[Spatiotemporal Distribution， Source Apportionment， and Influencing Factors of Antibiotics in Typical Rivers Receiving Reclaimed Water]

Abstract

The reuse of reclaimed water causes a large number of toxic and harmful substances （e.g.， antibiotics） to enter the rivers receiving the reclaimed water. However， study of the occurrence， sources， and influencing factors of antibiotics in the water and sediment of receiving rivers remains limited. In consideration of this fact， the Fuhe River Basin was selected as the study area， and 15 water and sediment samples were collected in the non-flood season （May） and flood season （August） of 2023， respectively. Ultra-high performance liquid chromatography-mass spectrometry （HPLC-MS/MS） was used to analyze the spatiotemporal distribution of 38 antibiotics in the water and sediment samples. In addition， the Unmix model was applied to analyze the sources of antibiotics. Spearman correlation analysis and multiple regression models were used to identify the main factors that influence the sources of antibiotics in the river. The results were as follows： ① Among the target antibiotics， 27 and 19 antibiotics were detected in water （ND-165.5 ng·L^-1） and sediment （ND-31.5 ng·g^-1）， respectively. ② The spatial distribution of the antibiotics concentration in water was in the order Xinjinxian River > Huanghuagou River > the main stream > Huandi River > Yimuquan River. In sediments， the antibiotics content ranking was Huanghuagou River > Yimuquan River > the main stream > Huandi River > Xinjinxian River in May and Yimuquan River > the main stream > Xinjinxian River > Huandi River > Huanghuagou River in August. ③ In May， aquaculture and livestock activities was the major source of antibiotics in both water （36.3%） and sediment （67.0%）； in August， surface runoff was the major source in water （49.3%）， while wastewater treatment plants were the major source for sediment （40.2%）. ④ The main influencing factors for the source of medical wastewater in the water were urban population and gross regional product， the main influencing factor for the source of sewage treatment plants in the water was permanent resident population， and the main influencing factor for the source of sewage treatment plants in the sediment was NO₃^--N. This study quantitatively analyzed the sources of antibiotics in receiving rivers and identified their main influencing factors， which provides theoretical and data support for precise control of antibiotics in the receiving rivers.

Keywords: Unmix model; antibiotics; reclaimed water; socioeconomic factors; source apportionment; urban rivers.