Environmental Behavior And Eco-toxicity Of Tetracycline Antibiotics In Soils

Batch sorption methods and indoor simulation methods were employed to reveal adsorption, desorption and degradation process of antibiotic tetracyclines in two tested soils (cinnamon soil and red soil). The effects of antibiotic tetracyclines on the eco-toxicity of wheat in two medium (water and soil) was also investigated. The results were as follows:Adsorption dynamic of tetracycline in two soils. Under different condition, the absorption of tetracycline in soil can reach stable equilibrium after 24h. With the decreasing of soil-to-solution ratio and the removal of soil organic matter, absorption rate of tetracycline in two kinds of soil was speeded up. Elovich equation and Exponent equation can better simulate the relationship tetracycline adsorption in the soil and time.Adsorption and desorption of antibiotic tetracyclines in two soils. Tetracycline and oxytetracycline were both strongly absorbed in soils. In this study, more than 80.00% antibiotic tetracyclines added in the solution were absorbed by soils under all condition. And the absorption of soils on tetracycline was stronger than oxytetracycline. Freundlich equation was better non-linear fitting to the antibiotics adsorption isotherm in soils. As the removal of soil organic matter and soil oxides, the absorption capacity of Soil on such antibiotics declined. Under Ca2+,K+,Na + medium, the adsorption of antibiotics in the soil was the weakest in Ca2+ medium. With the increasing of the soil-to-solution ratio, soil absorption capacity and absorption intensity of antibiotics decreased. When pH is above 5.5, soil absorption of tetracycline decreased with the increasing of pH in the final soil solution.Hysteresis index (HI) of desorption of anyibiotic in cinnamon soil was higher than in red soil, and HI of oxytetracycline was higher than tetracycline in same soil. Removal of soil organic matter is basically able to increase HI of desorption of such antibiotics in the soil. Under Ca2+,K+,Na + medium, HI of tetracycline in Ca2+ medium and oxytetracycline in K+ medium were higher than other condition. There was obvious effect of temperature on the absorption of antibiotics in soil. The adsorption of antibiotic tetracyclines in the soils mainly was physical adsorption.The degradation of antibiotic tetracyclines in two soils. The degradation of tetracycline and oxytetracycline in soils gradually slowed with the increasing of time. According to the half-life of antibiotic, tetracycline was easier to degrade and oxytetracycline was middle-easier to degrade. The degradation of tetracycline in cinnamon soil was faster than in red soil, and oxytetracycline was on the contrary. Removal of soil organic matter can decreased the degradation of tetracycline and oxytetracycline in soils. The effect of soil organic matter on tetracycline degradation was stronger than oxytetracycline. Indigenous soil microorganisms can not affect the antibiotics degradation in soil.The eco-toxicity of tetracycline antibiotics to wheat. The inhibition rate of root elongation was the most appropriate eco-toxicity index in following three parameters including seed germinating, root elongation and shoot elongation. Soil on tetracycline antibiotics pollution has an important buffer. Soil buffer on oxytetracycline was stronger than on tetracycline. In different medium, there was a significant logarithmic relationship between the concentration of antibiotics and the inhibition rates of root elongation (or inhibition rates of shoot elongation) of wheat. IC10 of tetracycline and oxytetracycline in water was 25.88mg/kg and 24.22mg/kg, respectively, however, their IC10 values were increased largely in soil with 377.8mg/kg and 717.6mg/kg, respectively. Aboved results showed that medium can strongly affect IC10 values.