Uptake of Per- and Polyfluoroalkyl Substances by Fish, Mussel, and Passive Samplers in Mobile-Laboratory Exposures Using Groundwater from a Contamination Plume at a Historical Fire Training Area, Cape Cod, Massachusetts

Abstract

Aqueous film-forming foams historically were used during fire training activities on Joint Base Cape Cod, Massachusetts, and created an extensive per- and polyfluoroalkyl substances (PFAS) groundwater contamination plume. The potential for PFAS bioconcentration from exposure to the contaminated groundwater, which discharges to surface water bodies, was assessed with mobile-laboratory experiments using groundwater from the contamination plume and a nearby reference location. The on-site continuous-flow 21-day exposures used male and female fathead minnows, freshwater mussels, polar organic chemical integrative samplers (POCIS), and polyethylene tube samplers (PETS) to evaluate biotic and abiotic uptake. The composition of the PFAS-contaminated groundwater was complex and 9 PFAS were detected in the reference groundwater and 17 PFAS were detected in the contaminated groundwater. The summed PFAS concentrations ranged from 120 to 140 ng L–1 in reference groundwater and 6100 to 15,000 ng L–1 in contaminated groundwater. Biotic concentration factors (CFb) for individual PFAS were species, sex, source, and compound-specific and ranged from 2.9 to 1000 L kg–1 in whole-body male fish exposed to contaminated groundwater for 21 days. The fish and mussel CFb generally increased with increasing fluorocarbon chain length and were greater for sulfonates than for carboxylates. The exception was perfluorohexane sulfonate, which deviated from the linear trend and had a 10-fold difference in CFb between sites, possibly because of biotransformation of precursors such as perfluorohexane sulfonamide. Uptake for most PFAS in male fish was linear over time, whereas female fish had bilinear uptake indicated by an initial increase in tissue concentrations followed by a decrease. Uptake of PFAS was less for mussels (maximum CFb = 200) than for fish, and mussel uptake of most PFAS also was bilinear. Although abiotic concentration factors were greater than CFb, and values for POCIS were greater than for PETS, passive samplers were useful for assessing PFAS that potentially bioconcentrate in fish but are present at concentrations below method quantitation limits in water. Passive samplers also accumulate short-chain PFAS that are not bioconcentrated.

Integration of Per- and Polyfluoroalkyl Substance (PFAS) Fingerprints in Fish with Machine Learning for PFAS Source Tracking in Surface Water

“…This modeling exercise was intended as a demonstration and not a definitive commentary on the source allocation of PFASs in surface water based on measurements of PFASs in fish. Further study of PFAS toxicokinetics in fish may be needed for the true accuracy of the methodology employed here and help inform the reason as to why specific PFASs (i.e., L-PFOS, PFUnDA, and PFTrDA) are the most important for source classification, though it is likely related to their higher bioaccumulation potential . In addition, whereas the effect of differing fish species was not a dominant factor controlling classification accuracy (see discussion in Section S.6), the data do show that PFASs bioaccumulate at higher levels in fish liver than muscle, and classifiers should only be applied to data from tissues that are included in the training data set.…”

“…Nevertheless, the results presented here suggest the underlying approach of using PFAS concentrations in nonmigratory fish for source tracking is likely sound, as this exercise demonstrated a generalizable model for source tracking of PFASs that bioaccumulate in fish across geographic areas. This type of source tracking may also be applicable for other bioaccumulative contaminants of concern (i.e., polychlorinated biphenyls) assuming their uptake is similarly rapid compared to fish life cycles . We hope that this work will inspire future research in these analogous domains.…”

“…This type of source tracking may also be applicable for other bioaccumulative contaminants of concern (i.e., polychlorinated biphenyls) assuming their uptake is similarly rapid compared to fish life cycles. 50 We hope that this work will inspire future research in these analogous domains.…”

“…All data cleaning, analysis, and modeling were conducted with Python 3.9.0. Data cleaning consisted of importing and cleaning (i.e., organization and replacing null/nondetect (ND) values) the machine-readable data from Langberg et al and the other independent sources. ,− All data were checked for consistency prior to ML modeling. Thorough preliminary analysis of the data as well as data subsets are available in Langberg et al; primary findings included higher PFAS levels in fish liver than fish muscle, distinct geographic trends, and distinct distributions of PFCAs and PFSAs based on principal component analysis (PCA) of non-normalized concentration data.…”

“…Fish can serve as a long-term integrator of contaminant exposure, and we hypothesize that fish data will serve as a robust indicator of PFAS fingerprints from different source types. 50 We used data reported for fish collected from lakes and rivers in Norway (n = 1057), 12 and we demonstrate the first multiclass classification for PFAS source tracking. We also discuss our approach to limit model overfitting, address censored data, and optimize calibration parameters.…”