CHECK STUDIES WITH HYALELLA AZTECA AND CHIRONOMUS TENTANS IN SUPPORT OF THE DEVELOPMENT OF A SEDIMENT QUALITY CRITERION FOR DIELDRIN

摘要

The development of sediment quality criteria (SQCs) for nonpolar compounds using equilibrium partitioning theory (EqP) requires three critical data elements for the compound of interest: (a) a reliable, measured K_(ow); (b) an acceptable minimum data set for the development of the final acute and final chronic values necessary to calculate a water-quality criterion (WQC); and (c) "check" experiments with appropriate freshwater and marine benthic organisms to ensure that their responses in spiked-sediment tests are in agreement with responses predicted based on EqP. This study presents the results of dieldrin check experiments with two freshwater species: the amphipod Hyalella azteca and the chironomid Chironomus tentans. Ten-day, flow-through, water-only dieldrin LC50 values for the amphipod and chironomid were 7.6 and 1.1 μg/L, respectively. The LC50 values for the two species based on organic carbon-normalized sediment concentrations of dieldrin were generally less variable than values based on dieldrin concentrations in sediments on a dry-weight basis. Ten-day LC50 values for H. azteca and C. tentans based on measured pore-water concentrations of dieldrin were greater than those based on EqP-predicted pore-water concentrations of dieldrin. An increase in the apparent water solubility of dieldrin as a result of binding to dissolved organic carbon appeared to account for this phenomenon. Ten-day LC50 values for H. azteca and C. tentans based on EqP-predicted pore-water concentrations of dieldrin were within a factor of 25 and 3 of their respective 10-d, water-only dieldrin LC50 values. Avoidance of the dieldrin-spiked sediments may offer a partial explanation for the concentration-response results observed with H. azteca and the greater difference observed for this species between water-only and predicted pore-water 10-d LC50 values for dieldrin. Inhibition of growth in C. tentans was also a sensitive end point with effects observed at pore-water concentrations of dieldrin as small as 5.5 μg/g organic carbon. Based on these results, it appears that EqP based upon sediment organic carbon content is an appropriate model for converting WQC for dieldrin to SQC. These results also highlight the importance of using multiple benthic test species (including at least one infaunal species), end points, and sediments in SQC sediment-spiking check studies.