The Effect Of Humus On The Pesticide Degradation

Pesticides play an important role in modern agriculture. Their application raised some very serious ecological problem connected to their toxicity, pollution of soil, water, and air. Residues of pesticides, which produced after using pesticides in field, contain protomer of pesticides, toxic metabolite and degradation product. When residues of pesticides exceed the permissive concentration, people will suffer from diseases induced by toxic substances. There are more and more countries to establish laws ensure food safety.Most countries in the world are faced with the problem of food safety related to the remediation of residues of pesticides. Consequently, research on the new methods for water and soil purification is developing in different ways, including chemical, biological treatment or photochemical processes. Among all kinds of water and soil purification techniques, photochemical processes of water has been receiving increased attention because the aqueous organic pollutants can be totally degraded and mineralized into harmless inorganics under mild conditions. The method shows potentialities to deal with industrial or domestic wastewater or contaminated soil.This dissertation consists of four parts. The first chapter summarized the progress of pesticides residues analysis. The first chapter also introduces some comirionly sample preparation methods and their applications In the analysis of pesticides residues. These methods Include solid phase extraction (SPE) , supercritical (SFE) , solid phase micro-extraction (SPME) , gel permeation chromatography (GPC) , matrix solid phase dispersion(MSPD) and accelerated solvent extraction(ASE) . At last analytical techniques such as GC, HPLC, TLC, CE and some methods for water and soil purification had been introduced. Chapter 2,3 are the main body of this thesis, in which detection, mechanism of reaction and analysis method of HCH are discussed, firstly, after comparing four kinds of methods, HCHs are decided to be extracted with a mixture of petroleum benzin and acetone (4:1,v/v) on a shaker at 40-45℃ for 4 hours. The analysis indicated that HCHs can be degraded by humic substance in the water. Add 5mg/ml humic substance into 20ng/ml, 30ng/ml, 50 ng/ml HCHs ( α,β,γ and δ ) , and HCHs isomers were analyzed on GC. About 97% HCHs are degraded. It is ¹O₂ and OH in the water, which generated by photochemical reaction of humic substance, that degrade the HCHs. Degradation product are octanol, heptanol, phenol. But in soil iron ion should be add to obtain good degradation. In chapter 4, mechanism of reaction ,detection and degradationexperiment of organophosphorus pesticides are discussed.