Mercury (Hg) is a persistent environmental contaminant and can accumulate and concentrate in food webs as methylmercury (MeHg), presenting a health risk to humans and wildlife. Multiyear monitoring and modeling studies have shown that atmospheric Hg in litterfall is an important form of Hg deposition to forests. Litterfall consists primarily of leaves with some amounts of twigs, bark, flowers, seeds, fruits, and nuts. Atmospheric Hg accumulates in the forest canopy material and transfers to the forest floor in litterfall. This data set is derived from monthly litterfall collected at the National Atmospheric Deposition Program (NADP) Mercury Deposition Network (MDN) site at El Verde, Puerto Rico, identification number PR20, during 2014-2016. The U.S. Geological Survey (USGS) provided passive litterfall collectors to the PR20 MDN site operator who systematically deployed them in a forest plot near the MDN equipment. Each collector was a 0.25 square meter box made of plastic lattice with a 20-micrometer mesh, polyester, netting liner. The operator retrieved the litterfall in the collectors on a monthly schedule and shipped the subsamples to the USGS Mercury Research Laboratory where concentrations of Hg and MeHg and litterfall dry mass and sample moisture were determined using published methods. More information about the litterfall Hg monitoring field and laboratory methods and quality assurance is available from the NADP at http://nadp.sws.uiuc.edu/newissues/litterfall/

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.

Mercury (Hg) is a persistent environmental contaminant and can accumulate and concentrate in food webs as methylmercury (MeHg), presenting a health risk to humans and wildlife. Multiyear monitoring and modeling studies have shown that atmospheric Hg in litterfall is an important form of Hg deposition to forests. Annual litterfall consists primarily of leaves with some amounts of needles, twigs, bark, flowers, seeds, fruits, and nuts. Atmospheric Hg accumulates in leaves and reaches an annual maximum concentration at autumn leaf drop. This data set is derived from autumn litterfall collected at 30 selected National Atmospheric Deposition Program (NADP) Mercury Deposition Network (MDN) sites in deciduous and mixed deciduous-coniferous forests from 16 states in the eastern United States during 2007-2009 and 2012-2015. The NADP administered litterfall collection at the MDN sites. The U.S. Geological Survey (USGS) distributed sets of passive litterfall sample collectors to MDN site operators for systematic retrieval of samples during the 8 to 16 weeks of autumn leaf drop each year at each site. Samples were processed and analyzed at the USGS Mercury Research Laboratory where concentrations of Hg and MeHg and litterfall dry mass and sample moisture were determined. All sites did not have data for all years. Most sites had four Hg concentrations per year and a few sites had less than or more than four Hg concentrations in specific years. MeHg concentrations were determined in one composite sample per site in 2007 and 2012-2015. Litterfall mass was determined from 4 to 8 samples per site per year. Seven annual groups of data were compiled into this dataset. More information is available from the NADP at http://nadp.sws.uiuc.edu/

Annual litterfall samples were collected and analyzed for THg (total mercury) and MHg (methyl mercury) at a site (WI95) on Bad River tribal lands during 2012 to 2018. Litterfall was collected at a second site, WI01, during 2012 only. Litterfall was sampled in eight collectors, from which annual mass was determined. Total mercury analyses were performed on only four samples from the collectors with the lowest numbers in the sequence. A mass weighted sample based on the four THg samples was analyzed for MHg. Neither the collection of litterfall samples nor the Hg analyses were performed by the U.S. Geological Survey, New York Water Science Center.

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.

This dataset presents mercury (Hg) and methylmercury (MeHg) concentration data in waters (surface river water and community drinking water), biota, plant, and sediments that were collected across eight communities along the Pra and Ankobra Rivers in Western Ghana. Water and sediment samples were collected in October 2024 from eight rivers along the Ankobra and Pra Rivers, two rivers heavily impacted by artisanal-scale gold mining (ASGM) activity. Fish and plant samples were obtained from the communities when available as samples of opportunity. This project was a part of the Embassy Science Fellowship program coordinated by the U.S. State department and all samples were collected in collaboration with the USGS Mercury Research Laboratory (MRL), the U.S. Embassy in Ghana, and Hen Mpoano, a non-governmental organization in Ghana. All samples were processed and analyzed at the USGS MRL in Madison, Wisconsin, USA.

The Hannibal Pool of the Ohio River is heavily industrialized and receives direct effluent discharges from coal power plants, chlor-alkali plants, and sewage treatment facilities. Mercury (Hg) is a contaminant of concern due to the risk of bioaccumulation at wildlife refuges also located within this region. Mercury concentrations and isotopes compositions were measured to assess the levels and source of Hg contamination, respectively within the system. Sediments and waters were measured to define isotopic end members within Hannibal Pool. Heelsplitter mussels, zebra mussels, and prey fish were also analyzed to determine if Hg source signatures were conserved within the food web. These data are a part of a larger study and an associated journal article documented in Integrated Environmental Assessment and Management (https://doi/10.1002/ieam.4308).

