Sources and Pathways of PFAS Occurrence in Water Sources: Relative Contribution of Land-Applied Biosolids in an Agricultural Dominated Watershed

May combine two claims.

Surface water is more vulnerable to PFAS contamination than well water, with maximum total PFAS concentrations of 169.5 ng/L in surface water and 15.7 ng/L in well water, and over 90% of wells having total concentrations below 5 ng/L.

“Overall, results indicate that surface water (∑PFAS ≤ 169.4 ng/L) is more vulnerable to PFAS contamination than well water (∑PFAS ≤ 15.7 ng/L).”

• Also stated in: § PFAS in Well and Surface Waters · plain

  “The maximum total PFAS concentration in surface water (169.5 ng/L) was higher than well water (15.7 ng/L) with over 90% of the wells having total concentrations <5 ng/L (Figure 2).”

May combine two claims.

At least one PFAS was detected above the LOD in 90% of surface water samples and 84% of well water samples, and none of the samples had more than 10 targeted PFASs of quantifiable concentration.

“At least one PFAS was detected above the LOD in 90 and 84% of the surface water and well water samples, respectively; however, none of the samples had more than 10 targeted PFASs of quantifiable concentration.”

May combine two claims.

Sixty-six percent of the wells sampled were within 2 km of an application site, with the nearest well located 0.05 km from a biosolid-receiving field.

“Sixty-six percent of the wells sampled were within 2 km of an application site with the nearest well located 0.05 km from a biosolid-receiving field.”

May combine two claims.

The distribution of PFAAs was similar between water sources, with PFCAs making up 67% of surface water and 63% of well water, and PFSAs comprising 29% of surface water and 27% of well water.

“The distribution of perfluoroalkyl acids (PFAAs) was similar between water sources, with perfluoroalkyl carboxylates (PFCAs) making up 67 and 63% and perfluorosulfonic acids (PFSAs) comprising 29 and 27% in surface water and well water, respectively.”

May combine two claims.

Temporal trends revealed an inverse relationship between streamflow and PFAS concentrations at surface water sites impacted by point discharges, and the opposite relationship at sites impacted by diffuse sources.

“Temporal trends revealed an inverse relationship between streamflow and concentrations in surface water sites impacted by point discharges and vice versa for diffuse sources, thereby providing complementary evidence of potential sources.”

May combine two claims.

Among all PFASs across all samples, PFBS had the highest maximum concentration of 87 ng/L, followed by PFPeA at 24 ng/L and PFBA at 17 ng/L, all in surface water samples.

“Among all the PFASs across all samples, PFBS had the highest maximum concentration of 87 ng/L followed by 24 ng/L for PFPeA and 17 ng/L for PFBA, all of which were in surface water samples.”

May combine two claims.

PFOA concentrations at N23, N60, and N62 were 1.8, 10.8, and 4.0 ng/L, and PFOS concentrations were 0.7, 3.7, and 1.5 ng/L, respectively.

“PFOA concentrations were 1.8, 10.8, and 4.0 ng/L, and PFOS concentrations were 0.7, 3.7, and 1.5 ng/L.”

May combine two claims.

Site N60 is 0.05 km from the source, while N23 and N62 are 0.7 and 1.9 km, respectively.

“Site N60 is 0.05 km from the source, while N23 and N62 are 0.7 and 1.9 km, respectively; therefore, the proximity to the source might explain the differences in concentrations between these three sites.”

May combine two claims.

PFBS, PFHxS, and PFOS were the major PFSAs in all water samples, with surface water having higher proportions of PFOS (68%) compared to well water (48%).

“PFBS, PFHxS, and PFOS were the major PFSAs in all water samples with surface water having higher proportions of PFOS (68%) compared to well water (48%).”

May combine two claims.

FBSA and EtFOSAA were detected in 11% and 3%, respectively, of surface water sampling locations.

“FBSA and EtFOSAA, two electrochemically derived precursors to PFSAs, were detected in 11 and 3%, respectively, of surface water sampling locations.”

May combine two claims.

For surface water in this study, the highest concentration of PFOA was 6.8 ng/L and of PFOS was 4.6 ng/L.

“For surface water in this study, the highest concentration of PFOA and PFOS measured was 6.8 and 4.6 ng/L, respectively.”

May combine two claims.

