The Effects Of Fe(?), Fe(?) On The Photodegradation Of Chlorothalonil In Aqueous Solution

Chlorothalonil is a broad-spectrum,high efficiency,low toxicity substitutive benzene fungicide,which is widely used in the crops,vegetables,trees,turf,ornamental plants on prevention and treatment of diseases.There is a certain residue of chlorothalonil in waters duing to the extensive use of it.Chlorothalonil is slightly toxic to humans,but it is a potential human carcinogen,known to affect the kidney,ureter,and bladder.There are different ways of degradation of chlorothalonil in waters including chemical degradation,microbial degradation and photodegradation,usually,chlorothalonil degrades faster through photodegradation.There is a certain amount of Fe(?),Fe(?)in waters,It plays an important role to human health,assessment of food and environment security researching the effects of Fe(?),Fe(?)to the photodegradation of chlorothalonil in aqueous solution,exploring its degradation mechanism and pathways,analyzing the properties of photodegradation metabolites.High performance liquid chromatography method have been established for dete ction of chlorothalonil,4-hydroxy chlorothalonil,2-chloro-1,3-dicyanobenzene,5-chlor o-1,3-dicyanobenzene,2,4-dichloro-1,3-dicyanobenzene,2,5-dichloro-1,3-dicyanobenzene in this paper.Chlorothalonil photodegradation was studied under the effects of Mg(?),Cu(?),Zn(?),Fe(?),Fe(?)and different initial concentrations of chlorothaloni l under high pressure mercury lamp in aqueous solution condition.The results confi rmed that 4-hydroxy chlorothalonil is one of chlorothalonil metabolites.and we mad e a further study of 4-hydroxy chlorothalonil at the same time.Other photodegradat ion metabolites of chlorothalonil were explored by using gas chromatography couple d with tandem mass spectrometry and liquid chromatography coupled with tandem mass spectrometry methods.We analyzed its possible photodegradation mechanisms and pathways of chlorothalonil.In addition,chlorothalonil photodegradation under th e effects of the mixture of Fe(?),Fe(?)and oligomeric proanthocyanidins,which i s a photosensitizer of chlorothalonil,was studied in aqueous solution.The result showed that Mg(?),Cu(?),Zn(?)have no effect on photodegradati on rate of chlorothalonil in aqueous solution,but Fe(?),Fe(?)does.Meanwhile,p hotodegradation rate of chlorothalonil increased with the rising of Fe(?),Fe(?)con centration under the treatments of this experiment,and when other factors were und er the same condition,the effect of Fe(?)was stronger than Fe(?)in chlorothalonil photodegradation.When the initial concentrations of chlorothalonil were at 0.376,0.94,1.88?mol/L,photodegradation rate of chlorothalonil was not effected by its initial concentratio n,photolysis half-life were almost the same.By using methylene blue as the hydroxyl radical trapping agent,we confirmed that hydroxyl radical produced in the experiment when Fe(?),Fe(?)acted as the photosensitizer of chlorothalonil and promoting the yield of 4-hydroxy chlorothalo nil in the process at the same time.4-hydroxy chlorothalonil can photodegrade itsel f under high pressure mercury lamp,and its photolysis half-life was significantly sh orter than that of chlorothalonil.Fe(?),Fe(?)have no impact on 4-hydroxy chloro thalonil photodegradation rate in the setted concentrations in aqueous solution.Fe(?),Fe(?)and oligomeric proanthocyanidins can both acted as the photosen sitizer of chlorothalonil.Chlorothalonil's photodegradation followed the oligomeric pr oanthocyanidins photodegradation pathway,when the system was treated by mixture of Fe(?),Fe(?)and oligomeric proanthocyanidins.It hardly happened that Fe(?),Fe(?)can promote the photodegradation rate of chlorothalonil.Besides,the combin ation of Fe(?),Fe(?)and oligomeric proanthocyanidins have some certain effects t o chlorothalonil photodegradation rate,generation of 2,4,5-chlorine isophthalonitrileis,2,5-dichloro-isophthalonitrile and 5-chloro-isophthalonitrile when they were added to the aqueous solution.