Abstract

 Metals are among the most commonly occurring contaminants encountered when conducting sediment evaluations. Lead is among the most prevalent metals associated with adverse impacts on aquatic health. However, few studies examining the chronic effects of lead contaminated sediment have been conducted. The SEM-AVS equilibrium partitioning model has been proposed as a screening tool for predicting bioavailability of metals in contaminated sediments. To date, few studies exist that have evaluated the predictive capacity of the model following chronic exposures. To address the paucity of chronic lead toxicity data and to further evaluate the SEM-AVS model utilizing chronic exposures, lead spiked sediment studies were conducted with Leptocheirus plumulosus and Neanthes arenaceodentata. The exposures were conducted following standardized 28-d chronic exposure methods. Clean sediment was spiked with increasing concentrations of lead. The measured lead sediment concentrations were 0, 931, 1510, 3980, 6290 and 12900 mg/kg (Leptocheirus plumulosus) and 394, 801, 1580, 3180, 5730 and 11000 mg/kg (Neanthes arenaceodentata). Leptocheirus plumulosus and Neanthes arenacedentata displayed similar sensitivity to lead with LOECs of 1580 and 1510 mg/kg, respectively. The LOECs were obtained through effects on growth. The Leptocheirus plumulosus LOEC of 1510 mg/kg lead corresponds to an SEM-AVS model value of 7.28 µmoles/gram sediment and falls within the range where toxic effects are possible (SEM-AVS concentration greater than 0) . The LOEC of 1580 mg/kg lead for Neanthes arenaceodentata corresponds to a SEM-AVS model value of -5.68 µmoles/gram sediment. The model would have accurately predicted absence of toxicity in the Leptocheirus plumulsosus study but would have predicted absence of toxicity where toxicity was observed in the Neanthes arenaceodentata study. Additional testing of the model is warranted before definitive statements regarding the uncertainties in its applicability to chronic exposures can be made.