Research On Mass Concentration Detection Of Atmospheric Particulate Matter Based On Multi-Angle MCF Model

Atmospheric particulate pollution has become an important environmental pollution problem in China and even the whole world.As particulate matter pollution shows the characteristics of small particle size and low concentration,higher requirements are put forward for particulate matter mass concentration measurement system.At present,the light scattering method uses known particles for system calibration,but it is difficult to meet the requirements of real-time measurement.To solve the above problems,a multi-angle mass concentration factor(MCF)model was proposed to detect the mass concentration of atmospheric particles.By establishing MCF model calibration system parameters,the real-time measurement of particulate mass concentration was realized.The main work of this article is as follows:The basic theory of light scattering is studied in depth,and the basic methods for measuring the mass concentration of particulate matter are discussed.On the basis of Mie scattering theory,the study of measuring the mass concentration of particulate matter based on the light scattering integral method was carried out.The selection principle of the optimal detection angle for mass concentration measurement of particulate matter was analyzed in depth,and the four evaluation parameters of mass concentration factor,drift,mass concentration coefficient and offset coefficient were constructed to evaluate the optimal detection angle.Based on the optimal detection angle,a multi-angle mass concentration factor(MCF)model is proposed to detect the mass concentration of atmospheric particulate matter,and the real-time measurement of particulate mass concentration is realized by establishing the MCF model calibration system parameters.Based on the measurement of mass concentration of particulate matter by light scattering ensemble method,the effects of particle size,detection angle and refractive index of particulate matter on the light scattering information of particulate matter were further discussed.The distribution of detection angle and mass concentration factor under different particle size segments was calculated and analyzed,and it was obtained that particle size had little influence on the measurement of scattered light in the submicron particle size segment.The changes of particle size and mass concentration factors at different detection angles were also analyzed,and it was found that the scattered light measurement at the forward angle was less affected by the detection angle.Finally,the changes of scattered light intensity of particles with different attributes with the change of detection angle are simulated,and the results show that the influence of particle properties on the measurement of scattered light information is minimal at the forward angle.Aiming at the proposed mass concentration measurement method,a multi-angle mass concentration measurement system platform for particulate matter is designed.The system consists of three parts:particle generation module,particle light scattering detection module and scattered light signal collection module.The standard particulate matter verifies the effectiveness of the experimental platform for light scattering signal acquisition.Based on the mass concentration detection system of multi-angle MCF model,the relationship between the scattered light intensity of particulate matter and the reference mass concentration was established,and the distribution of scattered light intensity and reference mass concentration of different substances at different particle sizes and detection angles was specifically analyzed.After theoretical calculation and comprehensive analysis of experimental results,the optimal detection angle of particulate matter is 45°.Combined with the relationship between asymmetric factor and mass concentration factor,the real-time calibration of mass concentration detection system parameters is realized.Finally,the experimental experiment of multi-angle mass concentration detection system and the standard instrument TSI-8530 was carried out.The results showed that the linear correlation coefficient of the four particle size segments(PM1,PM2.5,PM4,PM10)was greater than 0.95,and the average relative deviation was less than 7.8%.Through the above analysis,the effectiveness and accuracy of the method for detecting the mass concentration of atmospheric particulate matter based on the multi-angle MCF model are verified.