Important progress in the formation of new particles in the atmosphere

Recently, Professor Zhang Xiuhui, a Key Laboratory of School of chemistry and chemical engineering / Ministry of education of atomic molecular cluster science, Beijing University of technology, and his collaborators have made important progress in the field of new particle formation in the atmosphere The research results were published in proc natlacad SCI USA (DOI: 10.1073 / PNAS 1915459116) under the title of "unexpected queuing effect on new particle formation from the atmospheric reaction of methanol with so 3" Liu Ling, Ph.D student, School of chemistry and chemical engineering, Beijing University of technology, and Zhong Jie, Ph.D student, University of Nebraska Lincoln are the co authors Zhang Xiuhui, Professor, School of chemistry and chemical engineering, Beijing University of technology, Zeng Xiaocheng, Professor, University of Nebraska Lincoln, and Joseph S Francisco, University of Pennsylvania are the co authors Beijing University of technology is the first communication unit New aerosol particles are important sources of particles and cloud condensation nodules in the atmosphere, which have a significant impact on regional environmental quality, climate and human health The nucleation stage is the key to the formation of new particles, but the molecular level physical and chemical mechanism of the nucleation stage, especially the mechanism of aerosol nucleation in polluted areas, is still a mystery Alcohols widely exist in the atmosphere, with the characteristics of high concentration and wide source Due to the weak hydrogen bond between alcohols and common atmospheric nucleation precursors, it is generally believed that alcohols have little effect on the formation of new atmospheric particles Under the condition of air pollution, many kinds of pollutants lead to the coexistence of many chemical processes It is not clear whether the alcohols with certain chemical activity will affect aerosol nucleation through chemical transformation and the nucleation mechanism Professor Zhang Xiuhui and his collaborators combined quantum chemical calculation with atmospheric cluster dynamics simulation, and creatively added the conversion reaction of alcohols in the atmosphere and the influence factors of this process on the formation of other nucleation precursors to the study of aerosol nucleation simulation (Figure 1 ）It is found that methanol can react with so 3 to form methyl sulfate which can promote aerosol nucleation under the catalysis of common nucleation precursors (water, sulfuric acid and dimethylamine) under the condition of air pollution, and this process will inhibit the formation of key nucleation precursor sulfuric acid (so 3) through competition with so 3 in the dry pollution area with high methanol concentration Reaction with water, Fig 2, a) Based on the above factors, it is found that methanol has an unexpected inhibitory effect on the nucleation process of sulfuric acid dimethylamine (Fig 2, b) On the one hand, this study puts forward a new mechanism that methanol will participate in the formation of new aerosol particles through chemical transformation in the dry highly polluted areas, which provides new research ideas and theoretical clues for the study of the formation mechanism of new aerosol particles under the condition of compound air pollution in China; on the other hand, it also reveals the key chemical processes that affect the formation of atmospheric sulfuric acid in the dry polluted areas, so as to accurately predict the atmosphere At the same time, this study also shows the necessity of considering the competition process of nucleation precursor formation in the study of new particle formation mechanism, which provides an important new strategy for the improvement of the model of new particle formation mechanism Figure 1 Competitive formation process of nucleation precursors (sulfuric acid (SA) and methyl sulfate (MHS)) and their subsequent formation of clusters Methanol: Mo, dimethylamine: DMA (source: proc Natl Acad SCI USA) Figure 2 (a) the concentration of methyl sulfate (MHS) and sulfuric acid (SA) generated by so 3 varies with the concentration of methanol (MO) under different water concentrations (b) At different concentrations of water, the particle formation rate J (cm-3s-1) changes with Mo concentration (source: proc Natl Acad SCI USA)