Date of Award

Summer 1999

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry & Biochemistry

Program/Concentration

Chemistry

Committee Director

John R. Donat

Committee Member

John B. Cooper

Committee Member

David J. burdige

Call Number for Print

Special Collections LD4331.C45 B94

Abstract

Presented here are the first data on the vertical concentrations, complexation, speciation, and fluxes of total dissolved zinc and zinc complexing ligands, and zinc speciation in sediment pore waters in the Chesapeake Bay and Elizabeth River, Virginia.

Sediment pore waters were collected in mid and southern Chesapeake Bay in November 1997 and in the Elizabeth River (Pinner's Point) in March, April, and July 1998. Flux experiments were conducted in Elizabeth River sediment cores in April and July 1998. [TDZn] and zinc complexation were determined using differential pulse anodic stripping voltammetry at a hanging mercury drop electrode (DPASV-HMDE).

[TDZn] in the Chesapeake Bay pore waters ranged from ~5nM to 60nM. In the Elizabeth River, [TDZn] in pore waters ranged from ~ 1 to 350nM. In mid-Bay pore waters, two zinc-complexing ligand classes were detected: a strong ligand class (L 1; K' (znL1.zn2+) ≥ 1017.71 ± 1.37 ), and a weaker ligand class (L2; K' (znL2.Zn2+) ≥ 107.24 ± 1.04 ). L1 was not detected at any other station, either in the Bay or Elizabeth River. Both Chesapeake Bay stations showed L2 concentrations more than two orders of magnitude greater than TDZn concentrations. Speciation calculations indicate that the majority (~60 to 90%) of the TDZn is complexed by L2 in the Elizabeth River and that free Zn2 + is ~20% or less of the TDZn in the pore waters. Sulfide concentrations, combined with complexation calculations and previous work, suggest that the L1 and L2 ligand classes may be either organic, sulfidic, or possibly both.

L2 appeared to flux into the overlying waters and TDZn appeared to flux into the sediments in April 1998. In July 1998, the ligand flux to the overlying water was greater than April, and there is a flux of TDZn out of the sediments.

Zinc complexation causes the free [Zn2+] in Chesapeake Bay and Elizabeth River pore waters to be maintained between levels that are limiting or toxic to biota in the estuary. In addition, the pore waters may provide as much as 17% of the zinc-complexing ligands in the water column.

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DOI

10.25777/snf4-qw68

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