首页|Growth of nitrate contribution to aerosol pollution during wintertime in Xi'an,northwest China:Formation mechanism and effects of NH3

Growth of nitrate contribution to aerosol pollution during wintertime in Xi'an,northwest China:Formation mechanism and effects of NH3

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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 PM2.5 were measured in a suburban area of Xi'an,China during wintertime.Hourly concentration of total WSIIs is 39.8 μg m-3 on average,accounting for 50.3％of PM2.5 mass.In contrast to a slight decrease in the mass fraction of SO42-,NO3-shows a sig-nificant increase of the PM2.5 contribution with the aggravation of aerosol pollution.This suggests the importance of NO3-formation to haze evolution.Furthermore,homogeneous reactions govern the formation of NO3-,while alkali metals such as calcium and sodium play an additional role in retaining NO3- in PM2.5 during clean periods.However,the heterogeneous hydrolysis reaction contributed more to NO3-formation during the pollution periods under high relative humidity.Our investigation reveals that temperature,relative humidity,oxidant,and ammonia emissions facilitate rapid NO3- formation.Using the random forest(RF)model,NO3-concentrations were successfully simulated with measured variables for the training and testing datasets(R2＞0.95).Among these variables,CO,NH3,and N02 were found to be the main factors affecting the NO3-concentrations.Compared with the period without vehicle re-striction,the contributions of NO3- and NH4+ to PM2.5 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 NO2,SO2,and NH3 by 12.8％,5.9％,and 27.6％,respectively.The results demonstrate collaborative emission reduction of NOx and NH3 by vehicle restrictions,and using new energy vehicles(or electric vehicles)can effectively alleviate particulate matter pollution in northwest China.

PM2.5Water-soluble inorganic ionsNitrate formationExcess ammoniumVehicle restrictions

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

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State Key Laboratory of Loess and Quaternary Geology,Key Laboratory of Aerosol Chemistry and Physics,Institute of Earth Environment,Chinese Academy of Sciences,Xi'an 710061,China

Xi'an Institute for Innovative Earth Environment Research,Xi'an 710061,China

National Observation and Research Station of Regional Ecological Environment Change and Comprehensive Management in the Guanzhong Plain,Xi'an 710061,China

Shaanxi Key Laboratory of Atmospheric and Haze-fog Pollution Prevention,Institute of Earth Environment,Chinese Academy of Sciences,Xi'an 710061,China

University of Chinese Academy of Sciences,Beijing 100049,China

School of Chemical and Environmental Engineering,Jiangsu University of Technology,Changzhou 213001,China

Division of Atmospheric Sciences,Desert Research Institute,Reno NV89512,United States

Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China

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"西部之光"人才培养计划国家自然科学基金National Atmospheric Research Program

XAB2021YN05415031232017YFC0212200

2024

10.1016/j.partic.2023.09.014

颗粒学报(英文版)
中国颗粒学会　中国科学院过程工程研究所

颗粒学报(英文版)

CSTPCD
影响因子：0.632
ISSN：1674-2001
年,卷(期)：2024.87(4)
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