Grantee Research Project Results
2023 Progress Report: Evaluating PFAS Occurrence and Fate in Rural Water Supplies and Agricultural Operations to Inform Management Strategies
EPA Grant Number: R840082Title: Evaluating PFAS Occurrence and Fate in Rural Water Supplies and Agricultural Operations to Inform Management Strategies
Investigators: Lee, Linda S. , Pennell, Kurt , Preisendanz, Heather
Institution: Purdue University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2020 through April 29, 2025
Project Period Covered by this Report: September 1, 2022 through August 31,2023
Project Amount: $1,609,344
RFA: National Priorities: Research on PFAS Impacts in Rural Communities and Agricultural Operations (2020) RFA Text | Recipients Lists
Research Category: Land and Waste Management , Water
Objective:
Our overall goal is to address key data gaps in our understanding of PFAS occurrence and fate in the rural landscape and agricultural operations using a combination of field, laboratory and modeling activities.
Progress Summary:
For Obj. 1, Penn State completed sampling and analysis of 66 private wells from their rural well-owner network. Ten PFAS were detected with the highest being PFOA and PFOS 20 and 22 ng/L, respectively, and 7 wells above the EPA’s proposed drinking water standard of 4.0 ng/L. In IN, we collected and analyzed PFAS occurrence in surface water at 93 locations compared to well water. PFAS were detected in 99% of surface water samples evidence that surface water is more vulnerable to PFAS contamination compared to well water, which we hypothesized to be due to the extensive tile drainage and the glacial aquifer system limiting vertical transport. Total PFAS in groundwater and surface water was <LOQ – 24 ng/L and <LOQ – 93 ng/L, respectfully. Long-chain homologues were detected 2.6 times more frequently in surface water than well water. Surface water with the highest PFAS detection frequency and concentrations were in first-order streams draining from agricultural fields or impacted by NPDES discharge. In neither PA or IN studies was there a distinct spatial trend in total PFAS detected with respect to distance from biosolids applications.
For Obj. 2, bi-monthly sampling of influent and effluent from the Penn State plant was completed, compiled, and shared with facility operators. PFAS in monitoring well (MW) samples taken at the Penn State effluent spray-irrigation ‘Living Filter’ site was ubiquitous with totals as high as 157 ng/L. In the corn silage sampled, PFBA contributed 82-100% of PFAS concentrations.
For Obj. 3, the results of the VA reclamation site lysimeter study evaluating x1 and x5 biosolids application rate as well as effect of applying a biosolids-mulch blend, and blended was written up and is being submitted. In the VA HRSD study, groundwater from 7 MWs, soil cores, and runoff were collected prior and after the 2023 biosolids application (last application was 2017) to establish legacy PFAS levels and monitor temporal trends. Generally, the most detected PFAS in groundwater were short chain PFAAs (76% to 98% for C4-C6) and PFBS, PFOS, and PFOA were detected in >60% of all samples. PFOA had the highest concentration in groundwater (221.4 ng/l), followed by PFPeA (92.9 ng/L), PFHxA (78.2 ng/L) and PFBS (71.1 ng/L). In runoff, 20 PFAS were detected in samples collected pre-biosolid application with long chain PFAAs being dominant and PFOS having the highest average concentration of 686 ng/L. Similarly, PFOS was the most abundant in the 0-2 ft depth. Total PFAS in the 2023 biosolids was 257 ng/g with 84% being diPAPs. Pre-application data indicates that PFAS at the farm can be attributed to historic application of biosolids; however, all three rainwater collections also contained PFAS (~7 ng/L) with most being PFOS.
For Obj. 5 experimental and mathematical modeling studies were conducted to explore the competitive sorption of PFAS at the air-water interface. Solutions containing either PFOA or PFOS, or a mixture of PFOA and PFOS were analyzed to determine sorption to the solid phase (F-70 Ottawa sand), surface tension, and accumulation at the air-water interface through batch reactors and column experiments (49% saturation with constant Darcy velocity of 0.09 m/d). PFOA in the mixture exhibited chromatographic peaking and migrated faster than was anticipated based on the PFOA alone column study indicating competition between PFOS and PFOA at the air-water interface, where PFOS was preferentially retained over PFOA. The mathematical modeling of batch and column systems revealed that interfacial processes, including competition, can be described by the Szyszkowski and the extended Langmuir-Szyszkowski equations.
Future Activities:
A third and final round of well water samples will be collected through the Penn State Master Well Owner Network (Obj 1). Data from all three years will be compiled and mapped along with potential PFAS sources and groundwater data collected by the Pennsylvania Department of Environmental Protection. In Indiana, summer 2023 surface water samples from over 100 locations to are being analyzed to assess temporal trends in PFAS occurrence, followed by coupling well water and surface water data to evaluate sources and pathways of PFAS occurrence relative to land-applied biosolids. A manuscript will be submitted by the end of next year. For Obj. 2, analysis of the data collected from the Living Filter spray-irrigation site will be completed in Year 4 to assess temporal and spatial trends in the PFAS concentrations in the monitoring wells and crop samples, and soil samples (0-2 cm) collected across the site in Years 1-3. Management decisions for the site will be analyzed alongside the data to develop guidance regarding management strategies for reducing the impacts of PFAS in the irrigated wastewater on water, soil, and crop tissue quality. Additionally, we anticipate submitting a manuscript based on these results to the Journal of ASABE, or a similar peer-reviewed journal. Purdue will complete the extraction and analysis of post-application groundwater samples and six-foot soil cores, followed by data processing and synthesis to identify key factors impacting PFAS transport in the vadose zone (Obj 3) and preparation of a manuscript will begin. Purdue will also continue to explore the new Indiana site for setting up a PFAS uptake and mitigation site. Column studies at Brown University will continue for a range of water saturations to examine the effect of air-water interfacial area on PFAS transport (Obj. 5). In addition, unsaturated soil column experiments will be performed with Hudson soil, Penn State “Living Filter” site soil, with and without biosolids applied. The objective is to advance our understanding of solid phase sorption and adsorption at the air-water interface influence the fate and transport of PFAS mixtures in unsaturated field soils. Mathematically modeling will be performed on effluent and solid-phase concentration profiles obtained from each column experiment. We anticipate submitting several new manuscripts in 2024 (two from Obj. 1; one each from Obj. 2, 3, and 5).
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 21 publications | 5 publications in selected types | All 5 journal articles |
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Garza-Rubalvaca U, Klevan C, Pennell K, Abriola L. Transport and competitive interfacial adsorption of PFOA and PFOS in unsaturated porous media: Experiments and modeling. WATER RESEARCH 2025;268 |
R840082 (2023) R840082 (2024) |
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Supplemental Keywords:
biosolids, effluent irrigation, crop uptake, transport, biotransformation, interfacial adsorptionProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.