Adsorption and Degradation Behavior of Guvermectin in Four Soils of China

Guvermectin is a nucleoside metabolite produced by the fermentation of Streptomyces hygroscopicus. It shows antibacterial and antitumor activities and has often been used as a plant growth regulator to promote the growth of crops. In this paper, the adsorption and degradation behavior of guvermectin in soil was investigated to evaluate its environmental safety. The adsorption of guvermectin in soil was consistent with the Freundlich isotherm model, and Freundlich adsorption coefficients (KF-ads) obtained from the model were low. The soil organic matter content was significantly and positively correlated with KF-ads. The effects of surfactant, humic acid, and biochar on the adsorption of guvermectin were studied using Jilin soil. The amount of guvermectin sorbed by the soil decreased with the addition of surfactant. By contrast, the amount adsorbed gradually increased as the amount of humic acid increased. Soil adsorption test with biochar revealed that biochar can efficiently sorb guvermectin. The half-life (t0.5) of guvermectin in soil under aerobic degradation and standing water anaerobic degradation conditions ranged from 2.84 to 7.29 days and from 8.21 to 13.70 days, respectively. The adsorption and degradation tests of guvermectin in soil revealed that pollution by guvermectin is not a major risk to soil because it is not easily adsorbed, it is highly mobile, and it can be easily degraded.