Study On The Optical Absorption Coefficient Of PM_0.1 And PM₁ In Automobile Exhaust Based On Photoacoustic Spectroscop

Aerosols are one of the major pollutants in the atmosphere and can have important effects on atmospheric visibility,human health and radiative forcing.Atmospheric aerosols absorb and scatter solar radiation and have an impact on climate forcing with a high degree of uncertainty.Atmospheric aerosols have an impact on global climate change,and their contribution to global warming is second only to carbon dioxide.Particulate matter in vehicle exhaust is one of the sources of atmospheric aerosols,and its contribution to human health and climate change is highly uncertain.Therefore,it is very important to conduct studies on the optical absorption properties of aerosols in vehicle exhaust to reduce the uncertainty in global radiative forcing assessment and to predict local climate change.In measuring the optical absorption properties of aerosols,the photoacoustic spectroscopy technique is unique in that the natural suspension of aerosol particles is not altered during the measurement process,and the measurement results are not affected by multiple scattering of aerosols,which is one of the most effective methods for measuring the optical absorption properties of aerosols at present.In this paper,based on the photoacoustic spectroscopy system,a total of 39 vehicles were researched for the optical absorption of exhaust particles at idle speed using a differential method at the wavelength of 1064 nm,18 of which were used to measure the optical absorption coefficient of ultrafine particles(PM_0.1)and 21 of which were used to measure the optical absorption coefficient of submicron particles（PM₁）.The absorption was classified according to the model,vehicle weight,engine displacement and service life,and the optical absorption coefficients of vehicle exhausts were obtained.The experimental results showed that the optical absorption coefficients of PM_0.1and PM₁in vehicle exhaust decreased since the addition of emission limits for particulate matter in the National V standard.In addition,the optical absorption coefficients of PM_0.1and PM₁were positively correlated with the age,weight and engine displacement of the vehicle.The optical absorption coefficients measured at different sunlight times were also different,and showed an increase and then decrease with the sunlight time.The results of the study provide a data reference for studying the optical absorption coefficients of PM_0.1and PM₁in vehicle exhaust.