| The direct photolysis of Anilide herbicides acetochlor in aqueous solution irradiated by high pressure mercury lamp(HPML) and sunlight was investigated. Effects of hydrogen peroxide(H2O2), surfactants, triazine herbicides on the photolysis of acetochlor, and the mechanism of the photointeractions with PNDA as a .OH probe, were specifically studied. With PTLC, HPTLC and GC-MS as analytical techniques, we also explored the photoproducts of acetochlor in aqueous solution under HPML, possible degradative pathways, the effects of H2O2 and surfactant Nongru 601# on its photoproducts and degradative pathways. The main study results were summarized as follows:1.The direct photodegradation rate of acetochlor in aqueous solution by sunlight was slow, the half life of acetochlor was 23.1 hours. However it degradated very quickly under HPML irradiation, the half life of acetochlor was only 5.98 miniutes.2.H2O2 produced hydroxyl radical( OH) upon UV irradiation, then -OH proceeded to react with acetochlor, so that the photodegradation of acetochlor was greatly promoted. Under HPML irradiation, when the concentration of H2O2 was below or equal to 19.4mmol/L, the photolysis rates of acetochlor were improved with the increases of H2O2 concentration, about 1.53 ~ 2.40 times greater acetochlor photolysis rate enhancements was observed. However, the further addition of H2O2(more than 19.4mmol/L) would result in a retardation of the rates. The half-lives of acetochlor became longer than with lower concentrations of H2O2 in solution. This is because H2O2 itself could react with -OH so as to generate -OH2 free radical, which is less reactive than -OH. While under sunlight, the photolysis rate constants of acetochlor increased continuously with more H2O2 in solution. The half-lives of acetochlor were reduced to 8.45~1.93 hours with various concentrations of H2O2 from 23.1 hours in the absence of H2O2.3.Under HPML irradiation, direct photolysis half-life of acetochlor in 15℃ redistilled water was 6.91min. When water temperature reached to 30癈, photolysis rate constants of acetochlor reached to the maximum, with the smallest Ti/2 as 4.84 min. Over 30℃, the photolysis rate couldn't be improved further. At the same time, the photolysis T1/2 of acetochlor at the present of H2O2 in 10℃ aqueous solution was 5.94 min, which meaned that H2O2 had the least photosensitive ability at this time. From 15℃-35℃, H2O2 had the greatest photoreactivity, so acetochlor had the smallest T1/2 whose average was 2.65min. While in 40癈 solution, the photosensitiveability of H2O2 reduced dramatically, T1/2 was extended to 3.89min.4.Under HPML irradiation, anionic surfactant SDBS, nonionic Nongru 603* and Nongru 404# were mixed with acetochlor below 1:1 (dose ratio) respectively, they enhanced the photodegradation rate of acetochlor. When the dose ratio reached 5:1, they retarded the photodegradation of acetochlor. As to the surfactant mixture of 0206B(an anionic surfactant mixed with an ionic surfactant) and acetochlor, when their dose ratio was below 0.1:1, 0206B had a positive effect on the photolysis of acetochlor. When 1:1 and 1:5, 0206B had an adverse effect on the photolysis of acetochlor. Tween 80 acted as a photosensitizer in the photodegradation process of acetochlor, and improved the relative rate constant 1.06-1.17 times. CTAB, Nongru 500#, Nongru 601#, mixture of Nongru 500# and 603#(1:1), mixture of Nongru 500# and 601#(3:7), mixture of Nongru 404# and 603#(1:1) all had a quenching effect on the photolysis of acetochlor in their added doses range. The result showed that the degree of photosensitive or photoquenching effects of surfactants on the photolysis of acetochlor was affected by the properties of surfactants, UV spectra, the additive dosage and so on.5.The photodegradation of acetohclor in the mixture of surfactant/H2O2 solution was investigated at various doses of surfactants under HPML irradiation. The result showed that Tween 80, 0206B retarded the photolysis of acetochlor than with only H2O2 in solution. CTA...
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