effects of water chemistry parameters thereupon, such as dissolved organic carbon (DOC), pH, and water hardness.
The overall aim of the study was to calibrate existing speciation models to Ni speciation in natural surface waters and to use these data to validate and/or refine bioavailability models for aquatic organisms from three trophic levels, i.e. algae, invertebrates (daphnids), and fish. The developed chronic Ni toxicity models for daphnids, fish and algae exhibit sufficiently high predictive capacities to yield a marked reduction of uncertainty associated with differences in chronic Ni bioavailability among different test waters. This is due to the fact that they can predict both Ni2+ concentrations as a function of dissolved Ni and water chemistry (mainly DOC, pH, Ca, Mg), as well as the toxicity of the Ni2+ ion as a function of water chemistry (mainly pH, Ca, Mg). The use of the models presented in the present study for normalizing Ni toxicity data will therefore decrease the overall uncertainty of the risk assessment, provided that the variability of bioavailability modifying parameters across different EU regions and water bodies is acknowledged
