| The photolytic kinetics of Anilide herbicides pretilachlor in aqueous solution irradiated by HPML, UV and sunlight was investigated. The following effects on photolysis of pretilachlor under HPML were also studied: temperature, water types, pH buffers, surfactants, nitrate and nitrite, dyes, metallic ions and fertilizers. At the same time, the effect mechanism of H2O2 on pretilachlor was roughly expounded with PNDA as a·OH probe. The main results were summarized as follows:1. The direct photodegradation rate of pretilachlor in aqueous solution by sunlight was slow, the half-life was 87h. however it quickly under HPML and UV irradiation, the half-life was 5.12 and 39.8miniutes.the photolysis follow the first order kinetics.2. The photolysis of pretilachlor was greatly affect under different temperature. When the temperature was 10℃,25℃,40℃,the half life of pretilachlor was 26.65min,23.1min,21.3min. 3.The pH value has significant effect on pretilachlor photolysis, the photolysis rate constant pH9>pH7>pH4, the half-lift was 24.96min ,30.66min, 37.67min.At the same condition, pretilachlor could be easily photodegradated in alkaline solution.4.The photolytic rates of pretilachlor in five types of water ranged as: distilled water>reservoir water (DongPu)>lake water(ChaoHu)> pond water (HuPo)> paddy water. The half-life of pretilachlor was 22.65min with distilled water while 38.5min with paddy water. The effect mechanism was related to the physical and chemical properties of the water samples. 5.Under HPML, surfactant SDBS, CTAB, 0206B both showed photo-quenching effects to pretilachlor. But there mechanisms were different. Nonionic surfactant Tween-60 enhanced the photodegradation rate of pretilachlor. The result showed that the degree of photosensitive or photo-quenching effects of surfactants on the photolysis of pretilachlor was affected by properties of surfactants, UV spectra, the additive dosage and so on. The composition of the mixture surfactant 0206B: Nongru 500and Nongru 603 was mixtured by 1∶0,0∶1,1∶1,1∶2,2∶1, they both slow down the photolytic rate of pretilachlor. When 1:1, the photo-quenching rate was the biggest in their added dosage range, and they worked in coordination.6. Both nitrate and nitrite showed photoquenching effects on pretilachlor in their added dosage range. The photoquenching rate was improved with the increases of nitrate and nitrite concentration.7. Fe3+ enhanced the photodegradation rate of pretilachlor while Cu2+, Pb2+ exhibited photoquenching effects on pretilachlor. The mechanism has relation to the oxidative and reductive properties of metallic ions.8.Crystal Violet showed photo-quenching effect on pretilachlor. Different dosages crystal Violet made half-life of pretilachlor prolong from 24.31min to 26.35min, 27.18min, 32.53min. At the same time, crystal viboflavin sensitized the pretilachlor photolysis, and the photolytic rate was improved with the increases of crystal viboflavin concentration. Methyl green, methyl red, methyl blue and methyl orange had little effect on photolysis of pretilachlor. 9.Different dosages of KH2PO4 and KCl both showed photo-quenching effects on pretilachlor, and photo quenching rate improved with the increases of fertilizer concentration. NH4HCO3 and urea sensitized the pretilachlor photolysis. But their mechanisms were different. KH2PO4, NH4HCO3 and urea change the pH value of solution because of their properties. The Cl- of KCl could absorb·OH competing with pretilachlor. 10. H2O2 produced hydroxyl radical (·OH) upon UV irradiation, so the photodegradation of pretilachlor was greatly promoted. Under HPML irradiation, the photolysis rates of pretilachlor were improved about 4.55～1.74 times. But with the increasing of H2O2 dosage, the photosensitive rate was decreased. Under sunlight, the photolysis rates of pretilachlor were improved about 33.6～81.58 times with H2O2. and the photosensitive rate was improved with increasing dosage of H2O2. The photodegradation path of pretilachlor may be different und...
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