Legacy and emerging contaminants were measured in streams and rivers in the District of Columbia and the states of Maryland, Pennsylvania, Virginia, and West Virginia of the Chesapeake Bay watershed between 2005 and 2013. Passive sampling devices, SPMDs and POCIS, were used to sample these waterbodies, providing a time-integrated concentration of contaminants that are potentially bioavailable to native fishes. This data set is a compilation of data from eight separate studies, all focused on determining the potential exposure of organic chemicals to fish which may be responsible for instances of fish kills and intersex that were observed in these waterbodies.

This dataset consists of 262 variables which describe various known and suspected point and non-point sources of contaminants and endocrine disrupting compounds (EDCs) throughout the Chesapeake Bay Watershed. Contaminant data was summarized to the NHDPlus Version 2.1 catchment level (1:100K). Contaminant data summarized span a time range of 2001 to 2016 and include regulated facilities, pesticides, manure and biosolids application data, mercury deposition, animal feeding applications, septic systems, landfills, and land use and land cover. These data are presented in a comma separated file, which includes all variables summarized and the NHDPlus Version 2.1 FEATUREID field (also known as COMID). The FEATUREID field can be used to relate these summaries to the NHDPlus Version 2.1 data suite for mapping and other analytical purposes. Total (TOT) and Divergent (DIV) upstream summaries were generated using the NHDPlusV2 Catchment Attribute Allocation and Accumulation Tool (CA3TV2). Using this method, upstreams summaries are generated for 82,263 of the 83,637 NHDPlus catchments in the Chesapeake Bay Watershed. These data will be used to investigate source-sink linkages between contaminant sources, water quality issues, and impacted receptor populations (e.g., smallmouth bass) throughout the Bay Watershed. Information gained from this work may also be used to evaluate the success of mitigation activities and help to prioritize new locations for mitigation, implementation of best management practices, or habitat conservation actions.

Freshwater salinization is an emerging issue for freshwater environments in the Chesapeake Bay, USA region. Salinization is often described by measurements of specific conductance (SC). This data release contains specific conductance observations collected by multiple regional agencies for streams within the Chesapeake Bay Watershed. This inventory compiles and harmonizes data from the Water Quality Portal (WQP), which is a data repository developed by the National Water Quality Monitoring Council and supported by the U.S. Environmental Protection Agency and U.S. Geological Survey, and the U.S. Geological Survey National Water Information System (NWIS). Both discrete measures of SC, which are single measures taken on a particular time and day, and continuous measures of SC, which are repeated measures of SC taken at regular, short intervals, such as 15-minute or hourly intervals, were compiled for this data release. The discrete data were also processed to screen out non-relevant observations and harmonize units. The WQP uses "MonitoringLocationIdentifier" to identify each unique site and monitoring activities, and this term is used throughout the data release to differentiate among unique sites and monitoring activities as well. The data release includes four items: 1. ["Site_inventory_for_specific_conductance_measures.csv"]: This is a site inventory of all locations where SC data had been collected and compiled for the data release. This file includes information on the monitoring location (coordinates, state, and county), the organization responsible for the data collection, the type of data available (discrete, continuous, or both) and its unique monitoring location and activity. 2. ["Discrete_specific_conductance_results.txt"]: This file contains all discrete SC observations. Identifying information (coordinates, monitoring location name and identifier), along with the observation value, units, and multiple flagging columns which denoted whether any changes were made to the observation or units during the processing steps. Full details are included in the "readme_file_for_Ches_Bay_specific_conductance_inventory.pdf" file. 3. ["Continuous_specific_conductance_results.zip"]: This zipped folder contains 89 .csv files for all the continuous USGS SC data available in the Chesapeake Bay watershed. Each file name includes each unique MonitoringLocationIdentifier. 4. ["readme_file_for_Ches_Bay_specific_conductance_inventory.pdf"]: This document describes all the processing and harmonization steps to generate the site inventory and discrete SC dataset, and for downloading the high frequency SC datasets.

