Spatial and temporal variations in NO.sub.2 distributions over Beijing, China measured by imaging differential optical absorption spectroscopy

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2008.11.025 Byline: Hanlim Lee (a), Young J. Kim (a), Jinsang Jung (a), Chulkyu Lee (b), Klaus-Peter Heue (c), Ulrich Platt (c), Min Hu (d), Tong Zhu (d) Abstract: During the CAREBEIJING campaign in 2006, imaging differential optical absorption spectroscopy (I-DOAS) measurements were made from 08:00 to 16:00 on September 9 and 10 over Beijing, China. Detailed images of the near-surface NO.sub.2 differential slant column density (DSCD) distribution over Beijing were obtained. Images with less than a 30-min temporal resolution showed both horizontal and vertical variations in NO.sub.2 distributions. For DSCD to mixing ratio conversion, path length along the lines of I-DOAS lines of sight was estimated using the light-extinction coefficient and a'ngstrom exponent data obtained by a transmissometer and a sunphotometer, respectively. Mixing ratios measured by an in-situ NO.sub.2 analyzer were compared with those estimated by the I-DOAS instrument. The obtained temporal and spatial variations in NO.sub.2 distributions measured by I-DOAS for the two days are interpreted with consideration of the locations of the major NO.sub.x sources and local wind conditions. I-DOAS measurements have been applied in this study for estimating NO.sub.2 distribution over an urban area with multiple and distributed emission sources. Results are obtained for estimated temporal and spatial NO.sub.2 distributions over the urban atmosphere; demonstrating the capability of the I-DOAS technique. We discuss in this paper the use of I-DOAS measurements to estimate the NO.sub.2 distribution over an urban area with multiple distributed emission sources. Author Affiliation: (a) Advanced Environmental Monitoring Research Center (ADEMRC), Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Bukgu, Gwangju 500-712, Republic of Korea (b) Institute of Environmental Physics and Remote Sensing, University of Bremen, P.O. Box 33 04 40, D-28334 Bremen, Germany (c) Institute of Environmental Physics, University of Heidelberg, INF 229, D-69120 Heidelberg, Germany (d) State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences, Peking University, Beijing 100871, China Article History: Received 5 April 2008; Revised 9 November 2008; Accepted 23 November 2008