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projects > linking land, air and water management in the southern everglades and coastal zone to water quality and ecosystem restoration: task 1, mercury cycling, fate and bioaccumulation > 2001 Proposal

Integrated Geochemical Studies in the Everglades

Project Proposal for 2001

Project Title: Integrated Geochemical Studies in the Everglades

Project Chiefs: William H. Orem and David P. Krabbenhoft
Email: and
Phone: 703-648-6273 and 608-821-3843
Fax: 703-648-6419 and 608-821-3817
Mailing address: USGS, 12201 Sunrise Valley Drive, Reston, VA 20192 and
USGS, 8505 Research Way, Middleton, WI 53562

Co Primary Invesigators: George Aiken and Carol Kendall

Ecosystem: South Florida
Project Start Date: 10-01-99
Project End Date: 09-30-04

– Below is a description of the major work elements proposed by the Integrated Geochemical Studies in the Everglades project for FY2000. Individual Elements are grouped by discipline area for Orem (Water Quality), Krabbenhoft (Mercury Studies) and Aiken (DOC-Hg Studies). Note: Kendall has already distributed her materials to the Place Based Program managers at the time of this writing. (Go to Kendall's FY2001 Proposal)

After each work element, we have included a Status and FY2001 Plans section to relate our intentions for this work element during the FY2001 funding cycle.

FY 2000 Activities
The hypotheses we will be testing during FY2000 are listed specifically in the Objectives and Strategy section of this proposal

Water Quality Task (Orem, Lead Investigator):
1. Begin work on concentrations, accumulation rates, biogeochemical recycling, historical record, and sources of C, N, P, and S in the Kissimmee River/Lake Okeechobee drainage area. Focus here on cattle and dairy farming as sources of nutrients to the Kissimmee drainage area. Approach used will be similar to that used in Phase I studies of nutrient and sulfur contamination in the northern Water Conservation Areas from agricultural runoff of Everglades Agricultural Area fertilizer. We will use chemical analysis of surface water, porewater and sediments to examine accumulation and biogeochemical recycling of nutrients and sulfur in this part of the south Florida ecosystem. Coring will be conducted in agricultural and protected areas of the Okeechobee/Kissimmee drainage basin. Historical records of nutrient and sulfur accumulation will be developed using
210Pb, 137Cs, and 14C dating. Sources of phosphorus will be determined using uranium and uranium isotopes (Zielinski et al., 1999). Carbon, nitrogen, and sulfur sources will be examined using stable nitrogen isotope methods. This work is intended to tie in with the USGS Aquifer Storage and Recovery project (ASR). Water quality with respect to nutrients and sulfur will be of major concern in ASR feasibility studies.

Status and FY2001 Plans: Work begun on preliminary cores from Lake Okeechobee and water samples from Kissimmee River, Taylor Creek, and Fisheating Creek, additional fieldwork planned for 5/00 and 9/00. Work on this will continue in FY01.

2. Continue collaboration with Rudnick and others (SFWMD) on nitrogen and phosphorus geochemistry in Florida Bay and the mangrove transition zone. We will continue to develop historical accumulation records for C, N, and P in Florida Bay sediments, building on our previous work (Orem et al., 1999) showing recent nutrification events as well as historical nutrification events which may be tied to historical changes in onshore hydroperiod controlled by climate change. We will examine biogeochemical processes controlling N and P recycling in the important mangrove fringe zone which appears to act as a nutrient accumulator area.

Status and FY2001 Plans: Completing analytical and data processing work on C, N, and P accumulation rates in lakes bordering Florida Bay (Taylor Creek lakes, Monroe Lake, Seven Palm Lake); Fieldwork in Joe Bay and Biscayne Bay planned for 9/00). Additional work on nutrient history in Florida Bay planned for FY01 in collaboration with Seagrass History study Proposal by Brewster-Wingard and others.

3. Examine biogeochemical recycling of P and N from cattail and sawgrass peats. Areas dominated by cattails are accumulating and recycling nutrients very rapidly, in contrast to sawgrass peats where nutrient are accumulated and recycled much more slowly. It has been suggested that cattails degrade more quickly than sawgrass and thus release nutrients quickly. This raises questions about the long-term nutrient sequestering capacity of cattail peats, a critical question for managers since cattails appear to be the dominant macrophyte in the STA’s. We will examine this issue by determining the organic structural differences between cattail and sawgrass plants and peat. We will use organic geochemical methods such as 13C nuclear magnetic resonance spectroscopy and lignin phenol analysis to define any differences. We will also conduct laboratory and field experiments to evaluate differences in organic decomposition and nutrient recycling rates between cattail and sawgrass peats.

