Regional geochemistry of metals in organic-rich sediments, sawgrass and surface water, from Taylor Slough, Florida

Abstract

We report progress on the task "Processes in Organic-Rich Sediments of South Florida Mercury and Metals", part of the USGS-cooperative "Aquatic Cycling of Mercury in the Everglades" (ACME) project. Objectives of the task include: (1) definition of mercury and other element spatial concentration patterns and baselines, (2) definition of historical Hg and other element concentration trends in organic-rich sediments, and (3) development of an understanding of element uptake in sawgrass as it relates to element bioavailability in organic-rich sediments. The report focuses on work in Taylor Slough, Everglades National Park, because it is both the terminus of surface water flow for the eastern side of the Everglades and the main source of fresh water to the hyposaline eastern Florida Bay. Surface water, sawgrass leaf and root material, and cores of organic-rich sediments were collected in 1996 at eight sites within Taylor Slough along a predominantly north/south trend. The uppermost site was near the canal water discharge gate to the Slough and the lower two sites were within several km of Florida Bay. All samples were collected, preserved, transported and analyzed for mercury and other elements using accepted USGS QA/QC procedures and protocols. We present element concentration data for over thirty elements in the water, plant, and sediment samples collected. In addition to the cores used for element analysis, additional cores were collected at each site and used for nutrient and sulfur species studies, peat diagenesis studies, and geochronology (dating) determinations using 210Pb. The core dates and dry bulk density data were used to calculate sediment accumulation rates which were in turn used, in conjunction with the element concentration data, to calculate element accumulation rates (EAR). Very little variation in element concentration among cores was noted for the major elements. Several cores had higher Ca

Evaluation of the Possible Sources and Controlling Factors of Toxic Metals/Metalloids in the Florida Everglades and Their Potential Risk of Exposure

“…As, Cr, Cd, Ni, Cu, Zn, and Pb in the sediment of south Florida canals have been identified to be the chemicals of potential ecological concern (COPECs) . As, Cr, Hg, Ni, and Pb were also found to be over Florida TEC in the soil cores obtained from the Taylor Slough in the southern part of the Everglades . Cr and Ni in Florida Bay sediment and Cr, Pb, Hg, Cu, As, and Zn in Biscayne Bay sediment have also been detected at levels over the TEC in part of the sampling sites.…”

“…15 As, Cr, Hg, Ni, and Pb were also found to be over Florida TEC in the soil cores obtained from the Taylor Slough in the southern part of the Everglades. 41 Cr and Ni in Florida Bay sediment 42 and Cr, Pb, Hg, Cu, As, and Zn in Biscayne Bay sediment 43 have also been detected at levels over the TEC in part of the sampling sites. It should be noted that risk assessment in this work was conducted by comparing the total metal concentration in wetlands with guidelines without considering the bioavailability and speciation of the metal.…”

Peat porewater chloride concentration profiles in the Everglades during wet/dry cycles from January 1996 to June 1998: field measurements and theoretical analysis

“…Public Works (October 2006, page 42) termed the Comprehensive Everglades Restoration Plan (CERP) "the largest ecosystem restoration effort in the world". A quantitative understanding of water and solute exchange (Krest and Harvey, 2003;Harvey et al, 2004) between surface water and peat porewater is essential for successful Everglades restoration (Gough et al, 2000;Snodgrass et al, 2000).…”

The Distribution of Toxic and Essential Metals in the Florida Everglades

“…Two major sloughs in the Everglades, Taylor and Shark Sloughs, carry surface water sheet flow from WCAs and EAA to Everglades National Park. They might serve as sinks for elements from erosion of soils and weathering of the underlain sediment rocks (Gough et al 2000).…”