The Sacramento / San Joaquin River Delta (SSJRD) is contaminated with legacy mercury (Hg) from historical mining and mineral processing activities throughout the watershed, as well as from contemporary atmospheric and industrial inputs. The current project was designed for the purpose of developing high-resolution spatial and temporal models for estimating concentrations of mercury species in surface waters of the SSJRD. The field component of the project brings together three high-resolution platforms for collecting water-quality data (fixed continuous monitoring stations (CMS) outfitted with in-situ sensors, spatial mapping using boat-mounted flow-through sensors, and satellite-based remote sensing) coupled with a discrete sample collection program for mercury species and ancillary water-quality metrics. The four mercury species targeted in the study include both particulate and filter-passing fractions of total mercury and methylmercury. Field data were collected during the period July 2019 through July 2021. Sampling at the four primary CMS sites included discrete sample collections during all station operations and maintenance visits (approximately every six weeks) and during four 13-hour to 15-hour tidal sampling events, during which samples were collected every 2 hours (approximately) over a full tidal cycle. This tidal sampling occurred once per season (winter, spring, summer, and fall) at each of the four CMS locations. Likewise, four seasonal boat-mapping sampling events were conducted, each over a 3-day period and coincident with Landsat 8 satellite overpasses on the 2nd day of sampling and within 2 days of a Sentinel 2 A/B satellite overpass. Each boat-mapping event included collection of discrete water samples for mercury species and other water-quality metrics at 33 sites over a three-day period, covering approximately 210 kilometers through the SSJRD. The models constructed to estimate concentrations of mercury species are organized into four types (Tiers), which are based on which high-resolution water-quality data platform is being emphasized, as follow: Tier 1 Models – those based only on in-situ sensor derived turbidity and dissolved organic matter fluorescence, which are the two metrics most relevant to the satellite-based data collection platforms; Tier 2 Models – those based only on CMS in situ sensor data; Tier 3 Models – those based only on data from boat-mounted flow-through sensors, including spectrophotometric measurements, associated with the spatial mapping events; and Tier 4 models – based on sensor data from both the CMS sites and boat-mapping events, but limited to sensor data common to both. The information presented herein falls under six categories, which are associated with the following six Child pages: a) Discrete Sample Data – represents laboratory analytical results and field measurements associated with discrete surface-water samples collected from both the CMS and boat-mapping sampling events; b) Optical Spectral Data – represents excitation-emissions matrix spectra (EEMs) and absorption data associated with discrete surface-water samples collected from both the CMS and boat mapping sampling events; c) High-resolution (15 minute) Temporal Data from CMS Locations – includes time series in-situ sensor data collected from the four primary fixed CMS sampling locations; d) High-Resolution Boat Mapping Data – data collected with boat mounted flow-through sensor arrays during the four mapping events; e) Remote Sensing Data – GeoTIFF image files of turbidity and dissolved organic matter (DOM) products derived from Sentinel 2 A/B imagery of the SSJRD from June 2019 – May 2021; and f) Model Archive Summaries – documentation of the 16 top global models (four model types x four mercury species) in terms of modeling approach, model statistics, validation, and final equations. In addition, a geospatial file (SSJRD_Sites.kmz) is provided on this Parent page, which identifies all of the study fixed

The goal of this study was to develop a suite of inter-related water quality monitoring approaches capable of modeling and estimating the spatial and temporal gradients of particulate and dissolved total mercury (THg) concentration, and particulate and dissolved methyl mercury (MeHg), concentration, in surface waters across the Sacramento / San Joaquin River Delta (SSJRD). This suite of monitoring approaches included: a) data collection at fixed continuous monitoring stations (CMS) outfitted with in-situ sensors, b) spatial mapping using boat-mounted flow-through sensors, and c) satellite-based remote sensing. The focus of this specific Child Page is to present all field and laboratory-based data associated with discrete surface water samples collected as part of the CMS and boat mapping components of the study. The data provided in the table herein constitute a collection of field-based and laboratory-based measurements that coincide with the timestamps of samples collected at 33 sites across the Delta. Laboratory-based measurements presented herein were conducted by the U.S. Geological Survey (USGS) Organic Matter Research Laboratory (OMRL) in Sacramento, CA, the USGS Earths System Processes Division (ESPD) microbial biogeochemistry laboratory in Menlo Park, CA, the USGS Reston Stable Isotope Laboratory (RSIL) in Reston, VA and the USGS National Water Quality Laboratory (NWQL) in Denver, CO. The machine-readable (comma separated value, *.csv) file presented herein includes laboratory-based measurements for discrete samples collected from 33 established field sites (sampled repeatedly). In addition, field-based sensor data from continuous measurement platforms (CMS locations or as part of the mapping boat flow-through system) are also included in this discrete sample dataset by ensuring that the field sensor measurements were both spatially and temporally coincident with the physically discrete water sample collected for laboratory analysis.

