Distribution, residue level, sources, and phase partition of antibiotics in surface sediments from the inland river: a case study of the Xiangjiang River, south-central China.

In view of the increasing attention on antibiotic contamination and their scarce data in the inland river (especially for the sediment), the occurrence of 28 antibiotics in sediments from the Xiangjiang River was comprehensively analyzed, and 22 antibiotics were detected with a total concentration ranging from 4.07 to 2090 ng g-1. The residue was almost at a moderate or higher level in the aquatic environment around the world. Fluoroquinolones and tetracyclines were the dominant detected antibiotics, and the maximum total concentration could reach to 2085 ng g-1, though that in surface water was just 33.4 ng L-1. Oxytetracycline and chlortetracycline could be detected with high concentration in areas with lower population density. Usage profile of each antibiotic may be responsible for the spatial variation. Principal component analysis-multiple linear regression model indicated that direct discharge of domestic wastewater and livestock or aquaculture sewage could contribute 94.2% of the pollution. Redundancy analysis was used to screen out the environment variables, which were closely related to the pseudo-partitioning coefficients (Kd) of antibiotics in sediment and surface water for the first time, and showed that the Kd was correlated with sediment pH negatively and organic carbon, total phosphorus, and conductivity of the sediments positively. High sedimentary organic carbon was considered to promote the higher Kd in this river. This study would deepen the understanding of the occurrence of antibiotics in sediments from the inland rivers and provide scientific support for controlling the antibiotic contamination.