geochemical processes in organic-rich sediments of south florida - mercury and metals >
Program: FRAGILE ENVIRONMENTS (formerly called the Ecosystems Program) Co-Principal Investigator: Larry P. Gough Program Element(s)/Task(s)
Program: FRAGILE ENVIRONMENTS (formerly called the Ecosystems Program)
Co-Principal Investigator: Larry P. Gough
Project Summary: Human activities have led to the deterioration of the productivity, biodiversity, and stability of the south Florida ecosystem. The fate of anthropogenic contaminants incorporated into the organic-rich sediments is not fully understood. Physical, chemical, and biological processes may remobilize some of the contaminants and reintroduce them into water, atmosphere, and the biological community. Other contaminants may be transformed during diagenesis and remain in surficial materials until the system is disturbed. This project will examine the occurrence and cycling of mercury and metals in organic-rich sediments, pore fluids, and plants at selected sites in south Florida. In collaboration with other projects under the Program, this project will also examine peat diagenesis processes that affect the cycling of mercury and metals. The results of this study will contribute to the understanding of the relationships between diagenesis, occurrence, historical variation, speciation and cycling of environmentally important elements. A better understanding of the controls on the behavior of these elements is essential for the development of plans for the long-term remediation and management strategies for the wetlands of south Florida.
Project Justification: An understanding of the relationship between diagenesis, concentration, speciation, and historical variation of elements of environmental significance is essential for planners in developing long-term remediation and management strategies for wetlands of south Florida. A better understanding of the controls on the cycling of these elements is critical for making informed decisions regarding the regulation of water levels and anticipating, the impact of water regulation. Our biogeochemical studies and other studies of organic-rich sediments will provide a historical perspective of ecosystem conditions and variability. Our studies will also shed light on current biogeochemical processes that must be taken into account to refine predictive models used by resource managers.
Project Objectives: The objectives of this project are to (a) determine the distribution of mercury and metals in organic-rich sediments, selected water samples, and vegetation to understand spatial occurrence variations of these elements in parts of south Florida, (b) describe down core abundance variations of these elements to examine their historical variations and any natural cyclicity, (c) examine element accumulation rates to better describe historical variations, and (d) relate metal and mercury geochemistry to the geochemistry and diagenesis of peat and pore water in order to more fully describe their biogeochemical cycling.
Overall Strategy, Study Design, and Planned Major Products: We propose to use a combination of field and laboratory studies to examine the effects of geochemical processes on metal and mercury cycling. Geochemical analysis of surface water, vegetation, sediment cores and a select number of associated pore -waters will be used to study the abundance and forms of mercury and metals, diagenetic processes and cycling. Field and lab protocols used in this project include USGS, EPA, and other published and widely accepted practices. Analytical methodology includes: ICP-AES (metals and nutrients, in sediments, plants and water), ICP-MS (metals in sediment and water), cold vapor AA (Hg in sediment, plants and water), elemental analysis (C and S), hydride-AA (As in sediment, plants and water, and GC-MS (for any required organic analyses). The results of the studies of the characteristics of peat, nutrients, and other indicators of diagenetic processes (from same or parallel cores - solid phase data as well as pore water parameters) obtained from collaborators will be utilized with metal and mercury data from this project to understand the mobility and cycling of mercury and metals. Sediment accumulation rates derived from short-lived radionuclide analysis of parallel cores will be utilized to assess the accumulation rates of mercury and metals in the recent past. Planned products include interim reports, data releases, fact sheets, and summary report(s) in the form of journal articles and/or internal reports.
Overall: During FY 98 we plan to complete chemical analyses of samples collected in previous field seasons, complete data analysis and synthesize the data to produce summary reports. Metal and mercury data for various media collected in transects of the Taylor Slough area will be compiled. The Taylor Slough samples were collected with members of the projects of Orem and Holmes. Metal and mercury abundance data will be compared with peat geochemistry and nutrient geochemistry data resulting from the above projects.
Timeline: During FY98 we do not plan to conduct additional field work. Chemical analyses of samples collected in previous field trips are still pending. Our main focus will be to have the chemical analyses completed, finish data analysis and prepare summary reports. We anticipate that the reports will be available for review in the last quarter of FY 1998.
Planned Deliverables/Products: The following products are currently planned for FY 1998: (a) open file report(s) of metal and mercury data for sediment, vegetation and water samples collected in 1996 and 1997, (b) report on the accumulation rates of metals and mercury on all cores where chronology is available and data is reliable, (c) paper on metals and mercury abundance patterns, accumulation rates and any relationships to peat geochemistry and nutrient geochemistry, possibly for a journal, (d) contribution of data from this project to a GIS-type database being developed by project of Orem for better visualization of various geochemical parameters.
Planned Outreach Activities: As in previous years, during this final year we will participate in coordination meetings with clients and collaborators to share our data and interpretations. We will continue to share data and samples with the projects of Orem et al., Holmes et al., Krabbenhoft et al., Willard et al., other projects funded by the Program, SFWMD, and other agencies as needed.
New Directions, Expansion of Continuing Project (if applicable): Not applicable. This project will be completed at the end of FY 1998.
Accomplishments and Outcomes, Including Outreach: During FY 1997 progress was made toward overall project objectives. Some of the specific accomplishments are: (a) participation in field work during spring with collaborators to collect sediment cores, plants, and water samples along north-south and east-west transects in the Taylor Slough, (b) started subsampling of selected Taylor Slough cores for metal and mercury analyses, (c) participation in various project coordination meetings such as mercury investigators' meeting at Madison in the fall of 1996 to exchange data and plan future field sampling, (d) continued to evaluate chemical data for vegetation, sediment cores and water samples received during the year, (e) preparation of abstracts submitted during, the year. It should be noted that some of the chemical analysis is still pending as access to analytical chemistry in the Geologic Division has been negatively impacted by the reduction-in-force and reorganization during 1995 and 1996. The analytical chemistry contract is now in effect and we anticipate that pending sample analyses will be completed in the last part of FY 1997 and some in FY 1998.
Deliverables, Products Completed: (i) Kotra, R.K. and Gough, L.P. Geochemistry of mercury and trace elements in organic-rich sediments and vegetation from the Everglades. South Florida, Abstract submitted to the 4th International Symposium on Environmental Geochemistry, October 1997, (ii) Kotra, R.K., Gough, L.P., Holmes, C.W., and Hageman, P.L. Geochemistry of mercury and trace elements in organic-rich sediments, surface water. and sawgrass -- A progress report for the 1996 and 1997 field seasons, Abstract submitted to the USGS South Florida Symposium, August 1997.
Required Expertise: inorganic geochemistry, botany, organic geochemistry
Names of Key Project Staff: Gough and Kotra