Ecological Risk Assessment of Tetracycline Antibiotics in Livestock Manure and Vegetable Soil of Chongqing

Abstract

The residue of new organic pollutant antibiotics in the environment and their risks to the ecological environment have become important research issues at home and abroad. China is the largest country of antibiotic production and antibiotic use. Tetracycline antibiotics (TCs) have been used in large quantities, and they also have the highest residue in animal manure. Tetracycline antibiotics in animal manure are easily accumulated in the soil, and disturb the soil microbial community; furthermore, they are absorbed by crops and remain in agricultural products, thereby threatening human health and ecological security. At present, the pollution of antibiotics in animal manure and soil of southwest China has not been reported. An investigation and analysis were conducted to evaluate the environmental ecological risks of three agricultural tetracycline antibiotics [oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC)] in livestock manure of large farms and soil of main vegetable base in chongqing. The results showed that the average contents of OTC, TC, CTC, and TCs ∑TCs in pig and chicken manure in 2014 was 13.05, 91.81, 62.48, 167.34 mg ·kg-1, and 4.25, 4.60, 28.55, 37.40 mg ·kg-1, respectively. The average contents of OTC,TC,CTC, and ∑TCs in pig and chicken manure in 2019 were 3.39, 4.82, 5.92, 15.95 mg ·kg-1, and 1.10, 1.35, 4.22, 5.16 mg ·kg-1, respectively. The content of TCs in livestock and poultry manure of Chongqing in 2019 decreased significantly as compared to that in 2014. The ecological risk of TCs in chicken manure was lower than that in pig manure, and the ecological risk of TCs in livestock manure in 2019 was significantly lower than that in 2014. Moreover, the risk quotient was in the order of CTC > OTC > TC. The average contents of OTC,TC,CTC, and ∑TCs in the soil of the main vegetable bases and surrounding areas in Chongqing were 18.92, 39.10, 21.80, and 79.81 μg ·kg-1, respectively. The content of TCs was in the order of vegetable field near the farm > pollution-free vegetable base > common vegetable field. In the vegetable field near the farm, the content of TCs in open vegetable field was generally higher than that in greenhouse field. In contrast, in the pollution-free vegetable base, the content of TCs in the greenhouse field was higher than that in the pen field. The ecological risk quotients (HQ values) of TCs in the vegetable field were lower than 1 under various planting modes. The HQ values of the three TCs were in the order of CTC > OTC > TC. The content of ∑TCs in soil was in the order of leaves > melons > solanoids > legumes. The difference in contents of soil TCs was found in different vegetable fields with different vegetable types, and it may be related to the different vegetable cultivation patterns, type, and amount of livestock manure.