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 enantiosele...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.展开更多
The anti-seasonal hydrology with 30 m water fluctuations in the Three Gorges Reservoir （TGR） of China attracts growing environmental and ecological concems. We investigated the biotransformation of the herbicide pro...The anti-seasonal hydrology with 30 m water fluctuations in the Three Gorges Reservoir （TGR） of China attracts growing environmental and ecological concems. We investigated the biotransformation of the herbicide propanil in plants dominating in the littoral zone of the TGR by applying the 14C-ring-labeled herbicide into non-aseptic hydroponic plant systems （Cynodon dactylon, Nelumbo nucifera and Bidens pilosa）, aseptic plants （Lemna minor and Lemna gibba） and cell suspension cultures （C. dactylon and L. minor）. （1） Propanil absorbed in plants of the hydroponic systems was （12.46 ± 1.63）% of applied radioactivity （AR） （C. clactylon）, （52.36 ± 6.38）% （N. nucifera） and （76.55 ± 6.07）% （B. pilosa）, respectively. The 14C-residues in the plant extractable fractions and the corresponding media were confirmed by radio-Thin Layer Chromatography （TLC）, radio-High Performance Liquid Chromatography （HPLC） and Gas Chromatography-Electron Ionization Mass Spectrometry （GC-EIMS） as propanil, 3,4-dichloroaniline （DCA） and N-（3,4-dichlorophenyl）-β-D-glucopyranosylamine （Glu-DCA）. （2） About 8% of AR was taken up by both aseptic plants, from which 7.0% of AR was extracted and identified also as propanfl, DCA and Glu-DCA. {3） Concerning cell suspension cultures, （39.22 ± 9.39）% of AR was absorbed by C. dactylon after 72 hr, whereas the accumulated 14C-propanil by L. minor cell suspension culture amounted to （65.04 ± 1.72）% after 7 days. The identified compounds in cell cultures are consistent with those in the tested plants. Most of the pesticide residues in the intact plants were un-extractable, which are recognized as the end of the detoxificafion process. We therefore consider these plants as suitable for the phytoremediation of the herbicide propanil in the TGR region.展开更多
基金Financial support by the German Research Foundation (DFG) (SCHW750/9) in the frame of the Priority Program SPP 1315。
文摘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.
基金supported by the Yangtze project of German Federal Ministry of Education and Research (BMBF) (No. FKZ 02WT1141)the China Scholarship Council (CSC)
文摘The anti-seasonal hydrology with 30 m water fluctuations in the Three Gorges Reservoir （TGR） of China attracts growing environmental and ecological concems. We investigated the biotransformation of the herbicide propanil in plants dominating in the littoral zone of the TGR by applying the 14C-ring-labeled herbicide into non-aseptic hydroponic plant systems （Cynodon dactylon, Nelumbo nucifera and Bidens pilosa）, aseptic plants （Lemna minor and Lemna gibba） and cell suspension cultures （C. dactylon and L. minor）. （1） Propanil absorbed in plants of the hydroponic systems was （12.46 ± 1.63）% of applied radioactivity （AR） （C. clactylon）, （52.36 ± 6.38）% （N. nucifera） and （76.55 ± 6.07）% （B. pilosa）, respectively. The 14C-residues in the plant extractable fractions and the corresponding media were confirmed by radio-Thin Layer Chromatography （TLC）, radio-High Performance Liquid Chromatography （HPLC） and Gas Chromatography-Electron Ionization Mass Spectrometry （GC-EIMS） as propanil, 3,4-dichloroaniline （DCA） and N-（3,4-dichlorophenyl）-β-D-glucopyranosylamine （Glu-DCA）. （2） About 8% of AR was taken up by both aseptic plants, from which 7.0% of AR was extracted and identified also as propanfl, DCA and Glu-DCA. {3） Concerning cell suspension cultures, （39.22 ± 9.39）% of AR was absorbed by C. dactylon after 72 hr, whereas the accumulated 14C-propanil by L. minor cell suspension culture amounted to （65.04 ± 1.72）% after 7 days. The identified compounds in cell cultures are consistent with those in the tested plants. Most of the pesticide residues in the intact plants were un-extractable, which are recognized as the end of the detoxificafion process. We therefore consider these plants as suitable for the phytoremediation of the herbicide propanil in the TGR region.
