The dataset presented here represents the concentrations and stable isotopic composition of gaseous mercury (Hg) for 31 sites across the United States. This national-scale monitoring effort was performed by the National Atmospheric Deposition Program (NADP) and the USGS over a two-year period (March 2016 - May 2018). The network includes a highly diverse set of sites ranging from remote (e.g. Denali National Park, AK and Mauna Loa, HI) to highly urbanized (e.g. Bronx, NY and Boston, MA). Air samples were collected using a custom designed bulk air sampler, in which air was pumped at approximately 1 L/min through particulate and soda lime filters prior to passing through two quartz tubes containing gold coated glass beads where gaseous Hg was collected. Each sampling period was two weeks long. The Hg was thermally desorbed from the gold beads and collected in a liquid oxidizing trap. The total Hg concentration and isotopic composition was determined on this solution. The average total gaseous Hg concentration across sites was 1.23 ± 0.28 ng/m3, but higher concentrations were observed at sites closer to known Hg sources, such as Oak Ridge National Lab (6.53 ng/m3). For all sites, the average odd isotope mass independent fractionation (MIF, Δ199Hg), an indicator of photochemistry, was -0.20 ± 0.07‰ and had a range of -0.43 to 0.01 ‰. Mass dependent fractionation (MDF, δ202Hg), the commonly used isotope ratio for source tracking, was generally positive with a mean value of 0.45 ± 0.40‰, although intermittent negative MDF was also observed at some sites. Urban sites were consistently lighter in δ202Hg (0.34‰) compared to remote background sites (0.65‰), potentially indicating differences between emission sources. Though regional differences in odd MIF and MDF were small, we observed a trend showing enrichment of δ202Hg in the northeastern United States, from the Ohio River Valley to remote sites in northern Maine and Nova Scotia, suggesting a shift from localized emission sources to globally transported Hg across this region.

Data for "Tate, M. T., Janssen, S. E., Lepak, R. F., Flucke, L., & Krabbenhoft, D. P. (2023). National-scale assessment of total gaseous mercury isotopes across the United States. Journal of Geophysical Research: Atmospheres, 128, e2022JD038276. https://doi.org/10.1029/2022JD038276". This dataset is associated with the following publication: Tate, M., S. Janssen, R. Lepak, L. Fluke, and D. Krabbenhoft. Assessment and Application of an Active Total Gaseous Mercury Collector to Survey Mercury Sources Across the United States. Environmental Science & Technology Letters. American Chemical Society, Washington, DC, USA, 128(8): N/A, (2023).

In 2021, the U.S. Geological Survey (USGS) Mercury Research Laboratory (MRL) conducted a large-scale assessment of mercury (Hg) concentrations and Hg stable isotope values in tributaries of Lake Superior in order to define the sources and amounts of Hg entering the lake. Water samples were collected monthly from 18 tributaries in the United States from April through October in 2021 and during 2022 spring melt (May 2022). As a complement, 10 tributaries on the Lake Superior Northshore were sampled three times a year (spring, summer, and fall) by Lakehead University and Lakehead Region Conservation Authority. Nine tributaries were also sampled twice per year (spring and summer) in Pukaskwa National Park by Parks Canada. Filtered total Hg (THg) concentrations from United States and Canadian Northshore ranged from 0.2 to 8.8 nanograms per liter (ng L-1), with a median value of 1.2 ng L-1. Unfiltered THg in Pukaskwa National Park ranged from 0.6 to 5.0 ng L-1 with a median of 3.2 ng L-1, but encompassed both the filtered and particulate bound Hg. Median methylmercury (MeHg) values were approximately 0.1 ng L-1 for both filtered and unfiltered waters, but could reach levels greater than 1 ng L-1 during higher flow events. THg and MeHg concentrations were positively correlated to dissolved organic carbon (DOC) concentrations for most tributaries. Hg loads to Lake Superior were calculated for U.S. tributaries using the R package loadflex ( http://dx.doi.org/10.1890/ES14-00517.1 ), median loads for THg were 18 grams per day, but could increase to 590 grams per day under high flow and snow melt conditions.

The movement of mercury (Hg) from the atmosphere to the biosphere occurs by both wet and dry deposition to solid surfaces, water, and vegetation. Most of the annual dry atmospheric Hg deposition in deciduous forests is believed to originate from litterfall which consists mainly of dead leaves that fall to the earth’s surface, primarily during the autumn and winter seasons. Atmospheric Hg reaches an annual maximum concentration in leaves at the time of leaf fall. Analysis of litterfall samples helps to quantify total annual atmospheric Hg deposition to forests when combined with precipitation Hg data. This data set is derived from litterfall samples collected during 2017-18 and 2018-19 at 27 selected National Atmospheric Deposition Program (NADP) sites in 12 states located across the eastern half of the United States. Through the Litterfall Mercury Monitoring Initiative (LMMI), operated by the U.S. Geological Survey (USGS), litterfall sample collectors were distributed to the selected NADP sites where site operators retrieved multiple 4-week-long samples during the leaf fall period. These samples were collected and shipped to the USGS Mercury Research Laboratory where they were analyzed for concentrations of total Hg and methylmercury (MeHg), and litterfall dry mass was also determined. The samples for total Hg and MeHg analysis represent composites from 4 collectors across all sample collections at each site during the litterfall season. Litterfall dry mass was determined from all 8 sample collectors across all sample collections.

Automated collectors at Elkmont passively accumulated litterfall for two consecutive 4-week periods each in 2008 and 2009. Samples were collected, and submitted for analysis of mercury by low-level, trace-metals methods. Species of leaf included poplar, maple, birch, pine, dogwood, hemlock. and magnolia. The average concentration of total mercury in the eight samples was 32.6 nanograms per gram. The estimated litterfall deposition for the eight samples was 12.4 nanograms per square meter.

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.

Samples were collected from Clear Lake, California from 2019-2022 by the U.S. Geological Survey (USGS) California Water Science Center, the USGS Forest and Rangeland Ecosystem Science Center (FRESC), the US Environmental Protection Agency, and EA Engineering Science and Technology Inc. to assess the extent and cycling of legacy mercury (Hg) contamination from Sulphur Bank Mine. Samples of waste rock, sediments, groundwater, and biological tissue (zooplankton, bluegill, smallmouth bass, Mississippi silversides, and largemouth bass) were analyzed for Hg stable isotopes by the U.S. Geological Survey Mercury Research Laboratory. Mercury concentrations for sediments, waste rocks, and groundwaters are included within this data release and information for biological Hg concentrations can be found in the companion data release (https://doi.org/10.5066/P96912PN).