NO₂ Differential Absorption Lidar System Based On Dye Laser

Atmospheric Nitrogen dioxide(NO2)is a major pollutant that affects the environmental quality of the atmosphere.The rapid development of industry,the increase of cars and the burning of biomass are the sources of atmospheric NO2 emissions,which have an important impact on human health.The study of Differential Absorption Lidar(DIAL)technology for atmospheric NO2 active remote sensing have great academic significance and application value in the fields of climate change,environmental protection,environmental law enforcement and so on,which need accurately and reliably detect the distribution of NO2 near the ground.In this paper,the properties of NO2 and the basic characteristics of its distribution in the atmosphere are discussed,and the principle of DIAL for gas composition detection is introduced.Then,combined with the detection index,the echo signal of detecting atmospheric NO2 is simulated,and the required wavelength and energy for detection are analyzed by solid-state laser pumping dye laser.Thirdly,a DIAL system for measuring atmospheric NO2(N02-DIAL)is developed.The problems of combined transmission of NO2 channel with SO2 channel and the discrimination of multi-wavelength echo signal in the system are solved.Fourthly,the software of NO2 concentration inversion is developed.The DIAL system has the characteristics of tunable wavelengths,a multi-wavelength combined inversion algorithm is developed to correct the influence of aerosols.Fifth,the horizontal and vertical distributions of atmospheric NO2 were observed at Hefei,Huainan in Anhui Province and at Yangbajing,in Tibet,respectively.The experimental data were obtained and the inversion results were analyzed.Comparing with the atmospheric NO2 concentration issued by the official,it is found that the results are basically consistent,which verifies the validity of the observed data of NO2.Finally,the detection accuracy and error of are analyzed in the measurement of atmospheric NO2.The long-term experimental results show that the spatial resolution of the system is 15m,the effective distance is far from 3km and the measurement accuracy is±5ppb.The system is stable and reliable.