腈菌唑在茶园土壤中的对映体选择性降解与碳同位素分馏

运用对映体分馏分析(EFA)与单体同位素分析(CSIA)技术研究了三唑类杀菌剂腈菌唑在4种不同种植年限茶园土壤中的对映体选择性降解规律。腈菌唑的降解符合一级反应动力学方程，半衰期为28.4~70.5 d。4种茶园土壤中均表现为(+)腈菌唑优先降解，并均有碳同位素富集，表明发生了显著的微生物降解。腈菌唑在茶园土壤中的降解半衰期和对映体比在50年茶园土中最小，显著低于100年、20年和2年茶园土壤(P<0.05)。降解半衰期与砂粒含量显著相关(P<0.05)，对映体选择性与粉粒含量显著相关(P<0.05)。运用Rayleigh方程计算各土壤中腈菌唑的碳同位素富集因子，并建立生物降解评估模型。应用两种方法评估生物降解所得结果与总降解率趋势相同。

Enantioselective biodegradation and carbon isotope fractionation of myclobutanil in tea orchard soils

We studied the dissipation of chiral triazole fungicide myclobutanil in four tea orchard soils with different cultivating ages by enantiomeric fractionation analysis(EFA) and compound-specific isotope analysis(CSIA). The dissipation of myclobutanil in soils followed first order kinetics with half-lives ranging from 28.4 to 70.5 days. Enantioselective degradation occurred in all tea orchard soils where(+)myclobutanil was preferentially degraded. The dissipation half-life and enantiomer fraction of myclobutanil were significantly lower in 50year than in 100, 20, and 2year tea orchard soils (P<0.05), while degradation half-life and enatioselectivity were significantly correlated with sand and silt contents (P<0.05), respectively. We used the logarithmic forms of the Rayleigh equation in evaluating the carbon isotope enrichment factors for various soils and established the biodegradation assessment model. The biodegradation rates of myclobutanil evaluated by both enantiomeric and isotopic fractionation analysis were consistent with the observed degradation rates.