Per- and polyfluoroalkyl substances in water and soil in wastewater-irrigated farmland in Jordan

摘要

The Zarqa river (ZR) in Jordan receives >300,000 m³ day ~-1 of wastewater effluent from Assamra wastewater treatment plant (WWTP) and is a major source of irrigation water for vegetable crops and fodder downstream. ZR water quality is therefore highly important and directly influences crop and soil quality in irrigated fields. This study investigated the occurrence and concentration of 20 per- and polyfluoroalkyl substances (PFASs) in Assamra wastewater, ZR water, soils and crop plants (alfalfa (Medicago sativa), mint (Mentha spicata) and lettuce (Lactuca sativa)) along the ZR flow path between Assamra WWTP and Jerash spring. The combined PFAS concentration (∑ PFASs) in Assamra WWTP effluent (14-24 ng L~-1) was comparable to that in influent (10-15 ng L~-1), indicating poor removal of PFASs. The dominant PFAS in influent was perfluorodecanoate (PFDA), while perfluorooctanoate (PFOA) and perfluoropentanoate (PFPeA) dominated in effluent. ∑ PFASs in an unaffected upstream tributary (Sukhna station) was 4.7-5.4 ng L~-1. Farther downstream. ZR water contained 16-27 ng L_-1, with PFPeA, PFOA and PFDA dominating, and these levels did not change along the flow path to Jerash spring. PFASs in soil was generally low, 340 ± 150 pg g~' dry weight (dw) in alfalfa soil (mainly PFOA and PFDA) and 710 ± 420 pg g~-1 dw in mint soil and 970 ± 800 pg g~-1 dw in lettuce soil (mainly linear perfiuorooctane sulfonate (L-PFOS) in both cases). Soil-water partitioning coefficient (K_d) was generally low in all soils (range 24-62 L kg~-1, 20-46 L kg~-1 and 28 L kg~-1 for PFOA, PFDA and L-PFHxS, respectively). No PFASs were detected in alfalfa and mint plants. Overall, this investigation demonstrated that PFAS contamination in wastewater, surface water and soil in the ZR basin is very low in a global comparison, and that there is no accumulation of PFASs in the food and feed crops studied.