This dataset includes data for water, sediment, and biota samples collected at 250 locations in the northwestern Sierra Nevada and the Trinity Mountains during 1999–2012. The locations were chosen to assess potential effects from historical mining, with a focus primarily on mercury contamination associated with placer gold mines in the Sierra Nevada and the Trinity Mountains, and a hard-rock mercury mine in the Trinity Mountains. Trace elements and major elements were analyzed in selected samples. All analyses of mercury, methylmercury, and (or) trace and major elements in water and sediment were performed by U.S. Geological Survey laboratories. Biota samples (invertebrates, fish, and frogs) were analyzed for mercury, methylmercury and (or) trace elements at the Trace Element Research Laboratory in College Station, Texas.

This data set was collected throughout the Gallinas watershed in New, Mexico following the Hermit's Peak-Calf Canyon fires on April 6, 2022. The watershed has a history of mining and prospecting, which acts as an additional stressor to post-wildfire water quality and ecosystem health. Water samples were collected immediately post-fire. Water, sediment deposit and bed sediment samples were collected in October 2022 and April 2023, 6 months and 1-year post-fire. Samples were collected from Gallinas Creek and its tributaries. Geochemical analyses of water samples include major and trace metals via inductively coupled plasma optical emission spectroscopy and plasma mass spectrometry (ICP-MS), total organic carbon, and major anions (sulfate, nitrate). Sediment deposit samples were exposed to various extractions including water extractions, sequential extractions and aqua regia. The extractions were analyzed for major and trace metals via inductively coupled plasma optical emission spectroscopy (ICP-OES) and ICP-MS, total organic carbon, and major anions (sulfate, nitrate). Weight percentage of carbon and nitrogen in the sediment deposits were also analyzed. Bed sediments were digested with aqua regia and analyzed for metals via ICP-MS. The data collectively demonstrate the effects of wildfire in a disturbed environment on water quality and ecosystem health.

The Sulphur Bank Mercury Mine in Lake County, California, was the site of historical mercury mining from 1880s through 1973.Since 1990, the mine area has been a Superfund site managed by the U.S. Environmental Protection Agency (USEPA). As part of a Remedial Investigation, the USEPA and the U.S. Geological Survey (USGS) are collaborating on a groundwater investigation in a part of the Sulphur Bank mine site known as the Waste Rock Dam (WRD) area, which lies between Herman Impoundment (a flooded mine pit) and Clear Lake. 33 groundwater wells were sampled in the WRD area and adjacent areas of the mine site by USEPA and their consultants in six sampling events during 2022-23. Because of low water levels due to drought conditions in 2022, some wells could not be sampled. Surface water was sampled from Herman Impoundment and Clear Lake during all six sampling events, and surface water from the Northwest Pit was sampled during one event. This data release includes field and laboratory data for 295 environmental samples and 42 QA samples collected during these sampling events. Field parameters include water temperature, specific conductance, dissolved oxygen, turbidity, pH, and oxidation-reduction potential. Laboratory analyses include major cations, trace metals, mercury, anions (sulfate, chloride, bromide, and fluoride), alkalinity, forms of nitrogen (nitrate plus nitrite, and ammonium), and stable isotopes of hydrogen and oxygen in water, and of sulfur and oxygen in aqueous sulfate.

This U.S. Geological Survey (USGS) data release contains data from stream water, groundwater, and soil samples collected in 2019 and 2020 in the North Quartz Creek watershed in central Colorado. Fourteen streambank wells were installed in pairs at seven locations in August 2020 to capture the emerging groundwater from the left bank and right banks (relative to downstream-facing direction) and a synoptic sampling campaign was conducted to quantify metal contributions to the stream. A continuous, instream injection of sodium bromide (NaBr) was initiated at the head of the 5 km study reach several days prior to the synoptic sampling campaign and maintained throughout the duration of the study. Bromide concentrations were subsequently used to determine streamflow in the primary study reach (upper 1.3 km) using the tracer-dilution method, and as an indicator of hydrologic connections between North Quartz Creek and subsurface water. Streamflow was quantified in a secondary study reach (lower 3.7 km) using data from a series of sodium chloride slug additions wherein specific conductivity readings were used as a surrogate for the tracer concentration. Surface water samples were collected along North Quartz Creek including inflows from the left (LBI) and right (RBI) banks. Soil and sediment samples were collected along the transport path from source material (natural weathering and mine tailings/mine drainage) to the stream.

This U.S. Geological Survey (USGS) data release contains data from stream water, groundwater, and soil samples collected in 2019 and 2020 in the North Quartz Creek watershed in central Colorado. Fourteen streambank wells were installed in pairs at seven locations in August 2020 to capture the emerging groundwater from the left bank and right banks (relative to downstream-facing direction) and a synoptic sampling campaign was conducted to quantify metal contributions to the stream. A continuous, instream injection of sodium bromide (NaBr) was initiated at the head of the 5 km study reach several days prior to the synoptic sampling campaign and maintained throughout the duration of the study. Bromide concentrations were subsequently used to determine streamflow in the primary study reach (upper 1.3 km) using the tracer-dilution method, and as an indicator of hydrologic connections between North Quartz Creek and subsurface water. Streamflow was quantified in a secondary study reach (lower 3.7 km) using data from a series of sodium chloride slug additions wherein specific conductivity readings were used as a surrogate for the tracer concentration. Surface water samples were collected along North Quartz Creek including inflows from the left (LBI) and right (RBI) banks. Soil and sediment samples were collected along the transport path from source material (natural weathering and mine tailings/mine drainage) to the stream.

