Growth of nitrate contribution to aerosol pollution during wintertime in Xi'an,northwest China:Formation mechanism and effects of NH_(3)  

作　　者：Hui Su Ting Zhang Suixin Liu Yao Qu Huan Li Jiamao Zhou Zhuzi Zhao Qiyuan Wang Lu Li Minxia Shen Shuoyuan Chen Steven Sai Hang Ho Junji Cao 

机构地区：[1]State Key Laboratory of Loess and Quaternary Geology.Key Laboratory ofAerosol Chemistry and Plhysics,Institute of Earth Environment,Chinese Acadery of Sciences,Xi'an 710061,China [2]Xi'an Institute for Innovative Earth Environment Research,Xi'an 710061,China [3]National pbservation and Research Station of Regional Ecological Environment Change and Cornprehensive Management in the Guanzhong Plain,Xi'an 710061,China [4]Shaanxi Key Laboratory of Atmospheric and Haze fog Pollution Prevention,Institute of Earth Environment,Chinese Academy of Sciences,Xi'an 710061,China [5]University of Chinese Academy of Sciences,Beijing 100049,China [6]School of Chemical and Environmental Engineering,Jiangsu University of Technology,Changzhou 213001,China [7]Division of Atmospheric Sciences,Desert Research Institute,Reno NV89512,United States [8]Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China

出　　处：《Particuology》2024年第4期303-315,共13页颗粒学报（英文版）

基　　金：supported by the West Light Foundation of the Chinese Academy of Sciences (grant No.XAB2021YN05);the National Natural Science Foundation of China (grant No.41503123);the National Atmospheric Research Program (grant No.2017YFC0212200).

摘　　要：With the strengthened controls on SO2 emissions and extensive increases in motor vehicles'exhaust,aerosol pollution shifts from sulfate-rich to nitrate-rich in recent years in Xi'an,China.To further gain insights into the factors on nitrate formation and efficiently mitigate air pollution,highly time-resolved observations of water-soluble inorganic ions(WSIIs)in PM_(2.5) were measured in a suburban area of Xi'an,China during wintertime.Hourly concentration of total WSIIs is 39.8μg m-3 on average,accounting for 50.3%of PM_(2.5) mass.In contrast to a slight decrease in the mass fraction of SO_(4)^(2-),NO_(3)-shows a sig-nificant increase of the PM_(2.5) contribution with the aggravation of aerosol pollution.This suggests the importance of NO_(3)-formation to haze evolution.Furthermore,homogeneous reactions govern the formation of NO_(3)-,while alkali metals such as calcium and sodium play an additional role in retaining NO_(3)-in PM_(2.5) during clean periods.However,the heterogeneous hydrolysis reaction contributed more to NO_(3)-formation during the pollution periods under high relative humidity.Our investigation reveals that temperature,relative humidity,oxidant,and ammonia emissions facilitate rapid NO_(3)-formation.Using the random forest(RF)model,NO_(3)-concentrations were successfully simulated with measured variables for the training and testing datasets(R2>0.95).Among these variables,CO,NH_(3),and NO_(2) were found to be the main factors affecting the NO_(3)-concentrations.Compared with the period without vehicle re-striction,the contributions of NO_(3)-and NH4+to PM_(2.5) mass decreased by 5.3%and 3.4%in traffic re-striction periods,respectively.The vehicle restriction leads to the decreases of precursor gases of NO_(2),SO_(2),and NH_(3) by 12.8%,5.9%,and 27.6%,respectively.The results demonstrate collaborative emission reduction of NO_(x) and NH_(3) by vehicle restrictions,and using new energy vehicles(or electric vehicles)can effectively alleviate particulate matter pollution in northwest China.

关 键 词：PM_(2.5) Water-soluble inorganic ions Nitrate formation Excess ammonium Vehicle restrictions 

分 类 号：X51[环境科学与工程—环境工程]