The smog in China was such an issue before the Beijing Olympics last year that Chinese government officials placed restrictions on emissions. To determine just how much clearer the air was afterward, NASA used remote sensing instrumentation to evaluate changes in the pollutant levels. Tests showed that the concentration of nitrogen dioxide had dropped nearly 50 percent and carbon monoxide, about 20 percent.
Tracking pollutants
To look at sulfur dioxide (SO2) and tropospheric ozone, the researchers studied data from the Aura satellite that was taken using an ozone-monitoring instrument built by Dutch Space Holding BV of Ulvenhout and TNO Science and Industry of Eindhoven, both in the Netherlands, as well as a passive microwave limb sounding radiometer/spectrometer built by Caltech’s Jet Propulsion Lab of Pasadena, Calif. On the satellite Terra, a sensor called MOPITT (for measurements of pollution in the troposphere) used gas correlation spectroscopy to measure concentrations of carbon monoxide in 5-km layers vertically through the atmosphere, helping scientists track the gas to its source.
The team of researchers from NASA’s Goddard Space Flight Center in Greenbelt, Md., led by Jacquelyn Witte, used these Earth-observing instruments to make air quality assessments before, during and after the Olympic Games. What’s significant, Witte noted, is the success of the Chinese government’s efforts to improve the air quality over the city of Beijing. “The results of the intensive pollution emission controls put in place during the Olympics have not gone undetected from our current Earth-observing instruments.”
The information gathered by this and other Earth-observing studies is welcomed by the Chinese government, according to Witte, as the data shows significant positive changes in the air as a result of the stringent controls put in place.