Study On Migration Behavior In Environment And Photodegradation Of Mesotrione And Atrazine

Toxic organic pollutants atrazine and mesotrione are two kinds of effective herbicides in maize field and they possess broad application foreground in China. To master the two herbicides hazard and control their pollution, this paper has studied on the migration behavior of atrazine and mesotrione in maize field and the photodegradation of atrazine with a novel photocatalyst. The analysis methods of these two herbicides in maize and soil were developed. The dynamic migration and accumulation distribution laws were studied systematically. Besides, TiO2 photocatalysts coated mesoporous molecular sieves were prepared. The degradation behaviors of atrazine in soil were studied by using the TiO2 photocatalysts.GC analysis method of atrazine and HPLC analysis method of mesotrione were established by study in this paper. The extractant of atrazine is acetone. The recovery rates are between 83.28% and 110.16% and the coefficients of variation are between 0.96% and 3.24%. The extractant of mesotrione is acetonitrile. The recovery rates are between 82.46% and 97.38% and the coefficients of variation are between 0.92% and 2.86%.The dynamic migration and accumulation distribution laws of atrazine and mesotrione in maize and soil were studied by field experiment. The results show that the dynamic degradation processes of atrazine and mesotrione in maize accord with the first order kinetic model. Both of the half-lives of these two herbicides are less than 30 days. So they are easy degradation herbicides. At harvest time, the final residuals of atrazine in maize are not detected and the final residual of mesotrione in maize is 0.004 mg/kg. The maximum residue limit (MRL) of atrazine in raw grain according to the China--National Standard System (GB) is 0.05 mg/kg. With sprayed atrazine at recommended two times dosage, the residuals of atrazine in maize are safe. The MRL of mesotrione in maize according to the US--National Standard System is 0.01 mg/kg. With sprayed mesotrione at recommended two times dosage, the residuals of mesotrione in maize are safe.In this paper, the crystallization time and the surfactant ratio have been examined for the synthesis of the mesoporous molecular sieve materials. The results show that the best crystallization time is 24 hours and the best surfactant ratio is 0.24. Under this condition, the hexagonal phase mesoporous molecular sieves with high crystallinity degree are prepared. After the preparation of the novel photocatalysts coated the mesoporous molecular sieves, the photocatalysts were used in the experiment of atrazine photodegradation in soil. The results show that the photocatalysts prepared in this paper are more effective in the degradation of atrazine.