Elucidating severe urban haze formation in China

Abstract

Significance We illustrate the similarity and difference in particulate matter (PM) formation between Beijing and other world regions. The periodic cycle of PM events in Beijing is regulated by meteorological conditions. While the particle chemical compositions in Beijing are similar to those commonly measured worldwide, efficient nucleation and growth over an extended period in Beijing are distinctive from the aerosol formation typically observed in other global areas. Gaseous emissions of volatile organic compounds and nitrogen oxides from urban transportation and sulfur dioxide from regional industry are responsible for large secondary PM formation, while primary emissions and regional transport of PM are insignificant. Reductions in emissions of the aerosol precursor gases from transportation and industry are essential to mediate severe haze pollution in China.

Production of N<sub>2</sub>O<sub>5</sub> and ClNO<sub>2</sub> in summer in urban Beijing, China

“…As a result, extensive studies have been conducted to characterize the sources and formation mechanisms of haze episodes (Huang et al, 2014;Guo et al, 2014;Li et al, 2017). The results show that nitrate and its precursors have been playing increasingly important roles in pollution events since 2006 mainly due to the continuous decrease in SO 2 (van der A et al, 2017).…”

Atmospheric chemistry: China’s choking cocktail

“…There is so much that we do not know. Results are hard to predict because many physical and chemical processes -such as surface chemistry, oxidation, clustering and dynamical effects -happen simultaneously 4 .…”

In situ study of the mechanical properties of airborne haze particles

“…China, the world's largest developing country, is a striking example in past few years in this regard. Much of the country is currently suffering from intermittent severe air pollution [1][2][3][4][5]. The dense haze resulting from respirable suspended particles is now a common occurrence affecting large areas and population [1][2][3][4][5].…”

“…Much of the country is currently suffering from intermittent severe air pollution [1][2][3][4][5]. The dense haze resulting from respirable suspended particles is now a common occurrence affecting large areas and population [1][2][3][4][5]. The sizes of these particles are usually in the range of tens of nanometers to a few micrometers, which is comparable to the abrasive particles used for chemo-mechanical polishing in the semiconductor industry.…”

“…Therefore, in addition to the impacts of haze on visibility, human health and climate [6][7][8][9], it is likely that haze particles may reduce the service life of high-precision machine components through tribological wear, especially when under high-speed operation conditions and with the assistance of corrosive substances (i.e. NO x and SO 2 ) in the air [4].…”