Distribution characteristics and ecological risk assessment of selected antibiotics in Moon Lake, Ningbo City

Abstract

The main objective of this study is focused on distribution characteristics, ecological risk assessment of selected antibiotics in the typical urban Moon Lake, which is situated in the center of Ningbo City. Water samples were concentrated by solid-phase extraction and determined by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The environmental quotients posed by the selected antibiotics were assessed by using the methods of ecological risk quotients (RQ) and mixture risk quotients (MRQ). Composition analysis indicated that human-derived drugs significantly contributed to the total contamination of antibiotics in the lake. The ampicillin (AMS) was detected the highest concentration in the antibiotics and the range of concentration was ND to 382.0 ng/L. The maximum concentrations of cephalexin (LEX) and norfloxacin (NOR) were 283.0 ng/L and 267.0 ng/L, respectively, which were relatively lower than AMS concentration levels. The detected concentration range of sulfamonomethoxine (SMM), lincomycin (LIN), azithromycin (AZM), sulfathiazole (STZ), sulfamethoxazole (SMX), tylosintartrate (TYL) and sulfadiazine (SDZ) were ND-219.0 ng/L, 31.50-209.0 ng/L, ND-147.0 ng/L, 7.34-109.0 ng/L, ND-104.0 ng/L, ND-80.50 ng/L and 20.40-57.30 ng/L, respectively. In comparison, the maximum concentration of most antibiotics in our investigated area were higher than natural lakes. The results of ecological risk assessment showed that the RQ values of LIN, TYL, SMX, NOR and AMS were higher than 1. That means these antibiotics have high ecological risks and the remaining five antibiotics are at low or intermediate ecological risk. However, the calculated MRQ value for each sampling site was obviously higher than those from individual antibiotics, which suggested antibiotic mixtures could cause a higher detrimental effect to environment than individual antibiotic. This study will provide a scientific basis and foundation for the further study on the ecological risk of antibiotics in urban lakes.