Overall Evaluation of Antibiotics Occurrence from Large-Scale Livestock Farms in Sichuan Basin, China: Spatial Distribution, Source Apportionment, and Risk Assessment.

The widespread application of antibiotics in intensive livestock production is increasingly contributing to antibiotic contamination, and their potential ecological risk to environmental media by resourceful utilization of livestock manure as fertilizers in China has been recognized. This study conducted a comprehensive investigation on 79 large-scale livestock farms and collected 86 livestock excrements and 20 soil and 20 surface water samples distributed in Sichuan Basin, where no similar studies were carried out before. In total, four tetracyclines (TCs), eight sulfonamides (SAs), and eight fluoroquinolones (QNs) were monitored by liquid chromatography-triple quadrupole mass spectrometry. The findings revealed that antibiotics occurrence varied remarkably in excrement (feces or manure) among different livestock farms and different livestock species, following the descending order as QNs > TCs > SAs of detection rates and as TCs > QNs > SAs of detected concentrations, respectively. By source apportionment, livestock manure was demonstrated as a possible source for TCs and QNs detected in soil, while the detection of antibiotics in surface water was probably related to other sources. The central, south, and southwest of Sichuan Basin displayed a higher contamination of antibiotics from livestock manure. The ecological risk of antibiotics was obtained from a medium to heavy level, particularly TCs from swine farms to green algae, water flea, and inflated duckweed in aquatic water and QNs from all livestock farms to sensitive organisms in soil. Overall, the prioritized resource utilization of livestock manure would probably increase the contamination level and ecological risk to environment; hence, rational and effective measurement was highly recommended for antibiotics prevention in some regions of Sichuan Basin.