Spectrum Of Dynamic Aerosol Polarization Measurement Data And Its On-line Characterization Application

Aerosol particles are the scatterers under suspension system,how to characterized the chemical and physical properties of the aerosol qualitatively or quantitatively with the help of the emerging techniques is important for determining the sources of aerosols,understanding aerosol transitions,quantifying the impacts on air quality and public health.Since polarization is sensitive to microscopic properties of sample and can improve the information dimension,polarimetry has been widely used in biomedicine,atmospheric and oceanic measurement.Aiming at the hot spot of on-line dynamic analysis of aerosols,this thesis carried out a lot of debugging and measurement of the single particle multi-angle polarization vector synchronization device and proposed a scheme to aerosol type identification and property characterization.First,we discuss the polarization scattering process of single particle,set up a synchronous measurement device of multi-angle polarization indexes and solve a number of technical problems encountered in the field measurement.We adopt optimal design of sheath flow system and sliced light detection to ensure particles pass by detecting center one by one and improve the signal-to-noise ratio;furthermore,the lens and aperture are combined in the detection module to realize the spatial filtering so that the effectiveness of weak signal detection can be ensured;also,the multi-dimensional polarization channel of the instrument is calibrated with standard polydisperse polystyrene.The thesis collects the data of aerosol particles with various attributes and various regions,establishing a multi-dimensional polarization data spectrum which is multi-component,multi-attribute and multi-source.The thesis then proposes the analysis and classification of aerosol properties based on multi-dimensional polarization index center spectrum and distribution spectrum.Results show that the multi-dimensional polarization center spectrum has better temporal resolution and discrimination,and is more suitable to explain the physical attributes of the certain categories.The polarization distribution spectrum greatly expands the aerosol information,improving the identification accuracy and robustness of mixed aerosols,which is more suitable for the classification of aerosols and proportion analysis of mixed components of aerosols.Both polarization spectrums show good application potential in atmospheric monitoring.Finally,we present a way to estimate the aerosol properties based on a real time Stokes vector measurement technology,this method use the iterative Mie algorithm to retrieve the complex refractive index of aerosol,with the help of obtaining of particle size distribution and multiple polarization parameters at multiple angles of single particle scattering.The experimental results show that the complex refractive index retrieval of several typical aerosol samples are in good agreement with the references.Besides,we investigate the results of irregular shape samples,and the discrete dipole analysis(DDA)is introduced as a reference to further discuss the influence of morphology properties,the least square deviation is proposed to quantitatively describe the irregularity of particulate matter.