Comprehensive insights into the occurrence, distribution, risk assessment and indicator screening of antibiotics in a large drinking reservoir system.

Drinking water reservoir is threatened globally due to anthropogenic contamination and thus in need of more attention. Here, we comprehensively investigated the occurrence, distribution and risk assessment of representative antibiotics in a large drinking water reservoir (Fengshuba Reservoir, China). The total concentrations of antibiotics in the water phase, porewater phase, sediment phase and soil phase (drawdown area) were in the ranges of 195-569 ng/L, 47.1-333 ng/L, 114-272 μg/kg and 2.84-77.2 μg/kg, respectively. The dominant antibiotic was CIP in both the water and porewater phases, while it was OTC in the sediment phase. For the water phase, seasonal factor consisting hydrologic condition and pattern of antibiotic use could influence the occurrence level and environmental fate of antibiotics. In contrast, exogenous particles derived from the soils that had used manures during the spring planting season coupled with heavy rainfall was responsible for the occurrence level and composition of antibiotics in the sediment phase. Moreover, Chl-α, NO3-, TP and EC were the most dominant factor influencing the antibiotic distributions in the water phase, porewater phase, sediment phase and soil phase, respectively. Pseudo-partitioning coefficients indicated that PENV and PENG might accumulate more easily into the sediments from the aqueous phase compared with other antibiotics. Risk assessments suggested that TC might pose high risks to the aquatic ecosystem, but the antibiotics presented no risk to the health of consumers. Generally, TC could be used as a promising indicator for evaluating the occurrence and potential risk of antibiotics in Fengshuba Reservoir.