Study On The Fluorescence Characteristics Of Bioaerosols By Fluorescence-Raman Lidar Technique

Bioaerosol is an important part of atmospheric aerosol.Rapid,real-time and accurate detection of bioaerosol content has important scientific and practical significance for global climate change,biosafety,biological prevention and anti-terrorism and other fields.As a remote active remote sensing detection tool,fluorescence lidar has the advantages of high precision and high resolution,and is an important means to carry out biological aerosol detection at present.In this paper,the fluorescence characteristics of bioaerosols based on fluorescence Raman lidar are studied with the goal of detecting the characteristic parameters of bioaerosols.The main research work of the paper is as follows:First of all,based on the fluorescence effect of biological aerosols,the optimization design of fluorescence Raman lidar system was carried out on the basis of an existing set of ultraviolet Raman lidar system in the Lidar Remote Sensing Research Center of Xi’an University of Technology.Considering the strong absorption effect of atmospheric water vapor in the nearinfrared band,combined with the simulation analysis of the LiDAR system,the design of the near-infrared vibrational Raman scattering channel was completed,and the Mie-Rayleigh scattering channel（1064 nm）and vibrational Raman scattering channel（852.7 nm）in the nearinfrared band were added;Combining the Raman scattering effect and fluorescence spectrum characteristics of atmospheric molecules,the fluorescence scattering detection channel（466 nm）was optimized and designed,and a Fluorescence-Raman lidar detection system was constructed using a dual telescope receiving system,providing technical support for the detection and retrieval of biological aerosol characteristic parameters.Furthermore,the detection and inversion of fluorescence backscattering coefficient,fluorescence capacity and bioaerosol concentration are carried out.The detection performance of the 466 nm fluorescence channel was explored,and the inversion and analysis of these three characteristic fluorescence parameters were carried out based on the Raman scattering echo signal intensity at different wavelengths.The experimental results show that the fluorescence scattering channel can effectively detect fluorescence echo signals below 5 km,and the fluorescence backscatter coefficient value is less than 1 in the range of 1-4 km under sunny conditions 1 × 10^-7 km·^-1sr^-1;The range of fluorescence capacity is less than 3 × 10^-5;When air pollution is serious,the maximum concentration of bioaerosols can reach 80 particles·m-3,the fluorescence scattering channel can be used to detect the fluorescence characteristic parameters of bioaerosols.Finally,based on the Fluorescence-Raman lidar detection system,we carried out the research on bioaerosols under different weather conditions synchronous continuous detection,the simultaneous inversion of fluorescence backscattering coefficient,fluorescence capacity,bioaerosol concentration,and the profile of atmospheric aerosol backscattering coefficient at 355 nm and 1064 nm wavelengths is realized through the synchronous atmospheric echo signals of five scattering channels.The experimental results clearly show the temporal and spatial variation characteristics of the fluorescence intensity and fluorescence characteristic parameters of bioaerosols.The maximum value of the fluorescence backscattering coefficient at 3.5 km cloud layer is 1 × 10^-6 km^-1sr^-1,the maximum concentration of biological aerosol is 90 particles·m^-3,with a maximum fluorescence capacity 4×10^-4 at 1064 nm wavelength indicates that the fluorescence channel has stronger backscattering ability in the near infrared band band.The experimental results verify the detection performance of fluorescence Raman lidar system for the fluorescence characteristics of biological aerosols.