New Mexico Geological Society Annual Spring Meeting — Abstracts

Per- and polyfluoroalkyl substances (PFAS) are a group of human-made chemicals that are persistent in the environment. An ongoing USGS effort in cooperation with the New Mexico Environment Department to characterize the statewide distribution of PFAS in New Mexico began in 2020 and includes both surface water and groundwater sampling. During annual sampling between 2020 and 2024, PFAS were found in all major rivers of New Mexico (Rio Grande, Pecos, San Juan, Animas, Canadian, Gila, Rio Chama, and Rio Puerco), with concentrations generally increasing downstream. Surface water samples included detections of the following 13 out of 28 analyzed PFAS: perfluorobutanoate (PFBA), perfluoropentanoate (PFPeA), perfluorohexanoate (PFHxA), perfluoroheptanoate (PFHpA), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorodecanoate (PFDA), perfluorobutane sulfonate (PFBS), perfluoropentane sulfonate (PFPeS), perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), perfluorooctane sulfonamide (PFOSA), and 6:2 fluorotelomer sulfonate (6:2 FTS). Of the 165 surface water samples, PFAS were detected in 139 samples. PFAS in water of the Rio Grande increased by an order of magnitude from 4 to 46 ng/L as it flows through the Albuquerque urban area. Increased variability in concentration and PFAS composition was observed during monsoon season, when short-term high-intensity precipitation events flush runoff from the arid urban environment of Albuquerque to the Rio Grande in short duration pulses. The data suggest urban runoff and wastewater treatment plant effluent are sources, but more information regarding temporal and spatial variability within an arid urban environment is needed to characterize PFAS contributions from these sources.

PFAS was also detected in groundwater in New Mexico, though generally at a lower proportion of sites compared to surface water detections. For the 162 groundwater samples collected from 141 sites between 2020 and 2021, PFAS were detected in 27 sites. Of the 172 groundwater samples collected from unique sites between 2023 and 2024, PFAS were detected in 31 sites. Groundwater samples included detections of 16 of 28 analyzed PFAS including: PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFBS, perfluoroheptane sulfonate (PFHpS), PFPeS, PFHxS, PFOS, PFOSA, 4:2 fluorotelomer sulfonate (4:2 FTS), 6:2 FTS, and 8:2 fluorotelomer sulfonate (8:2 FTS). The majority of groundwater sites with PFAS detections were repeatable in subsequent sampling events, and only seven sites had sporadic PFAS detections. The results provide valuable information on the presence of PFAS in ground and surface waters of New Mexico and document an increase of PFAS concentrations in the Rio Grande as it flows through Albuquerque, an arid urban environment.