Mechanism for the promotional formation of NH_(4)^(+) by SO_(2) on different mineral dust surfaces

查看全文 作　　者：Hao [1]Li;Qingxin [1,2,3]Ma;Biwu [1,2,3]Chu;Hong [1,2,3]He 机构地区：[1]State Key Joint Laboratory of Environment Simulation and Pollution Control,Research Center for Eco-environmental Sciences,Chinese Academy of Sciences,Beijing,100085,China;[2]Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment,Chinese Academy of Sciences,Xiamen,361021,China;[3]Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing,100029,China 出　　处：《Particuology》索引2023年第4期,共10页 基　　金：supported by National Natural Science Foundation of China(grant Nos.22006158,22188102 and 221222610);the China Postdoctoral Science Foundation(grant Nos.2019M660818 and 2020TQ0339);Special Research Assistant Project of the Chinese Academy of Sciences. 摘　　要：Ammonium is an important atmospheric particulate component that dictates many environmental processes.The promotion of the heterogeneous conversion of NH_(3) to NH_(4)^(+) by SO_(2) on different mineral dust surfaces displays remarkable discrepancies,especially on MgO and α-Fe2O3 surfaces,however,the underlying mechanisms are not well known.Here,using periodic density functional theory(DFT)calculation and Born-Oppenheimer molecular dynamics(BOMD)simulation,we explored the hetero-geneous adsorption of NH_(3) on MgO(110)and α--Fe2O3(001)surfaces in the presence and absence of SO_(2).The results show that on MgO(110)surface,hydrogen-bonding interactions of NH_(3) on both adsorbed hydroxyl or bisulfite/bisulfate sites are observed no matter whether SO_(2) is present or not.While,on theα-Fe2O3(001)surface,significant conversion of NH_(3) to NH_(4)^(+)occurs with the coexistence of SO_(2),which is due to the hydrogen transfer reaction from surface HSO4 to N in NH_(3).The fundamental reason may be that the stronger electron affinity of Fe3+than Mg2+results in adsorbed bisulfate and/or bisulfite with greater acidity on α-Fe2O3 surface than MgO surface.Our results give a molecular-level explanation for the heterogeneous conversion of NH_(3) to NH_(4)^(+)on different mineral dust surfaces under complex air pollution conditions.Considering the fact that ammonium is abundant in secondary particulates,this work would help in understanding the rapid conversion of ammonia to ammonium and in developing classification governance policies for the key precursor pollutants in China. 关 键 词：Mineral dust Heterogeneous reaction Theoretical calculation AMMONIUM SO_(2)