CHED 261 |
| San Francisco Bay has historically been contaminated by mercury from mine tailings as well as industrial sources. Wetlands have commonly been regarded as sinks for mercury and other pollutants. In recent years, however, wetlands have increasingly been noted as sources of mercury export into the estuarine food web. The cause for this shift is not understood. Likewise, very little is known about the cycling of mercury and other heavy metals by common producers at the base the food webs, namely plants. The purpose of this experiment was to compare mercury uptake in the roots and shoots of native S. foliosa and non-native S. alterniflora-hybrid. Understanding mercury uptake and storage in these plants will help to characterize their roles in mercury biogeochemical cycling in the estuarine environment. Moreover, any potential capabilities for phytoextraction or phytostabilization can also be identified. Plants were selected based on geographic location, distinguishing physical characteristics, and positioning within the marsh tidal plain. Plants acclimated for seven days and were then divided into control, test, and baseline groups using a random number generator. Test plants were spiked with 1 ppm HgCl2 and grown hydroponically in bay water solution for seven days. Samples were digested with sulfuric and nitric acid, following EPA protocol 245.6, and then analyzed for mercury using CVAA and CVAA-GA. Initial, variable results suggest that both species store mercury largely in their roots, and that native S. foliosa may be somewhat more efficient at absorbing mercury than invasive S. alterniflora-hybrids. Results of Hg speciation using X-ray absorption spectroscopy will also be presented. |
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Undergraduate Research Poster Session: Environmental Chemistry
2:30 PM-4:30 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Poster
Division of Chemical Education |