Research On Hygroscopic Growth Characteristics Of Aerosol Scattering In Chengdu And Its Application

The hygroscopicity of atmosphere aerosols is the link between the aerosol microphysics and chemical parameters,and it is also the decisive parameter for the basic optical properties of aerosols,related research has important theoretica l significance and applicable value.To this end,by utilizing the hourly observed data from AURORA 3000 nephelometer and AE-31 aethalometer from October to December 2017 in Chengdu,as well as the simultaneous environmental meteorologic a l monitoring data(atmospheric visibility,relative humidity RH and N O₂ mass concentration),scattering extinction hygroscopic growth was systematically studied,and the visibility was predicted.The main conclusions are as follows:(1)Based on the analysis of correlation,the aerosol hygroscopic growth critical point and the optimal hygroscopic growth model show that,the variation characterist ics of the two aerosol extinction hygroscopic growth factors f₁(RH)(Based on the average unit mass of aerosol extinction coefficient in a dry environment)and f₂(RH)(Based on the scattering extinction coefficient of aerosol dried in a wet environment)are generally consistent and can be used to characterize the change law of aerosol hygroscopic extinction coefficient with relative humidity.Compared with the aerosol extinct io n hygroscopic growth factor f₁(RH),the aerosol extinction hygroscopic growth factor f₂(RH)is more well-thought-out,which takes into account the difference of optical effects of the same aerosol under different humidity conditions.(2)Based on the adaptability analysis of three international general models,it shows that the aerosol scattering hygroscopic growth model of quadratic polynomia l can best characterize the variation characteristics of f(RH)with RH in autumn and winter in Chengdu.In this paper,f(RH)equal to 2 is treated as the burst growth point of relative humidity from the steady increase to the steep increase of f(RH),and the point appears between RH 86%and RH 87%.When the relative humidity increases from 40%to the burst growth point,f(RH)increases more slowly and fluctuates to a minor extent,indicating that the capacity of aerosol scattering hygroscopic growth is weaker at this time;as the relative humidity continues to increase from the burst growth point,f(RH)begins to increase sharply,and the degree of fluctuation also increases significantly.(3)It was found that f(RH)in Chengdu was lower than the corresponding analys is results in the Pearl River Delta region,but was general y higher than the calculated values in the Beijing-Tianjin-Hebei,Yangtze River Delta,Brazil and Portugal regions.The proportion of sulfate and nitrate components of aerosol in Chengdu is relative ly high,and the separate or synergistic hygroscopic growth of the two will inevitably have an important effect on their optical effect,forming the particularity of land-city-t ype aerosol scattering hygroscopic growth for the western Sichuan,and to some extent,resulting in the evolution of haze.(4)Constructed with the particle mass concentration index C_BC/C_PM10,relative humidity RH and particulate matter concentration PM_2.5 as factors,88%RH obtained as the critical point,the aerosol scattering coefficient segmentation parameteriza t io n scheme was carried out,and the calculation results are better.(5)Constructed with the particle mass concentration index C_BC/C_PM10,relative humidity RH,particulate matter concentration PM_2.5,Gaseous pollutant absorption coefficient at 550nm wavelength,dry atmospheric scattering coefficient at 550nm wavelength and absorption coefficient at 550nm wavelength as factors,88%RH obtained as the critical point,the visibility segmentation parameterization scheme was carried out,and the calculation results are better.