Influence of organic fertilizer on degradation of oxytetracycline in soil in greenhouse experiment

Abstract: Antibiotics in soil were known for its adverse effect on the growth and development of plants and potential risk to the health of animals and human through the food chain.Therefore, efficient methods to control and remediate the pollution of antibiotics in soil are urgently needed. . Organic fertilizer which could change the basic soil physicochemical properties and microbial activities which may have an effect on the degradation of antibiotics in soil. In the present study, the effect of organic fertilizer on the degradation of oxytetracycline was explored. The experiment follow an orthogonal experiment design, consisting of three different soils, were spiked three concentrations (43.62μg?kg-1, 1638.78μg?kg-1, and 10936.38μg?kg-1) of oxytetracycline and two levels (5% and 10%) of organic fertilizer. After mixing thoroughly, 5 kg of soils for each? replicates or treatments was incubated under optimal temperature and light conditions. The moisture of soil were adjusted weekly?Samples were collected at 0, 7, 14, 21, 28, 35, and 42 days after the setting up of the experiment. The concentration of oxytetracycline in soil measured by UPLC-MS/MS and the degradation dynamics the half-life values (DT50) was calculated according to the Pseudo-first-order kinetics model. and . Results showed that the degradation of oxytetracycline kept a stable period after 28 days for both high and low concentration groups. In the soil spiked with low concentration of oxytetracycline, application of 5% and 10% organic fertilizer increased 17.71% and 16.03% of degradation rate, consequently the half-life was reduced by 9.02 days and 9.50 days, respectively. In the soil spiked with high concentration of oxytetracycline, the degradation rate was increased to 19.83% and 17.93% when applied 5% and 10% organic fertilizer to soil, and the half-life was reduced by 12.28 days and 13.38 days, respectively. Pearson Correlation Analysis was performed on soil properties and on oxytetracycline degradation dynamics. Results revealed a highly positive correlation between levels of organic fertilizer and soil organic matter, total nitrogen, and pH values. A certain positive correlation was also observed between levels of organic fertilizer and the degradation rate of oxytetracycline. Comparing to the control soil, the application of organic fertilizer accelerated the degradation of oxytetracycline. Such effect was enhanced as the initial concentration of oxytetracycline in soil increased. However, different levels of organic fertilizer have no significant effects on the degradation of oxytetracycline.