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.

In line with the Sustainable Development Goals, a comprehensive understanding and precise quantification of the temporal and spatial characteristics of water quality is essential to identify sources of pollution in basins and to protect river headwaters to maintain water safety throughout basins. However, there is a lack of systematic quantitative tracking of seasonal river pollution sources in hilly areas in southwest China. In this study, the spatial and temporal characteristics of the water environmental factors in the Yaoshi River basin, the causes of pollution, and the main sources of nitrogen pollution were systematically investigated using geographic information systems and statistics. The results showed that the main pollutants in the river as a whole included five-day biological oxygen demand (BOD₅), oxygen demand (COD), ammonium (NH₄⁺), total phosphorus (TP), and total nitrogen (TN). Nitrogen pollution was the most serious, and various environmental factors caused seasonal variations and different spatial distributions in this pollutant. Temporally, the TP and COD concentrations were highest during the wet season, while the NH₄⁺, TN, and BOD₅ concentrations were highest during the dry season. Spatially, BOD₅, COD, and TP concentrations were ranked upstream < downstream < midstream, while TN and NH₄⁺ concentrations were ranked downstream < midstream < upstream. The main sources of pollution in the study area were domestic activities (34.94%), agricultural activities (40.12%), and mixed organic and natural sources (24.94%). Notably, manure effluent dominates nitrate nitrogen sources, while fertilizer inputs minimally contribute during mean-flow and dry seasons, and atmospheric deposition contributes during the wet season. These findings provide important data for improving water quality in the Yaosi River Basin, promoting sustainable agricultural practices, alleviating water scarcity, and advancing the region’s Sustainable Development Goals. In addition, this study can provide reference for the development of sustainable development management strategies for seasonal rivers in other hilly areas and promote broader environmental sustainability efforts.