Model of PAH and PCB bioaccumulation in Mya arenaria and application for site assessment in conjunction with sediment quality screening criteria

Abstract

A review of six methods for deriving sediment quality criteria SQC was conducted. Each approach was analyzed according to cost, difficulty, applicability and reliability. Results of this analysis led to the recommendation that the state of Massachusetts should use a combination of the Equilibrium Partitioning modeling approach and the Threshold Effects Level/Probable Effects Level correlative approach to SQC derivation. Criteria should then be applied as screening values for evaluation of sediment toxicity. One significant component of sediment quality that all criteria approaches lack is the bioaccumulation/biomagnification of contaminants. Nor are there accurate, easily implemented models for benthically-coupled organisms such as Mya arenaria. In this document a bioaccumulation model for PAHs and PCBs was developed. The model considers contaminant partitioning into organism lipid and protein and incorporates organism exposure to contaminants through sediment and ingestion of contaminated food particles. Results show the model predicts PCB accumulation in M. arenaria with only a slight variation from observed data. Partitioning into sedimentary soot fraction was added to the model for PARs. Results showed an increase in model accuracy, but predicted concentrations still remain greater than observed concentrations. A combination of sediment quality criteria used as screening criteria and the bioaccumulation model for M.arenaria will improve the accuracy of site assessment of PAH and PCB compounds.