Hierarchical cluster analysis identified PFAS co-occurrence trends and spatial clustering of sites.

“Hierarchical cluster analysis identified PFAS co-occurrence trends and spatial clustering of sites (Figure 4).”

May combine two claims.

At N23, N60, and N62, PFOS levels were all below the proposed EPA drinking water standards, and PFOA exceeded the limit in only one location.

“While these are relatively high concentrations compared to the rest of the watershed, PFOS levels are all below the proposed EPA drinking water standards, and PFOA exceeds the limit in only one location.”

May combine two claims.

Sites associated with AFFF use for fire training activities (N11 and N12) had higher concentrations in spring than summer, possibly due to surface runoff.

“Sites associated with AFFF use for fire training activities (N11 and N12) also had higher concentrations in the spring than in the summer possibly due to surface runoff.”

May combine two claims.

PFAS concentrations were highest in summer for 46% of sites sampled temporally, with all sites but one recording approximately 2 times more total concentrations in summer compared to spring.

“PFAS concentrations were highest in the summer for 46% of sites sampled temporally, with all sites but one recording ∼2× more total concentrations in the summer compared to the spring (Figure 5).”

May combine two claims.

Average flow in summer and spring was 2300 and 10000 ft3/s, respectively.

“Average flow in the summer and spring was 2300 and 10000 f3/s, respectively.”

May combine two claims.

Sites associated with point discharges had peak concentrations in summer when low streamflow is expected, while locations impacted by nonpoint source release recorded higher concentrations in spring.

“Sites associated with point discharges had peak concentrations in the summer when low streamflow is expected, while locations impacted by nonsource point release recorded higher concentrations in the spring.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

For the remaining sites, there were no clear temporal trends, possibly due to increased downstream dilution for sites S78, S81, and S90 or sustained concentrations from year-round equitable flow conditions for sites along the river (R01, R02, R05, and R06).

“For the remaining sites, there were no clear temporal trends possibly due to increased downstream dilution for sites S78, S81, and S90 or sustained concentrations from year-round equitable flow conditions for sites along the river (R01, R02, R05, and R06).”

May combine two claims.

PFBS and other PFAAs were detected across all sites due to their ubiquitous use, while concentrations of less-documented FBSA were elevated downstream from a computer hardware manufacturer that is a previously reported novel source.

“PFBS and other PFAAs were detected across all sites due to their ubiquitous use, while concentrations of the less-documented FBSA were elevated downstream from a computer hardware manufacturer that is a previously reported novel source.47”

• cites [47] sourceNot checked yet

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May combine two claims.

The well in this study with the highest total PFAS concentration is approximately 0.9 km from an upstream biosolid-applied field, with a total well depth of 43 m and 1.5 m static water level.

“For example, the well in our study with the highest total PFAS concentration is ∼0.9 km from an upstream biosolid-applied field, with a total well depth of 43 m and 1.5 m static water level.”

May combine two claims.

PFAS concentrations in wells were relatively low and did not exceed enforceable EPA MCLs.

“Although PFAS concentrations in wells were relatively low and did not exceed the enforceable EPA MCLs”

May combine two claims.

Observed concentrations in wells near impacted surface water sites associated with known PFAS sources were comparable to other well water samples, indicating that groundwater in this area is generally protected from contamination.

“Also, observed concentrations in wells near impacted surface water sites associated with known PFAS sources were comparable to other well water samples, indicating that groundwater in this area is generally protected from contamination.”

May combine two claims.

The field has frequently received biosolids over the past 20 years at a loading rate between 1.0 and 4.8 dry tons/acre, except for an instance where biosolids were applied at approximately 30 dry tons/acre.

“The field has frequently received biosolids over the past 20 years at a loading rate between 1.0 and 4.8 dry tons/acre except for an instance where biosolids were applied at ∼30 dry tons/acre.”

Classified as probably not a substantial claim.

PFASs released from source zones during weathering and drainage events are delivered either via suspended solids in runoffs to surface waters or via leaching to groundwater.

“PFASs released from source zones during weathering and drainage events are delivered either via suspended solids in runoffs to surface waters or via leaching to groundwater.11−13”

• cites [11] sourceNot checked yet

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• cites [12] sourceNot checked yet

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• cites [13] sourceNot checked yet

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May combine two claims.