Freshwater salinization is an emerging issue for freshwater environments in the Chesapeake Bay, USA region. Salinization is often described by measurements of specific conductance (SC). This data release contains specific conductance observations collected by multiple regional agencies for streams within the Chesapeake Bay Watershed. This inventory compiles and harmonizes data from the Water Quality Portal (WQP), which is a data repository developed by the National Water Quality Monitoring Council and supported by the U.S. Environmental Protection Agency and U.S. Geological Survey, and the U.S. Geological Survey National Water Information System (NWIS). Both discrete measures of SC, which are single measures taken on a particular time and day, and continuous measures of SC, which are repeated measures of SC taken at regular, short intervals, such as 15-minute or hourly intervals, were compiled for this data release. The discrete data were also processed to screen out non-relevant observations and harmonize units. The WQP uses "MonitoringLocationIdentifier" to identify each unique site and monitoring activities, and this term is used throughout the data release to differentiate among unique sites and monitoring activities as well. The data release includes four items: 1. ["Site_inventory_for_specific_conductance_measures.csv"]: This is a site inventory of all locations where SC data had been collected and compiled for the data release. This file includes information on the monitoring location (coordinates, state, and county), the organization responsible for the data collection, the type of data available (discrete, continuous, or both) and its unique monitoring location and activity. 2. ["Discrete_specific_conductance_results.txt"]: This file contains all discrete SC observations. Identifying information (coordinates, monitoring location name and identifier), along with the observation value, units, and multiple flagging columns which denoted whether any changes were made to the observation or units during the processing steps. Full details are included in the "readme_file_for_Ches_Bay_specific_conductance_inventory.pdf" file. 3. ["Continuous_specific_conductance_results.zip"]: This zipped folder contains 89 .csv files for all the continuous USGS SC data available in the Chesapeake Bay watershed. Each file name includes each unique MonitoringLocationIdentifier. 4. ["readme_file_for_Ches_Bay_specific_conductance_inventory.pdf"]: This document describes all the processing and harmonization steps to generate the site inventory and discrete SC dataset, and for downloading the high frequency SC datasets.

This data release presents chemical results from investigations of surface-water quality in the Potomac River watershed (encompassing Washington, D.C. and parts of West Virginia, Virginia, Pennsylvania, and Maryland) conducted during low-flow conditions in July through September of 2022 and modeling results that support interpretative products. Water-quality sampling: A sampling campaign was conducted at 32 stream sites throughout the watershed (Table 1). A suite of field parameters and inorganic and organic chemical characteristics at each site were characterized using seven separate analytical methods at five laboratories (Table 2). The water-quality results are presented in Tables 3 and 4. Analytical methods and laboratories used were (1) major anions by ion chromatography at the U.S. Geological Survey Integrated Water Chemistry Assessment Laboratory in Boulder, Colorado (USGSIWCAL); (2) full fluorescence spectra in vectorized format, excitation-emission-matrix (EEM) fluorescence spectroscopy dissolved organic carbon (DOC), and total dissolved nitrogen (TDN) at the U.S. Geological Survey California Water Science Center Organic Matter Research Laboratory in Sacramento, California (CAWSCOMRL); (3) per-and polyfluoroalkyl substances (PFAS) using liquid chromatography with tandem mass spectrometry (LC-MS/MS), at the U.S. Geological Survey National Water Quality Laboratory in Denver, Colorado (USGSNWQL); (4) pesticides (PEST) by LC-MS/MS or gas chromatography with tandem mass spectrometry (GS-MS/MS) at the U.S. Geological Survey Organic Research Laboratory (USGSOGCA); (5) pharmaceuticals (PHARM) using LC-MS/MS at the USGSNWQL; and (6) Major elements and trace elements (TEs) using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) at the USGSIWCAL. Enzyme-Linked Immunosorbent Assay (ELISA) analyses were additionally performed at the U.S. Geological Survey Strategic Laboratory Science Branch in Boulder, Colorado (USGSSLSB) for the herbicides atrazine and glyphosate, the insecticide imidacloprid, and the consumer product chemical linear alkylbenzene sulfonate. Three analytes (atrazine, piperonyl butoxide, thiabendazole, and the thiabendazole surrogate standard thiabendazole-d4) were analyzed by the U.S. Geological Survey National Water Quality Laboratory (USGSNWQL) included with the pharmaceutical data in addition to being analyzed by the USGSOGCA with the pesticide data. The USGSNWQL results for these analytes were coded as replicate samples and additional time offsets were applied to create distinct times for these sample results. Samples were collected according to U.S. Geological Survey (USGS) protocols and procedures. A field blank and field replicate was collected for every analytical method, a matrix spike for PFAS, PHARM, and PEST was performed at three sites for quality assurance. Most sites were only sampled once for each parameter with the exception of four sites that had to be resampled due to samples arriving too warm to be processed for PFAS and PHARM parameters. Therefore samples for the remaining parameters were collected twice at these four sites. Water-quality modeling: This data release also contains inputs for and results from a wastewater reuse model that used data compiled from multiple sources to calculate the following estimates for each non-tidal National Hydrography Dataset Version 2.1 (NHDPlus V2) stream segment in the Potomac River watershed: (1) accumulated wastewater as a percent of total streamflow (ACCWW%) from municipal as well as municipal plus industrial PFAS wastewater treatment plants; and (2) predicted environmental concentrations (PECs, in nanograms per liter) of 14 pesticides and eight PFAS as well as the sum of the eight PFAS. ACCWW% values were calculated for mean-monthly and mean-annual streamflow conditions for municipal wastewater treatment plants (model results table: Table5_PotomacACCWW_municipal.csv) as well as

