Optical And Size Distribution Characteristics Of Smoke Particles From Biomass Burning

As one of the most important components of the Earth atmosphere,aerosol particles have received widespread attention for their influence on regional climate,visibility,air quality,and human health.The smoke particles from biomass burning(BB)are an important part of aerosol particles and have an important impact on the regional environment and global climate.There are abundant biomass resources in China,so aerosols emitted by straw and wood burning,forest fires and other types of biomass burning in China have important effect on the regional environment and global climate,with continuous development and changes in ways and degrees.Therefore,it is significant to study the optical properties and particle size distribution of smoke from biomass burning.It can provide basic data and methods to study aerosol radiative forcing and its impact on the regional environment and climate by revealing the physicochemical characteristics of BB smoke.The aim of this paper is to study the effects of combustion conditions and biomass species on the optical properties and particle size distribution of BB smoke.The study is to reveal the influence of gas flow,atmosphere,and heating temperature on the physicochemical characteristics and optical properties of smoke produced by stable combustion of biomass.It is also to analyze the influence of the chemical composition on the particle size distribution and optical properties of BB smoke.The study is to develop the particle identification method based on optical properties of aerosol particles and the angle improved method for smoke detection.Firstly,we established the combustion experimental platform based on a tube furnace was to receive a relatively stable combustion environment.We used the platform to study the influence of gas flow,atmosphere and heating temperature on the physicochemical characteristics of aerosol from biomass burning.The modified combustion efficiency(MCE)decreased but not significant with increasing of gas flow.The time of wood burning and the concentration of CO and CO2 also decreased with gas flow increasing.However,the influence of gas flow on the combustion state was not significant.The MCE increased with the temperature increasing,and the combustion state of wood changed from pyrolysis to flaming.The small size particles formed under high gas flow and high temperature,and the modal diameter of particles changed from an accumulation mode larger than 200 nm to an Aitken mode smaller than 100 nm.The light absorption of the collected aerosol particles depended on the wavelength.It indicated that the brown carbon existed in the aerosols generated from low-temperature combustion of biomass or in the nitrogen atmosphere,and the brown carbon existed in both water-soluble organic carbon and water-insoluble organic carbon.Then,a combustion platform to simulate open burning of biomass was established in the standard fire room.We studied the particle size distribution and optical properties of smoke form open burning of different types of biomass,including some kinds of crop residues and wood.The particle size distribution of smoldering smoke particles generated by open burning of biomass showed a bimodal lognormal distribution for crop residues,and a trimodal lognormal distribution for wood.The modal diameters were close to 10 nm and 50 nm,as nucleation modes less than 30 nm and Aitken modes between 30 nm and 100 nm.The particle size distribution of smoke particles from flaming showed a trimodal lognormal distribution,with the main peak size close to 60 nm.The single scattering albedo(SSA)of smoke from flaming was significantly smaller than that of the smoldering smoke.The extinction coefficient and scattering coefficient of smoldering smoke had a strong positive correlation with particle number concentration of diameter greater than 100 nm,while which of smoke from flaming had a strong positive correlation with particle number concentration of diameter less than 100 particles.The SSA and modal diameters of smoldering smoke had correlation with the chemical composition of biomass,including the contents of ultimate analysis and proximate analysis and their related parameters.The SSA had a negative linear relationship with VM/FC(volatile matter/fixed carbon).The change of moisture content affected the scattering coefficient and extinction coefficient of particles.However,it could not affect the SSA and the particle size distribution of particles.The optical properties of different kinds of particles at different wavelengths were simulated numerically.A method to distinguish different types of aerosol particles based on dual-wavelength light was developed,with the difference in the optical properties of particles.To distinguish different kinds of smoke particle and optimize the angles in smoke detection,we gave the relationship between the extinction and scattering characteristics of smoke particles and their angular distribution.