Sources of air pollution in China

In concrete terms, the composition of the rampant smog seen in major Chinese cities is an amalgamation of SO2, NOX, CO, O3 and particulate matter that has built up over time to dangerous levels (Greenpeace). Studies have shown a seasonal component, with soil dust waxing in the spring and waning in the summer (and SO2 and NOX appearing much more in winter) (Wang, 2004; Zhang, 2013); and changes also due to shifts in circumpolar vortex dynamics, cyclone events, etc. Six main sources have been identified for smog in Beijing: soil dust, coal combustion, biomass burning, traffic and waste incineration emission, industrial pollution, and secondary inorganic aerosol (Zhang, 2013). This complex mixture makes up PM2.5, the most hazardous of fine particulate matter. Generally it is produced by secondary pollutants (such as SO2 and NOX, both emitted from the combustion of coal) either condensing onto primary pollutants (such as soot), or reacting to form dangerously small new particles.