Comma-separated values (.csv) files containing data related to mercury in soil, water, sediment, in-stream leaf litter, periphyton, and aquatic invertebrates collected in 2021-2022 from headwater streams associated with wildfires in the northwestern U.S.

Comma-separated values (.csv) file containing data related to mercury in biota collected from the Hells Canyon Reservoir Complex on the Snake River, Idaho and Oregon.

Comma-separated values (.csv) file containing data related to mercury in biota collected from the Hells Canyon Reservoir Complex on the Snake River, Idaho and Oregon.

Comma-separated values (.csv) file containing data related to amphibian sampling across the United States between 2016 and 2021. Data files contain mercury concentrations in amphibian and dragonfly tissues, mercury concentrations in sediment, as well as amphibian morphometrics, and habitat and climate characteristics where the samples were collected.

Comma-separated values (.csv) file containing data related to mercury in biota from Cottage Grove Reservoir, and the rivers upstream of Cottage Grove Reservoir, Oregon.

Comma-separated values (.csv) file containing data related to mercury in biota collected from Clear Lake California.

Comma-separated values (.csv) file containing data related to mercury in biota collected from Clear Lake California.

This dataset includes the field measurements and laboratory analyses of surface water, seston, and sediment collected from Lake Powell, within Glen Canyon National Recreation area (GLCA), during high flow (May-June 2014) and low flow (August 2015) conditions. The study area includes 12-13 sampling sites that follow a transect spanning the entire length of the reservoir from the Colorado River inflow to the Glen Canyon dam, as well as the San Juan River arm, the Escalante River arm and West Canyon. Bed sediment samples were analyzed for mercury speciation, methylmercury production and degradation rates, total reduced sulfur, iron speciation, organic content, and 16S rRNA gene templates as a proxy for microbial abundances. Water samples were collected from 3-5 depths at each site and analyzed for: total mercury (filtered and particulate), methylmercury (filtered and particulate), dissolved organic and inorganic carbon with 13C isotopic ratios, nutrients, anions, cations, trace metals, particulate carbon (with 13C isotopic ratios) and particulate nitrogen (with 15N isotopic ratios). Water quality sonde (EXO) field measurements included specific conductivity, temperature, pH, dissolved oxygen, fluorescent dissolved organic matter, chlorophyll, and turbidity. Fish samples were also collected during November 2014 from Good Hope Bay (upper reservoir), Wahweap Bay (lower reservoir), and the San Juan arm and assayed for total mercury for comparison with previous striped bass samples collected by the state of Utah. There are nine files (*.csv) in this dataset: 1) data dictionary ; 2) sediment data; 3) water data; 4) seston data; 5) fish data; 6) EXO main channel profile data ; 7) EXO off channel profile data; 8) quality assurance data; and 9) molecular data.

This dataset includes the field measurements and laboratory analyses of surface water, seston, and sediment collected from Lake Powell, within Glen Canyon National Recreation area (GLCA), during high flow (May-June 2014) and low flow (August 2015) conditions. The study area includes 12-13 sampling sites that follow a transect spanning the entire length of the reservoir from the Colorado River inflow to the Glen Canyon dam, as well as the San Juan River arm, the Escalante River arm and West Canyon. Bed sediment samples were analyzed for mercury speciation, methylmercury production and degradation rates, total reduced sulfur, iron speciation, organic content, and 16S rRNA gene templates as a proxy for microbial abundances. Water samples were collected from 3-5 depths at each site and analyzed for: total mercury (filtered and particulate), methylmercury (filtered and particulate), dissolved organic and inorganic carbon with 13C isotopic ratios, nutrients, anions, cations, trace metals, particulate carbon (with 13C isotopic ratios) and particulate nitrogen (with 15N isotopic ratios). Water quality sonde (EXO) field measurements included specific conductivity, temperature, pH, dissolved oxygen, fluorescent dissolved organic matter, chlorophyll, and turbidity. Fish samples were also collected during November 2014 from Good Hope Bay (upper reservoir), Wahweap Bay (lower reservoir), and the San Juan arm and assayed for total mercury for comparison with previous striped bass samples collected by the state of Utah. There are nine files (*.csv) in this dataset: 1) data dictionary ; 2) sediment data; 3) water data; 4) seston data; 5) fish data; 6) EXO main channel profile data ; 7) EXO off channel profile data; 8) quality assurance data; and 9) molecular data.

The Hells Canyon Complex (HCC) is comprised of a series of three consecutive reservoirs (Brownlee, Oxbow, and Hells Canyon) along a 145 km reach of the Snake River bordered by Idaho to the east and Oregon to the west. Due to concerns regarding mercury (Hg) contamination within the HCC, in cooperation with Idaho Power Company, the U.S. Geological Survey has been leading an investigation into the sources, transport, microbial transformations, chemical speciation and bioaccumulation of Hg in this complex river-reservoir environment. This data release is focused on the sediment component of this larger effort and includes data collected between 2014 and 2018 from shallow surface sediment (≤ top 5 cm) and from sectioned deep cores ranging from 34 cm to 112 cm in length. While the majority of the data was collected from within the HCC, some limited additional data is included from a number of riverine bed sediment sites located in the watershed upstream of the HCC and from two additional reservoirs on the Boise River sampled as control sites (Anderson Ranch and Lucky Peak reservoirs). For shallow surface sediment, the list of mercury associated analytes reported in this dataset includes total mercury, methylmercury, and inorganic reactive mercury concentrations; as well as rate constants and calculated potential rates associated with microbial methylmercury production and degradation, derived from stable isotope amendment bottle incubations. The list of non-mercury analytes includes field measurements of temperature, oxidation-reduction potential and pH; percent dry weight; percent loss on ignition; wet bulk density; porosity; total reduced sulfur; and iron speciation. For a sub-set of the shallow sediment sampled there is additional data for: percent organic carbon (with isotopic 13C values), percent nitrogen (with isotopic 15N values), and grain size (percent < 64 µm). Of the eight sampling events conducted within the HCC, sediment porewater samples were collected from sediment-water interface cores on three occasions to estimate benthic-pelagic diffusive fluxes of a number of mercury and non-mercury constituents. The list of porewater analytes determined and reported herein include: total mercury, methylmercury, ortho-phosphate, ammonium, sulfide, dissolved organic carbon, dissolved organic matter specific ultra-violet absorption at 254 nm (SUVA254), acetate, sulfate, thiosulfate, nitrate, and elemental analysis of Al, As, B, Br, Ca, Cd, Cl, Cu, F, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Se, Si (as SiO2), U, and Zn. Of the eleven deep cores collected and sub-sectioned, all sediment samples were assayed for total mercury and percent loss on ignition, nine were assayed for methylmercury, and two were assayed for dry particle density and environmental radionuclides (137Cs, 210Pb and 226Ra) to assess sedimentation rates. This data release includes five data tables given both as Excel (*.xlsx) and machine readable 'comma-separated values' format (*.csv): 1) ‘T1_Data.Dictionary_HCC.2014-18’, the Data Dictionary, which provides definitions and details related to the other four data tables and includes analytical methods citations; 2) ‘T2_Shallow sed bulk_HCC.2014-18’, the shallow (bulk) sediment dataset; 3) ‘T3_Shallow sed porewater_HCC.2014-18’, the shallow sediment porewater dataset; 4) ‘T4_Deep cores_HCC.2014-18’, the deep core profile dataset; and 5) ‘T5_QA_HCC.2014-18’, quality assurance data summary for all major analyses. In addition, file ‘HCC 2014-18.kmz’ provides the sampling locations in a machine-readable geospatial file format (*.kmz).