^(14)C-哌虫啶光学异构体在土壤中的矿化、结合残留及其在腐殖质中的分布

Stereoisomer-specific Mineralization and Bound Residue Formation of ^(14)C-Paichongding in Soils and Its Distribution in Humus

本文以新烟碱类手性杀虫剂哌虫啶为对象,采用14C同位素示踪法,在光学异构体层面上,研究了哌虫啶4个光学异构体(5R7R-哌虫啶,5S7S-哌虫啶,5S7R-哌虫啶,5R7S-哌虫啶)在不同土壤中的矿化、结合残留及其在腐殖质中的分布规律。结果表明:(1)土壤施药后培养120d,哌虫啶4个光学异构体在3种不同土壤中的矿化量约为引入量的0.40%～11.59%,其中哌虫啶4个光学异构体在碱性滨海盐土(S2)中的矿化量(引入量的5.03%～11.59%)以及哌虫啶光学异构体SR和RS在中性黄松土(S3)中的矿化量(分别为引入量的8.92%和8.84%),达到欧盟有关农药在土壤中的矿化量最小限量要求(>引入量的5%);(2)哌虫啶4个光学异构体在3种不同土壤中的结合残留量约为引入量的14.34%～50.56%,均低于欧盟有关农药在土壤中的结合残留最高限量(<引入量的70%);(3)哌虫啶4个光学异构体在酸性红砂土(S1)中的结合残留和矿化量无显著性差异;而在中性土(S3)和碱性土(S2)中的结合残留和矿化量,差向异构体之间(RR和RS与SS和SR)存在显著差异(P<0.05),但对映异构体RR和SS以及RS和SR之间差异不显著;(4)较之非灭菌对照,哌虫啶4个光学异构体在灭菌土壤(MS3)中的结合残留和矿化量均显著小于对照土壤(P<0.05),表明土壤微生物影响手性哌虫啶的开环降解和结合残留的形成;(5)不同土壤中哌虫啶4个光学异构体的结合残留,其在腐殖质中的分布均呈现出富啡酸>胡敏素>胡敏酸的规律。

Paichongding is a novel neonicotinoid insecticide consisted of four optical stereoisomers 5R7R-Paichongding,5S7S-Paichongding,5S7R-Paichongding and 5R7S-Paichongding.In this study,the stereoisomer-specific mineralization and bound residue（BR） formation of Paichongding in soils were studied using 14C-isotope tracing.The results were as follows：（1） At 120 days after application,about 0.40%~11.59% of the applied amount was mineralized for four different optical isomers of Paichongding.The mineralization of optical stereoisomers in coastal saline soil（S2）（5.03%~11.59%） and the mineralization of optical isomers SR and RS in fluvio-marine yellow loamy soil（S3）（8.92% and 8.94%） met the minimum limit requirement proposed by EU（ 5% of the applied amount）.（2） Around 14.34%~50.56% of the initial radioactivity formed BR,lower than the maximum BR limitation by EU（ 70% of the applied amount）.（3） In the red clayey sand soil（S1）,no significant difference was observed among the four optical isomers for both the BR formation and mineralization.However,in S2 and S3,significant difference was only observed between the stereoisomers（P0.05）.（4） The BR and mineralization in the sterilized soil was significantly lower than the non-sterilized control（P0.05）,implying the significant role of microorganisms.（5） The content of 14C-Paichongding bound residue distributed in humus showed a tendency of fulvic acid humin humic acid.