Abstract Details

Mercury Accumulation and Speciation in San Francisco Bay Cordgrasses
Abstract ID	ENV-02
Presenter	Cynthia  Patty
Presentation Type	Poster
Full Author List	C. Patty (1) , B. Barnett (2) , B. Mooney (3) , A. Kahn (4) , J. C. Andrews (1)
Affiliations	(1) Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Rd., Menlo Park, CA 94025 (2) Department of Chemistry and Biochemistry, CSU East Bay, 25800 Carlos Bee Blvd, Hayward, CA 94542 (3) Department of Environmental Science, CSU East Bay, 25800 Carlos Bee Blvd, Hayward, CA 94542 (4) Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039
Category	Environmental Science
Abstract	San Francisco Bay has been contaminated by mercury from historical mine tailings and contemporary industrial sources. However, very little is known about the cycling of mercury and other heavy metals by producers at the base of the food webs, including plants. Native Spartina foliosa and non-native S. alterniflora-hybrid cordgrasses are dominant florae within the SF Bay estuary environment. Understanding mercury uptake and storage in these plants will help to characterize the significance of their roles in mercury biogeochemical cycling in the estuarine environment. Plants were selected based on geographic location, distinguishing physical characteristics, and positioning within the marsh tidal plain. Plants were spiked with 1 ppm HgCl2 and grown hydroponically in bay water solution for seven days. Samples were analyzed for total mercury using CVAA and CVAA-GA (gold amalgam). Bulk XAS Hg L3 edge analysis was utilized to compare the speciation of the mercury in plant roots of both species. Hair-like portions of S. foliosa roots were further analyzed by microprobe to spatially map the presence, distribution, and size of mercury particles, and to collect MicroXAS. CVAA results suggest that both species stored mercury largely in their roots, and that native S. foliosa may be more efficient at absorbing mercury than invasive S. alterniflora-hybrids. In both species, bulk XAS results suggest mercury speciation was dominated by methylmercury-sulfur binding, similar to methylmercury cysteine, and mercury-sulfur binding, similar to mercury (II) cysteine. Spatial mapping via microprobe indicated the presence of mercury particles near the tips of root structures, measuring about 1 micron in size.
Footnotes
Funding Acknowledgement	This work was supported by funds from California State University, East Bay. Portions of this research were carried out at the Stanford Synchrotron Radiation Laboratory, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. The SSRL Structural Molecular Biology Program is supported by the Department of Energy, Office of Biological and Environmental Research, and by the National Institutes of Health, National Center for Research Resources, Biomedical Technology Program.