Perfluoroalkyl substances (PFAS) in surface water and sediments from two urban watersheds in Nevada, USA

Abstract

This study measured 17 perfluoroalkyl substances (PFAS) in surface water and sediments collected from six locations along the Las Vegas Wash and Lake Mead and eight locations along the Truckee River, Lake Tahoe, and Pyramid Lake in Nevada, United States. Of the 17 PFAS analyzed, 12 were detected in the surface water (n = 18) and 14 were detected in the sediments (n = 21) of the two watersheds. The total concentration of PFAS in the Truckee River water was 441.7 ng/L and the PFAS detected in the Las Vegas Wash water was 2234.3 ng/L. The predominant PFAS species found in the water were perfluorohexanoic acid (PFHxA) (1.5-187.0 ng/L), followed by perfluoropentanoic acid (PFPeA) (below detection limit [BDL] to 169.9 ng/L), perfluorooctanoic acid (PFOA) (BDL to 65.5 ng/L), and perfluorobutane sulfonic acid (PFBS) (BDL to 44.7 ng/L). The total PFAS in the sediments was 272.9 μg/kg (dry weight) for the Truckee River and 345.7 μg/kg for the Las Vegas Wash. The predominant species in the sediments were perfluorodecane sulfonic acid (PFDS) (BDL to 88.2 μg/kg), PFHxA (BDL to 20.3 μg/kg), PFBS (BDL to 29.1 μg/Kg), and perfluoroundecanoic acid (PFUA) (BDL to 22.9 μg/kg). The results demonstrated that short-chain PFAS (C ≤ 8) were more prevalent in water, whereas long-chain PFAS (C > 8) were more detectable in sediments. The Las Vegas Wash water had much higher PFAS levels compared with the Truckee River water. The PFAS concentrations and detection frequencies also significantly decreased in summer compared with winter along the Las Vegas Wash.

Keywords: PFAS; Perfluoroalkyl carboxylic acid; Perfluoroalkyl substances; Perfluoroalkyl sulfonic acid; Urban watershed.