First simultaneous visualization of SO2 and NO2 plume dispersions using imaging differential optical absorption spectroscopy

Abstract

Imaging Differential Optical Absorption Spectroscopy (Imaging-DOAS) has been utilized in recent years to provide slant column density (SCD) distributions of several trace gas species in the plume. The present study introduces a new method using Imaging-DOAS data to determine two-dimensional plume structure from the plume emissions of power plant in conditions of negligible aerosol effects on radiative transfer within the plume. We demonstrates for the first time that two-dimensional distributions of sulfur dioxide (SO2) and nitrogen dioxide (NO2) in power plant emissions can be determined simultaneously in terms of SCD distribution. The SO2 SCD values generally decreased with increasing distance from the stack and with distance from the center of the plume. Meanwhile, high NO2 SCD was observed at locations several hundred meters away from the first stack due to the ratio change of NO to NO2 in NOx concentration, attributed to the NO oxidation by O3. The results of this study show the capability of the Imaging-DOAS technique as a tool to estimate plume dimensions in power plant emissions.