LIMITED BIOAVAILABILITY OF SEDIMENT PAH NEAR AN ALUMINUM SMELTER - CONTAMINATION DOES NOT EQUAL EFFECTS

A Sediment Quality Triad study involving synoptic measures of polycycl ic aromatic hydrocarbon (PAH) contamination, toxicity, and resident co mmunity (benthic infauna, crab) alteration was conducted to assess imp acts from an aluminum smelter discharge. No sediment toxicity was obse rved, despite extensive testing since 1988 on four test species. Evide nce of effects on resident communities was minimal. Effects were nor e xpected in areas >1 km from the smelter, because PAH concentrations ha ve decreased with recent effluent improvements to below levels associa ted with effects in other studies. However, concentrations within 1 km of the smelter were high (maximum concentration was 10,000 mg/kg tota l PAH, although most were <150 mg/kg). Based on the literature, those concentrations should have had significant effects on toxicity test re sponses and benthic communities. Because they did not, we conclude tha t availability of sediment PAH was limited. Concentrations of parent P AH and metabolites in Dungeness crab (Cancer magister) were also low, supporting the hypothesis of limited bioavailability. Bioavailability may be limited because much of the PAH is present as pitch or coal par ticles. This study indicates that high contaminant concentrations may not be associated with effects, if availability is limited.