Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7n. PFAS Source and Forensic Considerations

Formatted Title:

Sampling of PFAS in Aqueous Media to Determine Contaminant Signatures Using a State-Wide Approach

Background/Objectives:

The Unregulated Contaminant Monitoring Rule 3 sample results indicated a large number of the public and community water systems regulated by the Delaware Department of Natural Resources and Environmental Control (DNREC) were impacted by per- and polyfluorinated alkyl substances (PFAS). The information prompted DNREC to begin collecting confirmatory samples and to collect additional samples from select groundwater wells, surface water bodies, and private drinking water wells to determine the extent of the problem, if there was a pattern of detections across the state, and to identify private drinking water sources requiring mitigation.

Approach/Activities:

Since 2016, DNREC has collected over 1,000 aqueous PFAS samples in groundwater, surface water and drinking water. The data collected have been used to identify drinking water supplies that are contaminated with PFAS. The information has also been used to identify PFAS source areas and to characterize groundwater plumes. Samples were collected in both the Coastal Plain and Piedmont Provinces of the State and in both unconfined and semi-confined aquifers and in tidal and non-tidal surface waters.

The samples were analyzed by Delaware specified Method 537M to report 37 unique PFAS analytes. The analytes were selected based on their frequency of detection within Delaware. The analytes were also selected to determine a potential source signature based upon the analytes. The signatures synthesized during this state-wide study can be applied to individual sites across the state to determine potential source areas or if the concentrations are identified as being anthropogenic background.

Results/Lessons Learned:

Data analytics includes source mapping, heat maps of focus areas or site-specific concentrations, and PFAS analyte signature visualization to determine similar source areas. The data collected can also be used by others to assist in understanding PFAS concentrations in the Costal Plain and potential fractured crystalline bedrock formations. The data can also add to our understanding of the fate and transport of PFAS, the past and current use of these analytes, and to identify any potential groundwater signature of the analytes detected.

Data collected and analyzed assisted with making multi-programmatic asset allocation and potential regulatory and policy implementation.

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Ping Wang