@Article{Xu2020,
author="Xu, Jianzhong
and Ge, Xinlei
and Zhang, Xinghua
and Zhao, Wenhui
and Zhang, Ruixiong
and Zhang, Yuzhong",
title="COVID‐19 Impact on the Concentration and Composition of Submicron Particulate Matter in a Typical City of Northwest China",
journal="Geophysical Research Letters",
year="2020",
address="State Key Laboratory of Cryospheric Science, Northwest Institute of Eco‐Environment and Resources Chinese Academy of Sciences Lanzhou China ;; Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering Nanjing University of Information Science and Technology Nanjing China ;; School of Earth and Atmospheric Sciences Georgia Institute of Technology Atlanta GA USA ;; School of Engineering Westlake University Hangzhou China",
volume="47",
number="19",
keywords="COVID‐19;HR‐ToF‐AMS;NR‐PM1;Lanzhou",
abstract="In this study, we evaluated the variations of air quality in Lanzhou, a typical city in Northwestern China impacted by the COVID‐19 lockdown. The mass concentration and chemical composition of non‐refractory submicron particulate matter (NR‐PM<sub>1</sub>) were determined by a high‐resolution aerosol mass spectrometer during January‐March 2020. The concentration of NR‐PM<sub>1</sub> dropped by 50{\%} from before to during control period. The five aerosol components (sulfate, nitrate, ammonium, chloride, and organic aerosol [OA]) all decreased during the control period with the biggest decrease observed for secondary inorganic species (70{\%} of the total reduction). Though the mass concentration of OA decreased during the control period, its source emissions varied differently. OA from coal and biomass burning remained stable from before to during control period, while traffic and cooking related emissions were reduced by 25{\%} and 50{\%}, respectively. The low concentration during the control period was attributed to the lower production rate for secondary aerosols.",
issn="0094-8276"
}