USGS conducted preliminary assays on aged (3 mo.) surface sediment (0-4 cm) collected from 13 sites during October 1998 in order to decipher general spatial trends in Hg-speciation, microbiology and relevant biogeochemistry. During the second field campaign sample processing and incubations were conducted at ambient temperature within hours of sediment collection to provide a more accurate measure of in-situ process rates and analyte concentrations. The third field sampling (October 1999), involving 14 sampling and was conducted with a similar approach as in June 1999. The latter two data sets provide a direct seasonal comparison (summer/fall, high/lo flow conditions) of Hg transformation dynamics in the CRS. Sediment depth profiles (0-16 cm) were investigated at four sites during June 1999 and at two of these four during October 1999. Eroding vertical bank material was sampled in the Hg-contaminated Fort Churchill region during both 1999 dates. Laboratory experiments were conducted using sediment collected during the latter two sampling dates. The study purpose sought to: a) identify important zones of net methylmercury (MeHg) production and consumption within the CRS, b) determine which environmental factors most strongly influence these processes and c) provide estimates of seasonal variability. Measurements were made of microbial Hg-transformations (via radiotracer) and in-situ Hg speciation (total mercury (Hgt), MeHg, and particle-associated acid-extractable Hg(II)). Acid extractable Hg(II) was used as a surrogate measure for the Hg(II) most readily available to bacteria for methylation. A novel Hg-biosensor technique was also used to assess bioavailable Hg(II) in pore-water. A suite of ancillary microbial processes and sediment geochemical parameters were also measured to more fully characterize each site, and to relate these measurements to observed Hg-transformation rates and Hg-speciation. The EPA is publishing this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU2 Remedial Investigation Report (EPA, 2017), which describes the nature and extent of contamination from the Site. The report contains the Human Health Risk Assessment and Ecological Risk Assessment. Literature and other source Hg data are summarized in the RI for surface waters, sediments, and biological tissues.

Primary and secondary consumers are important links in the trophic transfer of methylmercury, and their methylmercury concentrations are often measured to assess the potential risk of toxicity to higher trophic level consumers, including humans. A better understanding of the link between methylmercury production in sediments and methylmercury bioaccumulation in tidal marsh primary and secondary consumers will improve the design of contaminant monitoring, remediation, and restoration efforts, thereby protecting human and wildlife health. To advance this goal, we characterized spatial variation in sediment biogeochemistry and methylmercury concentrations of sediments, water, and consumer tissues at a meso-scale among marsh subhabitats. Methylmercury concentrations and stable isotope ratios were measured in 15 genera of tidal marsh primary and secondary consumers (Genera: Assiminea, Myostotella, Geukensia, Macoma, Traskorchestia, Bembidion, Pardosa, Palaemon, Hemigrapsus, Tridentiger, Acanthogobius, Gillichthys, Gambusia, Gasterosteus, and Cottus). Samples were collected in four subhabitats: marsh edges, marsh interiors, 1st order channels, and 3rd order channels during summer of 2006.

USGS conducted preliminary assays on aged (3 mo.) surface sediment (0-4 cm) collected from 13 sites during October 1998 in order to decipher general spatial trends in Hg-speciation, microbiology and relevant biogeochemistry. During the second field campaign sample processing and incubations were conducted at ambient temperature within hours of sediment collection to provide a more accurate measure of in-situ process rates and analyte concentrations. The third field sampling (October 1999), involving 14 sampling and was conducted with a similar approach as in June 1999. The latter two data sets provide a direct seasonal comparison (summer/fall, high/lo flow conditions) of Hg transformation dynamics in the CRS. Sediment depth profiles (0-16 cm) were investigated at four sites during June 1999 and at two of these four during October 1999. Eroding vertical bank material was sampled in the Hg-contaminated Fort Churchill region during both 1999 dates. Laboratory experiments were conducted using sediment collected during the latter two sampling dates. The study purpose sought to: a) identify important zones of net methylmercury (MeHg) production and consumption within the CRS, b) determine which environmental factors most strongly influence these processes and c) provide estimates of seasonal variability. Measurements were made of microbial Hg-transformations (via radiotracer) and in-situ Hg speciation (total mercury (Hgt), MeHg, and particle-associated acid-extractable Hg(II)). Acid extractable Hg(II) was used as a surrogate measure for the Hg(II) most readily available to bacteria for methylation. A novel Hg-biosensor technique was also used to assess bioavailable Hg(II) in pore-water. A suite of ancillary microbial processes and sediment geochemical parameters were also measured to more fully characterize each site, and to relate these measurements to observed Hg-transformation rates and Hg-speciation. The EPA is publishing this data in support of the Carson River Mercury NPL Site in Nevada. Data was compiled and evaluated for the OU2 Remedial Investigation Report (EPA, 2017), which describes the nature and extent of contamination from the Site. The report contains the Human Health Risk Assessment and Ecological Risk Assessment. Literature and other source Hg data are summarized in the RI for surface waters, sediments, and biological tissues.