Dynamic Of Boscalid Degradation In Cucumber Plants And Soil

Boscalid is a new amide fungicides，mainly used to control powdery mildew,gray mold, rot, brown rot and root rot.Although a few research on residue detectionmethod processed both in China and abroad,there is lack of investigation on fate ofboscalid in environment. Recent study, boscalid was investigatedincluding foursections:(1)a analytical method established for determination residue of boscalid incucumber,cucumber leaves,soil and water;(2)boscalidabsorbed and transportedbycucumber plants;(3)the degradation rule of boscalid was studiedoncucumber,cucumber plant and soil(4)degradation of boscalid studied in buffer andsterillizated/un soil, and photolysis of boscalid performed in leaves.Boscalid in matrixextracted by QuEChERS method, and determining by gas chromatograph withelectron capture detector (GC-ECD).The limit of detection was0.01mg／kg.Recoveries of boscalid ranged from89.3%to98.4%with coefficient of variation of1.15%～11.03%in cucumber, cucumber leaves, soil and water. The results indicatedthat the accuracy and precision of the method is in line with the requirements forpesticide residue analysis.The tests of absorption and transportion of boscalid in cucumber plantsshowedthat boscalid can be quickly absorbed by the leaves, and transited to the topand bottom leaves/cucumbers.Thehighest level of boscalid in top cucumberswas0.66mg/kg after applying for4hours.There was0.51mg/kg in bottom cucumberfor1day. The highest level of boscalid in top leave was0.42mg/kg after applying for8hours. There was9.20mg/kg in bottom leaves for2day.Boscalid was fastly degradedboth in cucumber and leaves.Afterprocessing7days, the concentrationof boscalid was0.8-2.7%of initial level.Results of the pot experiment which boscalid applied into cucumber root showedthat boscalid absorbed through roots and transported to the other parts of theplant. At4hours, increased gradually in cucumber plant of boscalid concentration. That oldleaves, stems and leaves in different parts of the test results showed，The old leavesboscalid the highest concentration than other parts. Theresults of digestion of boscalid in cucumber, cucumber leaves, and soilshowed that the half-lives of boscalid digestion in cucumber are1.3d, the half-livesof boscalid digestion in cucumber leaves are3.5d, the half-lives of boscalid digestionin cucumber leaves are40d.The study reveals the effect of degradating for photolysis, hydrolysis, microbialand plant enzymes to boscalid in cucumber plants. Study found boscalid in bufferwith pH was1.2、5、7and9after5days in50℃, digestion rate varies from7.3％～14.6％, boscalid is difficult to hydrolysis. Comparing with shading leaves,light plays a role in degradation of boscalid, but not obviously, half-life from light3.6days increased to8.9days after shading.Boscalid degradation in different soils studyfound: The Soil Microbial acceleration boscalid degradation in soil. The half-lives ofboscalid were39.18～61.43days in three different soil, after sterilized soil, Half-lifeof growth in54.66～91.23days. The extraction of from cucumber Cytochrome p450,glutathione and esterase. the detection outside system enzyme degradation ofpesticides, The results showed that: P450of cucumbers、 Glutathione had nodegradation obviously to boscalid in reaction solution,esterase can play a significantcatalyst in digestion of boscalid,after8hours, the concentration of boscalid decreasedby60%.As a conclusion: Boscalid absorbed and transported bilaterally by cucumberplants.Boscalid was fastly degradedthrough enzymatic hydrolysis and photolysis bothin cucumber and leaves. Boscalid was stable in buffer.Althoughboscalid remained insoil,microbes can promote it degradation.