CAREBEIJING progresses air pollution control measures in Beijing

Beijing as seen through the recent smog episode. (Photo credit Flickr user: Infinite Jeff)

Beijing as seen through the recent smog episode. (Photo credit Flickr user: Infinite Jeff)

The severe air pollution in China’s capital, Beijing, has made the news around the world these past two months, with many wondering what was causing the smog. Professor Tong Zhu, of Peking University’s College of Environmental Sciences and Engineering in Beijing, delivered a special SOCAAR Seminar addressing the recent air pollution episode. He also highlighted steps that could be taken to improve the air quality in Beijing and the surrounding North China Plain.

The pollution observed in Beijing is not an isolated issue but is linked to the regional and megacity air pollution of China said Zhu. There is regional transport of air pollution as significant air mass from the southwest and southeast regions travel to Beijing. To better understand the situation, CAREBEIJING (Campaigns of Air Quality Research in Beijing and Surrounding Regions) was carried out using a mobile sampling vehicle from 2006 to 2008. Peking University led this international air quality campaign, which focused on understanding the transport and transformation process of air pollution in Beijing and the surrounding North China Plain.

According to Zhu, controlling volatile organic compounds (VOC) is an effective means for reducing ozone and particulate matter (PM). The campaign found 40 to 60 per cent of VOC come from vehicle related emissions. Traffic control policies which placed a daily limit on the number of vehicles on the road (depending on a vehicle’s licence plate) were first implemented in 2007. The traffic controls were then continued in 2008 during the Beijing Olympics. There were significant decreases in the levels of nitrogen oxide, carbon monoxide, ozone, and PM measured from 2006 to 2008.

Meteorological factors can also influence the distribution of air pollution; for example, the variable weather helped disperse pollution during the 2008 Beijing Olympics. But Zhu said the drastic reduction of black carbon and nitrogen oxide levels observed from CAREBEIJING suggest while both meteorology and traffic controls played a role, the latter is the main factor.

But compared to the CAREBEIJING data, Zhu said there was a larger meteorological influence in Beijing’s recent air pollution episode. Beijing experienced low air pressure systems and stagnant air throughout this past January, concentrating PM in the region. Also, winter time in Beijing means high levels of emissions from the use of coal heaters. Both meteorological influence and intensive emissions in the area contributed to the high PM levels and low visibility in Beijing during the recent air pollution episode.

Zhu also spoke of the next CAREBEIJING initiative scheduled for June 2013 which is aimed at understanding the process of particle formation, as well as the health impacts of air pollution. Specifically, the influence of photochemical reactions between particles remains a question. In the previous CAREBEIJING initiative, Zhu and his colleagues saw a higher organic composition in particles than expected. In the upcoming campaign, they will investigate how these organic particles are converted into aerosol particles.