Modelling and satellite technology improve atmosphere over Beijing
Hepeng Jia/Beijing, China
Chemists have played a vital role in improving Beijing’s air quality for the Olympics, guiding the government’s massive clean-up operation by highlighting and monitoring major pollution sources.
Beijing has pulled out all the stops in a bid to cut pollution, shutting down hundreds of chemical, cement and steel factories. It has also invested more than US$20 billion over the past seven years, moving away from coal-based power stations and towards cleaner natural gas-based facilities.
Biomass burning by farmers - a simple but environmentally harmful way to deal with farming waste - has been a major cause for concern. Shao Min and colleagues at Peking University have evaluated the impact that biomass burning has on Beijing’s urban air quality and in August 2004 monitored the levels of two chemicals emitted: acetonitrile and levoglucosan.. Beijing’s air quality was affected by the pollutants on two out of 22 days but Shao is optimistic that the city could be free from biomass pollutants for the duration of the Olympics. ’Beijing has intensified its monitoring and preventive measures again biomass burning by suburban farmers,’ he told Chemistry World.
Wang Zifa and colleagues from the Institute of Atmospheric Physics, Chinese Academy of Sciences (CAS), have developed a modelling system to measure and predict pollution in an area the size of some Olympic venues.
The system processes data on 71 pollutants such as sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, and particulate matter (PM) from various sampling sites. It can monitor pollutant movement and simulate up to 137 possible chemical and physical reactions. ’Our system can forecast air quality in certain Olympic venues 72 hours ahead,’ says Wang. This helps environmental agencies to take emergency measures.
Efforts made in Beijing alone are not enough to ensure air quality. In a separate study, Wang used a modelling tool developed by the US Environmental Protection Agency to simulate PM and ozone levels. PM2.5 - tiny solid or liquid particles suspended in the air with a diameter below 2.5 micrometres - is a major pollutant in Chinese cities. The researchers estimated that about 34 per cent of PM2.5 and 35 to 60 per cent of ozone during high ozone episodes at the Olympic Stadium site can be attributed to sources outside of Beijing.
’Controlling only local sources in Beijing will not be sufficient to attain the air quality goal set for the Beijing Olympics,’ warn the researchers.
The government has heeded such warnings and closed polluting factories near Beijing. But it is still possible that some factories and mines will resume production once control measures are loosened. ’The authorities must pay attention to this problem,’ Wang told Chemistry World.
Zhang Jiahua, a scientist with the Chinese Academy of Meteorological Sciences, says that satellite remote sensing can be used to detect if polluting factories near Beijing have re-opened illegally.
If a factory in the control area resumes operation, satellite sensors can detect the extra heat produced. The signal is then transmitted to a monitoring site where air quality analysis can be used to locate the polluters. ’The advantage for the Chinese system is that the powerful government can react quickly, sending in environmental surveillance teams and mobilising local police to shut down the factories,’ says Zhang.
The government has also clamped down on the movement of dangerous chemicals. Zhang Shanwen, head of radiotherapy at Beijing Cancer Hospital, says that every radioactive source in his hospital now has to be carefully recorded and checked. ’It is good to have a detailed management of radioactive sources. I hope that the effective management brought by the Games can be extended beyond the Olympic eras,’ he says.
Meanwhile, some hospitals in Qinhuangdao, an Olympic hosting city near Beijing, have run out of cobalt but cannot get new supplies because of the Olympic ban on transporting dangerous goods, says Zhang. As a result, many patients cannot get diagnosis by nuclear magnetic resonance and radiotherapy treatments.
et alAtmospheric Environment, ,41et alAtmospheric Environment, ,41, 480 (DOI: 10.1016/j.atmosenv.2006.08.046)