First Simultaneous Visualization of SO2and NO2Plume Dispersions using Imaging Differential Optical Absorption Spectroscopy

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.