| In this study,effects of initial concentration(Co),photosensitizer or photoquencher(Fe3+,Cu2+,NO3-,humic acid and TiO2),water types on photodegradation rates were investigated using rapid resolution liquid chromatography tandem triple quadrupled mass spectrometer(RRLC-QqQ-MS/MS)with multiple reaction monitoring(MRM)mode.The photoproducts were separated and identified via RRLC-QqQ-MS/MS combined with ultra performance liquid chromatography tandem quadrupled time of flight mass spectrometry(UPLC-IT-TOF-MS/MS)techniques.Based on the identified transformation products(TPs)and their kinetic evolutions,a tentative transformation mechanism of cyprodinil in water was proposed.At the same time,the effects of soil type,moisture,microbial effects on biodegradation rates of cyprodinil in soil were investigated using RRLC-QqQ-MS/MS.The Acinetobacter junii strain ATCC 17908,a high effective cyprodinil-degrader,was successfully obtained from the polluted soils with a long-term application.Microbial degradation products and transformation mechanism were studied using high performance liquid chromatography tandem quadrupled time of flight mass spectrometry(HPLC-QTOF-MS/MS).The main results in this paper were as follows.(1)The result of hydrolysis experiment showed that cyprodinil with an initial concentration of 10 mg/L was degraded by 0.60%,1.70%and 9.21%in pH 4.0,7.0 and 9.0 buffer solutions within 15 d,respectively.Therefore,the hydrolysis half-life(ti/2 25 ?)of cyprodinil would be more than one year,and it exhibited hydrolytic stability,according to the report from EPA 712-C-08-012.This result suggested that the effect of hydrolysis on photodegradation of cyprodinil in water could be ignored.(2)The results of photodegradation kinetics of cyprodinil in water showed that the half-lives of cyprodinil were 38.9,9.93 and 6.18 d in pH 5.0,7.0 and 9.0 buffer solutions,respectively.When the concentration of photosensitizers NO3-were 0.1,0.5,1.0,2.0 and 5.0 mg/L,respectively,the photo-degradation half-lives of cyprodinil(C0=2.0 mg/L)were 18.8,10.4,7.13,8.33 and 5.42 d.The half-lives of cyprodinil(C0=2.0 mg/L)were 23.3,23.2,18.9,16.8 and 12.8 d,respectively,when the concentration of Fe3+ in aqueous solution were 0.1,0.5,1.0,2.0 and 5.0 mg/L.When TiO2 were 0.1,0.5,1.0,2.0 and 5.0 mg/L,respectively,the half-lives of cyprodinil(C0=2.0 mg/L)in water were 15.2,10.6,9.22,9.78 and 8.13 d.With the humic acid(HA)of 0.1,0.5,1.0,2.0 and 5.0 mg/L,the half-lives of cyprodinil were 18.6,17.1,13.7,12.7 and 14.1 d respectively.The degradation half-lives of cyprodinil in water under the ultraviolet,fluorescent and solar light sources were 10.1 min,39.8 d and 28.9 d,respectively.Under the ultraviolet light source,degradation half-lives of cyprodinil in river water,lake water and ultrapure water were 4.96 d?7.25 d and 23.2 d,respectively.(3)Cyprodinil might undergo the photochemical transformation by three ways:(a)hydroxylation reaction;(b)Hofmann-Martius rearrangement and isomerization;(c)ring-opening,demethylation and binding hydrogen atom on three-element ring.The TPsl was proposed as the hydroxylation of a-H on the pyridine ring of cyprodinil,and its molecular formula and molecular weight(MW)were C14H15N3O and 241,respectively.TPs1 underwent further reactions involving addition of a H2O molecule,the subsequent loss of a methyl and combination of a hydrogen atom on the three-element ring to form TPs2 with the molecular weight of 246 and molecular formula C13H15N3O2.The para-position hydrogen atom on the benzene ring of TPs2 was further replaced by a hydroxyl radical to form TPs6 with an m/z 262[M+H].TPs3,TPs4 and TPs5 were three isomeric compounds from Hofmann-Martius rearrangement of cyprodinil under light radiation.(4)The results of degradation kinetics of cyprodinil(C0=2.0 mg/kg)in soil showed that the degradation behavior followed the first-order kinetics under aerobic and anaerobic conditions.The degradation half-lives of cyprodinil in three soils(red soil,black soil,cinnamon soil)under aerobic and anaerobic conditions were in the ranges of 66-257 d and 46-182 d,respectively.After directional cyprodinil-application in soil,microbes could accelerate its degradation obviously.In the soil-water suspension samples,cyprodinil(150 mg/kg)could be degraded by the microbial mixed bacteria to 1.90 mg/kg after the incubation of 11 d,and the degradation rate was up to 98.7%.(5)Study of degradation products and microbial biodegradation mechanism of cyprodinil in soil.Using sequential culture enrichments with cyprodinil as the sole carbon source,a Gram-negative cyprodinil-degrader from cyprodinil-polluted agricultural soil was isolated.The sequencing analysis of 16S rDNA indicated that the strain has a 99%homology to Acinetobacter sp.The strain could survive and use the high-concentration cyprodinil as a sole carbon source.This finding was very important for the study of microbial degradation products and transformation mechanism cyprodinil in soil.The result of microbial degradation of cyprodinil indicated that 9.94,19.6 and 49.3 mg/L of the added cyprodinil(50 mg/L)in MSM were degraded by dominant strain within 2.0 d,respectively,at the substrate concentrations of 10,20 and 50 mg/L.However,when the substrates were 100,150 and 200 mg/L,respectively,cyprodinil of 64.2,57.0 and 24.3 mg/L were degraded within 14 d.In this study,a novel microbial biodegradation pathway of cyprodinil was firstly proposed.Cyprodinil might undergo two enzyme-catalyzed reactions:(a)hydrolysis of amide bond;(b)hydroxylation.Cyprodinil was mainly hydrolyzed by amidohydrolase to yield an aniline compound TPs1.Only a small part of cyprodinil was transformed into the para-substituted metabolite attributing to the substitution para to the amino group on phenyl ring. |
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