Spatiotemporal patterns of PFAS in water and crop tissue at a beneficial wastewater reuse site in central Pennsylvania

Abstract

Per- and polyfluoroalkyl substances (PFAS) are a collective name for thousands of synthetic compounds produced to enhance consumer and industrial products since the 1940s. They do not easily degrade, and some are known to pose serious ecological and human health concerns at trace concentrations (ng L^-1 levels). Per- and polyfluoroalkyl substances persist in treated wastewater and are inadvertently introduced into the environment when treated wastewater is reused as an irrigation source. The Pennsylvania State University (PSU) has been spray-irrigating its wastewater at a 2.45 km² mixed-use agricultural and forested site known as the "Living Filter" since the 1960s. To understand the spatiotemporal patterns of 20 PFAS at the Living Filter, water samples were collected bimonthly from fall 2019 through winter 2021 from the PSU's wastewater effluent and from each of the site's 13 monitoring wells. Crop tissue was collected at the time of harvest to assess PFAS presence in corn silage and tall fescue grown at the study site. Total measured PFAS concentrations in the monitoring wells ranged from nondectable to 155 ng L^-1 , with concentrations increasing with the direction of groundwater flow. Concentrations within each well exhibited little temporal variability across sampling events, with mixed relationships between PFAS and groundwater elevation observed between wells. Further, >84% of the PFAS present in livestock feed crops were short-chain compounds, with PFAS consumed annually by livestock fed crops harvested from the site estimated to be 2.46-7.67 mg animal^-1 yr^-1 . This research provides insight into the potential impacts of long-term beneficial reuse of treated wastewater on groundwater and crop tissue quality.

FIGURE 1

(a) Per‐ and polyfluoroalkyl substance (PFAS) concentrations (ng L⁻¹), (b) mass loadings (mg d⁻¹), and (c) relative contribution (%) of each PFAS to total measured PFAS for each sampling date in the effluent of The Pennsylvania State University Water Reclamation Facility. Concentrations are from 24‐h composite samples collected from the final effluent prior to being pumped to the Living Filter spray‐irrigation site. Compounds are shown in order of increasing chain length for short‐chain perfluoroalkyl carboxylic acids (PFCAs) (blue), long‐chain PFCAs (green), short‐chain perfluoroalkane sulfonic acids (PFSAs) (dark purple), and long‐chain PFSAs (light purple); perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are shown with patterns. PFBA, perfluorobutanoic acid; PFBS, perfluorobutane sulfonic acid; PFDA, perfluorodecanoic acid; PFHpA, perfluoroheptanic acid; PFHxA, perfluorohexanoic acid; PFHxS, perfluorohexanesulfonic acid; PFNA, perfluorononanoic acid; PFPeA, perfluoropentanoic acid

FIGURE 2

Total measured per‐ and polyfluoroalkyl substance (PFAS) concentrations as function of groundwater elevations for the State Game Lands site (left) and the Astronomy site (right). Data for Wells W2 and W7 are not shown in this figure because the number of samples with detected PFAS concentrations was 0 for W2 and only 1 for W7 (see Table 1)

FIGURE 3

Average total measured per‐ and polyfluoroalkyl substance (PFAS) concentrations for each monitoring well location for the study period (October 2019–February 2021)

FIGURE 4

Per‐ and polyfluoroalkyl substance concentrations observed for each sampling date for each of the monitoring wells at the State Game Lands site (left) and the Astronomy site (right). Please note the differences in y‐axis ranges. Also note that W2 is not included on the figure because no measured PFAS were present at detectable levels. PFBA, perfluorobutanoic acid; PFBS, perfluorobutane sulfonic acid; PFHpA, perfluoroheptanic acid; PFHxA, perfluorohexanoic acid; PFHxS, perfluorohexanesulfonic acid; PFNA, perfluorononanoic acid; PFOA, perfluorooctanoic acid; PFOS, perfluorooctane sulfonate; PFPeA, perfluoropentanoic acid