The lower Fox River in Wisconsin is a heavily industrialized system and the major tributary to Green Bay within Lake Michigan. The region has been a listed as Area of Concern by the United States Environmental Protection Agency (USEPA), indicating severe impairment of the ecological health of the system. Remedial action has taken place along the river to remove extensive polychlorinated biphenyl (PCB) contamination. However, it was unknown if mercury (Hg), also derived from industrial activity, remained within sediments and actively bioaccumulated within the food web. Mercury stable isotopes were analyzed in sediments and waters collected below the DePere Dam and upstream at Lake Winnebago to compare if Hg sources within the Fox River and determine the extent of industrial contamination. Speciation, methylmercury (MeHg), and isotope measurements were made within biota (prey fish and invertebrates) below DePere Dam to determine if industrial Hg was bioavailable for methylation and bioaccumulation. The interpretation of these results can be found in a companion journal articles published in Environmental Science and Technology (https://doi.org/10.1021/acsestwater.1c00285)

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).

These data represent mercury (Hg), filtered total Hg (FTHg), filtered methylmercury (FMHg), particulate total Hg (PTHg), particulate methylmercury (PMHg), total mercury (THg), dissolved organic carbon (DOC) and total organic carbon (TOC) concentrations in surface water samples collected on Bad River Tribal lands. Several samples were collected at multiple locations on the Bad River and Tyler Forks Creek, and one location on Bull Gus Creek. Additionally, one sample was collected at each of four unknown locations on four Bad River tributaries and two samples at a lake of unknown location. All samples were collected during 2006 to 2016. Neither the collection of water samples nor the Hg analyses were performed by the U.S. Geological Survey, New York Water Science Center.

These data represent mercury (Hg), filtered total Hg (FTHg), filtered methylmercury (FMHg), particulate total Hg (PTHg), particulate methylmercury (PMHg), total mercury (THg), dissolved organic carbon (DOC) and total organic carbon (TOC) concentrations in surface water samples collected on Bad River Tribal lands. Several samples were collected at multiple locations on the Bad River and Tyler Forks Creek, and one location on Bull Gus Creek. Additionally, one sample was collected at each of four unknown locations on four Bad River tributaries and two samples at a lake of unknown location. All samples were collected during 2006 to 2016. Neither the collection of water samples nor the Hg analyses were performed by the U.S. Geological Survey, New York Water Science Center.

This dataset describes mercury (Hg) concentrations and methylation rate potentials that were measured in Lake Mendota, Wisconsin, US in 2020 and 2021. This work is a collaboration between the University of Wisconsin, University of California-Davis, and the U.S. Geological Survey. Samples were collected to examine the linkages between Hg methylation, biogeochemical conditions, and microbial community abundance during lake stratification (September and October). Samples were collected at depths ranging from 0-23 meters, exact values vary per sampling event and are detailed in the corresponding tables. Total Hg (THg) concentrations increased with depth across the anoxic hypolimnion and slightly increased from September to October but exhibited comparable concentrations between both sampling years. Filter-passing MeHg increased with depth across all four sampling dates. Across all incubations, the formation of MeHg under ambient conditions, quantified using a 198Hg(II) tracer, varied widely based on incubation depth and subsequent redox state and the methylation rate potential (Kmet) ranged from 0.001 day-1 to 0.165 day-1. Demethylation rates (Kdem) were quantified using a Me204Hg tracer. The filtered control incubations showed increasing Kdem values with increasing sulfide, leveling off to approximately 0.2 day-1. Concentration and methylation rate potential data were compared to metagenomics and transcripnomics measurements conducted by the University of Wisconsin and further detailed in the corresponding journal article (Peterson et al. 2025, TBD).

Under the Great Lakes Restoration Initiative, the U.S. Geological Survey Mercury Research Lab (USGS MRL) conducted a multiyear assessment of mercury across the Laurentian Great Lakes. Biannual sampling was conducted across all five lakes onboard the U.S. Environmental Protection Agency (US EPA) research vessel Lake Guardian (in years 2010–2014, 2018) at pelagic sampling locations established by the long-term US EPA Great Lakes monitoring program. In addition to the regularly scheduled biannual sampling, in September 2013 and 2014 Lake Michigan and Lake Erie (respectively) were sampled with increased focus on shallow nearshore locations. Throughout these sampling efforts, sediments, mussels, surface water, and plankton were collected from open-water locations within all five of the Great Lakes. Additionally, surface water from Great Lake tributaries were sampled by the USGS MRL and preceded (2005 or 2006) or overlapped (2010-2015) with the open lake sampling efforts. All surface water samples were analyzed for methylmercury, total mercury, and dissolved organic carbon. Plankton and mussel tissue were analyzed for methylmercury, total mercury, and carbon/nitrogen stable isotopes and concentrations (plankton only). Sediments were analyzed for methylmercury, total mercury, and carbon content.

Under the Great Lakes Restoration Initiative, the U.S. Geological Survey Mercury Research Lab (USGS MRL) conducted a multiyear assessment of mercury across the Laurentian Great Lakes. Biannual sampling was conducted across all five lakes onboard the U.S. Environmental Protection Agency (US EPA) research vessel Lake Guardian (in years 2010–2014, 2018) at pelagic sampling locations established by the long-term US EPA Great Lakes monitoring program. In addition to the regularly scheduled biannual sampling, in September 2013 and 2014 Lake Michigan and Lake Erie (respectively) were sampled with increased focus on shallow nearshore locations. Throughout these sampling efforts, sediments, mussels, surface water, and plankton were collected from open-water locations within all five of the Great Lakes. Additionally, surface water from Great Lake tributaries were sampled by the USGS MRL and preceded (2005 or 2006) or overlapped (2010-2015) with the open lake sampling efforts. All surface water samples were analyzed for methylmercury, total mercury, and dissolved organic carbon. Plankton and mussel tissue were analyzed for methylmercury, total mercury, and carbon/nitrogen stable isotopes and concentrations (plankton only). Sediments were analyzed for methylmercury, total mercury, and carbon content.

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.

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.

This data release includes mercury concentrations and mercury stable isotope measurements measured in sediments and biological tissues collected from the Saint Louis River located in Minnesota. Sediments and biota were collected by the U.S. Geological Survey, U.S. Environmental Protection Agency, U.S. Army Corps of Engineers, and federal contractors (Battelle) from 2017-2021. Collection regions included nearshore zones within the main estuary, remedial sites within the lower river, and upstream reservoir sites. Sediments were analyzed for total mercury, methylmercury, and mercury stable isotopes by the U.S. Geological Survey Mercury Research Laboratory (MRL, Madison, Wisconsin). Biological samples were analyzed for total and methylmercury by the MRL or the Contaminant Ecology Research Laboratory (CERL, Corvallis, Oregon); mercury stable isotopes were analyzed by the MRL.