This data release includes tables and time-series plots of results for volatile organic compounds (VOCs) analyzed in samples of groundwater used for public supply that were collected by the USGS National Water-Quality Assessment (NAWQA) Project and the California State Water Resources Control Board’s Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP) during 2013-19; results for associated quality-control samples also are included. All samples were analyzed by the USGS National Water Quality Laboratory (NWQL) using laboratory schedules 4436 and 4437. The table of groundwater data includes VOC results as reported by the laboratory, along with results that represent the application of censoring approaches described in the metadata file and associated journal article. The other seven tables included in this data release contain VOC results for the following types of quality-control samples: field blanks and replicates collected at field sites; laboratory blanks, reagent spikes, and matrix spikes prepared by the NWQL; and third-party blind blanks and blind spikes prepared by the USGS Quality Systems Branch. The tables of VOC results for matrix spikes and field replicates include the paired groundwater results. For convenience, plots are provided of reported VOC detections and concentrations in groundwater samples, field blanks, and laboratory blanks for individual compounds by analysis date. Plots also are provided of recoveries for laboratory reagent spikes, laboratory matrix spikes, and third-party blind spikes for individual VOCs by analysis date. This data release includes 8 tables and 2 series of laboratory results plots: Table1_GroundwaterData2013_2019.csv: VOC results for samples collected by NAWQA and GAMA-PBP of groundwater used for public supply, 2013-19. This table includes VOC results as reported by the laboratory, along with results that represent the application of censoring approaches described in the associated journal article. Results that were rejected or censored for data analysis for reasons described in the metadata document and in the associated journal article are identified using attribute values described in the process steps for this table. Table2_FieldBlankData2013_2019.csv: VOC results for field blanks collected at applicable groundwater sites by NAWQA and GAMA-PBP, 2013-19. Results that were rejected for data analysis for reasons described in the metadata document and in the associated journal article are identified using attribute values described in the process steps for this table. Table3_MatrixSpikeData2013_2019.csv: VOC results for samples collected for laboratory matrix spikes at applicable groundwater sites by NAWQA and GAMA-PBP, 2013-19. Results of paired groundwater samples are included. Results that were rejected for data analysis for reasons described in the metadata document and in the associated journal article are identified using attribute values described in the process steps for this table. Fields needed to calculate spike recovery as described in the data processing steps of the metadata file are included. Table4_FieldRepData2013_2019.csv: VOC results for field replicates collected at groundwater sites by NAWQA and GAMA-PBP, 2013-19. Results of paired groundwater samples are included. Fields needed to calculate variability in detection and (or) concentration as described in the data processing steps of the metadata file are included. Table5_LabBlankData2013_2019.csv: VOC results for laboratory blanks prepared by the National Water Quality Laboratory, 2013-19. Table6_LabReagentSpikeData2013_2019.csv: VOC results for laboratory reagent spikes prepared by the National Water Quality Laboratory, 2013-19. Table7_QSBBlindBlankData2016_2019.csv: VOC results for third-party blind blanks prepared by the Quality Systems Branch, 2016-19. Table8_QSBBlindSpikeData2013_2019.csv: VOC results for third-party blind spikes prepared by the Quality Systems Branch,

This data set includes results for hormone and pharmaceutical compounds analyzed in environmental and quality-control samples collected by the USGS National Water-Quality Assessment Project during 2013 through 2015 for a study of groundwater resources used for drinking-water supply across the United States. This data release includes: Table 1. Site information and ancillary data (including principal aquifer, rock type, well depth, groundwater age information, aridity information, and land-use information) for groundwater sites sampled for hormones and pharmaceuticals by the National Water-Quality Assessment Project, 2013-15. Table 2. Hormone and pharmaceutical results for groundwater samples collected by the National Water-Quality Assessment Project, 2013-15. Table 3. Hormone and pharmaceutical results for field related blank samples of known blank type collected by the National Water-Quality Assessment Project for groundwater, 2013-15. Table 4. Hormone and pharmaceutical results for laboratory matrix spikes and associated environmental samples collected by the National Water-Quality Assessment Project for groundwater, 2013-15. Table 5. Hormone and pharmaceutical results for replicate samples and associated environmental samples collected by the National Water-Quality Assessment Project for groundwater, 2013-15.

