Remote Monitoring of Gaseous Pollutants by Differential Absorption Laser Techniques

摘要

A single-ended laser radar (LIDAR) system was designed, built, and successfully operated to measure range-resolved concentrations of NO2, SO2, and O3 in the atmosphere using a Differential Absorption of Scattered Energy (DASE) LIDAR technique. The system used a flash-lamp pumped dye laser as the primary source of laser energy. For the NO2 measurements, the dye laser output was used directly in a novel simultaneous two wavelength output mode in which two wavelengths, one on and one off the resonance absorption of NO2 molecules are transmitted simultaneously and the relative attenuation determined for the two backscattered signals detected. This mode of operation effectively reduces errors due to scintillation and aerosol drift. For the SO2 and O3 measurements, it was necessary to frequency double the output of the dye laser to match the absorption spectra of the SO2 and O3 molecules. Field measurements, which were carried out over the Upper East Side of Manhattan for all three pollutants, produced range-resolved concentrations at ranges of over two kilometers.