Johnson et al. reviewed 96 studies for PFAS distribution in groundwater, of which AFFF-impacted sites made up 32% of known sources, 18% were in locations impacted by PFAS manufacturing and industrial activities, and only 3% were for biosolid application sites.

“For example, Johnson et al.28 reviewed 96 studies for PFAS distribution in groundwater of which AFFF-impacted sites made up 32% of known sources, 18% in locations impacted by PFAS manufacturing and industrial activities, and only 3% for biosolid application sites.”

• cites [28] sourceNot checked yet

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May combine two claims.

The relative contribution of biosolids to PFAS in water sources is poorly understood, partly due to knowledge gaps in tracing and connecting diffuse sources of PFAS to contamination of water sources.

“While several studies have evaluated the environmental occurrence of PFAS, the relative contribution of biosolids to PFAS in water sources is poorly understood, partly due to knowledge gaps in tracing and connecting diffuse sources of PFAS to contamination of water sources.24”

• cites [24] sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

Gottschall et al. detected PFOS and PFOA with maximum concentrations of 17 and 12 ng/L, respectively, in tile drains installed in a biosolid-applied field.

“Gottschall et al.18 detected PFOS and PFOA with maximum concentrations of 17 and 12 ng/L, respectively, in tile drains installed in a biosolid-applied field.”

• cites [18] sourceNot checked yet

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May combine two claims.

PFASs are consistently detected in wastewater treatment influents, effluents, and residuals including biosolids, which present pathways for PFAS redistribution in aquatic environments.

“The ubiquitous use of PFASs is reflected by their consistent detection in wastewater treatment influents, effluents, and residuals including biosolids,7−9 all of which present pathways for PFAS redistribution in aquatic environments.10”

• cites [7] sourceNot checked yet

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• cites [8] sourceNot checked yet

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• cites [9] sourceNot checked yet

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• cites [10] sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

Other non-PFAS tile-drained field studies have shown that agrochemicals including pesticides and inorganic fertilizers bypass the soil network and move horizontally through tile drainage into receiving water bodies.

“Other non-PFAS tile-drained field studies have shown that instead of vertical migration, agrochemicals including pesticides and inorganic fertilizers bypass the soil network and move horizontally through the tile drainage into receiving water bodies.19−22”

• cites [19] sourceNot checked yet

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• cites [20] sourceNot checked yet

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• cites [21] sourceNot checked yet

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• cites [22] sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

The higher FBSA than PFOS at sites S31 and N08 is possibly due to changes in the industrial use of long-chain PFASs over the past decade.

“possibly due to changes in the industrial use of long-chain PFASs over the past decade.”

Classified as probably not a substantial claim.

Site N08 is located approximately 2 km downstream of a computer chip manufacturing company.

“Site N08 is located ∼2 km downstream of a computer chip manufacturing company.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Dilution might explain the clustering pattern along the Wabash River in which sites with elevated PFOS concentrations (R01 and R02) located between three WWTP outfalls were separated from diluted downstream river sites (R03, R04, R05, and R06).

“Similarly, dilution might explain the clustering pattern along the Wabash River in which sites with elevated PFOS concentrations (R01 and R02) located between three WWTP outfalls were separated from diluted downstream river sites (R03, R04, R05, and R06).”

May combine two claims.

Site N60 is likely impacted by short-chain PFAAs that leached into tile drains following land application of biosolids in addition to surface runoff of long-chain PFAS sorbed to the soil.

“The site is likely impacted by short-chain PFAAs that leached into tile drains following land application of biosolids in addition to surface runoff of long-chain PFAS sorbed to the soil.12”

• cites [12] sourceNot checked yet

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May combine two claims.

AFFF use is another potential source at cluster 4 sites N11 and N12, which are located within approximately 0.3 km from a small airport with a nearby undisclosed fire training site.

“Another potential source is the use of AFFF as observed in cluster 4 sites (N11 and N12) that are located within ∼0.3 km from a small airport with a nearby undisclosed fire training site.”

Classified as probably not a substantial claim. May combine two claims.

Streamflow was not measured; changes in flow conditions were inferred from rainfall data and stream gauges placed in the Wabash River within the watershed.

“Although streamflow was not measured, changes in flow conditions were inferred from rainfall data and stream gauges placed in the Wabash River within the watershed (Figure S4).”

May combine two claims.

