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An Assessment of Aquifer Storage and Recovery and Mercury Methylation in the South Florida Everglades Ecosystem

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Frequently-anticipated questions:


What does this data set describe?

Title:
An Assessment of Aquifer Storage and Recovery and Mercury Methylation in the South Florida Everglades Ecosystem
Abstract:
The objective of this scope of work is to develop a hydrogeochemical framework of mercury and methylmercury in the hydrogeologic system in which ASR will be developed in the Upper Floridan Aquifer.
Supplemental_Information:
For more details of sample collection and processing, see SIR 2007-5420 at <http://pubs.usgs.gov/sir/2007/5240/>
  1. How should this data set be cited?

    Krabbenhoft, Dave, 2007, An Assessment of Aquifer Storage and Recovery and Mercury Methylation in the South Florida Everglades Ecosystem.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -80.5
    East_Bounding_Coordinate: -80
    North_Bounding_Coordinate: 27.5
    South_Bounding_Coordinate: -26

  3. What does it look like?

    <https://sofia.usgs.gov/projects/scopesofwork03/images/asr_hgfig1x.jpg> (JPEG)
    Proposed ASR systems in the Comprehensive Everglades Restoration Plan
    <http://pubs.usgs.gov/sir/2007/5240/#fig1> (JPEG)
    Map showing location of the study area in southeastern Florida (modified from Reese 2002).

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 2003
    Ending_Date: 2005
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: report

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      Indirect_Spatial_Reference: South Florida Everglades
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (24)

    2. What coordinate system is used to represent geographic features?

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    Data from specific chemical analyses from municipal wells include: water utility name; aquifer; utility well id; pH; conductivity (microMohs per centimeter); alkalinity (milligram per liter - mg/L); HgT (total mercury in nanogram per liter - ng/L) MeHg (methylmercury ng/L); MeHg/HgT ratio (ratio of methylmercury to total mercury); TOC (total organic carbon mg/L). ND = no data, sample not collected.

    Results of specific chemical analyses of major cations and anions from municipal wells include: calcium (mg/L); magnesium (mg/L); sodium (mg/L); potassium (mg/L); sulfate (mg/L); and chloride (mg/L).

    Results of specific chemical analyses of samples collected from laboratory incubation experiments include: sample/experiment id; sample date; ambient MeHg (ng/L); Me199Hg (ng/L); Me201Hg (ng/L); ambient Hg (ng/L); 199Hg (ng/L); 201Hg (ng/L); sulfate (mg/L); DOC (mg/L C - DOC expressed as milligrams per liter of carbon); and SUVA (specific ultraviolet absorbance)

    Entity_and_Attribute_Detail_Citation: USGS personnel


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

    • Dave Krabbenhoft

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    David P. Krabbenhoft
    U.S. Geological Survey
    8505 Research Way
    Middleton, WI 53562-3581
    USA

    608 821-3843 (voice)
    608 821-3817 (FAX)
    dpkrabbe@usgs.gov


Why was the data set created?

There are many uncertainties regarding the use of large-scale aquifer storage and recovery (ASR) technology in south Florida, including suitability of proposed ASR source waters, water quality concerns and the potential for mercury bioaccumulation (NRC 2002). The type of source waters used for aquifer recharge in south Florida includes treated drinking water, untreated ground or surface water, and reclaimed water. The source water planned for the Comprehensive Everglades Restoration Plan (CERP) ASR program is untreated or partially treated groundwater or surface water (Reese 2002).

Alternating periods of flooding and drying, called hydroperiods, vital to the historical functioning of the Everglades ecosystem, have been severely altered by human activities. Restoring these variations in water flows and levels is an integral part of the CERP. Specifically, the timing of water held and released into the ecosystem will be modified so that it more closely matches natural patterns (CERP 2002).

ASR has been proposed as a cost-effective water-supply alternative that can help meet the needs of agricultural, municipal, and recreational users and also be used for Everglades ecosystem restoration (Reese 2002). ASR is used to store excess surface water and shallow groundwater during wet periods for recovery during longer-term dry periods (NRC 2002). In an attempt to capture, store and redistribute fresh water previously lost to tides and to regulate the quality, quantity, timing and distribution of water flows, the CERP proposes the construction of over 300 ASR wells in south Florida (Reese 2002).