The goal of this study was to develop a suite of inter-related water quality monitoring approaches capable of modeling and estimating the spatial and temporal gradients of particulate and dissolved total mercury (THg) concentration, and particulate and dissolved methyl mercury (MeHg), concentration, in surface waters across the Sacramento / San Joaquin River Delta (SSJRD). This suite of monitoring approaches included: a) data collection at fixed continuous monitoring stations (CMS) outfitted with in-situ sensors, b) spatial mapping using boat-mounted flow-through sensors, and c) satellite-based remote sensing. The focus of this specific Child Page is to present all field and laboratory-based data associated with discrete surface water samples collected as part of the CMS and boat mapping components of the study. The data provided in the table herein constitute a collection of field-based and laboratory-based measurements that coincide with the timestamps of samples collected at 33 sites across the Delta. Laboratory-based measurements presented herein were conducted by the U.S. Geological Survey (USGS) Organic Matter Research Laboratory (OMRL) in Sacramento, CA, the USGS Earths System Processes Division (ESPD) microbial biogeochemistry laboratory in Menlo Park, CA, the USGS Reston Stable Isotope Laboratory (RSIL) in Reston, VA and the USGS National Water Quality Laboratory (NWQL) in Denver, CO. The machine-readable (comma separated value, *.csv) file presented herein includes laboratory-based measurements for discrete samples collected from 33 established field sites (sampled repeatedly). In addition, field-based sensor data from continuous measurement platforms (CMS locations or as part of the mapping boat flow-through system) are also included in this discrete sample dataset by ensuring that the field sensor measurements were both spatially and temporally coincident with the physically discrete water sample collected for laboratory analysis.

This dataset includes water-quality and sediment data for 647 environmental samples collected at 53 surface-water sites in Cache Creek (Cache C) watershed, Yolo County, California, between December 2009 and April 2019, and data for 190 associated quality-control samples (replicates and blanks). About 90 percent of the samples were collected at the following six primary sites that were sampled most frequently, and the other 39 extra sites were sampled only 1-5 times each. In addition, continuous turbidity measurements were made at 8 sites to aid with the calibration of turbidity measurements. The sites Cache C at Rumsey (11451800), Cache C at Yolo (11452500), and CCSB Inlet at Rd 102 (11452600) are upstream of the Cache C Settling Basin (CCSB); all other sites are in the CCSB and are shown on the map included in this data release. NWIS_Site_Number: Field_ID: 11451800 Cache C at Rumsey 11452500 Cache C at Yolo 11452600 CCSB Inlet at Rd.102 11452900 CCSB Outlet 11452800 CCSB S. Abutment Spillway 384115121402501 CCSB N. Abutment Spillway Constituents analyzed include total mercury and methylmercury in dissolved and particulate forms, reactive divalent mercury in particulate form, suspended sediment, dissolved organic carbon, and absorption-fluorescence data for dissolved organic matter. The grain-size distribution of suspended sediment in selected samples is also reported. Six data tables and a Data Dictionary were prepared for this data release. All tables are provided as machine readable tab-delimited text (*.txt) files and as Excel formatted (*.xlsx) files. The data dictionary provides definitions and details presented in the data tables, including analytical methods citations. Two of the six data tables present and summarize quality control results collected for the study.

