Local pollutant more responsible for Beijing's smog

Most air pollution in Beijing is actually the result of local emissions of pollutants, which accounted for 64-72 percent of the smog in the Chinese capital last year, according to the latest research from the city's environmental protection agency.

Automobile traffic, coal consumption, industrial production and dust were the main sources of the PM2.5 that reduced the air quality in Beijing; they respectively contributed 31.1 percent, 22.4 percent, 18.1 percent and 14.3 percent of the hazardous particles discharged into the city's air. Restaurants, auto repair shops, livestock breeding facilities and building construction and renovation are responsible for the remaining 14.1 percent of PM2.5 discharge.

As for the composition of PM2.5, organic matter (OM), nitrates (NO3-), sulfates (SO42-), crustal elements and ammonium salts (NH4+) took up the largest shares, respectively contributing 26 percent, 17 percent, 16 percent, 12 percent and 11 percent of the total mass of PM2.5 in Beijing's air.

The research also showed that secondary particles, i.e., particles formed by gaseous pollutants, accounted for 70 percent of all PM2.5 concentration, and were the primary reason for occasional heavy air pollution.

Automobiles also contributed considerably to the city's soaring PM2.5 readings. Apart from directly emitting polluting elements, vehicles also served as "blenders," stirring up dust in city streets.

Since cross-region transfer still constituted 28-36 percent of the PM2.5 mass concentration in Beijing, the research report urged joint efforts with Beijing's neighboring Tianjin Municipality and Hebei Province to reduce the region's overall emissions of pollutants.