Sites R03 and R04 are flanked by biosolid-receiving fields and thereby impacted by both nonpoint and upstream point sources.

“Unlike other sampling locations on the river, both sites are flanked by biosolid-receiving fields and thereby impacted by both nonpoint and upstream point sources.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Biosolids applied to agricultural fields were linked to PFAS contamination in the upper Moehne River in Heidelberg, Germany, with a maximum total concentration of 4,348 ng/L (seven PFASs with 83% being PFOA).

“In another study, biosolids applied to agricultural fields were linked to PFAS contamination in the upper Moehne River in Heidelberg, Germany, with a maximum total concentration of 4,348 ng/L (seven PFASs with 83% being PFOA).41”

• cites [41] sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Contaminated surface water locations could potentially impact downstream public water supplies or provide a pathway for exposure via fish consumption.

“However, contaminated locations could potentially impact downstream public water supplies or provide a pathway for exposure via fish consumption.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Lindstrom et al. reported total concentrations of up to 30,000 ng/L in surface water associated with land application of industrial-impacted biosolids.

“Lindstrom et al.40 reported total concentrations of up to 30,000 ng/L in surface water associated with land application of industrial-impacted biosolids.”

• cites [40] sourceNot checked yet

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May combine two claims.

In spring, high streamflow can dilute PFAS concentrations in point discharges or increase concentrations via surface runoff in locations impacted by nonpoint sources.

“In the spring, high streamflow can dilute PFAS concentrations in point discharges or increase concentrations via surface runoff in locations impacted by nonpoint sources.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Sorption to river sediment and bioaccumulation in biota are other potential attenuation pathways along the river reach.

“Sorption to river sediment and bioaccumulation in biota are other potential attenuation pathways along the river reach.13”

• cites [13] sourceNot checked yet

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May combine two claims.

In the early 2000s, biosolids were applied at site N60 at approximately 30 dry tons/acre, which is more than 10 times the regular application rate.

“Additionally, in the early 2000s, biosolids were applied at ∼30 dry tons/acre, which is >10× the regular application rate.”

May combine two claims.

Summer sampling followed periods of little to no precipitation, resulting in insufficient flow to dilute point discharges and thereby higher PFAS concentrations.

“Summer sampling followed periods of little to no precipitation resulting in insufficient flow to dilute point discharges and thereby resulted in higher PFAS concentrations.”

Probably not a substantial claim: may not pass S3 (load-bearing).

FBSA was reported as a short-chain substitute for PFOS in semiconductor production.

“In another study, FBSA was reported as a short-chain substitute for PFOS in semiconductor production.48”

• cites [48] sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

FBSA is a metabolite of N-methyl-perfluorobutanesulfonyl [C4F9SO2N(CH3)], a short-chain fluorinated surfactant used in Scotchgard products as an alternative to N-ethyl-perfluorooctanesulfonyl (a PFOS precursor).

“Chu and Letcher47 identified FBSA as a metabolite of N-methyl-perfluorobutanesulfonyl [C4F9SO2N(CH3)], which is a short-chain fluorinated surfactant used in Scotchgard products as an alternative to N-ethyl-perfluorooctaneslfonyl (C8F17SO2N(C2H5), a PFOS precursor).”

• cites Chu and Letcher47Not checked yet

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May combine two claims.

The high p value and z score of 0.62 signify absence of geospatial clustering for PFAS concentrations in wells, implying a random distribution of concentrations relative to landscape factors.

“The high p value and z score of 0.62 clearly signify the absence of geospatial clustering for PFAS concentrations in wells, thereby implying a random distribution of concentrations relative to landscape factors.”

May combine two claims.

Sites S21 and S22 are likely impacted not by nonpoint sources but by upstream ephemeral headwaters that receive point discharges but only have flowing water in spring, resulting in elevated PFAS levels during spring sampling.

“Both sites are likely impacted not by nonpoint sources but rather by upstream ephemeral headwaters that receive point discharges but only have flowing water in the spring, hence resulting in elevated PFAS levels during spring sampling.”

May combine two claims.

The glacial aquifer system protects groundwater from contamination in the study area, and subsurface drainage systems obscure transport pathways and source attribution, highlighting the importance of incorporating prevailing hydrogeological conditions into PFAS forensic studies.