Status and FY2001 Plans: Analytical work continuing on cores collected in FY99; presentation at carbon sequestration workshop in Patuxent, Maryland 4/00. Paper on this work planned for FY01.

4. Study biogeochemical recycling and sinks for N, P, and S in new STA’s and ENR. We will examine the major sinks for nutrients and sulfur in the STA’s, and the biogeochemical recycling of these elements.

Status and FY2001 Plans: Fieldtrip planned for 7/00 in ENR; work will continue into FY01 with focus on new STA’s.

5. Detailed examination of sulfate/sulfide distributions in area 3A. Site 3A-15 is a known "hot spot" for methylmercury within the ecosystem, and much of WCA 3A is considered to be an area of intense methylmercury production. The location of this "hot spot" in the ecosystem may be largely controlled by the sulfur geochemistry, but detailed sulfur maps of this area are lacking. We will examine the distribution of sulfur in surface water, porewater, and sediments in a series of transects in WCA 3A. A detailed map of current sulfur distributions will allow prediction of the overall area of high methylmercury production within the ecosystem.

Status and FY2001 Plans: Survey to be conducted during fieldwork 7/00. Open-File Report with detailed sulfur map (GIS) expected to be produced in FY01.

6. Begin analysis of marsh biota (periphyton, Gambusia, macrophytes) and sediments collected by REMAP II for d34S (and d13C and d15N) to extend our understanding of the spatial and temporal extent of S contamination and anthropogenic changes in marsh redox conditions.
-Begin investigation of whether there are significant amounts of S-35 in biota and DOC in selected areas, as an indicator of significant contributions of rain-derived S. Status and

FY2001 Plans: Primarily studies by Kendall and others; Orem will continue to provide additional information on sulfur in water and soil as needed.

7. Begin analysis of selected already-dated cores (USGS or SFWMD) for bulk d34S (and d13C and d15N), in areas where the modern biota show high values of d34S (suggesting anthropogenically-caused sulfate reduction) compared to the underlying peat.

Status and FY2001 Plans: Orem will provide dated core material for analysis by Kendall et al. and Bates.

8. Examine details of the reaction of sulfide with organic matter in Everglades peat. Organic sulfur represents the major sink of sulfur within the ecosystem. An understanding of the major forms of organic sulfur within the peat will provide information on the stability of this form of sulfur to environmental change, especially drought and fire.

Status and FY2001 Plans: Preliminary work completed; presentation on remobilization of sulfur by fire in the Everglades planned for Walt Dineen meeting 4/00; further sample collection and analytical work planned for summer 2000. Field and laboratory work expected to continue into FY01 with preliminary publication on effects of fire expected in FY01.

Mercury Studies in the Everglades Task (Krabbenhoft, Lead Investigator):

1. In the fall of 1999 we will begin planning for the design and emplacement of the mesocosums through coordination and collaboration with the SFWMD and FDEP. These activities will also include securing permission to use the mesocosums and Hg isotopes in the Water Conservation Areas, Loxahatchee National Wildlife Refuge, and Everglades National Park. We will execute three field trips in the winter, spring and fall time periods to begin testing of the isotopic method and to collect sediment and water from 10 locations in the Everglades with which we will transport to Madison, Wisconsin to conduct laboratory microcosm tests of the Hg isotope tracing methods. Also, we will test methods for making Hg stem-flow measurements, and make our initial sampling visit to the recently construct STA6 West to make comparative measurements with the original ENR facility.

Status and FY2001 Plans: Designs plans for test mesocosms are being finalized, and we will make our first field test of the methods in spring 2000. We will employ the use of our own constructed mesocosms as well as the use of those emplaced by the SFWMD (P. McCormick has agreed to our use of his mesocosms). Plans for our mesocosm experimental design will be presented at he Spring Meeting of the S. Florida Science Program Meeting (May 9-11, 2000).

2. Fall of 1999. Begin dual sulfur-DOC controlled laboratory experiment to help design field-enclosure scale deployment of these tests. Tests will be carried out by Dr. Andrew Heyes in collaboration with Orem, Krabbenhoft, Aiken, Hurley and Gilmour. All of these primary investigators have agreed to make facilities and materials available for these studies, such as Hg isotopes and analysis (Krabbenhoft), methylating bacteria (Gilmour), DOC fractions (Aiken) and laboratory space (Orem). For more details, see "Sulfur Task" and "Mercury Cycling and Bioaccumulation Task" in the "Project Objectives and Strategy" Sections above. To bring these tests from the laboratory scale the field scale, large quantities of the various DOC fractions will need to be isolated in a trace-metal clean manner to provide enough material for testing.

