New particle formation in Beijing, China: Statistical analysis of a 1‐year data set

Abstract

[1] Particle number size distributions between 3 nm and 10 mm were measured in Beijing, China. New particle formation events were observed on around 40% of the measurement days from March 2004 to February 2005 and were generally observed under low relative humidity and sunny conditions. Though occurring during all seasons, new particle formation events had highest frequency in spring and lowest frequency in summer. Events were classified as ''clean'' or ''polluted'' groups mainly according to the condensational sink and the local wind. The formation rate range was from 3.3 to 81.4 cm À3 s À1 . The growth rate varied from 0.1 to 11.2 nm h À1. The seasonal variation of condensable vapor concentration showed the highest values during summer months due to enhanced photochemical and biological activities as well as stagnant air masses preventing exchange with cleaner air.

Elucidating severe urban haze formation in China

“…Note that similar cycles in the variations of the particle mass concentration and size distribution (i.e., Fig. 1 A and B) are typical for other seasons in Beijing (11,26,27). For example, the frequency for the occurrence of new particle formation events is 50%, 20%, 35%, and 45% in the spring, summer, fall, and winter, respectively (11).…”

“…1 A and B) are typical for other seasons in Beijing (11,26,27). For example, the frequency for the occurrence of new particle formation events is 50%, 20%, 35%, and 45% in the spring, summer, fall, and winter, respectively (11). In addition, a springtime periodic cycle of aerosol optical thickness and trace gaseous species (i.e., sulfur dioxide, carbon monoxide, nitrogen oxides, and ozone) has been previously identified at a rural site in northern China (28).…”

“…Also, primary and secondary particles undergo chemical and physical transformations and are subjected to cloud processing and transport in the atmosphere (8,9). The formation mechanisms leading to severe haze episodes with exceedingly high PM 2.5 levels in China remain highly uncertain, and the abundance and chemical constituents of PM 2.5 vary considerably, depending on complex interplay between meteorology, pollution sources, and atmospheric chemical processes (10)(11)(12)(13)(14)(15)(16). For example, on the basis of ambient measurements and receptor model analysis, the contribution to the annual mean PM 2.5 in Beijing has been suggested to be mainly from industrial pollution and secondary inorganic aerosol formation, but negligibly from traffic emissions (14).…”

A simple model for the time evolution of the condensation sink in the atmosphere for intermediate Knudsen numbers

“…The average condensation sink on new particle formation event days is generally lower as compared with nonevent days 20 (Kulmala et al, 2001;Birmili et al, 2003;Hyvönen et al, 2005;Wu et al, 2007;Asmi et al, 2011;Pikridas et al, 2012;Young et al, 2013;Kanawade et al, 2014;Qi et al, 2015;Vana et al, 2016). Indeed, a large condensation sink means that a relatively large surface of aerosol is available for condensation and coagulation with clusters serving as precursors of newly forming particles.…”

“…Indeed, a large condensation sink means that a relatively large surface of aerosol is available for condensation and coagulation with clusters serving as precursors of newly forming particles. However, at highly polluted places such as megacities, the new particle formation events happen even for large CS (Wu et al, 2007;Xiao et al, 2015). The dynamics of CS is tightly connected with different atmospheric processes, including the effects of atmospheric chemistry, meteorology and solar radiation.…”