Atmospheric Oxidation Reactions Of Typical Oxygenated Volatile Organic Compounds

With the rapid development of the global economy,a large amount of volatile organic compounds（VOCs）are emitted into the atmosphere and increase the prominent global air pollution.Oxygenated volatile organic compounds（OVOCs）are important components of tropospheric pollutants,with a wide range of sources,many types and high reactivity.In the troposphere,they can react with many active oxygen species（such as NO₃,O₃,and NO₂）to produce the secondary pollutants,which significantly contribute to the formation of the atmospheric secondary organic aerosols（SOAs）,photochemical smog and other atmospheric particulate matter.Alcohols and ketones represent an important class of OVOCs,accounting for a large proportion.Alcohols and ketones are mainly emitted from anthropogenic and biological sources.They are not only broadly applied for industrial processes but also the products of atmospheric photooxidation for many VOCs.Moreover,alcohols and ketones are also the important source of HO_xradicals in the atmosphere.And the HO_xradicals can effectively contribute to SOA and have important impacts on the atmospheric environment.To better understand the fate of alcohols and ketones in the atmosphere,it is necessary to systematically investigate their atmospheric reactions and their impacts on the atmosphere.In this paper,we have investigated the atmospheric reaction processes of acetylacetone（Ac Ac）and OH-toluene adducts employing quantum chemical.We clarified the night atmospheric oxidation reactions of Ac Ac and the reaction mechanisms of OH-toluene adducts with NO₂.The results are as follows:（1）O₃/NO₃-addition to Ac Ac is a major contributing pathway in the atmospheric chemical reactions.The total degradation rate constants were calculated to be 2.36×10^-17and1.92×10^-17cm3 molecule^-1s^-1for the O₃-and NO₃-initiated oxidation of Ac Ac at 298 K,respectively.The half-life of Ac Ac+O₃in some polluted areas（such as,Pearl River Delta and Yangtze River Delta）is close to 3 h under typical tropospheric conditions.Due to its short half-life,the ozonolysis of Ac Ac plays a more significant role in the nighttime hours,leading to fast transformations to form primary ozonides（POZs）.A prompt,thermal decomposition of POZs occurred to yield methylglyoxal（MG）,acetic acid（AA）and Criegee intermediates,which mainly contributed to the formation of SOA.The obtained results reveal that the atmospheric oxidation of Ac Ac can successively contribute to the formation of SOA under polluted environments regardless of the time（day-time or night-time）.（2）The pathway for N attacking active sites is the dominant pathway for the reactions of OH-toluene adducts with NO₂.At 298 K,the total rate constant for the reaction of OH-toluene adducts with NO₂is about 9.92×10^-12cm³molecule^-1s^-1.In the reactions of three isomeric forms of OH-toluene adducts（o-,m-,p-OH-toluene adduct）with NO₂.The o-OH-toluene adduct contributes the most ratio（90%）of the total rate constan.The main products for the reactions of OH-toluene adducts with NO₂are cresol and nitrous acid（HONO）.The kinetic results of the reactions for OH-toluene adducts with NO₂/O₂indicate that both NO₂and O₂mainly react with o-OH-toluene adduct and the main product is o-cresol.And the rate constant of the reaction for o-OH-toluene adduct with NO₂is8.76×10^-12cm³molecule^-1s^-1,which is about three orders of magnitude higher than that of O₂.While the atmospheric boundary layer[NO₂]is 10¹⁵cm^-3,which is three orders of magnitude lower than that of[O₂].Hence,the reactions of OH-toluene adducts+NO₂/O₂is of equal importance.And the reactions of OH-toluene adducts+NO₂/O₂contribute to the formation of cresol in the atmosphere.Moreover,the reactions of OH-toluene adducts+NO₂can also generate HONO.HONO is the main substance to form SOA in the atmosphere.HONO is a mutagen,which can cause carcinogenesis in humans.HONO is also conducive to the deposition of acid in the environment and has more direct significance to the environment.