Evaluation of simultaneously extracted metals-acid volatile sulfide (SEM-AVS) in lacustrine sediment (Lake Champlain), estuarine sediment (Narragansett Bay) and under laboratory conditions

In the process of development of sediment quality criteria, trace metal bioavailability is an essential consideration because different sediments can exhibit differing degrees of toxicity for the same concentration of contaminant. Various sediment phases are responsible for binding trace metals and rendering them non-bioavailable. In 1990, it was shown that acid volatile sulfide (AVS) is responsible for binding certain divalent metals on a molar basis. By measuring AVS and the simultaneously extracted metals (SEM), potential trace metal bioavailability may be determined. In this research, sediments from Lake Champlain and Narragansett Bay were analyzed by a variety of methods to determine the extent and distribution of trace metal contamination and to further the development of relevant sediment quality criteria.; The field sites selected for characterization, Burlington Harbor in Lake Champlain and Allen Harbor and McAllister Point in Narragansett Bay, are regions of significant contamination. In Burlington Harbor, analysis of core samples gave an indication of historical trace metal accumulation for the region. Trace metal accumulation in the Burlington Harbor region reached a peak in 1968. Subsequent declines in trace metal accumulation are likely due to regulations that reduced trace metal inputs. At Allen Harbor and McAllister Point, the sediment trace metal data were combined with information from other analyses (i.e., pore water concentrations) to group the data and develop spatial trends. Although the field locations exhibited a range of trace metal concentrations and a range of trace metal bioavailabilities, in general, bioavailability predictions based on SEM-AVS analyses compared favorably with sediment toxicity testing results.; Laboratory experiments were performed to determine the sediment phases responsible for binding trace metals, thereby reducing bioavailability. In addition to AVS, base extractable (humic) substances are important for binding particular trace metals, especially copper. For the development of sediment quality criteria, the following equation may be used:{dollar}{dollar}eqalign{lcub}rm SQC &= rm AVS+Ksb{lcub}d,h{rcub}sp* fsb{lcub}h{rcub}sp* WQCcr rm Where{lcub}:{rcub}qquad SQC &= rm sediment quality criteriacr rm AVS &= rm molar concentration of AVScr rm Ksb{lcub}d,h{rcub} &= rm partition coefficient between humic substancescr &quad rm and pore watercr rm fsb{lcub}h{rcub} &= rm fraction of humic substancescr rm WQC &= rm water quality criteria for individual trace metalcr{rcub}{dollar}{dollar}; This equation takes into account trace metal partitioning into organic material and also allows the calculation of relevant sediment quality criteria in low AVS environments.