A comparative study on black carbon aerosol observations in regions of Beijing and Lhasa in 2006

A comparative study is made for black carbon aerosol (BC) in this text based on BC and PM10 observations as well as their air pollution indices during January-December 2006 in Beijing and Lhasa regions. BC concentration is considerably higher in Beijing than in Lhasa because of anthropogenic activities, with an annual mean of 9.3 μg/m3 versus 3 μg/m3 from the standard channel of 880 nm (below is the same). It is higher in winter and lower in summer for both of the regions, with the value in a heating season being more than twice as high as in non-heating season in Beijing area. The highest monthly means of 16.8 μg/m3 vs 5.5 μg/m3 occur in January in Beijing and Lhasa regions, respectively; whereas the lowest values of 4.5 μg/m3 vs 2.2 μg/m3 are in July. The daily higher values of BC in Beijing start from 1600 BST (Beijing standard time) and maintain until 0700 BST of the next day, with keeping lower values during other daytime hours, especially around the noon. The daily maximum and minimum values of 30 μg/m3 and 1.4 μg/m3 happens in December and April in Beijing in 2006, respectively. Generally, BC emissions in Lhasa are much smaller than in Beijing, with relative high values observed in the morning and afternoon; the 2006 daily maximum and minimum of 12.4 μg/m3 and 0.8 μg/m3 appear in the December and the March, respectively. The BC in Lhasa mainly comes from the local emission from vehicles to the atmosphere.