Remote sensing of atmospheric SO2 using the differential absorption LIDAR technique

The paper reports an investigation of the capabilities of a UV differential absorption lidar (DIAL) system for remote measurements of sulfur dioxide emissions. Two features of the present DIAL system are an absorption cell permitting the determination of the difference in SO2 absorption coefficients for the two transmitted wavelengths and a calibration cell permitting the linearity and performance of the system to be evaluated. The DIAL technique is described along with the transmitter, receiver, data-adquisition, and data-processing components of the investigated system. Quantitative measurements of the average SO2 concentration in a region surrounding the exhaust stack of a steam-generating plant are discussed which show that the present system has measurement sensitivities of 10 ppb at a range of 0.8 km and 20 ppb at 1.9 km. Based on performance characteristics obtained during a calibration of this system, it is predicted that a measurement sensitivity of less than 4 ppb over a 1-km path will be attained.