This data release presents chemical results from investigations of surface-water quality in the Potomac River watershed (encompassing Washington, D.C. and parts of West Virginia, Virginia, Pennsylvania, and Maryland) conducted during low-flow conditions in July through September of 2022 and modeling results that support interpretative products. Water-quality sampling: A sampling campaign was conducted at 32 stream sites throughout the watershed (Table 1). A suite of field parameters and inorganic and organic chemical characteristics at each site were characterized using seven separate analytical methods at five laboratories (Table 2). The water-quality results are presented in Tables 3 and 4. Analytical methods and laboratories used were (1) major anions by ion chromatography at the U.S. Geological Survey Integrated Water Chemistry Assessment Laboratory in Boulder, Colorado (USGSIWCAL); (2) full fluorescence spectra in vectorized format, excitation-emission-matrix (EEM) fluorescence spectroscopy dissolved organic carbon (DOC), and total dissolved nitrogen (TDN) at the U.S. Geological Survey California Water Science Center Organic Matter Research Laboratory in Sacramento, California (CAWSCOMRL); (3) per-and polyfluoroalkyl substances (PFAS) using liquid chromatography with tandem mass spectrometry (LC-MS/MS), at the U.S. Geological Survey National Water Quality Laboratory in Denver, Colorado (USGSNWQL); (4) pesticides (PEST) by LC-MS/MS or gas chromatography with tandem mass spectrometry (GS-MS/MS) at the U.S. Geological Survey Organic Research Laboratory (USGSOGCA); (5) pharmaceuticals (PHARM) using LC-MS/MS at the USGSNWQL; and (6) Major elements and trace elements (TEs) using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) at the USGSIWCAL. Enzyme-Linked Immunosorbent Assay (ELISA) analyses were additionally performed at the U.S. Geological Survey Strategic Laboratory Science Branch in Boulder, Colorado (USGSSLSB) for the herbicides atrazine and glyphosate, the insecticide imidacloprid, and the consumer product chemical linear alkylbenzene sulfonate. Three analytes (atrazine, piperonyl butoxide, thiabendazole, and the thiabendazole surrogate standard thiabendazole-d4) were analyzed by the U.S. Geological Survey National Water Quality Laboratory (USGSNWQL) included with the pharmaceutical data in addition to being analyzed by the USGSOGCA with the pesticide data. The USGSNWQL results for these analytes were coded as replicate samples and additional time offsets were applied to create distinct times for these sample results. Samples were collected according to U.S. Geological Survey (USGS) protocols and procedures. A field blank and field replicate was collected for every analytical method, a matrix spike for PFAS, PHARM, and PEST was performed at three sites for quality assurance. Most sites were only sampled once for each parameter with the exception of four sites that had to be resampled due to samples arriving too warm to be processed for PFAS and PHARM parameters. Therefore samples for the remaining parameters were collected twice at these four sites. Water-quality modeling: This data release also contains inputs for and results from a wastewater reuse model that used data compiled from multiple sources to calculate the following estimates for each non-tidal National Hydrography Dataset Version 2.1 (NHDPlus V2) stream segment in the Potomac River watershed: (1) accumulated wastewater as a percent of total streamflow (ACCWW%) from municipal as well as municipal plus industrial PFAS wastewater treatment plants; and (2) predicted environmental concentrations (PECs, in nanograms per liter) of 14 pesticides and eight PFAS as well as the sum of the eight PFAS. ACCWW% values were calculated for mean-monthly and mean-annual streamflow conditions for municipal wastewater treatment plants (model results table: Table5_PotomacACCWW_municipal.csv) as well as

