Concentrations of total mercury (HgT) and methylmercury (MeHg) in Great Salt Lake (GSL) water, superficial sediment, brine flies, and ducks collected before (2007-2012) and after (2015-2016) closure of the culverts in the railroad causeway in late 2013. These data are discussed in the publication: Valdes, C., Black, F.J., Stringham, B., Collins, J.N., Goodman, J.R., Saxton, H.J., Mansfield, C.R., Schmidt, J.N., Yang, S., and Johnson, W.P., 2017. Total mercury and methylmercury response in water, sediment, and biota to destratificaiton of the Great Salt Lake, Utah, USA. Environmental Science and Technology, 51: 4887–4896.
Water column chemical and physical conditions were characterized at locations across the south arm of GSL. Water samples were collected at 0.2 m below lake surface and 0.5 m above lake bottom, referred to as shallow and deep samples, respectively. Water column temperature, specific conductance, pH, and dissolved oxygen (DO) were measured in the field using a calibrated YSI probe. Sulfide was measured in filtered water samples in the field using a photometric method (CHEMetrics). Water samples were collected by peristaltic pump using acid-washed teflon tubing and bottles. Filtered water samples were passed through a 0.45-micron pore size, capsule filters in the field. Water samples for HgT and MeHg were acidified to 0.5% using sulfuric acid the same day as sampling, then refrigerated until analyzed.
Water for HgT was oxidized by amendment to 5% BrCl. HgT was determined via reduction with SnCl2, purge and trap onto gold, thermal desorption, with quantification by cold vapor atomic fluorescence spectroscopy (CVAFS). MeHg concentration in water was measured after distillation with ammonium pyrrolidine dithiocarbamate, aqueous phase ethylation, purge and trap onto tenax, thermal desorption, pyrolitic decomposition, and CVAFS. Water samples for dissolved organic carbon analysis were placed on ice in the field, refrigerated, and measured (TOC-5000a, Shimadzu) within one week of collection using EPA Method 1684.
Surficial sediment was sampled at eleven sites in the GSL, and were collected by peristaltic pump using acid-washed PTFE tubing into FLPE bottles, and stored on ice in the field. Subsamples were oven dried at 105°C for 12 hours and re-weighed to determine water content and allow conversion between wet and dry weight (without salt correction). HgT was extracted from sediment by digestion in a 7:3 mixture of HNO3:H2SO4 at 80°C for 6 hours, followed by amendment to 5% BrCl. MeHg was leached from sediment with a mixture of potassium bromide, sulfuric acid, and copper sulfate, extracted into methylene chloride, back extracted into water, followed by aqueous phase ethylation, purge and trap, thermal desorption, pyrolitic decomposition, and CVAFS detection. Certified reference materials (CRMs) for HgT (MESS-3) and MeHg (CC-580) in sediment were analyzed.
Adult brine flies (Ephydra spp.) were collected from Lady Finger Point on Antelope Island. Flies were collected with nets, transferred into polypropelene tubes, placed on ice in the field, and frozen in the lab. Waterfowl were harvested with shotguns using non-lead from the GSL and surrounding wetlands. The age of each bird was determined by physical characteristics. The species sampled were Northern Shovelers (Anas clypeata), Mallard (Anas platyrhynchos), Gadwall (Anas strepera), and Cinnamon Teal (Anas cyanoptera). Tissue samples were frozen, later thawed, the skin removed, and breast muscle tissue was harvested.
Brine fly and waterfowl samples were freeze-dried and homogenized prior to analysis, and thus all HgT concentrations in biota are reported on a dry weight basis. Brine flies were digested in a 2:1 mixture of HNO3:H2SO4. Samples predigested at room temperature for 1 hour, then at 100 °C for 4 hours, then were amended to 1% BrCl. Digested samples were measured by oxidation with BrCl, reduction with SnCl2, purge and trap using dual-stage gold trap amalgamation and quantification by CVAFS. The duck muscle tissue was analyzed using thermal decomposition, amalgamation, and atomic absorption spectrophotometry using a DMA-80. Each analysis run included each of the CRMs TORT-2 and DORM-3.
Data contributors and project collaborators include Carla Valdes, Frank J. Black, Jeffrey N. Collins, James R. Goodman, Heidi J. Saxton, Christopher R. Mansfield, Joshua N. Schmidt, Shu Yang, William P. Johnson, Neil Swanson, Brooks Black, Abigail Rudd, Greg Carling, Diego P. Fernandez, John Luft, JimVan Leeuwend, Ryan Rowland, and Christine Rumsey.
Funding sources include the National Science Foundation, iUTAH-innovative Urban Transitions and Aridregion Hydro-sustainability, NSF Award Number 1208732, the Utah Division of Forestry, Fire, and State Lands (FFSL) of the Utah Department of Natural Resources, the W.M. Keck Foundation via the BRINE project, and NSF Award Number 1637196.