Biogeochemical processes are key drivers of chemical solubility and mobilization. Understanding these processes will lead to improved predictive capabilities and may aid with watershed management decisions. This data release presents results from the Boulder Creek, Colorado watershed, including analyses of water and sediment. From April to August 2019, water samples were collected weekly at 2 sites along Boulder Creek and 4 tributary sites draining into Boulder Creek. In August 2022, water samples were collected every 2 hours for 34 hours at 2 sites on Boulder Creek (upstream and downstream of the city of Boulder). Samples for both studies were analyzed for major cations and anions, dissolved organic carbon, UV absorbance, total dissolved nitrogen, ammonium, nitrate, alkalinity, trace metals, water isotopes, and field parameters including dissolved oxygen, pH, water temperature, and specific conductance. In August 2022, bed sediment (0-3 cm depth) samples were collected at 8 sites along Boulder Creek. The sediment was dried, sieved, pulverized, digested, and then analyzed for metals, total carbon, sulfur, and carbonate. In 2021 and 2022, laboratory incubations of sediment and stream water were conducted to assess how different oxidation-reduction conditions affect metal and nutrient concentrations. Sediment cores (0-5 cm and 5-10 cm depth) and surface water were collected from Boulder Creek at three sites upstream, within, and downstream of the city of Boulder. Samples were collected from incubation reactors over time and analyzed for major cations and anions, dissolved organic carbon, UV absorbance, total dissolved nitrogen, ammonium, nitrate, trace metals, total arsenic, pH, and specific conductance. Sediments used for the incubations were further characterized by sequential extractions with hydroxylamine and dithionite and analyzed for major cations and trace metals. Site information, soil characterization details, incubation preparation and biogeochemical nutrient data, sediment sequential extraction data, and water-quality data are presented in this data release as ten comma-separated values (.csv) formatted tables. A data dictionary file describes the data found in the .csv files. Method details and references are located in the metadata file “Boulder Creek Watershed Data (2019-2023).xml.”

Biogeochemical processes are key drivers of chemical solubility and mobilization. Understanding these processes will lead to improved predictive capabilities and may aid with watershed management decisions. This data release presents results from the Boulder Creek, Colorado watershed, including analyses of water and sediment. From April to August 2019, water samples were collected weekly at 2 sites along Boulder Creek and 4 tributary sites draining into Boulder Creek. In August 2022, water samples were collected every 2 hours for 34 hours at 2 sites on Boulder Creek (upstream and downstream of the city of Boulder). Samples for both studies were analyzed for major cations and anions, dissolved organic carbon, UV absorbance, total dissolved nitrogen, ammonium, nitrate, alkalinity, trace metals, water isotopes, and field parameters including dissolved oxygen, pH, water temperature, and specific conductance. In August 2022, bed sediment (0-3 cm depth) samples were collected at 8 sites along Boulder Creek. The sediment was dried, sieved, pulverized, digested, and then analyzed for metals, total carbon, sulfur, and carbonate. In 2021 and 2022, laboratory incubations of sediment and stream water were conducted to assess how different oxidation-reduction conditions affect metal and nutrient concentrations. Sediment cores (0-5 cm and 5-10 cm depth) and surface water were collected from Boulder Creek at three sites upstream, within, and downstream of the city of Boulder. Samples were collected from incubation reactors over time and analyzed for major cations and anions, dissolved organic carbon, UV absorbance, total dissolved nitrogen, ammonium, nitrate, trace metals, total arsenic, pH, and specific conductance. Sediments used for the incubations were further characterized by sequential extractions with hydroxylamine and dithionite and analyzed for major cations and trace metals. Site information, soil characterization details, incubation preparation and biogeochemical nutrient data, sediment sequential extraction data, and water-quality data are presented in this data release as ten comma-separated values (.csv) formatted tables. A data dictionary file describes the data found in the .csv files. Method details and references are located in the metadata file “Boulder Creek Watershed Data (2019-2023).xml.”

Rio Tinto, Spain, is an example of a fluvial system strongly influenced by acid rock and acid mine drainage. During the spring of 2018 and 2019, samples of stream waters and mine waters, biofilms, sediments, and rocks, were collected in the field by Aubrey Zerkle. These samples were analyzed for comprehensive geochemistry, including Cr isotope geochemistry, anions and cations. Mineralogical analysis was conducted on powdered sediments and rocks.

Rio Tinto, Spain, is an example of a fluvial system strongly influenced by acid rock and acid mine drainage. During the spring of 2018 and 2019, samples of stream waters and mine waters, biofilms, sediments, and rocks, were collected in the field by Aubrey Zerkle. These samples were analyzed for comprehensive geochemistry, including Cr isotope geochemistry, anions and cations. Mineralogical analysis was conducted on powdered sediments and rocks.