Date of Award

1997

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Oceanography

Department

Oceanography

First Advisor

John King

Abstract

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:

Where:

SQC = AVS + Kd,h*fh*WQC

SQC = sediment quality criteria

AVS = molar concentration of AVS

Kd,h = partition coefficient between humid substances and pore water

fh = fraction of humic substances

WQC = water quality criteria for individual trace metal

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.

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