Using stable isotopes to trace sources and formation processes of sulfate aerosols from Beijing, China

Particulate pollution from anthropogenic and natural sources is a severe problem in China. Sulfur and oxygen isotopes of aerosol sulfate (delta S-34(sulfate) and delta O-18(sulfate)) and water-soluble ions in aerosols collected from 2012 to 2014 in Beijing are being utilized to identify their sources and assess seasonal trends. The mean delta S-34 value of aerosol sulfate is similar to that of coal from North China, indicating that coal combustion is a significant contributor to atmospheric sulfate. The delta S-34(sulfate) and delta(18)O(sulfate)values are positively correlated and display an obvious seasonality (high in winter and low in summer). Although an influence of meteorological conditions to this seasonality in isotopic composition cannot be ruled out, the isotopic evidence suggests that the observed seasonality reflects temporal variations in the two main contributions to Beijing aerosol sulfate, notably biogenic sulfur emissions in the summer and the increasing coal consumption in winter. Our results clearly reveal that a reduction in the use of fossil fuels and the application of desulfurization technology will be important for effectively reducing sulfur emissions to the Beijing atmosphere.