Manipulation of freshwater food web through species introduction has been used to control the increasing algae in the Wuliangsuhai Lake, which affects not only the pathways of carbon source and energy transfer, but also the transfer of contaminants through food web. Food web relationships between biomanipulation area (BMA) and non-biological manipulation area (NBMA) were investigated using stable carbon (δ13C) and nitrogen (δ15N) isotope analysis. In BMA, the δ13C values in fish species were enriched while δ15N depleted due to the increased inter-species competition. Among the same fish species between BMA and NBMA, lower trophic levels were observed in BMA. Concentrations of target PFASs (ΣPFAS) in fish from BMA were significantly (p < 0.05) lower than those from NBMA. Whilst elevated trophic magnification factors (TMFs) of PFASs, especially for perfluoroalkyl carboxylic acids (PFCAs) with long carbon chain length (C9-10), perfluorooctane sulfonate (PFOS), and 6:2 chlorinated polyfluorinated ether sulfonate (F-53B) were exhibited in BMA. We found that biomanipulation through species introduction played an important role in control over lake eutrophication and trophic transfer patterns of PFASs in biota from the altered aquatic ecosystem.
Polyfluoroalkyl substances (PFASs) enter the environment through multi-media diffusion and long-distance migration during the long-term manufacture and use of products containing PFASs. This study analyzed 17 PFASs in surface water samples collected from the Wuliangsuhai watershed in the wet and dry seasons, and investigated the temporal and spatial distribution characteristics, potential sources, and ecological risks of PFASs in the study area. PFASs were detected in all surface water samples at concentrations ranging from 4.00 to 263.45 ng·L-1. The spatial distribution of PFASs was affected by local human activities and showed two main types of characteristics. The first type was associated with Yellow River and canal water, which had relatively low concentrations of PFASs and was dominated by perfluorobutanoic acid (PFBA). The second type was associated with drain and lake water receiving industrial, agricultural, and domestic wastewater from the Hetao irrigation area, which had relatively high levels of PFASs and was dominated by perfluorooctanoic acid (PFOA). The PFAS concentrations in water samples collected during the dry season were higher than those collected in the wet season, being affected by the increased production of short-chain PFASs and seasonal changes in the amount of water from the Yellow River. The results of PFOS/PFOA, PFOA/PFNA, and PFHpA/PFOA indicated that the PFASs in the study area originate from atmospheric deposition and point source pollution. The risk assessment results showed that the current risk level from PFOA and PFOS in the study area is relatively low but their long-term cumulative effects cannot be ignored due to the cumulative characteristics and long-distance migration ability of PFASs.
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