This dataset includes mercury and other constituent concentration and physical properties data for surface sediment, pore water and surface water collected as part of the South San Francisco Bay Salt Pond Restoration Phase 1 (2010 to 2018) studies. The overarching focus of these studies was to monitor mercury (Hg) biogeochemistry in both sediment and water in response to management actions associated with the conversion of former salt producing ponds to contemporary wetland habitat. The two primary management actions included the breaching of Pond A6 during December 2010, and the construction and operation of an adjustable tidal control structure (TCS) associated with the Pond A5/A7/A8 Complex beginning in June 2011. The TSC that reconnects the Complex to Alviso Slough (specifically referred to as the A8-TCS), a historically Hg contaminated waterway that represents the terminus of watershed drainage that includes the New Almaden mercury mining district. The A8-TCS consists of eight gates, each five feet wide. During the initial testing period (starting in June 2011) only one gate was opened, and the structure was closed again during the winter-spring months (from December until the following June). Over the subsequent seven years, the number of gates open was increased to three (15 feet, June 2012), to five (25 feet, September 2014), and eventually to all eight (40 feet, June 2017). Beginning in 2014 the A8-TCS was opened year-round. Field sampling occurred in both ponds and sloughs. In addition to sampling within the Complex ponds, two control ponds (A3N and A16) were also sampled. Similarly, in addition to sampling within Alviso Slough, two nearby control sloughs (Mallard Slough a.k.a Artesian Slough and Guadalupe Slough) were sampled (beginning in 2014 for Guadalupe Slough). Sediment sampling was conducted for the period of May 2010 through August 2011, which represents the period immediately prior to and immediately after the two above mentioned management actions. Additional sediment sampling was conducted in Mallard Slough exclusively during the August- September period 2011-2013, 2015, and 2017. Surface water sampling was conducted during three periods. The first period was in conjunction with the sediment sampling (May 2010 through August 2011). The second period involved a unique series of high temporal resolution sampling events conducted at a single site in mid-Alviso Slough, when water samples were collected hourly over a 25-hour period to capture the Hg dynamics associated with two full tidal cycles. A total of five such high-resolution ‘diel’ sampling events were conducted between May 2012 and February 2013, which included each of the four seasons and the annual ‘first flush’ event associated with the initiation of the 2012-13 rainy season. The third period, from February 2014 through February 2018, represents when all ponds and sloughs were again sampled (akin to the first period). This third period also represents when the A8-TCS was sequentially opened from 15 feet (3 gates open) to 40 feet (all 8 gates open), and when the A8-TCS management transitioned from being closed during the winter months to being opened year-round, beginning in 2014. This data release includes five data tables given both as Excel (*.xlxs) and machine readable 'comma-separated values' format (*.csv): 1) ‘SBSP.Data.Dictionary_2010-18’, the Data Dictionary, which provides definitions and details related to the other four data tables and includes analytical methods citations; 2) ‘SBSP.SED_2010-17’, the surface sediment analytical dataset; 3) ‘SBSP.SW_2010-18’, the primary surface water analytical dataset; 4) ‘SBSP.SW_Diel_2012-13’, the surface water diel sampling dataset; 5) ‘SBSP.QA_2010-18’, quality assurance data summary for the sediment and water datasets.

