| Tobacco black shank is one of the most important disease in infecting the leaves of tobacco in china and some other countries all over the world. The extent is very serious and damaged seriously. In the latest 30 years, as the conception that prevention for the first and control from many aspects becomes more and more popular, a lot of pesticides, which are high efficient and low in the residue, are used in the process of tobacco planting. As an important index of tobacco leaf secuurity, pesticide residue is crucial in the commerce of tobacco industry. In this study, GAP field trials on tobacco about 5 germicides to control tobacco black shank, such as dimethomorph, metalaxyl, mancozeb, fosetyl -aluminum, and propamocarb were carried out. We further studied degradation method and residue level and detection technique of pesticide residues. Meanwhile, statistical methods to analyse thedegradation of pesticide residue, risk assessment, as well as quality and safety evaluation in this paper. The major findings are as follows:Based on the means of pesticide residue detection, through the contrast tests, best way to purification and the detection conditions optimization tests, a efficient detection mean was generated. Dimethomorph residue:collected by acetone, liquidliquid extracted by NaCl and dichloromethane, purificated by Florisil-SPE, detected by HPLC(UV). metalaxyl residue:collected by acetonitrile, purificated by NH2-SPE, detected by HPLC(UV). mancozeb residue:collected by the salt solution of stannous chloride, detected by GC-FPD. It's metabolites, ethylene thiourea(EUT) are collected by methanol and water solution,liquidliquid extracted by nhexane, purificated by Florisil-SPE,and detected by HPLC(UV). fosetyl-aluminum residue:it released ethanol gas in the solution of NaOH, quantitative assay by the FID. And the level of fosetyl-aluminum are determined by ethanol. propamocarb residue:collected by acid-acetone,liquidliquid extracted and purificate by nhexane and dichloromethane, detected by GC(NPD). These germicides were examined on the fresh tobacco leaves, dry tobacco leaves and soil in five different levels. The add recovery tests comply with the requirements.From 2009 to 2010, a series of GAP field trials, in different doses, different application times, and different harvest intervals time, were carried out in Shandong and Hunan on these five germicides. The results showed that, the original residue level of dimethomorph, metalaxyl, mancozeb, fosetyl-aluminum, and propamocarb were 17.2-35.9mg/kg,20.5-31.2 mg/kg,440～535 mg/kg,6.84～13.8 mg/kg and 21.5-34.7mg/kg in tobacco leaf; the half-life were 1.73-3.92 days, 1.17～1.96 days,3.16～4.49 days,10.7～19.3 days and 0.77～1.37 days. They are all easy to be degradated, and after 21 days,90% of the germicide were degradated. In the soil, the half-life is longer. Their half-life were 6.94～13.78 days,3.79～20.5 days, 3.16～4.49 days,10.70～19.31 days and 1.79～4.68 days. After collecting tobacco leaf in the 7,14, and 21 days after the last application, we found that the level of these germicides' residue were 0.133～4.67mg/kg,0.026～6.17mg/kg,9.88～24.44mg/kg, 0.228～22.06 mg/kg,0.09～5.47 mg/kg, and 1 less than 0.005 mg/kg, which won't damage the environment and next stage crops. The residue in tobacco of metalaxyl, mancozeb, fosetyl-aluminum are influenced by the interval time directly, but dimethomorph and propamocarb are influenced by the interval dose, and metalaxyl, mancozeb and fosetyl-aluminum are all influenced by interval dose and times. According to CORESTA guidance, the residue of dimethomorph, metalaxyl, mancozeb and fosetyl-aluminum are follow the limit requirement after applying the germicides for 21 days. So the safety interval is 21 days. After 14 days, propamocarb's residue is under the required level, so it's safty interval is 14 days.Degradation of tobacco residue is significant during curing, and the residues in cured tobacco leaf were respectively 34.3%,38.6%,24.6%,64.4%,47.8% of fresh tobacco leaves, compared with the non-degression samples. residue degradation in tobacco is clear during storage, and the half-life is 68.7,73.6,60.4,56.8,68.3days respectively. Study of risk assessment showed that dimethomorph, metalaxyl, mancozeb, fosetyl-aluminum and propamocarb were all low-toxic germicides, and the ADI were 0～0.1,0～0.08,0～0.1,0～3.0 and 0～0.4 mg/kg bw respectively. The toxicity to animals and environments was in the safe range. Information on process of cigarette burning shows that transfer rate of pesticide residues from Cigarette to smoke is 0-6.3%, which belongs to the lower range. In diet, tobacco intaking is low, so tobacco residue on human health is very safe from the above risk assessment analysis.
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