This data release presents chemical results from investigations of surface-water quality in the Potomac River watershed (encompassing Washington, D.C. and parts of West Virginia, Virginia, Pennsylvania, and Maryland) conducted during low-flow conditions in July through September of 2022. This sampling campaign was conducted at 32 stream sites throughout the watershed (Table 1). A suite of field parameters and inorganic and organic chemical characteristics at each site were characterized using seven separate analytical methods at five laboratories (Table 2). The water-quality results are presented in Table 3. Analytical methods and laboratories used were (1) major anions by ion chromatography at the U.S. Geological Survey Integrated Water Chemistry Assessment Laboratory in Boulder, Colorado (USGSIWCAL); (2) excitation-emission-matrix (EEM) fluorescence spectroscopy dissolved organic carbon (DOC), and total dissolved nitrogen (TDN) at the U.S. Geological Survey California Water Science Center Organic Matter Research Laboratory in Sacramento, California (CAWSCOMRL); (3) per-and polyfluoroalkyl substances (PFAS) using liquid chromatography with tandem mass spectrometry (LC-MS/MS), at the U.S. Geological Survey National Water Quality Laboratory in Denver, Colorado (USGSNWQL); (4) pesticides (PEST) by LC-MS/MS or gas chromatography with tandem mass spectrometry (GS-MS/MS) at the U.S. Geological Survey Organic Research Laboratory (USGSOGCA); (5) pharmaceuticals (PHARM) using LC-MS/MS at the USGSNWQL; and (6) Major elements and trace elements (TEs) using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) at the USGSIWCAL. Enzyme-Linked Immunosorbent Assay (ELISA) analyses were additionally performed at the U.S. Geological Survey Strategic Laboratory Science Branch in Boulder, Colorado (USGSSLSB) for the herbicides atrazine and glyphosate, the insecticide imidacloprid, and the consumer product chemical linear alkylbenzene sulfonate. Three analytes (atrazine, piperonyl butoxide, thiabendazole, and the thiabendazole surrogate standard thiabendazole-d4) were analyzed by the U.S. Geological Survey National Water Quality Laboratory (USGSNWQL) included with the pharmaceutical data in addition to being analyzed by the USGSOGCA with the pesticide data. The USGSNWQL results for these analytes were coded as replicate samples and additional time offsets were applied to create distinct times for these sample results. Samples were collected according to U.S. Geological Survey (USGS) protocols and procedures. A field blank and field replicate was collected for every analytical method, a matrix spike for PFAS, PHARM, and PEST was performed at three sites for quality assurance. Most sites were only sampled once for each parameter but four sites had to be resampled due to samples arriving too warm to be processed for PFAS and PHARM parameters. Therefore samples for the remaining parameters were collected twice at these four sites.

This dataset provides baseline concentrations (from 2014) of polycyclic aromatic hydrocarbon (PAH), other aromatic organic compounds, mercury (Hg), and trace metal concentrations in sediment and biota collected from two sites along an existing rail line used for coal transport in the Columbia River Gorge, Washington. For this study, aquatic surface sediments, aquatic insects, and juvenile fish were collected in 2014 from Horsethief Lake in Columbia Hills State Park and Steigerwald Lake National Wildlife Refuge (NWR), both located in close proximity to the rail line and within the Columbia River Gorge National Scenic Area. Samples were collected from two subsites in each area: one closer to the rail line and one farther from the rail line. Fish species collected for analysis included anadromous salmonids and resident yellow perch, sculpin, pumpkinseed, northern pikeminnow, and smallmouth bass.