Nitrogen dioxide levels in the troposphere over China are increasing at an alarming rate far higher than had been predicted.

Nitrogen dioxide levels in the troposphere over China are increasing at an alarming rate far higher than had been predicted, according to data collected by satellite instruments.

So-called Gome and Sciamachy instruments (see Chemistry World, May 2005, p40) were used to collect tropospheric NO2 columns from 1996 to 2004. A team led by John Burrows at the Institute of Environmental Physics, University of Bremen, Germany, used the information to follow changes in NO2 levels across different areas of the globe over that time.

The results show that NO2 levels over Europe have begun to decrease, but levels over industrialised parts of China have increased by around 50 per cent, and the rate of increase is getting faster. This increase is much larger than the 13 per cent increase in NO2 suggested by bottom-up estimates.

Burrows concludes that the rapid growth in China’s economy is the main cause of this trend. ’The data retrieved from space are objective,’ Burrows cautioned, but added, ’we consider that the evidence is very compelling that NO2 is increasing [over China] and that this arises from increasing [NOx] emissions.’

The findings are important and timely, says Mark Schoeberl, chief scientist at the Earth Sciences Directorate, Nasa Goddard Space Flight Center, US. Schoeberl works on a Nasa project that has been monitoring air quality and the ozone hole with an ozone monitoring instrument (OMI) on board the satellite Aura. ’Aura’s OMI instrument, which  has not been operating as long as Sciamachy and Gome, is seeing the same thing - very high values of NO2 over China,’ Schoeberl told Chemistry World. ’High levels of NO2 are needed for tropospheric ozone production, although very high levels can reduce ozone,’ he said. 

Burrows is involved in several initiatives to alert governments to pollution problems, especially in China where industrial output is expanding rapidly. These include the European Space Agency Dragon project, which involves ESA space resources in conjunction with Chinese programmes to monitor pollution from space. 

’I and my colleagues are working on both scientific and outreach issues. I am also a member of COSPAR (committee on space research), which advises the UN on space related matters, including those of environmental concern,’ said Burrows. Katharine Sanderson