Research Project 3
| EPA Grant Number: | R828771-0-01 |
|
Title: |
Geochemistry, Biochemistry, and Surface/Groundwater Interactions for As, Cr, Ni, Zn, and Cd with Applications to Contaminated Waterfronts |
| Investigators: | Barth F. Smets,
Ph.D. (PI), Allison A. MacKay, Ph.D. (co-PI), Nikolaos P. Nikolaidis
(co-PI) |
| Institution: | University of Connecticut |
| Project Period: | October 1, 2001 to September 30, 2004 |
| Objectives/Hypotheses: |
| We will investigate the mechanisms controlling the off-site transport of subsurface heavy metal contaminants from industrial waterfront sites to adjacent water bodies. We hypothesize that the upgradient heavy metal flux is governed by anaerobic microbial activity that may mobilize or retard the transport of metal species. The activity of anaerobic microbial communities is hypothesized to be governed by the availability of assimilable organic matter and the bioavailability of SO42- and/or Fe3+ in the contaminated zone. Furthermore, we hypothesize that the migration of dissolved and colloidal heavy metals from the groundwater to the surface water is mitigated by direct and indirect metal immobilization in the groundwater/surface water interface (the hyporheic zone). Controlling factors include chemical Fe2+ oxidation and chemolithotrophic and chemoheterotrophic microbial activities. |
| Approach: |
| We propose to study groundwater metal transport at a waterfront site (Stratford, CT) using field observations and laboratory studies. Solid and groundwater samples will be collected from the upgradient groundwater zone and the groundwater/surface water interface. The spatial distributions of heavy metal contaminants (As, Cr, Ni, Zn, Cd) will be quantified in solid and liquid samples. Using genotypic probing techniques, the relative abundances of chemolithotrophic and chemoheterotrophic microbial activities will be determined in solid samples from the hyporheic zone. The significance of dissimilatory sulfate and iron reduction in the direct, or indirect, immobilization of cationic species (Cd, Ni, Zn) and oxyanions (CrO42-) will be determined in microcosm experiments. Microcosm experiments will also be used to assess the mobilization of arsenic species from solid samples under reducing conditions and the relative importance of chemical vs. biological Fe2+ oxidation in the hyporheic zone. Finally, in situ samplers will be used to collect solid precipitates formed in the hyporheic zone for elemental and spectroscopic analyses. |
| Expected Results: |
| The purpose of this project is to develop the first detailed description of the processes that govern the fate of heavy metals discharging to water bodies at contaminated waterfront sites. Results will enable the development of mechanism-based fate models to be used by water and sediment quality managers for assessing the ecological risks of exposure to groundwater heavy metals released to surface waters and sediments in urban areas. These decision-making tools will lead to more expedient reclamation of those waterfront sites. |
| Keywords: |
| GSI, metal transport, arsenic, chromate, bacteria |