A new method to determine the mixing state of light absorbing carbonaceous using the measured aerosol optical properties and number size distributions

Abstract

In this paper, the mixing state of light absorbing carbonaceous (LAC) was investigated with a two-parameter aerosol optical model and in situ aerosol measurements at a regional site in the North China Plain (NCP). A closure study between the hemispheric backscattering fraction (HBF) measured by an integrating nephelometer and that calculated with a modified Mie model was conducted. A new method was proposed to retrieve the ratio of the externally mixed LAC mass to the total mass of LAC (<i>r</i><sub>ext-LAC</sub>) based on the assumption that the ambient aerosol particles were externally mixed and consisted of a pure LAC material and a core-shell morphology in which the core is LAC and the shell is a less absorbing material. A Monte Carlo simulation was applied to estimate the overall influences of input parameters of the algorithm to the retrieved <i>r</i><sub>ext-LAC</sub>. The diurnal variation of <i>r</i><sub>ext-LAC</sub> was analyzed and the PartMC-MOSAIC model was used to simulate the variation of the aerosol mixing state. Results show that, for internally mixed particles, the assumption of core-shell mixture is more appropriate than that of homogenous mixture which has been widely used in aerosol optical calculations. A significant diurnal pattern of the retrieved <i>r</i><sub>ext-LAC</sub> was found, with high values during the daytime and low values at night. The consistency between the retrieved <i>r</i><sub>ext-LAC</sub> and the model results indicates that the diurnal variation of LAC mixing state is mainly caused by the diurnal evolution of the mixing layer

Aerosol Mixing State: Measurements, Modeling, and Impacts

“…Field closure studies found that complex partially‐internally mixed assumptions give the best closure and that the best fit mixing state varies over the course of the day, with spatial location (Cheng et al, , ; Ma et al, ), with season (Dey et al, ), and with level of pollution (Wehner et al, ). The fact that a signification variation in enhancement is observed and found to depend on environmental conditions makes it challenging to develop a predictive capability for aerosol optical properties on regional and global scales.…”

Impact of aerosol hygroscopic growth on retrieving aerosol extinction coefficient profiles from elastic-backscatter lidar signals

“…Wuqing site is located between two megacities (Beijing and Tianjin) of NCP, and can represent the pollution conditions of the NCP (Xu et al, 2011). This study uses the measured datasets of PNSD, black carbon (BC) (Ma et al, 2012) and aerosol hygroscopicity (Chen et al, 2014;Liu et al, 2014) during the field campaign. Details about this field campaign and instruments used can be found in the references.…”

“…Mixing states of BC come from the measurement during the Hachi Campaign. In previous work, BC mixing states during the Hachi campaign were presented as both core-shell mixed and externally mixed (Ma et al, 2012). Ma et al (2012) provides the ratio of BC mass concentration under externally mixed state to total BC mass concentration as follows:…”

Analysis of extinction properties as a function of relative humidity using a κ-EC-Mie model in Nanjing

“…The particle number size distribution and chemical composition and relative refractive index 4148 Z. Zhang et al: Analysis of extinction properties using a κ-EC-Mie model in Nanjing are the important parameters that affect the optical properties of the particles (Day et al, 2000;Ma et al, 2012;Cheng et al, 2008a;Wen and Yeh, 2010). However, many of the aerosol components are hygroscopic and take up water as a function of the relative humidity (RH) (Clarke et al, 2004;Covert et al, 1972;Swietlicki et al, 2008).…”