ASSESSING POTENTIAL BIOAVAILABILITY OF METALS IN SEDIMENTS - A PROPOSED APPROACH

Due to anthropogenic inputs, elevated concentrations of metals frequen tly occur in aquatic sediments. In order to make defensible estimates of the potential risk of metals in sediments and/or develop sediment q uality criteria for metals, it is essential to identify that fraction of the total metal in the sediments that is bioavailable. Studies with a variety of benthic invertebrates indicate that interstitial (pore) water concentrations of metals correspond very well with the bioavaila bility of metals in test sediments. Many factors may influence pore wa ter concentrations of metals; however, in anaerobic sediments a key ph ase controlling partitioning of several cationic metals (cadmium, nick el, lead, zinc, copper) into pore water is acid volatile sulfide (AVS) . In this paper, we present an overview of the technical basis for pre dicting bioavailability of cationic metals to benthic organisms based on pore water metal concentrations and metal-AVS relationships. Includ ed are discussions of the advantages and limitations of metal bioavail ability predictions based on these parameters, relative both to site-s pecific assessments and the development of sediment quality criteria.