ASR technology has been tested and implemented in some areas of south Florida. Existing and historical ASR sites in southern Florida are mostly associated with public water utility systems located along the southeast and southwest coasts


How was the data set created?

  1. From what previous works were the data drawn?

  2. How were the data generated, processed, and modified?

    Date: 2005 (process 1 of 1)
    Task 1 - Conceptual Mercury Model

    A conceptual model of mercury within the Floridan Aquifer System (FAS) in south Florida will be developed by assembling information from reports in the literature and other available data. The conceptual model will include background chemistry of aquifer materials, groundwater, and surface water and will attempt to put mercury, ASR, and the hydrogeology of south Florida in a consistent framework.

    Task 2A and 2B - Field Collection of Water Samples and Laboratory Analyses

    While in the field, water samples will be analyzed with a portable field probe for dissolved oxygen (DO), pH, redox, temperature, specific conductance, and dissolved organic carbon (DOC). Water samples will be analyzed for major cations and anions as well. Also, a series of water samples will be collected for mercury analysis using trace metal ultraclean techniques as outlined by Krabbenhoft and Babiarz (1992), to eliminate direct contact between the sample gear and field personnel. These water samples will be analyzed by the USGS Mercury Research Lab (Wisconsin District Mercury Laboratory) for mercury using method 1631, the analytical method approved by the USEPA that allows determination of mercury at a minimum level of 0.4 ppt (parts-per-trillion), and supports measurements at the ambient water quality criteria for mercury published in the National Toxics Rule (40 CFR 131.36) and in the Final Water Quality Guidance for the Great Lakes System (60 FR 15366). Methylmercury will be determined using the distillation and ethylation procedure first described by Horvat et al. (1993), and is used the standard operating procedure by the USGS Mercury Lab.

    The only known true groundwater samples that have been analyzed for total mercury and methylmercury in south Florida were those reported by Harvey et al. (2002). Samples acquired for that data set were taken from piezometers screened in the surficial aquifer, above the Hawthorn and Floridian Aquifers. Nevertheless, in that sample set of 50 groundwater samples, about 10 percent of the samples contained high levels of MeHg (1-8 ng/L), and thus underscoring the reason for possible concern for large-scale implementation of ASR. However, not enough information was available to infer whether the MeHg present in these samples was produced with in the shallow aquifers, or if the MeHg was possible contained in surface waters that recharged the aquifer.

    Task 2C - Obtaining Aquifer Cores Samples

    Selection and acquisition of core materials will be coordinated with the USACE technical lead overseeing the drilling and other associated project tasks. To be most effective, core materials needed for this component of the project would be derived from portions of the FAS that will be used in the operational phase of the ASR project. Samples that represent a range of aquifer material types (texture, mineralogy and chemistry) would provide the best testing materials for this work. Although intact cores from pilot wells would be ideal for these tests, cuttings would also be usable for these evaluations. Core samples must be received by August 2003 for the tests for up to 6 months before taking final samples.

    Task 3 - Water-Rock Incubation Studies

    Although incubation tests used to assess methylmercury formation rates have been used by mercury researchers for over a decade (Krabbenhoft et al., 1998), there are no known published reports on studies using carbonate aquifer materials, or studies that target the evaluation of methylation potential and methylation rates at time scales of weeks to months. As such, we will adopt the best approach for conducting the methylation studies after we complete the synoptic field sampling and have had opportunity to evaluate what types of materials may be available for testing, what procedure would be most appropriate and feasible, and over what time scales. In essence, however, one of the following methods will be used: column studies using intact Floridian Aquifer cores; column studies of unconsolidated Floridian Aquifer materials; or, batch studies using unconsolidated Floridian Aquifer materials. With any of these procedures, we will employ geochemical controls (redox, chloride, sulfate, DOC, and mercury isotopes) to test whether these constituents affect aqueous MeHg formation rates. Representative water types and sources will also be used in these studies, such that the mixing of native surface water and groundwater will be evaluated under varying redox regimes. A series of six (6) to ten (10) column studies will be set up in the laboratory using Floridan Aquifer materials and native surface water and groundwater. The experiments conducted for this portion of the study will be conducted for time periods up to six months.

