New particle formation and haze events in Beijing, China

An estimated 2.5 million people in China die each year from the health effects of indoor and outdoor air pollution. The concentration of airborne pollutants in China’s megacities can reach many hundreds of times that of European and American cities. Severe haze pollution events are routinely observed in Beijing over the winter months, with PM2.5 levels often exceeding several times the China National Ambient Air Quality Standard. The formation and evolution mechanisms of these haze events are not fully understood. In addition to the nature of the emission sources, it is known that there is a significant influence of meteorological conditions such as wind direction and speed, temperature and humidity. Some studies have shown that the haze particle concentrations are driven to a large extent by secondary aerosol formation..