The effect of COVID-19 restrictions on atmospheric new particle formation 1 in Beijing

The effect of COVID-19 restrictions on atmospheric new particle formation 1 in Beijing 2 3 Chao Yan1,2,#, Yicheng Shen3,#, Dominik Stolzenburg2, Lubna Dada2,4, Ximeng Qi5, Simo 4 Hakala2, Anu-Maija Sundström6, Yishuo Guo1, Antti Lipponen7, Tom V. Kokkonen5, Jenni 5 Kontkanen2, Runlong Cai2,3, Jing Cai1,2,Tommy Chan2, Liangduo Chen5, Biwu Chu2, Chenjuan 6 Deng3, Wei Du1,2, Xiaolong Fan1, Xu-Cheng He2 , Juha Kangasluoma1,2, Joni Kujansuu1,2, 7 Mona Kurppa2, Chang Li1, Yiran Li3, Zhuohui Lin1, Yiliang Liu8, Yuliang Liu5, Yiqun Lu8, 8 Wei Nie5, Jouni Pulliainen6, Xiaohui Qiao3, Yonghong Wang1,2, Yifan Wen3, Ye Wu3, Gan 9 Yang8, Lei Yao2, Rujing Yin3, Gen Zhang9, Shaojun Zhang3, Feixue Zheng1, Ying Zhou1, Antti 10 Arola7, Johanna Tamminen6, Pauli Paasonen2, Yele Sun10, Lin Wang8, Neil M. Donahue11, 11 Yongchun Liu1, Federico Bianchi2, Kaspar R. Daellenbach2,4, Douglas R. Worsnop2,12, Veli12 Matti Kerminen2, Tuukka Petäjä2,5, Aijun Ding5,*, Jingkun Jiang3,*, Markku Kulmala1,2,5* 13 14 Affiliations: 15 1 Aerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, 16 Beijing University of Chemical Technology, Beijing, China 17 2 Institute for Atmospheric and Earth System Research / Physics, Faculty of Science, University of Helsinki, 18 Finland 19 3 State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environmental Protection 20 Key Laboratory of Sources and Control of Air Pollution Complex, School of Environment, Tsinghua University, 21 Beijing, China 22 4 Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland. 23 5 Joint International research Laboratory of Atmospheric and Earth System Research (JirLATEST), School of 24 Atmospheric Sciences, Nanjing University, Nanjing, China. 25 6 Finnish Meteorological Institute, 00560 Helsinki, Finland 26 7 Finnish Meteorological Institute, 70211 Kuopio, Finland 27 8 Department of Environmental Science & Engineering, Fudan University, Shanghai, China 28 9 State Key Laboratory of Severe Weather & Key Laboratory of Atmospheric Chemistry of China Meteorological 29 Administration (CMA), Chinese Academy of Meteorological Sciences, Beijing 100081, China 30 10 Institute of Atmospheric Physics, Chinese Academy of Science, Beijing, China 31 11 Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA 32 12Aerodyne Research Inc., Billerica, Massachusetts 01821, USA 33 # these authors contributed equally to this work 34 * Correspondence to: 35 Markku Kulmala, markku.kulmala@helsinki.fi 36 Jingkun Jiang, jiangjk@tsinghua.edu.cn 37 Aijun Ding, dingaj@nju.edu.cn 38 39