This data set includes results for hormone and pharmaceutical compounds analyzed in environmental and quality-control samples collected by the USGS National Water-Quality Assessment Project during 2013 through 2015 for a study of groundwater resources used for drinking-water supply across the United States. This data release includes: Table 1. Site information and ancillary data (including principal aquifer, rock type, well depth, groundwater age information, aridity information, and land-use information) for groundwater sites sampled for hormones and pharmaceuticals by the National Water-Quality Assessment Project, 2013-15. Table 2. Hormone and pharmaceutical results for groundwater samples collected by the National Water-Quality Assessment Project, 2013-15. Table 3. Hormone and pharmaceutical results for field related blank samples of known blank type collected by the National Water-Quality Assessment Project for groundwater, 2013-15. Table 4. Hormone and pharmaceutical results for laboratory matrix spikes and associated environmental samples collected by the National Water-Quality Assessment Project for groundwater, 2013-15. Table 5. Hormone and pharmaceutical results for replicate samples and associated environmental samples collected by the National Water-Quality Assessment Project for groundwater, 2013-15.

The National Water-Quality Assessment (NAWQA) Program and National Stream Quality Accounting Network (NASQAN) are U.S. Geological Survey (USGS) monitoring programs that measure pesticide concentrations in the Nation’s streams and rivers, herein collectively referred to as streams. The NAWQA Program began monitoring pesticides in 1992 and the NASQAN Program began monitoring pesticides in 1995. The programs were recently merged to form the USGS National Water Quality Network for Rivers and Streams. Water samples are analyzed for pesticides by the USGS National Water Quality Laboratory (NWQL) using methods developed by the NWQL’s Methods Research and Development team. The NWQL extensively used two analytical methods, gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry, to measure pesticides in filtered water samples during 1992–2012 (old method). In October 2012, the monitoring programs began using direct aqueous-injection liquid chromatography tandem mass spectrometry as a new analytical method for pesticides (new method). The change in analytical methods, however, has the potential to inadvertently introduce bias in analysis of datasets that span the change. The data sets provided in this report were used to document performance of the new method in a variety of stream-water matrices and help quantify potential changes in measurement bias or variability that could be attributed to changes in analytical methods (Martin and others, 2016). Users should consult the report by Martin and others (2016) to understand how these data were collected and used. Measured concentrations and calculated recoveries of 281 pesticides and degradates in paired environmental background water samples and matrix spiked water samples collected at 48 stream-water sites from June 11, 2012 to September 6, 2012 are provided in seven tab-delimited ASCII files with relational database (RDB) format header. A tab-delimited ASCII file (DataDictionaryList.txt) listing DataSet attributes and RDB column formats is also included in this data release. Martin, J.D., Norman, J.E., Sandstrom, M.W., and Rose, C.E., 2016, A field study of selected U.S. Geological Survey analytical methods for measuring pesticides in filtered stream water, June-September 2012: U.S. Geological Survey Scientific Investigations Report, 2017-5049

The National Water-Quality Assessment (NAWQA) Program and National Stream Quality Accounting Network (NASQAN) are U.S. Geological Survey (USGS) monitoring programs that measure pesticide concentrations in the Nation’s streams and rivers, herein collectively referred to as streams. The NAWQA Program began monitoring pesticides in 1992 and the NASQAN Program began monitoring pesticides in 1995. The programs were recently merged to form the USGS National Water Quality Network for Rivers and Streams. Water samples are analyzed for pesticides by the USGS National Water Quality Laboratory (NWQL) using methods developed by the NWQL’s Methods Research and Development team. The NWQL extensively used two analytical methods, gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry, to measure pesticides in filtered water samples during 1992–2012 (old method). In October 2012, the monitoring programs began using direct aqueous-injection liquid chromatography tandem mass spectrometry as a new analytical method for pesticides (new method). The change in analytical methods, however, has the potential to inadvertently introduce bias in analysis of datasets that span the change. The data sets provided in this report were used to document performance of the new method in a variety of stream-water matrices and help quantify potential changes in measurement bias or variability that could be attributed to changes in analytical methods (Martin and others, 2016). Users should consult the report by Martin and others (2016) to understand how these data were collected and used. Measured concentrations and calculated recoveries of 281 pesticides and degradates in paired environmental background water samples and matrix spiked water samples collected at 48 stream-water sites from June 11, 2012 to September 6, 2012 are provided in seven tab-delimited ASCII files with relational database (RDB) format header. A tab-delimited ASCII file (DataDictionaryList.txt) listing DataSet attributes and RDB column formats is also included in this data release. Martin, J.D., Norman, J.E., Sandstrom, M.W., and Rose, C.E., 2016, A field study of selected U.S. Geological Survey analytical methods for measuring pesticides in filtered stream water, June-September 2012: U.S. Geological Survey Scientific Investigations Report, 2017-5049

This dataset presents the results of 475 unique organic compounds collected from 54 wadeable streams within the Southeastern, USA, collected within 10 weeks during 2014. Maximum and median exposure conditions were evaluated in relation to watershed characteristics and for potential biological effects. This dataset contains the summary statistics (maximum and median concentrations)of detected compounds, as well as a summary of quality-assurance (blanks and replicates) samples. Also included are the statistical summaries as related to analyte specific contaminant detection/concentration data and site-specific land-use matrices, spearman-rank correlations, and ToxCast evaluations.