    Task 4 - Leaching of Aquifer Materials

    Leaching experiments will be performed to determine whether aquifer materials are acting as net sources or sinks of mercury within the aquifer. If mercury is found to be associated with specific minerals and/or geologic units, efforts will be made to perform experiments using samples characteristic of each type of mercury occurrence. The design of the leaching experiments and the selection of leaching solutions will focus on specific processes likely to occur. Details of the experiments will be developed after analyzing the information gained from the groundwater chemistry and mineralogy data to be assembled and collected in phases 1 and 2 of this project. The experiments will be designed to simulate conditions in the field as much as possible. If the results of the groundwater chemistry sampling indicate that variations in pH and /or redox conditions are important controls on mercury mobility, the pH and dissolved oxygen content of the leaching solutions will be varied accordingly. Although microbial processes affect mercury mobility, they will not be addressed in this project. To insure the processes observed in the leaching experiments are solely abiotic, the experiments will be performed under sterile conditions.

    Our leaching experiments will be conducted in a fashion similar to that of Fadini and Jardim (2001), who outlined a method for leaching mercury from soils. Different samples of aquifer materials are suspended in MilliQ® water to simulate a possible phase transfer between soil and water due to weathering processes (although we will likely use native surface and ground water). Aliquots of soil 0.4 g dry base are then suspended in 100 ml of MilliQ® water in Erlenmeyer flasks with Teflon® stoppers and placed in an orbital shaker at 120 strokes min-1 for 2 hours. After 7 days of quiescent equilibrium, 30 ml aliquots are removed from each flask and centrifuged. Total mercury concentration in the supernatant solution is determined in the sub-samples by detection using USEPA method 1631, and methylmercury by the procedure of Horvat et al. (1993) at the USGS Mercury Research Lab. In addtion, our leaching experiments will employ the use of stable mercury isotopes (e.g., Me199Hg or 202Hg) to specifically determine whether Hg or MeHg contained in surface water may adsorb to the aquifer material, methylate during contact with the aquifer materials, chemically reduce to gaseous elemental Hg0, or possibly undergo demethylation. The use of stable isotopes facilitates the discrimination of Hg and MeHg in injected surface water from Hg and MeHg possibly contained in carbonate aquifer or native groundwater. The mercury stable isotope analyses for total and methylmercury will be performed at the USGS Mercury Research Lab.

    Task 5 - Geochemical Modeling

    The geochemical environment that ASR waters will be expected to change radically from surface water conditions to groundwater conditions, and then back to surface water upon recovery. As indicated above, groundwater in the Floridian Aquifer is relatively high in chloride, which should have a strong effect on mercury speciation. However, other competing ligands may also be present (e.g., DOC, sulfide, hydroxide) at sufficiently high levels to "out compete" for the mercury, and/or possibly promote or retard mercury bioavailability for methylation. Recent research (e.g., Benoit et al., 1999) has suggested that the formation of zero charged complexes (HgCl2, HgS, Hg(OH)2) in the aqueous environment are the bioavailable species of mercury to methylating microbes, as opposed to charged species (e.g., HgCl3-, HgS2=). For this project, we will incorporate the analytical results of the primary ligands for mercury (Cl, S, OH, DOC) and perform chemical speciation calculations using standard geochemical models (e.g., MINEQL) to estimate the geochemical speciation of mercury in aqueous samples for source waters, "injected" groundwater, and recovered water.

    Task 6 - Report Preparation and Oral Presentation of Results

    Throughout the project, the USGS will provide quarterly status reports to the USACE project manager and technical manager. The quarterly status reports are a brief summary of the tasks completed during the quarter and status of the ongoing effort. These reports should describe any issues or concerns that may impact completion of tasks. Generally, the quarterly report is no more than one page. The final report, a citable USGS Water-Resources Investigations Report, will be a web-distributed report and will document the project results and methods used. The final report will provide guidance on how ASR can best be implemented to minimize the potential for MeHG formation.

