A nationwide probabilistic risk assessment and a new insight into source-specific risk apportionment of antibiotics in eight typical river basins in China: Human health risk and ecological risk.

China is the largest producer and consumer of antibiotics, a nationwide study on the contamination of antibiotics in China is urgently needed, and source apportionment towards risks associated with antibiotics is now attracting increasing attention. In this study, based on eight antibiotics at 666 sampling sites, spatial variations and probabilistic risks (human health and ecological risk) of antibiotics in eight river basins in China were analyzed. Source-specific health and ecological risk associated with antibiotics in a typical basin was apportioned quantitatively. Results showed that mean antibiotic concentration in Haihe River Basin (HaiRB) and Yellow River Basin (178.25 and 257.36 ng·L, respectively) was higher than other basins. In HaiRB, the contribution of livestock and poultry breeding (31.89 %) was the largest of all sources for health risk, whereas pharmaceutical wastewater (35.97 %) was the most dominant source for ecological risk. To determine the most important source for risks associated with antibiotics, the concept of risks-targeted key source was proposed, and a risks-targeted key source apportionment model was developed. Results showed that pharmaceutical wastewater should be prior controlled among all sources. The concept and apportionment model of risks-targeted key source proposed in this study are applicable and referential for related studies.