title: Total- and methyl-mercury concentrations and methylation rates across the freshwater to hypersaline continuum of the Great Salt Lake, Utah, USA.
abstract: We examined mercury (Hg) speciation in water and sediment of the Great Salt Lake and surrounding wetlands, a locale spanning fresh to hypersaline and oxic to anoxic conditions, in order to test the hypothesis that spatial and temporal variations in Hg concentration and methylation rates correspond to observed spatial and temporal trends in Hg burdens previously reported in biota. Water column, sediment, and pore water concentrations of methylmercury (MeHg) and total mercury (THg), as well as related aquatic chemical parameters were examined. Inorganic Hg(II)-methylation rates were determined in selected water column and sediment subsamples spiked with inorganic divalent mercury (204Hg(II)). Net production of Me204Hg was expressed as apparent first-order rate constants for methylation (kmeth), which were also expanded to MeHg production potential (MPP) rates via combination with tin reducible 'reactive' Hg(II) (Hg(II)R) as a proxy for bioavailable Hg(II). Notable findings include: 1) elevated Hg concentrations previously reported in birds and brine flies were spatially proximal to the measured highest MeHg concentrations, the latter occurring in the anoxic deep brine layer (DBL) of the Great Salt Lake; 2) timing of reduced Hg(II)-methylation rates in the DBL (according to both kmeth and MPP) coincides with reduced Hg burdens among aquatic invertebrates (brine shrimp and brine flies) that act as potential vectors of Hg propagation to the terrestrial ecosystem; 3) values of kmeth were found to fall within the range reported by other studies; and 4) MPP rates were on the lower end of the range reported in methodologically comparable studies, suggesting the possibility that elevated MeHg in the anoxic deep brine layer results from its accumulation and persistence in this quasi-isolated environment, due to the absence of light (restricting abiotic photo demethylation) and/or minimal microbiological demethylation.
authors.affiliation: Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, United States. Electronic address: william.johnson@utah.edu.
authors.forename: William P
authors.initials: WP
authors.lastname: Johnson
authors.affiliation: Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, United States.
authors.forename: Neil
authors.initials: N
authors.lastname: Swanson
authors.affiliation: Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, United States.
authors.forename: Brooks
authors.initials: B
authors.lastname: Black
authors.affiliation: Brooks-Rand LLC, 4415 6th Ave NW, Seattle, WA 98107, United States.
authors.forename: Abigail
authors.initials: A
authors.lastname: Rudd
authors.affiliation: Department of Geological Sciences, Brigham Young University, Provo, UT 84602, United States.
authors.forename: Greg
authors.initials: G
authors.lastname: Carling
authors.affiliation: Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, United States.
authors.forename: Diego P
authors.initials: DP
authors.lastname: Fernandez
authors.affiliation: State of Utah Division of Wildlife Resources, 1594W North Temple, Suite 2110, Box 146301 Salt Lake City, UT 84114, United States.
authors.forename: John
authors.initials: J
authors.lastname: Luft
authors.affiliation: State of Utah Division of Wildlife Resources, 1594W North Temple, Suite 2110, Box 146301 Salt Lake City, UT 84114, United States.
authors.forename: Jim
authors.initials: J
authors.lastname: Van Leeuwen
authors.affiliation: United States Geological Survey, Menlo Park, CA 94025, United States.
authors.forename: Mark
authors.initials: M
authors.lastname: Marvin-DiPasquale
mesh_terms: D004784:Environmental Monitoring; D060106:Lakes / Q000737:chemistry*; D008745:Methylation; D008767:Methylmercury Compounds / Q000032:analysis*; D054712:Salinity; D014589:Utah; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical
keywords: Aqueous geochemistry; Limnology; Toxic elements; Trace elements