Degradation of the fungicide metalaxyl and its non-extractable residue formation in soil clay and silt fractions  

作　　者：Roschni KALATHOOR Jens BOTTERWECK Andreas SCHÄFFER Burkhard SCHMIDT Jan SCHWARZBAUER 

机构地区：[1]Institute of Geology and Geochemistry of Petroleum and Coal,RWTH Aachen University,Aachen 52062(Germany) [2]Institute for Environmental Research,RWTH Aachen University,Aachen 52062(Germany) [3]School of the Environment,Nanjing University,Nanjing 210023(China)

出　　处：《Pedosphere》2021年第4期549-559,共11页土壤圈（英文版）

基　　金：Financial support by the German Research Foundation (DFG) (SCHW750/9) in the frame of the Priority Program SPP 1315。

摘　　要：The proportion of organic matter and mineral composition are important factors determining the formation and type of non-extractable residues(NERs) of pesticides in soil. In this study, we investigated the enantioselectivity in degradation and NER formation of the chiral fungicide metalaxyl in soil particle size fractions(silt and clay). Microbial and extracellular enzyme activities during these processes were monitored in incubation of silt and clay samples isolated from sterilized and non-sterilized soil samples collected from a long-term agricultural field experimental site in Ultuna, Sweden. The temporal influence on the fate of the fungicide was noted by short-term(10-d) and long-term(92-d) incubations. Besides the acquisition of quantitative data with gas chromatography-mass spectrometry(GC/MS), stereoselective analyses were performed with chiral GC/MS. Quantitative results pointed to a higher metabolism rate of the pesticide through microbial activity than through extracellular enzyme activity. This was also confirmed by the enantioselective depletion of R-metalaxyl and the subsequent formation of R-metalaxyl acid in microbially active samples from non-sterilized soil. The silt fraction containing a high amount of organic matter exhibited a significant hydrolyzable proportion of metalaxyl NERs that was releasable under alkaline conditions. On the contrary, the clay fraction showed an enhanced affinity for covalently bound residues. Based on our results, we recommend differentiating between reversibly and irreversibly bound proportions of pesticides in persistence and environmental risk assessment because the reversible fraction contained potentially bioavailable amounts of residues that may be released under natural conditions.

关 键 词：chiral fungicide ENANTIOSELECTIVITY metalaxyl enantiomer non-extractable pesticide residues organo-mineral complex pesticide degradation extracellular enzymes soil particle size fractions 

分 类 号：X592[环境科学与工程—环境工程]