Characteristics of regionalized distribution of antibiotics and ARGs in Daliao River-Liaodong Bay waters and their environmental impact factors.

This paper takes the water body of Daliao River-Liaodong Bay as the research object, divides it into three regions: river, estuary, and offshore, and analyzes the changes of antibiotics and antibiotic resistance genes (ARGs) from inland rivers to the sea and the environmental impact factors from this perspective. The results showed that in general, the pollution of antibiotics and ARGs in Daliao River-Liaodong Bay belonged to the medium-low level, and levels of antibiotics and ARGs were nd-106.23 ng/L and nd-1.95 × 108 copies/L, respectively. The concentrations and types of antibiotics and ARGs decreased from inland to sea regions. Analysis of the distributional characteristics of antibiotics and ARGs from a regionalized perspective revealed significant differences among the three regions in sulfonamide antibiotics, tetracycline antibiotics, and dominant ARGs. Sulfonamide antibiotic levels were significantly higher in the estuarine zone than in the riverine and offshore zones; tetracycline antibiotic levels were significantly higher in the riverine and estuarine zones than in the offshore zone. Aminoglycosides were dominant in the riverine and estuarine zones, and macrolides were dominant in the offshore zone. We characterized the effects of environmental factors on the assignment of antibiotics and ARGs and found that overall temperature contributed the most to variation in antibiotics and ARGs; the contribution of dissolved oxygen was the lowest. The estuarine zone was most affected by these factors, followed by the offshore zone and finally the riverine zone.