The Molecular Ecological Mechanism Of Stereoselective Behaviors For Chiral Triadimefon Fungicide In Different Soils

The environmental behavior of chiral pesticide study is a hot issue in an environmental chemistry field.More than 30% of used pesticides are chiral.The study on chiral pesticide environmental behavior can help to understand the process of this pesticide in the environment and evaluate comprehensively.In this paper,three different types of soils from forestry areas in China(slight alkaline soil from Beijing,neutral soil from Changchun and acidic soil from Wuhan)were used to investigate the molecular ecological mechanism of triadimefon enantiomerization and stereoselective degradation in these soils.The main results are as follows:1)The impact of the chiral triadimefon on the soil’s microbial communitiesIn this study,the optical pure R(R),optical pure S(S)and racemate(Rac)compounds of chiral triadimefon fungicide(TF)were incubated as pollutants in the soils,to assess the change in the microbial community structure.The metagenomic(Highthroughput sequencing technology)was used to screening and determine a change in the structure of microbial communities.The results showed that microbial community structure varied among blank soils,the soil samples from Beijing had higher species richness and diversity than soil samples from Changchun,while the soil samples from Wuhan had a lower species richness and diversity.Moreover,Firmicutes and Actinobacteria were predominant phyla in the soil from Changchun and Beijing respectively,while in the soil from Wuhan,the Proteobacteria and Acidobacteria were the predominant phyla.After R,S and Rac incubation,most of the predominant bacterial taxa(phylum to genus)identified in these soils showed a significant reduction.While the most genera showed resistance to these compounds were belonged to Proteobacteria phylum and 90% of them showed resistance to S and Rac compounds.Furthermore,all the predominated phyla and genera identified in the slightly alkaline soil from Beijing and neutral soil from Changchun showed a positive correlation pH value and negative correlation to water contents.While the acidic soil from Wuhan showed a positive correlation to water contents and negative correlation to pH value.In addition,the soil content of organic matters can enhance the microbial activity.2)The influence of microbial communities on triadimefon enantiomerization in the soilsOptical pure R(R)and optical pure S(S)of triadimefon were used for this study and incubated in the three types of soils.To explore target analytes quantitatively,and bacterial taxa related to the conversion process,the chromatography analysis(HPLC)and high-throughput sequencing technology were used.The conversion results showed a significant difference among the soils.The slight alkaline soil samples from Beijing had a faster conversion rate corresponding to higher abundance of Arthrobacter and Halomonas genus than neutral soil samples from Changchun,while the acidic soil samples from Wuhan had no conversion rate corresponding to scare abundance of Arthrobacter and Halomonas genus.Moreover,Arthrobacter and Halomonas were responsible for converting S to R-(-)and R to S-(+)in soil samples from Beijing and soil samples from Changchun,respectively.Furthermore,the Arthrobacter and Halomonas had a positive correlation with soil pH and negative correlation with the water content.3)Enantioselective degradation and ecological mechanism of racemate triadimefon in the soilsIn this study,the racemate(Rac)triadimefon was incubated in the three types of soils.To explore target analytes quantitatively,and bacterial taxa related to the conversion process,the chromatography analysis(HPLC)and high-throughput sequencing technology were used.The degradation results revealed a significant difference between the three types of soils.The slight alkaline soil samples from Beijing had faster degradation than slight alkaline soil samples from Changchun,while the acidic soil samples from Wuhan had slower degradation rate.Moreover,the result indicated that the loss of TF-Rac in these soils was enantioselective,and the S-(+)always reacted(conversion)fast than the R-(-)one.These differences were due to Arthrobacter oxydans sp.abundance in these soils with following sequence(Beijing > Changchun > Wuhan soil samples).Furthermore,the Arthrobacter oxydans sp.had a positive correlation with soil pH and negative correlation with the water content.Our findings are crucial to understanding microbial communities related to R,S and Rac triadimefon residues behavior in different types of soils in China and can be used to evaluate microbial communities for scientific applications such as bioremediation projects.