Clear Lake is a 180 km2 freshwater lake located approximately 120 km northwest of Sacramento in the California Coast Range. The lake is a popular sport-fishing destination, however, there are fish consumption advisories associated with mercury (Hg) contamination for several species. The lake has three arms: a large open-water region to the northwest (Upper Arm), a smaller and narrower region to the southeast (Lower Arm), and the smallest and narrowest region to the east (Oaks Arm). The Sulfur Bank Mercury Mine (SBMM), located on the eastern shore of the Oaks Arm, was mined by underground methods starting in the 1870s and then open-pit methods during the 1920s to 1950s. Since 1992, the SBMM has been a Superfund site managed by the U.S. Environmental Protection Agency. This former Hg mining area is thought to be the dominant contributor of Hg to Clear Lake and is the focus of continued remediation to minimize Hg impacts to Clear Lake. The SBMM area is an active geothermal area with springs and gas fumaroles. Clear Lake is eutrophic to hypereutrophic, based on elevated concentrations of nutrients (various forms of nitrogen, N, and phosphorus, P) that cause excessive algal blooms and periodic fish kills. There are current studies underway (by the University of California, Davis, UCD) to improve the understanding of nutrient cycling within the lake. The UCD group is developing a three-dimensional hydrodynamic computer model (https://resources.ca.gov/-/media/CNRA-Website/Files/Initiatives/Blue-Ribbon-Committee-for-the-Rehabilitation-of-Clear-Lake/2022-BRC-Annual-Report-_20230110_DraftFinal.pdf ) of the lake that simulates periodic stratification of temperature and dissolved oxygen as well as nutrient dynamics. An effort is planned during 2023-2025 to add mercury cycling to the 3-D model. Monitoring and modeling efforts are being implemented to improve understanding of the ways that nutrient dynamics affect the cycling, transport and bioaccumulation of Hg, which remains poorly understood. This data release documents the results of water-quality sampling during June 2020 through June 2022. It includes three data tables given as machine readable 'comma-separated values' format (*.csv): 1) ‘T1_CL_DataDictionary’, the Data Dictionary, which provides definitions and details related to the other two data tables and includes citations of analytical methods; 2) ‘T2_CL_Discrete_SW’, the discrete-sample surface-water dataset including concentration data for Hg species (including total mercury and methylmercury in dissolved and particulate forms) and nutrients (including several forms of N and P); and 3) ‘T3_CL_QA_SW’, a quality assurance data summary for the discrete water samples. In addition, file ‘Clear Lake Coordinates_SW 2020-22_052324’ provides the sampling locations in a machine-readable geospatial file format (*.kmz).

Clear Lake is a 180 km2 freshwater lake located approximately 120 km northwest of Sacramento in the California Coast Range. The lake is a popular sport-fishing destination, however, there are fish consumption advisories associated with mercury (Hg) contamination for several species. The lake has three arms: a large open-water region to the northwest (Upper Arm), a smaller and narrower region to the southeast (Lower Arm), and the smallest and narrowest region to the east (Oaks Arm). The Sulfur Bank Mercury Mine (SBMM), located on the eastern shore of the Oaks Arm, was mined by underground methods starting in the 1870s and then open-pit methods during the 1920s to 1950s. Since 1992, the SBMM has been a Superfund site managed by the U.S. Environmental Protection Agency. This former Hg mining area is thought to be the dominant contributor of Hg to Clear Lake and is the focus of continued remediation to minimize Hg impacts to Clear Lake. The SBMM area is an active geothermal area with springs and gas fumaroles. Clear Lake is eutrophic to hypereutrophic, based on elevated concentrations of nutrients (various forms of nitrogen, N, and phosphorus, P) that cause excessive algal blooms and periodic fish kills. There are current studies underway (by the University of California, Davis, UCD) to improve the understanding of nutrient cycling within the lake. The UCD group is developing a three-dimensional hydrodynamic computer model (https://resources.ca.gov/-/media/CNRA-Website/Files/Initiatives/Blue-Ribbon-Committee-for-the-Rehabilitation-of-Clear-Lake/2022-BRC-Annual-Report-_20230110_DraftFinal.pdf ) of the lake that simulates periodic stratification of temperature and dissolved oxygen as well as nutrient dynamics. An effort is planned during 2023-2025 to add mercury cycling to the 3-D model. Monitoring and modeling efforts are being implemented to improve understanding of the ways that nutrient dynamics affect the cycling, transport and bioaccumulation of Hg, which remains poorly understood. This data release documents the results of water-quality sampling during June 2020 through June 2022. It includes three data tables given as machine readable 'comma-separated values' format (*.csv): 1) ‘T1_CL_DataDictionary’, the Data Dictionary, which provides definitions and details related to the other two data tables and includes citations of analytical methods; 2) ‘T2_CL_Discrete_SW’, the discrete-sample surface-water dataset including concentration data for Hg species (including total mercury and methylmercury in dissolved and particulate forms) and nutrients (including several forms of N and P); and 3) ‘T3_CL_QA_SW’, a quality assurance data summary for the discrete water samples. In addition, file ‘Clear Lake Coordinates_SW 2020-22_052324’ provides the sampling locations in a machine-readable geospatial file format (*.kmz).

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

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

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.