PARENT SESSION
PW11 - Site-Specific Risk Assessments
Wednesday, 20 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P848) Application of Biotic Ligand Models in regional risk assessment procedures: a case-study with zinc.
Heijerick, Dagobert*,1,2, Van Sprang, Patrick2, Vangheluwe, Marnix2, Vandenbroele, Marleen2, Janssen, Colin1, 1 Ghent University, Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent, Belgium2 EURAS, Ghent-Zwijnaarde, Belgium
ABSTRACT- Recently developed Biotic Ligand Models are receiving increasing attention as a way to incorporate metal bioavailability in Water Quality Criteria derivation procedures. Validation studies with these models with both standard test media and field samples have demonstrated their potential to predict (within a factor of 2) acute and chronic effect levels for organisms belonging to different trophic levels of the aquatic environment (algae, daphnids and fish). In this study, monitoring (measured ambient) data covering five regions in different European countries (Belgium, England, Sweden) were collected and used as input data to calculate, using the BLMs, toxicity of zinc in these waters. By integrating the results of these BLMs, one safe environmental Zn-concentration is derived for each of the sampling stations. This site-specific Predicted No Effect Concentration (PNEC) is considered to provide long-term protection for at least algal and daphnid populations. These local BLM-derived PNECs are then used for the derivation of region-specific PNEC-distributions which are compared to establish region-specific differences. Finally, the predicted site-specific PNECs are compared to the actual measured Zn-concentrations and the potential risk of Zn is assessed by calculating the ratio between measured Zn-concentration and site-specific PNEC: a ratio > 1 indicates a potential risk of Zn for algae and/or daphnids. Based on the site-specific ratios, a potential risk distribution is developed for each region. The results of this study demonstrate that safe Zn-concentrations are clearly region-specific due to differences in the water chemistry in the studies areas (pH and/or hardness). The calculated potential-risk distributions allow to compare the degree of Zn-induced adverse effects between the different areas, taking into account the various mechanisms that alter metal bioavailability and toxicity.
Key words: Biotic Ligand Model, PNEC, zinc, site-specific assessment