Distribution characteristics and risk assessment of antibiotics in soil and crops near pig farms in karst mountainous areas of Guizhou, China

This study selected three typical mountain pig farms in Bozhou District, Zunyi City, Guizhou Province. The residual concentrations of 44 antibiotics (including SAs, FQs, TCs, and MLs) in the surrounding soil and crops were measured using high-performance liquid chromatography-tandem mass spectrometry. Ecological and health risk assessment were carried out using the risk quotient (RQ) method and the acceptable daily intake hazard quotient (ADI-HQ) method. The results showed that a total of 15 antibiotics were detected in the soil, and the total residual concentrations (μg/kg) ranked as follows: TCs (3183.72) >FQs (970.61) >MLs (365.34) >SAs (65.28). A total of 18 antibiotics were detected in crops, with total residual concentrations (μg/kg) in the order of FQs (345.88) >SAs (133.96) >TCs (55.84) >MLs (1.83). Antibiotics in the soil exhibited a significant ‘distance decay’ trend, with the highest pollution levels and ecological risks observed in the near area (0–50 m). TCs dominated the soil but were rarely detected in crops, whereas SAs had the lowest residues in soil but were significantly enriched in crops such as chilli pepper (overall enrichment coefficient: 1.91). The ecological risk assessment results showed that soil antibiotics generally posed a high risk (total RQ range: 41.54–1276.86), with the risk ranking as TCs > SAs > FQs >MLs. The health risk assessment indicated that only Orbifloxacin was classified as moderate risk, while the overall acute health risk from ingesting other antibiotics through crops was relatively low. This study demonstrates that tetracycline antibiotics are the main pollutants in the soil around pig farms in karst mountainous areas and pose significant ecological risks. Although the health risks of antibiotics in crops are generally low, it is necessary to strengthen the control of antibiotic pollution in the soil surrounding farms and to enhance the supervision of veterinary drug use.