The Residue And Degradation Of Bromochlorocyanuric Acid In Tobacco Field And Its Effect On The Quality Of Tobacco

Bromochlorocyanuric Acid is a kind of urea class low-toxic fungicide, which is efficient and broad-spectrum. It has independent intellectual property rights in China. It is now recommended for using on tobacco field in China, which is mainly used for preventing wildfire. In order to evaluate its status of residue and safety of environment, this paper does a systematic study on its degradation residue in soil planted and tobacco leaf. It also studies its effect on enzyme activity and the quality of tobacco leaves. These researches give a comprehensive evaluation to the ecological environment safety after Bromochlorocyanuric Acid was used in tobacco field. And it has an important guiding significance for tobacco production, which will be more scientific and rational. The main conclusions are as follows:(1) By HPLC, the analysis method of Bromochlorocyanuric Acid residue was established in soil planted tobacco and tobacco leaves with the fortified recovery test, when its fortified concentration were0.05,0.50,1.00mg/kg respectively, its average recoveries changed from81.87%to92.44%,with its relative standard deviation ranged from1.01%to6.09%. Its Minimum Detectable Amount was5.0×10-10g, its minimum detectable concentration was1.25×10-2mg/kg for soil planted tobacco,2.5×10-2mg/kg for fresh tobacco leaves and2.5×10-2mg/kg for dried tobacco leaves respectively. So it can make a conclusion that this method can be used to study the residue and degradation of Bromochlorocyanuric Acid in tobacco field.(2) There were two testing points in Changsha city of Hunan and Shandong city of Qingdao where the50%wettable powder of Bromochlorocyanuric Acid was applied in tobacco field to carry on the residue test in2009and2010.The results show that the degradation of Bromochlorocyanuric Acid both in tobacco leaves and soil conforms the1st level kinetic equation of Chemical reaction, and the half-life period of digestion in fresh tobacco leaves was between5.39d and8.57d, between which average value was7.02d and it was between3.33d and3.95d in the tobacco soil, between which average value was3.57d.(3) The amount of residue of Bromochlorocyanuric Acid in tobacco soil was different:The value was between0.501and0.868mg/kg at the7th day after the last time of spraying, which was more than0.50mg/kg; At14th day, it was between0.189and0.405mg/kg, which was less than0.50mg/kg; When it came to21st day, it was equal or less than the value between0.025(LOD of tobacco soil) and0.152mg/kg, which was less than0.50mg/kg. The amount of residue of Bromochlorocyanuric Acid in dried tobacco leaves was also different:The value was5.401and6.917mg/kg at the7th day after the last time of spraying, which was more than2.00mg/kg; At14th day, it was between1.845and3.415mg/kg, which was partly more than2.00mg/kg; When it came to21st day, it was between1.002and1.543mg/kg, which was less than2.00mg/kg. The residue of Bromochlorocyanuric Acid in tobacco soil and dried tobacco leaves were less than their corresponding MRL (the tentative MRL of Bromochlorocyanuric Acid in tobacco soil and dried tobacco leaves were0.50mg/kg and2.00mg/kg, which was referred to the MRL of other pesticides on tobaccos). Therefore, tobacco leaves harvested at or after21st day of last time of spraying were the safest.(4) The Bromochlorocyanuric Acid has a remarkable influence on the number of soil bacteria and fungus. The deeper concentration, the more remarkable the influence will be. But it only has little influence on actionmyces in soils. The results show that the Bromochlorocyanuric Acid of disposing the concentration had restraint effect on soil bacteria from the1st day to the14th day, and the number of bacteria recovered gradually after14th day; The number of soil fungi of disposing the concentration decreased from1st day to7th day, and it recovered to normal after the7th day. The number of actinomyces of had a comparetively low increase between1st day and3rd day and it reached the maximum at the3rd day. Therefore, the high concentration soil had restraint effect on actinomyces.(5) The use of Bromochlorocyanuric Acid has almost zero influence on output of tobacco; There is no obvious effect on increasing or decreasing production. Under the condition of recommended concentration, the content of chloridion in tobacco leaves is a little high than that of control group and it increased slightly with the deeper of concentration. The mainly component content of nicotine, total sugar and protein have no obvious difference. It proved that the frequent usage and high concentration of Bromochlorocyanuric Acid has a slight effect on the quality of tobacco.