Research On Inversion Mechanism Of Atmospheric PM2.5 Concentration Based On Forward Scattering Lidar

With China's economic conditions developing rapidly,the residents' living conditions and the requirements for environmental quality have been continuously improved.However,the current evaluation policy for air quality is not perfect and effective.How to control environmental pollution in China is imminent.At present,the ways to measures PM2.5 concentration using light-scatter laser radar are side-scatter laser radar and back-scatter laser radar.Because of the dead zone when use the back-scattered laser radar,it is impossible to measure PM2.5 concentration nearing the ground.Besides,the amount of scattered light information received by side-scatter is relatively little,resulting in loss of effective information.This paper mainly studies the mechanism of inverting PM2.5 concentration by forward-scatter laser radar.The contents are as follows:(1)Expound the background of the topic briefly,describe the monitoring technology of used at home and abroad.Besides,introduce the monitoring status and the research status of light scattering method at home and abroad,and analyze the future development trend.(2)Describe the light scattering characteristics of the particles in the air,and analyze the characteristics of the Mie scattering theory and the numerical calculation process in detail.The effects of different particle size and different particle concentration on the forward-scatter light intensity distribution are simulated,and the proportions of forward-scatter light intensity distribution and backscattered light intensity distribution are compared.(3)According to the Mie scattering theory,an experimental device based on CCD forward-laser scatter radar is built.The echo signal maps under different concentration conditions are obtained by using this device.According to the total gray value of the echo signal map,the grades are divided into S(0),S(20),S(40),S(60),S(80),fitting the formula of the total light intensity and the measured value of the PM2.5 monitored.Then use this fitting formula to invert the PM2.5 concentration and analyze error.(4)This content analyses the results when using lateral and back-scattered lidars under the condition of S(20)model.Meanwhile,fit the echo signal map gray value to invert the PM2.5 concentration,and analyze the PM2.5 concentration and the concentration by BAM-1020.In order to analyze the measurement effectiveness of the three scatter laser radar prediction models better,the measurement errors of three laser scatter laser radar prediction models are analyzed from three levels of low concentration,medium concentration and high concentration,and give the conclusions.(5)This content propose a real-time image processing software based on Delphi7.0.Since the initial data of aerosol concentration measured by laser scatter radar is the echo signal map collected by CCD,and the picture processing is cumbersome which needs to be superimposed,denoised,cropped and extracted.The software realizes the real-time processing of the echo signal map captured by laser scatter radar.In order to solve the problem of image distortion,this software uses the double buffer acquisition method.