R6 PM Bioavailability
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in 324-326

(GUS-1117-820869) Do Contaminant Mixtures Alter Contaminant Bioavailability?

Gust, K¹, ¹ Louisiana State University, Baton Rouge, LA, USA

ABSTRACT- Although individual models developed to assess metal or hydrocarbon bioavailability in sediments (i.e. SEM-AVS relationships or equilibrium partitioning theory respectively) generally provide accurate determinations of contaminant bioavailability for each individual class of contaminants, effects of metal-hydrocarbon mixtures on model predictions have not been tested. Sediment bioassays were conducted to investigate effects of PAH on physical-chemical parameters indicative of metal bioavailability including: SEM-AVS relationships, sediment pH and dissolved metal concentrations in porewater and overlying water. As well, metal effects on PAH bioavailability were tested using biota-sediment accumulation factor (BSAF). To determine if the above parameters provided accurate estimates of contaminant bioavailability, both PAH effects on metal bioaccumulation and toxicity and metal effects on PAH bioaccumulation and toxicity were tested. The PAH phenanthrene (Phen) and the toxic metal Cd were used as model contaminants. Results indicated Phen had no affect on SEM-AVS relationships or sediment pH and had marginal effects on Cd concentrations in both overlying water and porewater. However, in sediment exposures, Phen dramatically increased Cd bioaccumulation and lethality in the freshwater amphipod Hyalella azteca. Conversely, Phen reduced Cd bioaccumulation in the freshwater tubificid oligochaete Ilyodrilus templetoni thereby reducing lethality in sediment exposures. Effects in each species resulted from Phen-mediated effects on Cd bioaccumulation via sediment feeding. Cadmium had no effect on BSAF for Phen, Phen bioaccumulation or Phen toxicity in I. templetoni and similar effects are suggested to have occurred in H. azteca. Based on these results, BSAF appears to be an accurate indicator of PAH bioavailability regardless of the presence of metal. However, although the physical-chemical parameters used as surrogate measures of metal bioavailability were not affected by PAH, PAH-mediated effects on metal bioaccumulation via feeding were observed in test organisms and these effects were species specific. Therefore, sublethal effects of hydrocarbons in metal-hydrocarbon mixtures may render standard measures of metal bioavailability inaccurate.

Key words: bioavailability, sediment, metals, hydrocarbons