The California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP) analyzed for per-and polyfluoroalkyl substances (PFAS) in groundwater samples collected from domestic and public drinking water supply wells in California. GAMA-PBP is a cooperative program between the U.S. Geological Survey and the California State Water Resources Control Board. This data release contains data for samples collected from May 2019 through December 2022 and includes revisions to earlier data (Kent, 2021) that were either screened or removed after analysis of quality-control data. Please see the quality-control and other descriptions of the data in the processing steps in the xml file. Subsequent updates will include data for samples collected after December 2022. Data are also publicly available for download from Jurgens and others (2018). The dataset consists of 4 tables. Table 1 lists the names and abbreviations of the twenty-eight PFAS constituents analyzed. Table 2 contains information about each site visited, including location and well depth information. Table 3 contains results for each PFAS constituent analyzed and includes quality-control sample results where applicable. Table 4 contains a list of every sample collected at each site and has a summary of all the PFAS detections for each sample. This data release supercedes previous PFAS data release versions reported by Kent (2021). Version 2.0 of the previous data release (Kent, 2021) contained data for samples collected from May 2019 through June 2021. Data from Kent (2021) is available upon request from the authors of this data release. References: Kent, R.H., 2021, Data sets for: Sampling for Per-and Polyfluoralkly Substances (PFAS) by the GAMA Priority Basin Project (GAMA-PBP)(2019-2021) (ver. 2.0, October 2021): U.S. Geological Survey data release, https://doi.org/10.5066/P92IPRJD. Jurgens, B.C., Jasper, M., Nguyen, D.H., and Bennett, G.L., 2018, USGS CA GAMA-PBP Groundwater Quality Results--Assessment and Trends: U.S. Geological Survey website, available at https://doi.org/10.5066/P91WJ2G1.

The U.S. Geological Survey Groundwater Ambient Monitoring and Assessment-Priority Basin Project (USGS GAMA-PBP) collected samples to be analyzed for per-and polyfluoroalkyl substances (PFAS) from domestic and public supply wells from May 2019 to June 2021. The datasets presented here include identification of the 28 PFAS constituents monitored by the project, Identification and brief characterization of the 395 GAMA-PBP wells for which samples were analyzed for PFAS during the study period, and analytical results for those groundwater samples, along with results for quality control samples.

The U.S. Geological Survey Groundwater Ambient Monitoring and Assessment-Priority Basin Project (USGS GAMA-PBP) collected samples to be analyzed for per-and polyfluoroalkyl substances (PFAS) from domestic and public supply wells from May 2019 to June 2021. The datasets presented here include identification of the 28 PFAS constituents monitored by the project, Identification and brief characterization of the 395 GAMA-PBP wells for which samples were analyzed for PFAS during the study period, and analytical results for those groundwater samples, along with results for quality control samples.

Concentrations of inorganic constituents, dissolved organic carbon (DOC), tritium, per- and polyfluoroalkyl substances (PFAS), volatile organic compounds (VOCs), and pharmaceuticals were measured in groundwater samples collected from 254 wells in 2019 and 2020. Concentrations of inorganic constituents, DOC, VOCs, and pharmaceuticals were measured at the U.S. Geological Survey (USGS) National Water Quality Laboratory in Lakewood, Colorado. Concentrations of tritium were measured at the USGS Tritium Laboratory in Menlo Park, California. Concentrations of PFAS were measured at SGS Laboratory in Orlando, Florida. In addition, several geospatial parameters were determined, including: percentages of selected land uses within 500-meter buffers around sampled wells, nitrogen loading from septic systems within 500-meter buffers around sampled wells, distance to nearest wastewater treatment plant, and distance to selected industry and other potential point sources that could be sources of PFAS to the environment. The data were collected as part of the USGS National Water-Quality (NAWQA) project. This data release contains 12 tables of well information, laboratory results, geospatial output, and a data dictionary, including: 1) PFAS_Data_Dictionary.csv – Parameters in each table are defined in this table. 2) PFAS_BLANK.csv – Concentrations of PFAS in equipment, field, and source-solution blank samples. 3) PFAS_ENV.csv – Concentrations of PFAS in environmental samples. 4) PFAS_GEOSPATIAL.csv – Percentages of selected land uses within 500-meter buffers around sampled wells; nitrogen loading from septic systems within 500-meter buffers around sampled wells; distance to nearest wastewater treatment plant; distance to selected industry and other potential point sources that could be sources of PFAS to the environment. 5) PFAS_INORGANICS_AND_OTHER.csv – Concentration of inorganic constituents, DOC, and tritium. 6) PFAS_LAB_BLANK.csv – Concentrations of PFAS in laboratory blank samples. 7) PFAS_PHARMA.csv – Concentrations of pharmaceutical compounds in environmental samples. 8) PFAS_REP.csv – Concentrations of PFAS in replicate samples. 9) PFAS_SPIKE_FIELD.csv – Percent recovery for PFAS in field matrix-spike samples. 10) PFAS_SPIKE_LAB.csv – Percent recovery for PFAS in laboratory reagent-spike and matrix-spike samples. 11) PFAS_VOCs.csv – Concentrations of VOCs in environmental samples. 12) PFAS_WELLS.csv – Site characteristics of the sampled wells.

