Laboratory study of Se speciation in the sediment and oligochaete Lumbriculus variegatus from an aquatic environment.

Abstract

Sediments are the major sink for selenium (Se) in aquatic environments. Se speciation in sediments is crucial for its bioavailability and toxicity in benthos, but this is relatively understudied. In this study, the background levels of Se in the river sediments, fish flakes, and Lumbriculus variegatus were also detected. Then, the dynamic changes of selenium speciation and concentrations in sediments were investigated after adding selenite (Se(IV)) and seleno-L-methionine (Se-Met) in the sediments for 90 and 7days, and the accumulation and depuration of Se(IV) and Se-Met for 7days in the oligochaete L. variegatus were also explored. Without the presence of worms, the levels of Se(IV) in the sediments were relatively stable within 7days but showed a decreasing trend during the 90days of aging. In contrast, Se-Met in the sediments showed a sharp decrease within 3days of aging. The LC50-96h values of Se(IV) and Se-Met in L. variegatus were 372.6 and 9.4μg/g, respectively. Interestingly, the dominant Se species in Se(IV)- or Se-Met-treated L. variegatus was Se-Met, whose level was increased with time in 7days of exposure. Se was barely depurated from L. variegatus during the 8days of the depuration period. This study has provided indispensable data on the levels of total Se in the abiotic and biotic matrices and the biodynamics of Se in a representative benthos, which could better understand the ecological risk of Se to the freshwater benthic communities.