Journal Article

Atmospheric new particle formation from sulfuric acid and amines in a Chinese megacity

Mazon, Stephany Buenrostro, Yang, Xin, Ehn, Mikael, Qiao, Liping, Petäjä, Tuukka, Chen, Jianmin, Worsnop, Douglas R., Wang, Dongfang, Geng, Fuhai, Kontkanen, Jenni, Sipilä, Mikko, Fu, Qingyan, Xiao, Shan, Lu, Yiqun, Li, Li, Wang, Xinke, Wang, Mingyi, Zhang, Bowen, Kerminen, Veli-Matti, Paasonen, Pauli, Junninen, Heikki, Yan, Chao, Garmash, Olga, Wang, Hongli, Bianchi, Federico, Chen, Hangfei, Wang, Lin, Kulmala, Markku, Zheng, Jun, Yao, Lei

2018

Overview

Atmospheric particulates can be produced by emissions or form de novo. New particle formation usually occurs in relatively clean air. This is because preexisting particles in the atmosphere will scavenge the precursors of new particles and suppress their formation. However, observations in some heavily polluted megacities have revealed substantial rates of new particle formation despite the heavy loads of ambient aerosols. Yao et al. investigated new particle formation in Shanghai and describe the conditions that make this process possible. The findings will help inform policy decisions about how to reduce air pollution in these types of environments. Science , this issue p. 278 Atmospheric new particle formation in heavily polluted cities can occur in certain chemical environments. Atmospheric new particle formation (NPF) is an important global phenomenon that is nevertheless sensitive to ambient conditions. According to both observation and theoretical arguments, NPF usually requires a relatively high sulfuric acid (H 2 SO 4 ) concentration to promote the formation of new particles and a low preexisting aerosol loading to minimize the sink of new particles. We investigated NPF in Shanghai and were able to observe both precursor vapors (H 2 SO 4 ) and initial clusters at a molecular level in a megacity. High NPF rates were observed to coincide with several familiar markers suggestive of H 2 SO 4 –dimethylamine (DMA)–water (H 2 O) nucleation, including sulfuric acid dimers and H 2 SO 4 -DMA clusters. In a cluster kinetics simulation, the observed concentration of sulfuric acid was high enough to explain the particle growth to ~3 nanometers under the very high condensation sink, whereas the subsequent higher growth rate beyond this size is believed to result from the added contribution of condensing organic species. These findings will help in understanding urban NPF and its air quality and climate effects, as well as in formulating policies to mitigate secondary particle formation in China.

• Publisher: The American Association for the Advancement of Science
• Subject: Aerosols / Air pollution / Air quality / Amines / Atmospheric pollution deposition / Climate effects / Clusters / Condensation / Dimers / Growth rate / Megacities / Molecular chains / Particulates / Pollution control / Precursors / Sulfuric acid / Vapors / Water pollution