Using satellite-derived NO2 column data from Ozone Monitoring Instrument（OMH）, we analyzed the characteristics and factors affecting the spatio-temporal distribution of tropospheric NO2 column density in Beijing-Tianjin-Hebei Region from 2005 to 2014. Results demonstrated that（1） tropospheric NO2 column density considerably fluctuated on the temporal scale and increased at an annual rate of3.35%, with the highest column density in 2011; NO2 level increased during 2005 to 2011, ignoring changes in 2008, and decreased from2012 to 2014.（2） The spatial distribution of tropospheric NO2 column density significantly changed, with the lowest distribution found in the northwest part and the highest in the southeast part. Tropospheric NO2 column density was low in Zhangjiakou and Chengde in north Beijing-Tianjin-Hebei Region but high in Beijing-Tianjin-Tangshan and Shijiazhuang-Xingtai-Handan.（3） Beijing-Tianjin-Hebei is surrounded on three sides by mountains in north and is not conducive to NO2 distribution. Precipitation exhibited a highly negative correlation with NO2 concentration because of atmospheric wet deposition.（4） Pollution sources were highly determined by industrial and energy structures.The tertiary industry is dominant and increases steadily in Beijing, where coal consumption is low, but car ownership increases 1.5 times; as such, the main source of NO2 in Beijing is motor vehicle exhaust emissions. The second industry of Tianjin is slightly higher than the third industry; in this area, coal consumption is twice higher than that in Beijing but car ownership is only half of that in Beijing; thus, industrial emissions and motor vehicles are a common source of NO2 in Tianjin. A high proportion of secondary industry is found in Hebei, where coal accounted for 80.6% of that in the Beijing-Tianjin-Hebei Region; hence, Hebei industrial emissions are the main source of NO2, although vehicle emissions have increased with increased vehicle ownership in the recent years.

Tropospheric NO2 column density;OMI;satellite remote sensing monitoring;spatial-temporal change;impact factors;Beijing-Tianjin-Hebei Region