Chinese Haze Sources Identified

Air pollution leading to dense haze in Chinese cities is driven by formation of aerosol particles in the atmosphere stemming from a variety of organic and inorganic precursor materials, according to a report (Nature 2014, DOI: 10.1038/nature13774). The results suggest that reducing health-harming particulate matter—the Chinese State Council’s goal is to get to 75% of 2012 levels by 2017—will require control of the precursors. The study, which was led by Jun-Ji Cao of the Chinese Academy of Sciences and André S. H. Prévôt of Switzerland’s Paul Scherrer Institute, looked at the composition of atmospheric particles in Beijing, Shanghai, Guangzhou, and Xi’an in January 2013. Excluding dust, the researchers found that a majority of particles with a diameter less than 2.5 µm are formed in the atmosphere rather than being emitted directly. As in urban settings elsewhere in the world, reducing airborne particulate matter in China will therefore require not just controlling primary emissions but also particle precursors such as SO₂, NO_x, and volatile organic carbon compounds released by fossil-fuel and biomass burning, the study’s authors note.