Effects of photochemical oxidation on the mixing state and light absorption of black carbon-containing aerosols in Shenzhen
In February 2021,we conducted a study in Shenzhen to measure the mixing state and optical properties of black carbon(BC)-containing aerosols.Simultaneously,we analyzed odd oxygen(Ox)to explore the effects of photochemical oxidation on coating,morphology,and light absorption of BC-containing aerosols in an urban environment.The results show that,during the observation period,the mean bulk-averaged relative coating amounts(coating-to-core mass ratio,MR)over particle population was 4.3±0.7.The mean effective density was(1.35±0.10)g/cm3,and about 70％of the observed period exhibited spherical morphology,indicating that the BC-containing aerosols in Shenzhen were predominantly composed of internally mixed particles with moderately irregular shapes.Photochemical oxidation played an important role in the mixing state evolution of BC-containing aerosols.With rising Ox concentrations,the bulk-averaged MR increased by about 38％,the effective density increased from 1.32g/cm3 to 1.44g/cm3,and the dynamic shape factor decreased from 1.05 to 1.00,indicating that the photochemical oxidation process resulted in the accumulation of non-BC components and reshaped more compact spherical particles with core-shell structure.Additionally,as Ox concentrations increased,the light absorption enhancement(Eabs)exhibited an approximately 20％increase,with a growth rate of 0.002/ppbv,suggesting the key role of photochemical oxidation in enhancing light absorption of BC-containing aerosols in an urban site.
万方数据
维普
