The severe haze pollution event in China at the beginning of 2013 was driven to a large extent by secondary aerosols, which form within the atmosphere from precursor gases. This finding, reported in Nature this week, indicates that strategies to control haze pollution should aim to reduce the emission of secondary aerosol precursors, such as from fossil fuel or biomass burning, as well as to mitigate the release of primary pollution sources (particles that are directly emitted to the atmosphere).
In China, particulate pollution is a serious environmental problem that influences air quality, climate, and human health. The severe and persistent haze pollution that affected around 800 million people in 2013 prompted the Chinese State Council to set a target to reduce fine particle concentrations by up to 25% relative to 2012 levels by 2017. However, such efforts require an understanding of the factors that govern fine particle concentrations.
Junji Cao, André Prévôt and colleagues show that during January 2013, secondary aerosol formation contributed on average to around 30–77% of fine particle concentrations and 44-71% of organic aerosols in Beijing, Shanghai, Guangzhou and Xi’an. On average, the contribution of secondary organic aerosol and secondary inorganic aerosol (mainly including sulphate, nitrate and ammonium) are found to be of similar importance (SOA/SIA ratios range from 0.6 to 1.4). Sources of secondary aerosol precursors (SO2, NOx, NH3, and, in particular, VOCs) include fossil fuel combustion and biomass burning. Thus, the authors conclude that reducing emissions from these sources is likely to be important for controlling China's particulate pollution and for reducing the environmental, economic and health impacts resulting from particulate pollution.
Dr. Rujin Huang is the first author of this paper. Drs. Junji Cao and Andre Prevot are the corresponding authors.
This paper is the first study about air pollution to publish in Nature as letter from mainland China.
Composition and source contributions of PM2.5 over Beijing, Shanghai, Guangzhou and Xi’an during haze period in January 2013
Jun-Ji Cao (Chinese Academy of Sciences, Xi’an, China)