Status and FY2001 Plans: Planning for this begun; preliminary work planned for 5/00 and 7/00 in collaboration with Krabbenhoft, Gilmour, and Aiken. Hiring of Dr. Heyes has been delayed due to the unavailability of funding until recently and Dr. Heyes’ desire to find a permanent job and is awaiting offers from universities. Whether Dr. Heyes is hired or not, we will identify another candidate and expected to continue this work into FY01.

3. Examine rates of mercury methylation and release of P, N and S from fire events. This will follow up on preliminary work conducted in FY 99 on fires in the northern part of WCA 3. We will conduct laboratory simulations of fire and rewetting events to examine remobilization of nutrients following fire or extended dry periods when peat oxidation may occur. Field studies of nutrient remobilization following fire or drying events and rewetting will be conducted in field enclosures, and in actual burned or dried natural areas as circumstances permit.

Status and FY2001 Plans: Presentation of the P,N, and S release planned for Walt Dineen Meeting 4/00; mercury methylation studies will be presented at the International Conference On Heavy Metals In The Environment 8/00. New field work and sample collection planned for 5/00. Continued Field and laboratory simulation work in FY01 with preliminary Open File report in FY01.

4. Examine sulfur concentrations, speciation, and distribution in field-enclosure studies (coordination with mercury field-enclosure studies). The purpose of the field-enclosure work will be to examine how changes in environmental parameters accompanying the restoration effort will affect sulfur geochemistry. Field-enclosure sites will be selected to represent various types of environments in the Everglades, such as eutrophic sites, oligotrophic (background) slough/marsh sites, and marl prairies.

Status and FY2001 Plans: Planning of enclosures to be used is underway; initial installation of small enclosures (USGS) and initial experiments in large (SFWMD enclosures) planned for 5/00, with follow up work in 7/00 and 9/00. Enclosure experiments expected to continue into FY01. Presentations on preliminary results expected for FY01.

DOC-Mercury Task (Aiken, Lead Investigator):

1. Deploy mesocosm experiments at select locations to be used in experiments designed to test hypotheses concerning DOC’s effects on Hg speciation and reactivity. These experiments will be carried out in conjunction with other team members (Krabbenhoft, Orem, eg). We will contribute to mesocosm and experiment design, we will handle analyses of DOM in the experiments, and we will provide isolates of organic matter from different locations to be used in altering DOM within the mesocosms.

Status and FY2001 Plans: Planning of enclosures to be used is underway; initial installation of small enclosures (USGS) and initial experiments in large (SFWMD enclosures) planned for 5/00, with follow up work in 7/00 and 9/00. Enclosure experiments expected to continue into FY01. Presentations on preliminary results expected for FY01.

2. Collect large water samples from select locations to isolate organic matter for future mesocosm experiments and to provide organic matter for ongoing lab experiments assessing the interactions of Hg with DOM that may control bioavailability.

Status and FY2001 Plans: Plans for the mesocosm experiments are being developed with the use of DOC fraction additions in mind. First use of the DOC fractions in our experiments will occur in spring or summer 2000.

3. Collect water samples via clean techniques for ongoing lab studies. In addition, sediment samples will also be collected.

Status and FY2001 Plans: Sample for this aspect of the study will be collected during the first field trip and those to follow. Lab studies will be initiated soon after the material is in hand (target date, summer 2000).

4. The following studies are ongoing, and are continuations of our work under the ACME project. All of these studies are expected to continue into FY2001.

a. Binding studies (Hg-DOM). We are continuing ion-exchange studies, and, developing new techniques to assess factors controlling reactivity of DOM with Hg and the strength of binding interactions. This work is important for accurate modeling of these interactions.

b. Further study of the interactions of the DOM with HgS which will provide insight into ability of DOM to stabilize colloidal HgS. This is a potentially significant process effecting the bioavailability of Hg.

c. We are studying the "partitioning" of Hg between dissolved and particulate phases after entering the system as precipitation. Corroboration of "field" based partitioning coefficients is necessary for accurately modeling Hg behavior in the Everglades. This work will be completed this fiscal year.

d. As part of our efforts in Phase 2, we are interested in exploring and developing chemical techniques to assess factors controlling bioavailability. These methods are in the planning stage, but, we hope to make progress on preliminary measurements this FY.


