ASSESSING THE BIOACCUMULATION OF CONTAMINANTS FROM SEDIMENTS OF THE UPPER MISSISSIPPI RIVER USING FIELD-COLLECTED OLIGOCHAETES AND LABORATORY-EXPOSED LUMBRICULUS-VARIEGATUS

Concern with the redistribution of contaminants associated with sedime nt in the upper Mississippi River (UMR) arose after the flood of 1993. This project is designed to evaluate the status of sediments in the U MR and is one article in a series designed to assess the extent of sed iment contamination in navigational pools of the river. Companion arti cles evaluate sediment toxicity and benthic community composition in n avigation pools of the river. The objectives of the present study were to: (1) to assess the bioaccumulation of sediment-associated contamin ants in the UMR using laboratory exposures with the oligochaete Lumbri culus variegatus, and (2) to compare bioaccumulation in laboratory-exp osed oligochaetes to field-collected oligochaetes. Sediment samples an d native oligochaetes were collected from 23 navigational pools on the Upper Mississippi River and the Saint Croix River. Contaminant concen trations measured in the L. variegatus after 28-day exposures to sedim ent in the laboratory were compared to contaminant concentrations in f ield-collected oligochaetes from the 13 pools where these sediments we re collected. Contaminant concentrations were relatively low in sedime nts and tissues from the pools evaluated. Only polycyclic aromatic hyd rocarbons (PAHs) and total polychlorinated biphenyls (PCBs) were frequ ently measured above detection limits. The majority of the biota-sedim ent-accumulation factors (BSAFs) for PAHs were within a range of about 1.0 to 2.6, suggesting that the theoretical BSAF value of 1.7 could b e used to predict these mean BSAFs with a reasonable degree of certain ty. A positive correlation was observed between lipid-normalized conce ntrations of PAHs detected in laboratory-exposed and field-collected o ligochaetes across all sampling locations. Rank correlations for conce ntrations of individual compounds between laboratory-exposed and field -collected oligochaetes were strongest for benzo(e)pyrene, perylene, b enzo(b,k)fluoranthene, and pyrene. About 90% of the paired PAH concent rations in laboratory-exposed and field-collected oligochaetes were wi thin a factor of three of one another indicating laboratory results co uld be extrapolated to the field with a reasonable degree of certainty .