Concentrations of inorganic constituents, dissolved organic carbon (DOC), tritium, per- and polyfluoroalkyl substances (PFAS), volatile organic compounds (VOCs), and pharmaceuticals were measured in groundwater samples collected from 254 wells in 2019 and 2020. Concentrations of inorganic constituents, DOC, VOCs, and pharmaceuticals were measured at the U.S. Geological Survey (USGS) National Water Quality Laboratory in Lakewood, Colorado. Concentrations of tritium were measured at the USGS Tritium Laboratory in Menlo Park, California. Concentrations of PFAS were measured at SGS Laboratory in Orlando, Florida. In addition, several geospatial parameters were determined, including: percentages of selected land uses within 500-meter buffers around sampled wells, nitrogen loading from septic systems within 500-meter buffers around sampled wells, distance to nearest wastewater treatment plant, and distance to selected industry and other potential point sources that could be sources of PFAS to the environment. The data were collected as part of the USGS National Water-Quality (NAWQA) project. This data release contains 12 tables of well information, laboratory results, geospatial output, and a data dictionary, including: 1) PFAS_Data_Dictionary.csv – Parameters in each table are defined in this table. 2) PFAS_BLANK.csv – Concentrations of PFAS in equipment, field, and source-solution blank samples. 3) PFAS_ENV.csv – Concentrations of PFAS in environmental samples. 4) PFAS_GEOSPATIAL.csv – Percentages of selected land uses within 500-meter buffers around sampled wells; nitrogen loading from septic systems within 500-meter buffers around sampled wells; distance to nearest wastewater treatment plant; distance to selected industry and other potential point sources that could be sources of PFAS to the environment. 5) PFAS_INORGANICS_AND_OTHER.csv – Concentration of inorganic constituents, DOC, and tritium. 6) PFAS_LAB_BLANK.csv – Concentrations of PFAS in laboratory blank samples. 7) PFAS_PHARMA.csv – Concentrations of pharmaceutical compounds in environmental samples. 8) PFAS_REP.csv – Concentrations of PFAS in replicate samples. 9) PFAS_SPIKE_FIELD.csv – Percent recovery for PFAS in field matrix-spike samples. 10) PFAS_SPIKE_LAB.csv – Percent recovery for PFAS in laboratory reagent-spike and matrix-spike samples. 11) PFAS_VOCs.csv – Concentrations of VOCs in environmental samples. 12) PFAS_WELLS.csv – Site characteristics of the sampled wells.

Samples were collected for a comparison method development study with the University of Minnesota and the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) in Lakewood, Colorado. Widely used liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods fail to capture large fractions of total organofluorine in environmental samples confounding the assessment and remediation of fluorinated pollution. Fluorine nuclear magnetic resonance (19F-NMR) is an inclusive method for organofluorine analysis that preserves chemical information about chemical compound classes of organofluorine.

This metadata record contains one table and one shapefile with results from field sampling at locations of groundwater discharge (seeps) identified by autonomous boat survey at the Lower Darby Creek Area (LDCA) Superfund Site, near Folcroft, Pennsylvania, in 2024. Included in the dataset are (1) PFAS concentrations, volatile organic compound (VOC) concentrations, cations/trace metals data, total organic carbon (TOC) content, anion concentrations, dissolved gas concentrations, total and ferrous iron concentrations, sulfide concentrations, water quality measurements, and their associated field sampling information for porewater samples collected from seeps and (2) water quality parameters (pH, turbidity, dissolved oxygen, specific conductance, and water temperature) and coordinates measured in creeks in LDCA by a remote-controlled autonomous boat as part of seep identification surveys.

This metadata record contains one table and one shapefile with results from field sampling at locations of groundwater discharge (seeps) identified by autonomous boat survey at the Lower Darby Creek Area (LDCA) Superfund Site, near Folcroft, Pennsylvania, in 2024. Included in the dataset are (1) PFAS concentrations, volatile organic compound (VOC) concentrations, cations/trace metals data, total organic carbon (TOC) content, anion concentrations, dissolved gas concentrations, total and ferrous iron concentrations, sulfide concentrations, water quality measurements, and their associated field sampling information for porewater samples collected from seeps and (2) water quality parameters (pH, turbidity, dissolved oxygen, specific conductance, and water temperature) and coordinates measured in creeks in LDCA by a remote-controlled autonomous boat as part of seep identification surveys.

Data were collected at 19 groundwater monitoring wells and 3 surface water locations across McHenry County, Illinois, in 2020 by staff from the U.S. Geological Survey (USGS) Central Midwest Water Science Center. Quality control samples (2 blanks and 1 replicate) were also collected to assess data reliability and precision. Samples were submitted to the USGS National Water Quality Laboratory in Denver, Colorado, and were analyzed for per- and polyfluoroalkyl (PFAS) substances in late 2022 and results provided in April of 2023. PFAS were detected in 16 of the 19 groundwater monitoring wells and in all 3 surface water sites sampled.

Data were collected at 19 groundwater monitoring wells and 3 surface water locations across McHenry County, Illinois, in 2020 by staff from the U.S. Geological Survey (USGS) Central Midwest Water Science Center. Quality control samples (2 blanks and 1 replicate) were also collected to assess data reliability and precision. Samples were submitted to the USGS National Water Quality Laboratory in Denver, Colorado, and were analyzed for per- and polyfluoroalkyl (PFAS) substances in late 2022 and results provided in April of 2023. PFAS were detected in 16 of the 19 groundwater monitoring wells and in all 3 surface water sites sampled.