Hygroscopic growth of urban aerosol particles in Beijing (China) during wintertime: a comparison of three experimental methods

Abstract

Abstract. This paper presents hygroscopicity measurements of aerosol particles in the urban atmosphere of Beijing carried out in January 2005. Therefore, three different methods were used: 1) Combining Humidifying Differential Mobility Particle Sizer (H-DMPS) and Twin Differential Mobility Particle Sizer (TDMPS) measurements; 2) Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) technique; 3) Calculating hygroscopic growth factors on the basis of a solubility model quantified by Micro Orifice Uniform Deposit Impactor (MOUDI) samples. Particle number size distributions from H-DMPS and TDMPS were evaluated to derive size-resolved descriptive hygroscopic growth factors (DHGF) of 30–400 nm particles at relative humidities (RH) of 55%, 77% and 90%. The atmospheric particles in Beijing were rather hydrophobic, with a maximum growth factor in the accumulation mode around 1.40 (±0.03) at 90% RH. The descriptive hygroscopic growth factors decreased significantly towards the lower measurement limit (1.04 (±0.15) at Dp=30 nm). A good agreement was found between the DHGFs and the H-TDMA-derived hygroscopic growth factors in the accumulation mode (100–400 nm), the DHGFs underestimated the values from the H-TDMA in the Aitken mode (<100 nm) by up to 0.1 at 90% RH. The calculation of hygroscopic growth factors based on the measured chemical composition showed that different modes of combining the inorganic ions caused a variation in growth factor of 0.1 at 90% RH. The solubility model was able to reproduce the size-dependent trend in the growth factor found by the other methods. In two cases of ion-dominated aerosol, the composition-derived growth factors tended to agree (±0.05) or underestimate (up to 0.1) the values measured by the other two methods. In the case of the organic-dominated aerosol, the reverse was true, with an overestimation of up to 0.2. The results shed light on the real experimental and methodological uncertainties that are still connected with the determination of hygroscopic growth factors.

Dust events in Beijing, China (2004–2006): comparison of ground-based measurements with columnar integrated observations

“…The average RH during the dust events was mostly lower than 30%. Particle hygroscopic growth factor at RH = 40% in Beijing did not exceed 1.01 in January 2005 and the particles did not show obvious growth below RH 60% (Meier, et al, 2009). Therefore, the hygroscopic growth of the particles was not considered in the Mie calculations.…”

Continuous Measurement of Ambient Aerosol Liquid Water Content in Beijing

“…In Guangzhou and Shanghai, optical methods (using nephelometers, transmissometer and photometer) were employed for the determination of hygroscopic growth factor and evaluation of scattering and light extinction of ambient aerosol (Liu et al, 2008;Jung et al, 2009;Cheng et al, 2014). While in the North China Plain a series of interrelated studies (Achtert et al, 2009;Massling et al, 2009;Meier et al, 2009;Bian et al, 2014;Liu et al, 2014) evaluated the chemical and physical influence on hygroscopic growth of atmospheric sub-micrometer particles using HTDMA, Twin Differential Mobility Particle Sizer (TDMPS), and Humidifying Differential Mobility Particle Sizer (HDMPS) for rural and urban areas. So far, direct measurement of aerosol water content at ambient conditions using a DAASS system has not been performed in China.…”

Hygroscopicity of ambient submicron particles in urban Hangzhou, China

“…Massling et al [7] and Meier et al [8]reported the particle hygroscopicity in the urban atmosphere of Beijing, indicating that the hygroscopicity varied with particle size, level of pollution and season. In contrast to the dry weather in inland and Northern China, high humidity is ubiquitous in Southern China, where the hygroscopicity of aerosols is of great value to understand humidity-sensitive phenomena such as haze and fog.…”

“…In China, only a few studies have been performed with regards to the hygroscopicity of ambient aerosols [7][8][9][10]. Massling et al [7] and Meier et al [8]reported the particle hygroscopicity in the urban atmosphere of Beijing, indicating that the hygroscopicity varied with particle size, level of pollution and season.…”