1. Measurement report: The effect of aerosol chemical composition on light scattering due to the hygroscopic swelling effect
- Author
-
Rongmin Ren, Hao Wu, Zhanqing Li, Wei Wang, P. Yan, Xiaoai Jin, Yanan Li, Maureen Cribb, Dongmei Zhang, and Yuying Wang
- Subjects
chemistry.chemical_classification ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,Chemistry ,Physics ,QC1-999 ,Analytical chemistry ,010501 environmental sciences ,01 natural sciences ,Light scattering ,Aerosol ,Mass concentration (chemistry) ,Particle ,Relative humidity ,Organic matter ,QD1-999 ,Chemical composition ,Mass fraction ,0105 earth and related environmental sciences - Abstract
Liquid water in aerosol particles has a significant effect on their optical properties, especially on light scattering, whose dependence on chemical composition is investigated here using measurements made in southern Beijing in 2019. The effect is measured by the particle light scattering enhancement f(RH), where RH denotes the relative humidity, which is found to be positively and negatively impacted by the proportions of inorganic and organic matter, respectively. Black carbon is also negatively correlated. The positive impact is more robust when the inorganic matter mass fraction was smaller than 40 % (R=0.93, R: the Pearson's correlation coefficient), becoming weaker as the inorganic matter mass fraction gets larger (R=0.48). A similar pattern was also found for the negative impact of the organic matter mass fraction. Nitrate played a more significant role in aerosol hygroscopicity than sulfate in Beijing. However, the deliquescence point of ambient aerosols was at about RH = 80 % when the ratio of the sulfate mass concentration to the nitrate mass concentration of the aerosol was high (mostly higher than ∼ 4). Two schemes to parameterize f(RH) were developed to account for the deliquescent and non-deliquescent effects. Using only one f(RH) parameterization scheme to fit all f(RH) processes incurs large errors. A piecewise parameterization scheme is proposed, which can better describe deliquescence and reduces uncertainties in simulating aerosol hygroscopicity.
- Published
- 2021