These data were collected in cooperation with the Virginia Department of Environmental Quality (VADEQ) to document the occurrence of Per- and Polyfluoroalkyl Substances (PFAS) in streams and rivers of Virginia. Specifically, this effort was initiated to: 1. Collect and analyze samples for PFAS at USGS-sampling stations in the Chesapeake Bay River Input Monitoring Network and Non-Tidal Network; 2. Collect and analyze samples for PFAS at VADEQ Probabilistic Monitoring stations; 3. Collect and analyze samples for PFAS at additional DEQ-selected locations; and 4. Quality Assure all data collected in accordance with USGS policies and publicly release those data as a citable USGS Data Release. Description of Available Datasets: These data are available in 2 Excel (.xlsx) files that contain water-quality and quality-assurance results. The Excel files are duplicated as tab-delimited text files to increase accessibility to nonproprietary formats. The files titled VA_StateWide_Surface_Water_Results contain analytical results for 166 samples of PFAS in surface water collected at 73 locations in the State. These files also contain associated field blanks, lab blanks, and replicates used for quality control. Lab blanks are used to assess contamination imparted by the analytical process. Field blanks were collected using certified analyte-free water at the sampling point and used to assess possible cross contamination from sampling materials and sampling technique in the field. Field replicates were collected concurrently with the environmental sample and used to understand the variability of results.
The attached XML file titled VA_StateWide_Metadata contains metadata explaining the provenance of the data and should be thoroughly read to understand data structure and limitations. The files titled Data_Dictionary may be used as a reference to explain codes, terms, and abbreviations used in these datasets. The files titled Ongoing_Precision_and_Recovery contain quality assurance samples reported by the lab which establishes additional confidence in results over time. Data Validation and Quality Assurance: U.S. Environmental Protection Agency (EPA) Draft Method 1633 (U.S. Environmental Protection Agency, 2021) was used to determine PFAS concentrations in surface water. Samples were analyzed at SGS AXYS in British Columbia, Canada, which is accredited by the U.S. Department of Defense Environmental Laboratory Accreditation Program for analysis of PFAS using Draft Method 1633. Reporting and detection levels for PFAS results are specific to the analyte, sample matrix, instrumentation, and laboratory performance. Results throughout this dataset that are reported with a less than qualifier represent values that were not detected above the reporting level for that sample and specific analyte. The reporting levels show in this dataset are synonymous with the minimum level of quantitation as defined by U.S. Environmental Protection Agency (2021).
A combination of field blanks, laboratory method blanks, isotopically labeled compound recoveries, and ongoing precision and recovery samples were used to assess field techniques and validity of the reported results. Three samples for 6:2 fluorotelomersulfonate (6:2 FTS), two samples for perfluorooctanesulfonamide (PFOSA), and one sample for perfluorooctanesulfonate (PFOS) did meet quality assurance criteria. Analytical results for these analytes were rejected in six different samples and are represented in the dataset with an “R” qualifier.
References: U.S. Environmental Protection Agency, 2021, Draft Method 1633 - Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/MS: U.S. Environmental Protection Agency Document EPA 821-D-21-001, 65 p., accessed July 14, 2022, at https://www.epa.gov/system/files/documents/2021-09/method_1633_draft_aug-2021.pdf.