This dataset presents the results of 475 unique organic compounds collected from 54 wadeable streams within the Southeastern, USA, collected within 10 weeks during 2014. Maximum and median exposure conditions were evaluated in relation to watershed characteristics and for potential biological effects. This dataset contains the summary statistics (maximum and median concentrations)of detected compounds, as well as a summary of quality-assurance (blanks and replicates) samples. Also included are the statistical summaries as related to analyte specific contaminant detection/concentration data and site-specific land-use matrices, spearman-rank correlations, and ToxCast evaluations.

This data release contains the concentration and quality-assurance results for inorganic constituents, organic compounds (volatile organic compounds [VOC], per- and polyfluoroalkyl substances [PFAS], pesticides, and disinfection byproducts [DBP]) collected in tapwater from locations in Alabama and Mississippi. Tapwater samples (11 public supply and 1 private well) were collected on December 13-14, 2022, in Dallas and Wilcox Counties, Alabama. Fifteen tapwater samples (14 public supply and 1 private well) were collected in Panola and Oktibbeha Counties in Mississippi on February 6-7, 2024. Pharmaceuticals (for Alabama samples only), VOC, and PFAS were analyzed at the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) in Denver, Colorado. Pharmaceutical samples for the 15 samples collected in Mississippi, were analyzed at the USGS Organic Geochemistry Research Laboratory (OGRL) in Lawrence, Kansas. Pesticides and DBP were analyzed at the USGS Organic Chemistry Research Laboratory (OCRL) in Sacramento, California. Inorganic contaminants were analyzed at the USGS Redox Chemistry Laboratory (RCL), Boulder, Colorado, and the Analytical Trace Element Chemistry Laboratory (ATECL), Boulder, Colorado. Microbiological indicators were analyzed for samples collected in Mississippi at the Michigan Bacteriological Research Laboratory in Lansing, Michigan.

This data release contains the concentration and quality-assurance results for inorganic constituents, organic compounds (volatile organic compounds [VOC], per- and polyfluoroalkyl substances [PFAS], pesticides, and disinfection byproducts [DBP]) collected in tapwater from locations in Alabama and Mississippi. Tapwater samples (11 public supply and 1 private well) were collected on December 13-14, 2022, in Dallas and Wilcox Counties, Alabama. Fifteen tapwater samples (14 public supply and 1 private well) were collected in Panola and Oktibbeha Counties in Mississippi on February 6-7, 2024. Pharmaceuticals (for Alabama samples only), VOC, and PFAS were analyzed at the U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL) in Denver, Colorado. Pharmaceutical samples for the 15 samples collected in Mississippi, were analyzed at the USGS Organic Geochemistry Research Laboratory (OGRL) in Lawrence, Kansas. Pesticides and DBP were analyzed at the USGS Organic Chemistry Research Laboratory (OCRL) in Sacramento, California. Inorganic contaminants were analyzed at the USGS Redox Chemistry Laboratory (RCL), Boulder, Colorado, and the Analytical Trace Element Chemistry Laboratory (ATECL), Boulder, Colorado. Microbiological indicators were analyzed for samples collected in Mississippi at the Michigan Bacteriological Research Laboratory in Lansing, Michigan.

The U.S. Geological Survey collected groundwater samples from 71 wells used for domestic and small system drinking water supplies in Stanislaus and Merced counties of California during 2020-2021. The wells were sampled for the Modesto-Turlock-Merced Domestic-Supply Aquifer Study Unit of the State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic and small system drinking water supplies. The study unit was defined by the extent of the Modesto, Turlock, and Merced subbasins of the San Joaquin Valley groundwater basin. The study unit was divided into 62 grid cells and one or more domestic or small system well was sampled in 60 of the cells. Groundwater samples from a total of 71 sampled wells were analyzed for field water-quality parameters, volatile organic compounds, pesticides and pesticide degradants, stable isotopes of water, nutrients, major ions and trace elements, hexavalent chromium, perchlorate, per- and polyfluoroalkyl substances (PFAS), and microbial indicators. Groundwater levels were measured in 56 out 71 wells.