Seasonal dynamics, sources, and ecological risk of estrogens in a freeze-thaw basin: Implications for aquatic ecosystems

Estrogens have attracted extensive attention because of their harmful effects on organisms such as endocrine disturbance and reproductive toxicity. This study investigated the spatial and temporal distribution and ecological risk assessment of 7 targeted estrogens in surface water in a seasonal freeze-thaw basin. It mainly includes three natural estrogens, estrone (E1), 17β-estradiol (E2) and estriol (E3), two synthetic estrogens, 17α-ethinylestradiol (EE2) and diethylstilbestrol (DES), and two phenolic environmental estrogens, bisphenol-A (BPA) and nonylphenol (NP). The total estrogen concentration was 15.30-489.62 ng·L^-1. BPA, NP, DES and E3 were the major estrogenic pollutants in the basin. The targeted estrogens showed significant seasonal differences in the freeze-thaw process, and the total concentration was from high to low in wet, thawing and freezing seasons. Principal sources of estrogens primarily originated from mixed discharge of livestock and domestic sewage and landfill leachate. Increased runoff promoted pollution sources into rivers, increasing the concentration during wet and thawing seasons, and the latter posed a higher ecological risk to aquatic organisms that would be in the breeding season. Targeted estrogens posed a high total ecological risk to fish and a moderate ecological risk to algae and crustaceans. The total estradiol equivalent concentrations (EEQ_T) of targeted estrogens in all seasons exceeded the safe concentration threshold. Therefore, it is suggested to strengthen the monitoring frequency of estrogens in different seasons and adopt strict sewage treatment measures and discharge monitoring to reduce the harm to the ecological environment.