Transformation Mechanism Of The Novel Fungicide Fluopyram In Environment And Biological Toxicity Of Its Transformation Products

The organisms may be exposed to mixtures of pesticides and their transformation products?TPs?as pesticides can be susceptible to abiotic and biotic degradation after application.Extensive sdudies have shown that TPs may include the active moiety of the parent compound,be the active component of a pro-pesticide,have the greater bioconcentration factor and have a different and more potent mode of action than that of the parent.TPs make a minor,even major contribution to toxicity of pesticides for non-target organisms to some extent.Therefore,TPs have received more and more attention and are considered relevant within the group of the so-called emerging contaminants in recent years.However,the information about transformation mechanism and TPs of many pesticides,especially the novel pesticides,is very sparse.Fluopyram is a novel broad-spectrum fungicide from the pyridinyl-ethyl-benzamide class developed by Bayer Cropscience and is applied widely around the world including China.However,to our best knowledge,no study has reported the transformation of fluopyram and safety risks of its TPs.Thus,it is necessary to obtain the information of fluopyram transformation and its TPs.In this thesis,the photochemical degradation of fluopyram in aqueous solution has been systemically studied,and degradation in soil and toxicity of fluopyram and its photodegradation products have also been done under laboratory conditions.The major findings are as follows:1.The hydrolysis rate of fluopyram was less than 8.1%in the dark at 50±1?in aqueous solutiom of pH 4.0,7.2,9.0,which indicated that half-lives of fluopyram hydrolysis at 25?was more than 1 year and fluopram was stable to hydrolysis.Therefore,degradation by hydrolysis was negligible during photodegradation experiments.2.Three typical photoproducts were identified by LC-QqQ-MS/MS and LC-IT-TOF-MS/MS in aqueous solution under UV-visible irradiation.They were 2,9-bis?trifluoromethyl?-6,7-dihydropyrido[2,3-e][2]benzazocin-8?5H?-one?TP??with more than 20%initial concentration of fluopyram,N-?2-[3-hydroxy-5-?trifluoromethyl?-2-pyridinyl]ethyl?-2-trifluoromethyl)benzamide?TP??with about 9%and N-?2-[5-?trifluoromethyl?-2-pyridinyl]ethyl?-2-?trifluoromethyl?benzamide?TP ??with less than 1%.The difference of photodegradation rate andlevels of three products showed that pathway of TP ? formation wasintramolecular elimination of HC1 via free radical intermediates.TP ? wassubstitution of reactive oxygen species and TP ? was hydrogen extraction fromsolvent.Six photocatalysed products by TiO₂ were identified by the same LC-MStechnique under xenon lamp irradiation.Among them,two were the same as TP ?and TP ?.Others were 3-chloro-5-?trifluoromethyl?-2-pyridinylethylene-amine?TP ??,3-chloro-5-?trifluoromethyl?-2-pyridinylethyl formamide?TP ??,N-?2-[3-chloro-5-?trifluoromethyl?-2-pyridinyl]ethyl?-2-trifluoromethyl-4-hydroxy)benzamide?TP ??and N-?2-[3-chloro-5-?trifluoromethyl?-2-yridinyl]ethyl?-2-trifluoro-methyl-6-hydroxy)benzamide?TP ??.The pathways of theseproducts were intramolecular elimination of HC1,substitution of reactive oxygenspecies,hydroxyl-substitution in benzene ring and breakage of amido bond.Sevenproducts by Fe???photosensitization were indentified under xenon lampirradiation.Others have identified in aquous solution or TiO₂ suspension solutionapart from 3-chloro-5-?trifluoromethyl?-2-pyridinyl acetamide?TP ??.Thepathway included photooxidation and above-mentioned reaction.3.The effect of Fe???,Cu???,?NO₃?^-,fulvic acids,humic acid,riboflavin,pH and TiO₂ on fluopyram photodegradation rate was studied under high pressuremercury and xenon lamp irradiation.The results showed fluopyramphotodegradation was faster in neutral solution than that in acidic and alkalinesolutions.The presence of fulvic acids,?NO₃?^-,Fe???and TiO₂ slightly affected thephotodegradation of fluopyram,whereas humic acid and riboflavin remarkablyinhibited with 10-fold and 12.5-fold at the highest test concentration,respectively,under UV irradiation.Under xenon lamp irradiation,Fe???and TiO₂ dramaticallyaccelerated fluopyram photodegradation with 17-fold and 79-fold at the highesttest concentration,fulvic acids inhibited fluopyram photolysis,nitrate and Cu???accelerated fluopyram photolysis at low concentration and inhibited at highconcentration,riboflavin inhibited fluopyram photolysis at low concentration andaccelerated at high concentration and the effect was not relevant to humic acidconcentration.4.An analysis method was developed and validated for determination offluopyram in red,black and cinnamon soil.The average recoveries were from 97to 105%with RSDs of 39-11.6%.The limit of quantitation was 0.1 mg kg^-1,limitof detection was 5.0-7.5?g L^-1 and correlation coefficient of matrix matchedcalibration curve was more than 0.99.The validated method was applied to studyfluopyram degradation in soil.The results showed that half-lives of fluopyram indifferent types of non-sterile soil and moistures were range of 55.4-69.3 d,which suggested that fluopyram moderately degrades and soil moistures and types barely affected fluopyram degradation rates in soil.Microbial degradation was main way of fluopyram degradation in soil because half-lives of fluopyram in sterile soil were more than 6-fold in non-sterile soil.In addition,no major products were found by comparing LC chromatograms at different sampling interval,e.g.0,7,30,60 d.5.The reults of luminescent bacteria toxicity test showed that acute toxicity of direct photolysis solutions of fluopyram to Vibrio fischeri increased with increasing of irradiation time and TP?,which was obtained by chemical synthesis,was more toxic than fluopyram to Vibrio fischeri.Toxicity prediction results using ECOSAR and T.E.S.T.software showed that all TPs were about as toxic as or higher than fluopyram,especially TP?and TP?,which were about 10×more toxic than fluopyram.In conclusion,the environmental and health risks of fluopyram TPs,especially TP?and TP?,should be further assessed.