Development of an Electrochemical Surrogate for Copper, Lead, and Zinc Bioaccessibility in Aquatic Sediments
Abstract
To help enable the use of metal bioavailability as a site cleanup criterion, the goal of this project was to measure the chemical stability and molecular diffusivity of sub-micromolar concentrations of dissolved Cu(II), Pb(II), and Zn(II) in model estuarine sediment pore waters using scanned stripping chronopotentiometry (SSCP). The criteria for success of the project are (1) automation of data acquisition and processing, (2) determination of chemical stability and diffusivity using a physicochemical model of experimental data, (3) qualitative agreement between expected and SSCP-derived chemical stabilities, and (4) capability of SSCP to predict relative differences in the outcome of a bioavailability process; specifically, Cu-, Pb-, and Zn sulfide precipitation. To evaluate the success of this project on the basis of these criteria, we needed to perform SSCP measurements in synthetic, chemically defined media in the laboratory to (a) perform enough SSCP measurements to determine the method s capabilities and improve its execution, (b) ensure that we knew beforehand the relative chemical stabilities of dissolved metal-organic complexes, which we achieved by using well-characterized organic matter isolated from natural waters as well as synthetic organic compounds, and (c) examine metal-precipitation across a range of metal-organic ligand ratios at a fixed sulfide concentration. In addition to being able to measure dissolved metal speciation at the 0.25 mol/L concentration level (16 g Cu and Zn/L and 52 g Pb/L), the SSCP results confirmed what we expected would be the relative chemical stabilities of the metal-DOM complexes and discerned these stabilities across conditions that subtly varied with respect to carbon aromaticity and organic sulfur content.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2011
- Accession Number
- ADA600037
Entities
People
- Aaron J. Slowey