Sources identification of antibiotic pollution combining land use information and multivariate statistics.

To quantify the extent of antibiotic contamination and to identity the dominant pollutant sources in the Tiaoxi River Watershed, surface water samples were collected at eight locations and analyzed for four tetracyclines and three sulfonamides using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The observed maximum concentrations of tetracycline (623 ng L(-1)), oxytetracycline (19,810 ng L(-1)), and sulfamethoxazole (112 ng L(-1)) exceeded their corresponding Predicted No Effect Concentration (PNEC) values. In particular, high concentrations of antibiotics were observed in wet summer with heavy rainfall. The maximum concentrations of antibiotics appeared in the vicinity of intensive aquaculture areas. High-resolution land use data were used for identifying diffuse source of antibiotic pollution in the watershed. Significant correlations between tetracycline and developed (r = 0.93), tetracycline and barren (r = 0.87), oxytetracycline and barren (r = 0.82), and sulfadiazine and agricultural facilities (r = 0.71) were observed. In addition, the density of aquaculture significantly correlated with doxycycline (r = 0.74) and oxytetracycline (r = 0.76), while the density of livestock significantly correlated with sulfadiazine (r = 0.71). Principle Component Analysis (PCA) indicated that doxycycline, tetracycline, oxytetracycline, and sulfamethoxazole were from aquaculture and domestic sources, whereas sulfadiazine and sulfamethazine were from livestock wastewater. Flood or drainage from aquaculture ponds was identified as a major source of antibiotics in the Tiaoxi watershed. A hot-spot map was created based on results of land use analysis and multi-variable statistics, which provided an effective management tool of sources identification in watersheds with multiple diffuse sources of antibiotic pollution.