Long-term NO2 Monitoring by Satellite in the Pearl River Delta

Recently, the air quality has been continuing to deteriorate and threaten public health in the Pearl River Delta. China, the host country for the 2010 Asian Games, faced the great challenge of air quality issues, particularly in the Pearl River Delta, where the Asian Games were held. The major aim of this study is to reveal the spatial and temporal characteristics of NO2 in the Pearl River Delta during October 2004 to December 2010. The long-term characteristics and variations of the NO2 column concentration before and during the 2010 Asian Games were analyzed by using the NO2 product OMNO(2)e from the Ozone Monitoring Instrument (OMI). Results show that the annual average of the NO2 column concentration has a significant downward trend from 2005 to 2010 in the Pearl River Delta: the total column concentration of NO2 (TotNO(2)) in the atmosphere decreased from 9.207x10(15) molec/cm(2) to 8.173x10(15) molec/cm(2), with an average annual rate of -2.247%; the tropospheric column concentration of NO2 (TropNO(2)) decreased from 6.685x10(15) molec/cm2 to 5.646x10(15) molec/cm(2), with an average annual rate of -3.109%. The ratio TropNO(2)/TotNO(2) indicating the amount of NO2 exhausted by human activities also decreased from 0.726 in 2005 to 0.691 in 2010. During the 2010 Asian Games, the weekly average of the TropNO(2) in Pearl River Delta was maintained at a low level. The NO2 average distribution in the Pearl River Delta is characterized by the maximum in the geometric center, outwardly smaller, and the shrinking areas with high TropNO(2) concentration from 2005 to 2010. Foshan, Jiangmen and Kwangchowan were severely polluted cities during the Games. However, the air quality of the Pearl River Delta was improved compared to its historical periods due to governmental preventive/control measures during the 2010 Asian Games.