    In September 2004, most of the analyses and interpretations will be completed. The project staff will present the results to date to the ASR Regional Study project delivery team (PDT) in September or October. Following that presentation, the final report will be completed, reviewed, and approved for USGS publication by March 2005

    Any use of trade, product, or firm names is for descriptive purposes only and does not constitute endorsement by the U.S. Government

    Person who carried out this activity:

    David P. Krabbenhoft
    U.S. Geological Survey
    8505 Research Way
    Middleton, WI 53562-3581
    USA

    608 821-3843 (voice)
    608 821-3817 (FAX)
    dpkrabbe@usgs.gov

  3. What similar or related data should the user be aware of?

    Reese, Ronald S. , 1994, Hydrogeology and the distribution and origin of salinity in the Floridan aquifer system, southeastern Florida: USGS Water Resources Investigations Report 94-4010, U.S. Geological Survey, Tallahassee, FL.

    Online Links:

    Other_Citation_Details: accessed as of 12/30/2009
    Reese, Ronald S., 2002, Inventory and Review of Aquifer Storage and Recovery in Southern Florida: USGS Water-Resources Investigations Report 02-4036, U.S. Geological Survey, Tallahassee, FL.

    Online Links:

    Other_Citation_Details: accessed as of 12/30/2009
    Harvey, Judson W. Krupa, Steven L.; Gefvert, , 2002, Interactions between surface water and ground water and effects on mercury transport in the north-central Everglades: USGS Water Resources Investigations Report 02-4050, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details: accessed as of 12/29/2009
    Sacks, L. A. Tihansky, A. B., 1996, Geochemical and Isotopic Composition of Ground Water, with Emphasis on Sources of Sulfate, in the Upper Floridan Aquifer and Intermediate Aquifer System in Southwest Florida: USGS Water-Resources Investigations Report 96-4146, U.S. Geological Survey, Tallahassee, FL.

    Online Links:

    Other_Citation_Details: accessed as of 12/30/2009
    Benoit, J. M. Gilmour, C. C.; Mason, R. P, 1999, Sulfide Controls on Mercury Speciation and Bioavailability to Methylating Bacteria in Sediment Pore Waters: Environmental Science and Technology v. 33, n. 6, p. 951-957, American Chemical Society, Washington, DC.

    Online Links:

    Other_Citation_Details:
    accessed as of 12/29/2009

    The full article is available via journal subscription or single article purchase. The abstract may be viewed online

    U.S. Army Corps of Engineers South Florida Water Management District, 2002, Comprehensive Everglades Restoration Plan (CERP): U.S. Army Corps of Engineers, Jacksonville, Fl.

    Online Links:

    Other_Citation_Details: accessed as of 12/29/2009
    Gilmour, C. C. Henry, E. A.; Mitchell, R., 1992, Sulfate Stimulation of Mercury Methylation in Freshwater Sediments: Environmental Science and Technology v. 26, n. 11, p. 2281-22887, American Chemical Society, Washington, DC.

    Online Links:

    Other_Citation_Details:
    accessed as of 12/29/2009

    The first page of the report is available online in lieu of an abstract. The full article is available via journal subscription or single article purchase.

    Horvat, M. Bloom, N. S.; Liang, L., 199309, Comparison of distillation with other current isolation methods for the determination of methyl mercury compounds in low level environmental samples: Part 1. Sediments: Analytica Chimica Acta v. 281, n. 1, p. 135-152, Elsevier Science B. V., Amsterdam, The Netherlands.

    Online Links:

    Other_Citation_Details:
    accessed as of 12/29/2009

    The full article is available via journal subscription or single article purchase. The abstract may be viewed on the Science Direct website by selecting the volume and issue number.

    Krabbenhoft, D. P. Babiarz, C. L., 1992, The Role of Groundwater Transport in Aquatic Mercury Cycling: Water Resources Research v. 28, n. 12, 3119-3128, American Geophysical Union, Washington, DC.

