| The most important part to understand the formation of haze is to understand the photochemical reaction mechanism of VOC,persistent organic pollutants and oxidants such as NOx and ozone in the atmosphere.Firstly,we studied the transformation behavior and kinetic behavior of 1,3-BD/NO in the clean air matrix and the actual haze atmosphere matrix.Combined with the indoor smog chamber,thermal desorption device,electron spin resonance spectroscopy and the gas chromatography mass spectrometry,the effects of clean air matrix and actual haze atmosphere matrix on the conversion efficiency of photochemical transformation of 1,3-BD/NO reaction system were simulated.And we determined the kinetic constants of 1,3-BD in the reaction system,which provides a comparison between the reaction rate constants of olefin VOCs and NO,and provides experimental basis for model calculation.we used an electron spin resonance instrument to detect free radicals on collected PM2.5 particles and found that PM2.5 particles contained·OH and O2-·free radicals.The conversion of 1,3-BD and the consumption of ozone and nitric oxide in different systems were analyzed.Results showed that the conversion efficiency of 1,3-BD in the actual haze atmospheric matrix was higher than that of the clean air matrix,and the consumption of nitric oxide and the formation of NO2 and O3 were also higher than that of the clean air matrix.The first-order and second-order kinetic fitting of 1,3-BD in the clean air matrix system and the actual haze matrix system was carried out at a temperature of35?.their reaction rate constants were 0.04031 h-1and 0.06137 h-1,0.166?×?10-13?cm3?molecule-1?h-1(0.461?×?10-17?cm3molecule-1?s-1)and0.187?×?10-13?cm3?molecule-1?h-1(0.519?×?10-17?cm3?molecule-1?s-1).And then we studied the effect of the relative humidity in the clean air matrix of the 1,3-BD/NO system on the transformation behavior and kinetics during the photochemical reaction.We used EPR and+APPI FT-ICR-MS to investigate the effects of different humidity on·OH radical distribution and macromolecular compounds in reaction systems.The strongest intensity for the·OH radical was observed at an RH of40%,which might contribute to the rapid progress of the photochemical reaction of 1,3-BD–NO system at this humidity.The macromolecular products with carbon numbers between 10 and 36 have been characterized.There was a wider range of macromolecular products in the reaction system at an RH of 40%than 0%,which indicates that certain RH values can increase the product diversity.Furthermore,the product which can be ionized was also analyzed by ion chromatography.Finally,a photochemical reaction mechanism for the 1,3-BD–NO system was proposed from the detected NO2,O3,·OH,HNO2,HNO3,organic acids and macromolecular products.A lot of organic pollutants exist in the atmospheric environment,besides VOCs there are persistent organic pollutants.Since HCBD is a typical representative of newly defined POPs,we then studied HCBD photodegradation transformation in a clean air matrix,HCBD wall effects,photochemical reactions of HCBD in different oxidant systems,and photochemical reactions under NO conditions of 250 ppb.This provides a comparison of the reaction rate constant between POPs and NO,and provides experimental basis for model calculation.The wall effects of HCBD under dark conditions were analyzed,and it was found that the HCBD had wall effect but not high,which provided the basis for the subsequent photochemical reaction.The conversion of reactants HCBD in different oxidant systems under light conditions indicates that HCBD is not particularly stable in the presence of atmospheric environment,it is able to photochemical with oxidants present in the atmosphere.The photochemical reaction of HCBD with NO is faster than that with O3.We thoroughly studied the photochemical reactions HCBD under NO conditions of 35?250 ppb and fitted the first and second order reaction kinetics.The reaction rate constants were 0.00962 h-1 and0.5801?×?10-14?cm3?molecule-1?h-1(0.161?×?10-17?cm3?molecule-1?s-1),respectively.The results found that the conversion of 1,3-butadiene is faster than that of HCBD,and the pseudo-first-order kinetic constant and pseudo-second-order kinetic constant of1,3-BD are both larger than HCBD.Although the HCBD is a persistent organic compound,photochemical reaction also occurs under extreme conditions,and its photochemical reaction in the atmosphere is slower than that of 1,3-BD. |
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