Air quality improvement in a megacity: implications from 2015 Beijing Parade Blue pollution control actions.

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Date: Jan. 2, 2017
From: Atmospheric Chemistry and Physics(Vol. 17, Issue 1)
Publisher: Copernicus GmbH
Document Type: Report; Author abstract; Brief article
Length: 358 words

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Abstract :

The implementation of strict emission control measures in Beijing and surrounding regions during the 2015 China Victory Day Parade provided a valuable opportunity to investigate related air quality improvements in a megacity. We measured NH.sub.3, NO.sub.2 and PM.sub.2.5 at multiple sites in and outside Beijing and summarized concentrations of PM.sub.2.5, PM.sub.10, NO.sub.2, SO.sub.2 and CO in 291 cities across China from a national urban air quality monitoring network between August and September 2015. Consistently significant reductions of 12-35 % for NH.sub.3 and 33-59 % for NO.sub.2 in different areas of Beijing during the emission control period (referred to as the Parade Blue period) were observed compared with measurements in the pre- and post-Parade Blue periods without emission controls. Average NH.sub.3 and NO.sub.2 concentrations at sites near traffic were strongly correlated and showed positive and significant responses to traffic reduction measures, suggesting that traffic is an important source of both NH.sub.3 and NO.sub.x in urban Beijing. Daily concentrations of PM.sub.2.5 and secondary inorganic aerosol (sulfate, ammonium and nitrate) at the urban and rural sites both decreased during the Parade Blue period. During (after) the emission control period, concentrations of PM.sub.2.5, PM.sub.10, NO.sub.2, SO.sub.2 and CO from the national city-monitoring network showed the largest decrease (increase) of 34-72 % (50-214 %) in Beijing, a smaller decrease (a moderate increase) of 1-32 % (16-44 %) in emission control regions outside Beijing and an increase (decrease) of 6-16 % (-2-7 %) in non-emission-control regions of China. Integrated analysis of modelling and monitoring results demonstrated that emission control measures made a major contribution to air quality improvement in Beijing compared with a minor contribution from favourable meteorological conditions during the Parade Blue period. These results show that controls of secondary aerosol precursors (NH.sub.3, SO.sub.2 and NO.sub.x) locally and regionally are key to curbing air pollution in Beijing and probably in other mega cities worldwide.

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Gale Document Number: GALE|A476087599