Hygroscopic properties of submicrometer atmospheric aerosol particles measured with H-TDMA instruments in various environments—a review

Abstract

A B S T R A C TThe hygroscopic properties play a vital role for the direct and indirect effects of aerosols on climate, as well as the health effects of particulate matter (PM) by modifying the deposition pattern of inhaled particles in the humid human respiratory tract. Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA) instruments have been used in field campaigns in various environments globally over the last 25 yr to determine the water uptake on submicrometre particles at subsaturated conditions. These investigations have yielded valuable and comprehensive information regarding the particle hygroscopic properties of the atmospheric aerosol, including state of mixing. These properties determine the equilibrium particle size at ambient relative humidities and have successfully been used to calculate the activation of particles at water vapour supersaturation. This paper summarizes the existing published H-TDMA results on the sizeresolved submicrometre aerosol particle hygroscopic properties obtained from ground-based measurements at multiple marine, rural, urban and free tropospheric measurement sites. The data is classified into groups of hygroscopic growth indicating the external mixture, and providing clues to the sources and processes controlling the aerosol. An evaluation is given on how different chemical and physical properties affect the hygroscopic growth.

Marine aerosol hygroscopicity and volatility, measured on the Chatham Rise (New Zealand)

“…Smaller contributions from externally mixed particles with very high hygroscopicity (number fraction of up to approximately 0.3) and low hygroscopicity (number fraction of up to approximately 0.4) were also observed. The aerosol composition appears to be broadly consistent with observations from other locations using hygroscopicity methods [3].…”

“…This is consistent with an external mixture dominated by non-sea salt sulfate with sea salt aerosol (SSA) and organics and/or anthropogenic pollution [3].…”

“…SSA is rarely a dominant contributor to the sub 100nm diameter remote marine aerosol [3]. Wind speed is thought to be a key driver of SSA concentration [5].…”

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

“…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). When the RH is high, even under subsaturated conditions, the hygroscopic growth of the particles can lead to an increase in size and a decrease in the refractive index, which has significant effects on the extinction properties (Cheng et al, 2008b;Covert et al, 1972;Stock et al, 2011).…”

The 1-by-3 Tandem Differential Mobility Analyzer for Measurement of the Irreversibility of the Hygroscopic Growth Factor

“…As three examples, Pitchford and McMurry (1994) studied deliquescence transitions of ambient particles in the Grand Canyon, Santarpia et al (2004) studied both deliquescence and efflorescence transitions in southeast Texas, and Khlystov et al (2005) studied the particle water content (thus inferring aqueous or solid state) in Pittsburgh. The design of the HTDMA, however, is optimized for primary measurements of hygroscopic growth factors (Swietlicki et al 2008), from which information about particle phase and phase transitions can be inferred as a derived quantity (Pitchford and McMurry 1994;Santarpia et al 2004;Khlystov et al 2005). A purpose-designed instrument to study the phase transitions of ambient particles has not been deployed previously, and such an instrument could be expected to provide more sensitivity, new statistics, and further insights into the phase transitions of ambient particles.…”