San Francisco Bay, California is considered a mercury-impaired watershed. Elevated concentrations of mercury are found in water and sediment as well as fish and estuarine birds. Sources of mercury to the watershed since 1845 include sediment-associated mercury from mercury mining, mercury losses from gold amalgamation activities in mines of the Sierra Nevada, aerial deposition of mercury from global and regional emissions to air, and the direct discharge of mercury to Bay waters associated with the urbanization and industrialization of the estuary. We assessed historical trends in mercury bioaccumulation by measuring mercury concentrations in feathers of the endangered California Ridgway’s rail (formerly California Clapper Rail) using museum specimens. We developed a structural equation model to attribute variation in historical mercury bioaccumulation in rails to sources of mercury, and estimated the toxicological consequences of extreme mercury exposure to rails from known correlations between feather and blood mercury concentrations.

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).

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).

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.

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.

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.

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

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

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