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Herbicide residues in surface waters pose a potential hazard to aquatic ecosystems. Moreover, there is a scarcity of data regarding the occurrence of herbicide residues in lakes predominantly surrounded by non-agricultural land. This study aimed to monitor and assess seasonal variations in four commonly used herbicides (i.e., acetochlor, pretilachlor, butachlor, and atrazine) in the surface waters of the Hulun Lake Basin in China. The results indicated that the target herbicides were widely distributed throughout the study area. The residues of the four herbicides in surface water ranged from non-detectable levels to 1,978.60 ng L−1. Among the herbicides, atrazine had the highest detection rate (90.48 %). When considering the temporal factor, the median concentration of the selected herbicides in the lake was significantly higher during summer (102.68 ng L−1) than that during spring (97.59 ng L−1) and autumn (6.78 ng L−1). Furthermore, there were spatial variations in the surface waters of the Hulun Lake Basin. The residual levels in the lake exceeded those found in the inlet river, and the concentrations of herbicides in the estuary of the Kerulen River and central area of Hulun Lake were higher. The environmental risk assessment results indicated that the selected herbicides posed acceptable risks to fish in the aquatic environment of Hulun Lake. However, the risk quotient (RQ) values for acetochlor and atrazine in relation to algae exceeded 0.10. Similarly, the RQ values for butachlor in relation to algae and crustaceans exceeded 0.10 during the summer and autumn seasons and even surpassed 1.00 in certain samples. This can potentially endanger the survival of aquatic organisms. The findings of this study offer valuable insights to support efforts in pollution control, environmental safety assessments, and decision-making regarding water resource management in the Hulun Lake Basin. |
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