Water Quality Task (Orem, Lead Investigator):

  • Nutrients and Geochemical Processes Synopsis Report (Orem et al.)
    Status: Underway, planned to be completed by 7/00
  • "Accumulation Rates of C,N, and P in Sediments from Taylor Slough, Everglades National Park" (Orem et al.; Soil Science)
    Status: Draft completed, in internal USGS review, to be submitted to journal 4/00
  • "Sulfur in the Everglades: Sources, Sinks, and Biogeochemical Cycling" (Bates et al.; USGS Open-File Report
    Status: Completed 12/99
  • "Biogeochemical Cycling of Phosphorus in the Northern Everglades" (Orem et al.; Biogeochemistry)
    Status: Draft underway, expected completion 6/00
  • "Diagenetic Processes and Redox Chemistry of the Everglades" (Orem et al.; USGS Open-File Report)
    Status: Not started yet, expected to be completed by 9/00

Mercury Studies in the Everglades Task (Krabbenhoft, Lead Investigator):

  • Mercury Cycling in the Everglades, USGS Circular, Synthesis Report (Krabbenhoft et al.), anticipated review draft to be completed by the end of FY00, with printing of the circular by the end of the current calendar year.
  • Photochemical Demethylation and Mercury Reduction in the Everglades (Krabbenhoft et al.;), Submitted to Environmental Science and Technology, awaiting response from journal.
  • Sediment-Water Fluxes of Mercury and Methylmercury in the Florida Everglades (Hurley and Krabbenhoft and others), Manuscript in colleague review, and to be submitted to Environmental Science and Technology.
  • Phase II Mercury Studies in the Florida Everglades: Controlled Experiments to Address Ecosystem Management Concerns (Krabbenhoft, USGS Fact Sheet), will begin drafting 6/00, and expected printing in 9/00.
  • Bioaccumulation of Methylmercury in the Everglades: Ties to Sedimentary Processes, by D. Krabbenhoft, L. Cleckner, J. Hurley, and C. Gilmour Target journal: Environmental Science and Technology.
  • Methyl-Mercury Degradation Pathways: A Comparison Among Three Impacted Ecosystems, by M. Marvin-Dipasquale, R. Oremland, D. Krabbenhoft, and C. Gilmour. Submitted to Environmental Science and Technology, awaiting response from journal.

DOC-Mercury Task (Aiken, Lead Investigator):

We have authored a number of high quality journal articles describing our efforts in Phase 1. This effort will continue in FY 2000. In addition to submitting our contributions to the synthesis report, the following reports are anticipated this FY:

  • Reddy, M. M., Aiken, G. R., and Schuster, P. F., Hydroperiod driven solute transport at the peat-water interface in the Florida Everglades: Hydrophobic acid diffusion from peat. Journal article scheduled for review by Sept. 30, 2000.
  • Reddy, M. M., and Aiken, G. R., Fulvic acid-sulfide ion competition for mercury ion binding in the Florida Everglades. Scheduled for submission to Water, Air and Soil Pollution by Sept. 30, 2000.
  • Ravichandran, M., Aiken, G. R., Reddy, M. M., and Ryan, J. N., Complexation of mercury by dissolved organic matter isolated from the Florida Everglades. Journal article scheduled for review by Sept. 30, 2000.
  • Aiken, G. R., Reddy, M. M., and Schuster, P. F., Organic geochemistry of dissolved organic carbon in the northern Everglades, Florida Journal article scheduled for review by Sept. 30, 2000.
  • Hurley, J. P., Cleckner, L. B., Krabbenhoft, D. P., and Aiken, G. R., Pigment distribution in plankton and periphyton of the Florida Everglades. Journal article scheduled for review by Sept. 30, 2000.
  • Benoit, J. M., Mason, R. P., Gilmour, C. C., and Aiken, G. R., Mercury binding constants for dissolved organic carbon isolates from the Florida Everglades, to be submitted to Limnology and Oceanography. Scheduled for review by May 2000.

Stable Isotopes and Food Webs Task (Kendall, Lead Investigator):

  • "Use of Isotopic Techniques for Tracing Fish Migration and Mercury Sources in the Everglades" (Kendall, Lange, et al.; Can. J. of Fish. and Aq. Sc.)
  • "Tracing mercury bioaccumulation with stable isotopes" (Krabbenhoft, Kendall, Hurley, Garrison; Environ. Sc. and Technol.)
  • Second paper (summary) on fatty acid isotopes as trophic indicators (combining fatty acid isotopes, Hg data, and other tools) (Dias et al.; Limnol. & Ocean.) &
  • Second (summary) paper on controls on spatial variability in foodwebs (adding Hg data and REMAP story to our isotope story at USGS sites) (Kendall et al.; Limnol. & Ocean.)

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