Advanced mobile-DOAS techniuqes for locating and identifying urban area emission sources

Pollutant concentration distribution and emission are important ways to understand regional pollution. To investigate the distribution characteristics and identify individual sources rapidly, a new mobile passive differential optical absorption spectroscopy (DOAS) instrument has been developed, which set two angle telescopes (90°,30°) to receive the scattered light respectively, and set two mechanical shutters to switch the optical path quickly in the mobile platform. The instrument collected the zenith scattered light in the UV or visible region and it was used to derive the vertical column density of trace gases above the measurement route. The slant column density in two different viewing directions were detected, and combined with the geometric approximation, the vertical column density of trace gas was obtained. After obtaining the column concentration distribution, the data were analyzed by semi variance analysis combined with geographical information. Monte Carlo simulation was used to reconstruct the high spatial resolution pollutant concentration distribution, combined the wind field data during the observation, the high spatial resolution emission flux in the area can be quickly obtained. A field experiment was performed in Beijing and some industrial area. The distribution information of vertical column density along the route in Beijing was derived, the concentration distribution of NO₂ at 200m *200m resolution and the 0.01° *0.01°resolution emission flux data are obtained further. The new mobile multi light DOAS instrument were operated on a car. The NO₂ column density spatial distribution and the emission flux spatial distribution are obtained with the maximum value of 8.57×1016 molec./cm² and 34.8 ug/m²/s over the Beijing fifth ring road area. The scheme can provide a new method to verify pollutant concentration distribution and emission inventory.