    Online Links:

    Other_Citation_Details:
    accessed as of 1/05/2010

    The full article is available via journal subscription or single article purchase. The abstract may be viewed online

    Krabbenhoft, D. P. Gilmour, C. C.; Benoit, J. , 1998, Methyl mercury dynamics in littoral sediments of a temperate seepage lake: Canadian Journal of Fisheries and Aquatic Sciences v. 55, n. 4, p. 835-844, National Resource Council Canada, Canada.

    Online Links:

    Other_Citation_Details:
    accessed as of 12/29/2009

    The full article is available via journal subscription or single article purchase. The abstract may be viewed on the National Research Council Canada website

    Mason, R. P. Lawson, N. M.; Lawrence, A., 1999, Mercury in the Chesapeake Bay: Marine Chemistry v. 65, issues 1-2, p. 77-96, Elsevier Science B. V., Amsterdam, The Netherlands.

    Online Links:

    Other_Citation_Details:
    accessed as of 12/29/2009

    The full article is available via journal subscription or single article purchase. The abstract may be viewed on the Marine Chemistry website by selecting the volume and issue number.

    Metz, P. A. Brendle, D. L., 1996, Potential for Water-Quality Degradation of Interconnected Aquifers in West-Central Florida: USGS Water Resources Investigations Report 96-4030, U.S. Geological Survey, Tallahassee, FL.

    Online Links:

    Other_Citation_Details:
    accessed as of 12/30/2009

    Prepared in cooperation with the Southwest Florida Water Management District

    Ullrich, S. M. Tanton, T. W.; Abdrashitova, 2001, Mercury in the Aquatic Environment: A Review of Factors Affecting Methylation: Critical Reviews in Environmental Science and Technology v. 31, n. 3, p. 241-293, Taylor & Francis, Philadelphia, PA.

    Online Links:

    Other_Citation_Details:
    accesssed as of 12/30/2009

    The full article is available via journal subscription or single article purchase. The abstract may be viewed on the website below.

    Wiener, J. G. Krabbenhoft, D. P.; Heinz, , 2002, Ecotoxicology of Mercury: CRC Press, Boca Raton, FL.

    Other_Citation_Details:
    Pages 407-461 in Book of Ecotoxicology, 2nd ed.; Hoffman, D. J.; Rattner, B. A.; Burton, Jr., G. A.; Cairns, J., editors
    Fadini. P. S. Jardim, W. F., 200107, Is the Negro River Basin (Amazon) impacted by naturally occurring mercury?: The Science of the Total Environment v. 275, p. 71-82, Elsevier Science B. V, Amsterdam, The Netherlands.

    Online Links:

    Other_Citation_Details:
    accessed as of 1/4/2010

    The full article is available via journal subscription or single article purchase. The abstract may be viewed on the Science Direct website by selecting the volume and issue number.

    Krabbenhoft, D. P. Aiken, G. R.; Anderson, M. , 2007, An Assessment of the Potential Effects of Aquifer Storage and Recovery on Mercury Cycling in South Florida: USGS Scientific Investigations Report (SIR) 2007-5420, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    accessed as of 1/4/2010

    Prepared in cooperation with the U. S. Army Corps of Engineers, Jacksonville, FL


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Permission to sample the wells will be obtained from representatives of municipalities, private owners, existing ASR well project sites, and pilot ASR sites. ASR wells 20 (LO), 27 (SL), and those found in Palm Beach and Broward Counties will be targeted, as well as USGS monitoring wells located in Glades, Hendry, Palm Beach, and Broward Counties. Although the wells listed above are targeted for sampling, final determination of the sampling network will depend upon obtaining permission to sample the wells.

  5. How consistent are the relationships among the observations, including topology?

    Sampling wells will be selected to obtain a representative distribution of sampling points.


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: none
Use_Constraints: none


Who wrote the metadata?

Dates:
Last modified: 24-Mar-2010
Metadata author:
Heather Henkel
U.S. Geological Survey
600 Fourth Street South
St. Petersburg, FL 33701
USA

727 803-8747 ext 3028 (voice)
727 803-2030 (FAX)
sofia-metadata@usgs.gov

Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)


This page is <https://sofia.usgs.gov/metadata/sflwww/asr_hg.faq.html>

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