“Overall, the glacial aquifer system protects groundwater from contamination in the study area, and subsurface drainage systems obscure transport pathways and source attribution, which highlight the importance of incorporating prevailing hydrogeological conditions into PFAS forensic studies.”

May combine two claims.

This particular location is unlikely to be impacted by industrial sources due to absence of NPDES discharges and likely represents the worst case scenario of PFAS contamination from biosolid applications in the study area.

“This particular location is unlikely to be impacted by industrial sources due to the absence of NPDES discharges and likely represents the worst case scenario of PFAS contamination from biosolid applications in the study area.”

Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

Such transport models can inform risk assessment at a large scale but sometimes have limitations at capturing location-specific nuances.

“Such transport models can inform risk assessment at a large scale; however, they sometimes have limitations at capturing location-specific nuances.”

May combine two claims.

The results provide evidence of PFAS transport down the soil profile, but the impact from land application of biosolids and other sources is confounded by multiple interdependent transport factors.

“our results provide evidence of PFAS transport down the soil profile, but the impact from land application of biosolids and other sources is confounded by multiple interdependent transport factors.”

May combine two claims.

Artificial drainage systems facilitate horizontal transport of porewater from soils to agricultural ditches and surface water bodies and thereby are critical sources of PFASs in the study area.

“These artificial drainage systems facilitate the horizontal transport of porewater from soils to agricultural ditches and surface water bodies and thereby are critical sources of PFASs in the study area.”

• AssumptionRests on an assumption: Preferential flow through tile drains can increase PFAS export to ditch networks during storm events, resulting in a direct relationship between streamflow and concentrations.

Probably not a substantial claim: may not pass S3 (load-bearing).

This alteration in drainage might explain why distance from upstream sources as a factor was not apparent in well water.

“This alteration in drainage might explain why the distance from upstream sources as a factor was not apparent in well water.”

May combine two claims.

Prevalence of subsurface drainage in the study mediates transport of chemicals to groundwater; rather than vertical transport, soil porewater is redirected to ditches and other waterbodies.

“In addition to geological factors, the prevalence of subsurface drainage in the study mediates transport of chemicals to groundwater; rather than vertical transport, soil porewater is redirected to ditches and other waterbodies.”

May combine two claims.

Aquifer characteristics appear more critical than distance to upstream location for the highest-PFAS well, because the well was completed in parts of the Till Veneer aquifer system where protective clay layers are thin or absent.

“Although the distance to the upstream location might play a role in this case, aquifer characteristics appear to be more critical considering that the well was completed in parts of the Till Veneer aquifer system where protective clay layers are thin or absent.”

May combine two claims.

In such scenarios, concentrations are often highest immediately after source application, which aligns with the spring timeline for biosolid application in the watershed.

“In such scenarios, concentrations are often highest immediately after source application, which aligns with the spring timeline for biosolid application in the watershed.”

• AssumptionRests on an assumption: In scenarios of intense storm events and biosolid application, concentrations are often highest immediately after source application.

Probably not a substantial claim: may not pass S3 (load-bearing).

Statistical models that identify drivers of PFAS concentrations in groundwater have been reported in statewide or regional studies.

“Statistical models that identify drivers of PFAS concentrations in groundwater have been reported in statewide or regional studies.55−57”

• cites [55] sourceNot checked yet

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• cites [56] sourceNot checked yet

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• cites [57] sourceNot checked yet

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Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

The current study area does not adequately capture a combination of factors that could increase contamination risk; therefore, more studies across diverse agricultural landscapes within the region are needed to sufficiently characterize causative factors driving PFAS transport to groundwater.

“Our current study area does not adequately capture a combination of these factors; therefore, more studies across diverse agricultural landscapes within the region are needed to sufficiently characterize causative factors driving PFAS transport to groundwater.”

May combine two claims.

Differences in PFAS concentrations in this study cannot be explained by a generalized model and transport from potential sources to groundwater is location specific.

“This suggests that differences in PFAS concentrations in this study cannot be explained by a generalized model and that transport from potential sources to groundwater is location specific.”

May combine two claims.

Gaining streams are prevalent in the watershed; therefore, PFAS-impaired surface water is unlikely to impact groundwater.

“Moreover, gaining streams are prevalent in the watershed; therefore, PFAS-impaired surface water is unlikely to impact groundwater.”

• AssumptionRests on an assumption: Gaining streams are prevalent in the watershed.