4_g__-_PFAS_Summary.pdf

Initial results of PFAS in water samples from the Ash Meadows National Wildlife Refuge

Background: Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals that have been used in manufacturing processes since the late 1940s for their water-repellant and heat-resistant properties in products like carpets, textiles, food packaging, aqueous film-forming foams (AFFF), and hydraulic fluids (OECD, 2015). Long-term persistence in the environment and low biodegradability have resulted in low-level contamination of most environmental media worldwide. This is a concern because PFAS has high bioaccumulation is known to increase embryotoxicity, metabolic syndrome, infertility, and death in aquatic species (McCarthy et al., 2017; Squadrone et al., 2015).

As a first step towards assessing the degree of PFAS contamination in the remote waters of the Ash Meadows National Wildlife Refuge, water samples were collected from Devils Hole, the Ash Meadows Fish Conservation Facility (AMFCF), and Crystal Reservoir from February 28 to March 1, 2024, and analyzed for 29 common PFAS species. To assess the vertical distribution of PFAS throughout the water column at each location, samples were collected from the water surface and at depths ranging between 31 to 71 mm below the water surface. At Devils Hole and the AMFCF tank, samples were collected from the shelf and the deep pool. The AMFCF production well was also sampled. Finally, a surface and depth sample were collected from Crystal Reservoir.

Initial Results: PFAS were detected in all water samples collected, with the sum of all measured species ranging from 23.81 ng/L in the shelf column at AMFCF to 444.77 ng/L in the Crystal Reservoir surface sample. These concentrations exceed typical ambient background levels in surface waters in the region (DeNicola et al., 2023). Contaminants may accumulate in the Crystal Reservoir, explaining the notably high concentrations. Overall, the measured concentrations are comparable to, or exceed in the case of Crystal Reservoir, concentrations measured by Bai and Son (2021) in the urban waterway of the Truckee River (12.4 to 203 ng/L). Overall, the concentrations measured exceed PFAS levels measured in 15 lakes and 10 rivers in northern Nevada and northeastern California, where concentrations ranged from ~2-15 ng/L in urban areas and <3 ng/L in remote areas (DeNicola et al., 2023).

PFAS tend to concentrate within the top ~100 µm of the water surface. Consistent with this fact, concentrations were greater in surface samples than depth samples at Devils Hole, Crystal Reservoir, and the AMFCF shelf. However, at the AMFCF pool, the depth concentration exceeded the surface concentration. Mixing/turnover can increase concentrations in the water column, which can have adverse effects on aquatic wildlife.

To aid with characterization, describe toxicity, and assist with source attribution, PFAS compounds are commonly divided into categories. For example, long-chain PFAS (PFAS with ≥8 carbon atoms) are generally understood to be more toxic than short-chain PFAS (C<8). As a result, short-chain PFAS are extensively used as alternatives to long-chain PFAS in manufacturing processes. Additionally, species that are resistant to transformation and are persistent in the environment are “terminal degradation products”, while “precursors” are species that undergo environmental transformation into terminal degradation products. Overall, short chain PFAS were found at higher concentrations, suggesting contemporary sources of contamination. The two exceptions include the AMFCF well and the surface sample from Crystal Reservoir, which both contain greater concentrations of older or “legacy” compounds. Crystal Reservoir also contains high levels of precursor compounds (i.e., fluorotelomer sulfonic acids) that commonly degrade into the long-chain terminal degradation products that were detected.

Composition profiles, or the relative abundance of PFAS species detected in each water sample, are also useful for identifying potential PFAS sources, changes in sources, and the stability/transformation of PFAS species over time. Similar composition profiles between sites might suggest common sources (e.g., atmospheric or groundwater). For example, similar compositions between the AMFCF Well and Devils Hole may indicate a groundwater source.

Next Steps: To build off these initial results, we propose a study that will 1) aid in identifying sources and transport pathways of PFAS to surface water and groundwater resources in the Ash Meadows area and the greater Death Valley region and 2) assess the degree of bioaccumulation of PFAS in aquatic species. Groundwater samples will be collected along the regional groundwater flow path to assess the spatial distribution and transformation of species. Atmospheric deposition samplers will be installed near critical surface water bodies for monitoring of atmospheric inputs during both dry (dust) and wet (precipitation) conditions. To quantify regional atmospheric sources, an atmospheric sampler will also be installed at the ridge of surrounding mountains. A trophic-level assessment of PFAS uptake will be conducted by collecting and processing biota of different trophic levels (i.e., algae, wetland grasses, macroinvertebrates, and fishes) throughout the region. Nitrogen (δ15N) and carbon (δ13C) isotope measurements will be utilized to determine trophic levels of contaminants and assess the biological magnification between trophic levels.

References

Bai, X., & Son, Y., 2021. Perfluoroalkyl substances (PFAS) in surface water and sediments from two urban watersheds in Nevada, USA. Science of The Total Environment, 751, 141622.

DeNicola, M., Lin, Z., Quiñones, O., Vanderford, B., Song, M., Westerhoff, P., Dickenson, E., Hanigan, D., 2023. Per- and polyfluoroalkyl substances and organofluorine in lakes and waterways of the northwestern Great Basin and Sierra Nevada. Sci Total Environ. 2023 Dec 20;905:166971. doi:

10.1016/j.scitotenv.2023.166971. Epub 2023 Sep 11. PMID: 37699477.

McCarthy, C., Kappleman, W., & DiGuiseppi, W., 2017. Ecological considerations of per-and polyfluoroalkyl substances (PFAS). Current Pollution Reports, 3(4), 289-301.

OECD, 2015. Working towards a global emission inventory of PFASs: focus on PFCAS - status quo and the way forward. Paris, France, 85 p.

Squadrone, S., Ciccotelli, V., Prearo, M., Favaro, L., Scanzio, T., Foglini, C., & Abete, M., 2015.

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA): emerging contaminants of increasing concern in fish from Lake Varese, Italy. Environmental monitoring and assessment, 187(7), 438.