The Theoretical Study On The Degradation Mechanism Of The Organic Pesticide In Atmosphere

Organic pesticides are widely used to kill insects, epiphytes and any other pests. They are typical environmental pollutants and make up of the hugest volumes of most toxic chemical substance inputted into the environment by human. Organic pesticides have diverse structures and categories. The application of organic pesticides promotes the modern agriculture, forestry, animal husbandry and fishery. However, the organic pesticides could cause the severe environmental pollution and cause a variety of adverse health effects. Some organic pesticides have endocrine disrupting effects, and some also have the "3 the role" effect (lead to cancer, lead to mutation and lead to deformity) or potential "3 the role" effect. No matter in what ways they are sprayed, some of the organic pesticides directly go into the soil, or into the atmosphere. Due to their longtime-application, organic pesticides have caused serious atmospheric pollution, posed threats to human health and ecological safety. Therefore, organic pesticide pollutants and their behavior in atmosphere have been paid more and more attention by researcher in many countries. Organophosphorus pesticides, organochlorine pesticides and carbamate pesticides arc representative organic ones. Some organic pesticides are also typical persistent organic pollutants (POPs), and other pesticides are volatile organic compounds (VOCs). DDT is a typical persistent organic pollutant (POPs), and has been listed in the Stockholm Convention.In this paper, three different categories of organic pesticides are investigated as representative organic pesticides. There are organophosphorus pesticide trichlorfon, organochlorine pesticide DDT and DDE, and carbamate pesticide isoprocarb. All calculation results were obtained at the MPWR1K/6-311+G(3df,2p)// MPWB1K/6-31+G(d,p) level using Gaussian 03 program. Some valuable results are listed as follows:1. Oxidation reaction pathways by OH radicals are the main degradation channels of trichlorfon. H abstraction reactions are the most important initial steps. In chapter 2, all the important reactions between trichlorfon and OH radical are studied at the high level. This work indicates that H abstractions from methyl, H abstractions from methylene and OH additions to P atom are the key initial processes. The reactions of intermediates oxidized by O2/NO are studied and the main products are: .2. In chapter 3, we also investigated the degradation of DDT via atmospheric oxidation reaction at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level using Gaussian 03 program. Calculation indicates that the main degradation channel is H abstraction from C1. The main degradation products are C6H4Cl and CCl3. In addition, we also investigated the degradation of DDE and found that the main degradation channel is OH addition to C=C. The mail degradation products are and CCl2O3. In chapter 4, the degradation reaction processes of isoprocarb initiated by OH radicals are calculated to obtain all chemical information, for example, the energy and structure of reactants, intermediates, transition states and products. These research results could help us to better understand the atmospheric degradation. The H abstraction reactions of different position (C1, C2, C3 and N) are main degradation channels for isoprocarb in the atmosphere and the main degradation products are: and CH3COCH3.