Occurrence and risk assessment of tetracycline antibiotics in soils and vegetables from vegetable fields in Pearl River Delta, South China

Antibiotic pollution in vegetable fields is widely concerned, yet the residual levels and distribution of antibiotics in China are still obscure. This study investigated the occurrence of tetracycline antibiotics (TCs) in soils and vegetables collected from multiple vegetable fields in Pearl River Delta, South China. Factors influencing the distribution of TCs as well as their health and ecological risks were evaluated. Three TCs including tetracycline, oxytetracycline, and chlortetracycline were detected in 44 soil and 42 vegetable samples by high performance liquid chromatography tandem mass spectrometer. Results showed that 85% soil samples had three TCs, with an average concentration of 78.05 μg/kg and oxytetracycline being the major type. The concentration of TCs in 5.3% of soil samples exceeded the ecotoxic effect trigger value (100 μg/kg). Manure application was the main source of TCs in soil (r = 0.735), whereas the concentration of TCs in soil had insignificant correlation with most soil physicochemical properties (P ˃ 0.05) except for Cu2+ concentration. All vegetables showed uptake of TCs from soil, with a total vegetable detection rate of 36% for oxytetracycline and chlortetracycline and an average concentration of 0.39 μg/kg; whereas tetracycline was below detection limit. Health risk assessment suggested that the maximum human consumption amount of TCs (2.50 μg/d) was well below the acceptable daily intake values (1800 μg/d). Ecological risk assessment based on the Species Sensitivity Distribution method indicated that most vegetable fields in the Pearl River Delta had low risk (i.e., risk quotient < 0.1) of soil pollution with TCs.