Simultaneous measurements of new particle formation in 1-second
time resolution at a street site and a rooftop site
Yujiao Zhu1,*, Caiqing Yan2,*, Renyi Zhang2,3, Zifa Wang4, Mei Zheng2, Huiwang Gao1, Yang Gao1, and Xiaohong Yao1,51Key Lab of Marine Environmental Science and Ecology, Ministry of Education, Ocean University of China, Qingdao 266100, China 2State Key Joint Laboratory for Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China 3Departments of Atmospheric Sciences and Chemistry, Center for the Atmospheric Chemistry and the Environment, Texas A&M University, College Station, TX 77843, USA 4State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China 5Qiangdao Collaborative Center of Marine Science and Technology, Qingdao 266100, China *These authors contributed equally to this work.
Received: 22 Dec 2016 – Accepted for review: 27 Dec 2016 – Discussion started: 02 Jan 2017
Abstract. This study is the first time to use two identical Fast Mobility Particle Sizers for simultaneously measuring particle number size distributions (PNSD) at a street site and a rooftop site within 500 m distance in winter and spring times in Beijing. The obtained datasets in 1-second time resolution allow reasonably deducting the freshly emitted traffic particle signal from the measurements at the street site and thereby pave the way to study reduced or enhanced effects on new particle formation (NPF) in urban atmospheres through the site-by-site comparison. The number concentration of newly formed particles, i.e., smaller than 20 nm, and the NPF rate in the springtime were smaller at the street site than at the rooftop site. In contrast, NPF was enhanced in the wintertime at the street site with NPF rates increased by 3–5 times, characterized by a shorter NPF time and higher new particle yields than those at the rooftop site. Our results imply that the street canyon likely exerts distinct seasonal effects on NPF because of on-road vehicle emissions, i.e., stronger condensation sinks that may be responsible for reduced NPF in the springtime but efficient nucleation and partitioning of gaseous species that contribute to the enhanced NPF in the wintertime. We also analyzed the occurrence or absence of apparent growth for > 10 nm new particles. The oxidization of biogenic organics in the presence of strong photochemical reactions was argued to play an important role in growing > 10 nm new particles, but sulfuric acid was unlikely the crucial specie for the apparent growth.
Zhu, Y., Yan, C., Zhang, R., Wang, Z., Zheng, M., Gao, H., Gao, Y., and Yao, X.: Simultaneous measurements of new particle formation in 1-second
time resolution at a street site and a rooftop site, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1143, in review, 2017.