Quantitative Assessment of Degradation Degree of Metalaxyl in Soil and Plant by Compound-Specific Isotope Analysis

Compound-Specific Isotope Analysis (CSIA) is employed to investigate the biodegradation of metalaxyl in soil and plant. By studying the degradation of metalaxyl in unsterilized and sterilized soil with two initial concentrations of metalaxyl, microbial degradation has the most significant effect on the degradation of metalaxyl in soil. In addition, biodegradation and isotope fractionation of metalaxyl in water spinach with root application and leaf application are investigation by CSIA. It is shown that both absorption and degradation of metalaxyl in the roots and leaves of water spinach can cause the shift of delta C-13 values. Specifically, the delta C-13 values decreased during absorption while increased in degradation of metalaxyl in the roots and leaves of water spinach, indicating that the lighter isotope is absorbed in the absorption process at first and then degraded. Furthermore, the relationship between carbon isotope ratios and residual concentration of metalaxyl can be described by the Rayleigh equation, and the biodegradation rate of metalaxyl could be calculated by using CSIA without measuring the concentration of metalaxyl both in soil and plant. Therefore, the use of CSIA can quantitatively assess the degradation behavior of pesticide pollution in the environment and provide a certain scientific evidence and technical support in the process of environmental remediation.