J. K. Bohlke L. N. Plummer, T. B. Coplen, E. Busenberg, E. A. Shinn (ret) Unpublished Material http://sofia.usgs.gov/projects/grndwtr_geochem/ This project involves sampling surface waters and ground waters from Florida Bay, the Keys, and offshore to the barrier reef. Analyses will be done on a variety of isotopic and chemical species that have been used elsewhere to determine ground-water ages, contaminant sources, and geo- chemical reactions. Water Research Discipline researchers will coordinate ground water sampling and analytical work; Geologic Discipline researchers will provide access to wells and back- ground data, handle field logistics, etc. A significant issue of concern in South Florida is the potential effect of anthropogenic pollutants from the Florida Keys or elsewhere on the water quality and health of offshore marine ecosystems. It has been suggested that certain contaminants (e.g., bacteria, excess nutrients) found in some offshore ground waters may be transported 'in the subsurface to discharge sites beneath Florida Bay or the reef tract, where they may be contributing to declining ecosystem health. But not much is known about the origins of the ground waters underlying the region, how the subsurface flow systems operate, and what is the fate of contaminants emplaced in ground water in the Keys. Ground waters are potential sources, sinks, and carriers of nutrients and other contaminants beneath the Florida Keys and offshore regions to the north and south. This project is designed to provide new data on the sources, flow directions, exchange rates, and chemical characteristics of ground waters underlying the region of Florida Bay, the Keys, and offshore reefs. The results, to be derived in part from analyses of environmental tracers and isotopes, will provide general empirical information about subsurface transport processes and their potential impact on surface water chemistry. This project ended in FY 1999. No data is available through the SOFIA Data Exchange pages. 1996 1998 ground condition Complete None planned -82.2 -79.82 25.69 24.27 none geochemistry chemistry groundwater nutrients contaminants hydrology isotope geochemistry chronology ISO 19115 Topic Category environment inlandWaters 007 012 Department of Commerce, 1995, Countries, Dependencies, Areas of Special Sovereignty, and Their Principal Administrative Divisions, Federal Information Processing Standard (FIPS) 10-4, Washington, D.C., National Institute of Standards and Technology United States US U.S. Department of Commerce, 1987, Codes for the identification of the States, the District of Columbia and the outlying areas of the United States, and associated areas (Federal Information Processing Standard 5-2): Washington, D. C., NIST Florida FL Department of Commerce, 1990, Counties and Equivalent Entities of the United States, Its Possessions, and Associated Areas, FIPS 6-3, Washington, DC, National Institute of Standards and Technology Monroe County none Florida Bay Central Everglades Florida Keys none Any data are subject to change and are not citeable until reviewed and approved for official publication. J. K. Bohlke U.S. Geological Survey mailing address

431 National Center

Reston VA 20192 USA 703 648-6325 703 648-5274 jkbohlke@usgs.gov Griggs, E. M. Krump, L. R., Bohlke, J. K. 2003 report Estuarine, Coastal and Shelf Science 58 Amsterdam, Netherlands Elsevier Science BV unavailable unknown Samples for analysis are to be collected during 2 intensive field campaigns from observation wells, seepage collectors, and surface waters, to be accessed largely by boat. One of those collections occurred in 1996; another is planned for summer 1997 to complete the regional survey. The following types of analyses are to be done: 1 - Major-element water chemistry and dissolved gases. These data are essential for comparing water types and for calculating potential reaction relations among different waters (e.g., seawater reduction, mixing, etc.). 2 - Nitrogen isotopes in ammonium, nitrate, and N2 gas. Concentrations and isotope mass balances will be examined for evidence relating high ammonium in offshore ground waters to potential sources such as waste water and natural sedimentary organic matter. 3 - Chlorofluorocarbons (CFC's). Contamination levels of CFC's may indicate anthropogenic point sources; ambient levels may be useful in dating the recharge (entry into the subsurface) of the ground waters; no CFC's could indicate ages more than 50 years, or possibly degradation of CFC's. 4 - Tritium and He isotopes. Tritium-helium dating may indicate the residence times of ground waters since recharge from the ocean or the bay or the Keys; these data may be necessary as backup for the CFC's because of the possibility of CFC degradation in some of the reducing waters, or they may be used in conjunction with the CFC's to indicate ground-water mixing or dispersion phenomena. 5 - C-14 and stable carbon isotopes in carbonate, methane, and dissolved organic carbon. Isotopes and chemistry of around waters will be used for calculating reactions that might represent conversion of seawater into reduced marine ground water; information about the sources of organic constituents may be derived; very old waters may be detected. 6- Sulfur isotopes in sulfide and sulfate, plus mass balance of sulfate reduction. Sulfur derived from modern seawater (or Florida Bay) may be distinguishable from sulfur coming out with deep old ground waters; these data are also needed for reaction modeling. 7- Stable oxygen and hydrogen isotopes of water. Water isotopes are potentially useful for distinguishing water units such as evaporated, meteoric, marine, glacial/intergiacial, etc. The major accomplishments for FY98 were an intensive sampling effort in November, 1997 and subsequent analytical work on the samples. Approximately 1200 samples were collected from about 40 sites, mainly in Florida Bay, and including a few representatives of surface waters, water supplies, and nested piezometers. This sample set complements the one obtained in FY96 by extending the coverage of the project throughout Florida Bay, by including more vertical resolution at selected sites, and by including some shallow ground waters and seepage meters at one of the ocean-side experimental tracer sites. 1998 In FY99 analyses and data summaries of samples collected in FY96-FY98 will be completed. A small number of additional samples will be collected and analyzed for a subset of chemical and isotopic constituents, to fill specific gaps in the sets collected so far, and to provide some indication about short-term changes at selected sites over the course of the study (collections with aid from Shinn and Reich; analyses by Bohlke, Plummer, and Busenberg). Results will be compiled and evaluated in terms of ground water sources, residence times, and geochemical reactions. Reports will be written on (1) origins and residence times of marine ground waters, and (2) nutrient chemistry of marine ground waters. 1999 J. K. Bohlke U.S. Geological Survey mailing address

431 National Center

Reston VA 20192 USA 703 648-6325 703 648-5274 jkbohlke@usgs.gov J. K. Bohlke U.S. Geological Survey mailing address

431 National Center

Reston VA 20192 USA 703 648-6325 703 648-5274 jkbohlke@usgs.gov data from Chronology and isotope geochemistry of groundwaters in the Florida Keys and offshore areas No warranties are implied or explicit for the data. unknown none Contact J. K. Bohlke for data from this project. 20061026 Heather Henkel U.S. Geological Survey mailing and physical address

600 Fourth Street South

St. Petersburg FL 33701 USA 727 803-8747 ext 3028 727 803-2030 sofia-metadata@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998