An optical remote sensing method for determination of total volume of air pollutants (such as SO2, NO2) emitted from sources is studied, by use of a passive differential optical absorption spectroscopic (DOAS) instrument to scan the plume from pollution source on a mobile platform (such as a car). The column density of air pollutant is retrieved from processing of the scattered sun light spectra in the zenith sky collected by the instrument by means of the spectral analysis method of passive DOAS. Combination with the meteorological (wind field) information during the measurement, the average flux value of air pollutant during the measurement can be estimated then the total emission value can be derived. DOAS method used to obtain the vertical column density the plume and the method used to derive emission flux are described in detail. The passive DOAS instrument was carried by a car to scan the plume from a thermo-power plant in a field measurement. The measurement results and the comparison with the total volume from an on-line monitoring instrument indicate this method based on passive DOAS can be used for rapid remote sensing of the total emission volume from pollution sources.