Differential absorption measurements of the NO 2 , SO 2 atmospheric pollutants

Abstract

Differential absorption measurements made in laboratory on air samples containing NO2 and SO2 atmospheric pollutants are reported. This type of measurements is necessary to calibrate remote sensing equipment conceived to monitor NO2 and SO2 in open atmosphere using LIDAR techniques and to perform preliminary laboratory studies on differential absorption specific to NO2 and SO2 molecules.To monitor the mentioned pollutants, a nitrogen laser pumped tunable dye laser s used, the laser pulse having the following characteristics: energy per pulse 40 iJ, repetition rate 5pps, pulse time width iOns. The dye ivelengths used to detect NO2 were 7on 2off 432.6 nm obtained from POPOP in DMSO and the spectral bandwidth was 0.7 nm; for SO2, ;k0 298 nm, 2off 299.5 nm and the spectral bandwidth was 0.2 nm, the laser beam being obtained from R6G and further SHG by an ADP crystal. The concentration interval for NO2 detection was 18.4 ppm to 26.4 ppm, whereas the measurements for SO2 pollutant ware performed at 6.4 ppm. The studied gases ware home made and the samples pollutant concentration was measured by mass spectrometry.