1State Key Laboratory for Structural Chemistry of Unstable and Stable
Species, CAS Research/Education Center for Excellence in Molecular Sciences,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R.
China
2University of Chinese Academy of Sciences, Beijing 100049, P. R. China
3The Institute of Chemical Physics, School of Chemistry and Chemical
Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
4Center for Excellence in Regional Atmospheric Environment, Institute
of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, P. R.
China
1State Key Laboratory for Structural Chemistry of Unstable and Stable
Species, CAS Research/Education Center for Excellence in Molecular Sciences,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R.
China
2University of Chinese Academy of Sciences, Beijing 100049, P. R. China
3The Institute of Chemical Physics, School of Chemistry and Chemical
Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China
4Center for Excellence in Regional Atmospheric Environment, Institute
of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, P. R.
China
Received: 27 Oct 2017 – Discussion started: 22 Nov 2017 – Revised: 26 Mar 2018 – Accepted: 27 Mar 2018 – Published: 16 Apr 2018
Abstract. While nitrate salts have critical impacts on environmental effects of atmospheric aerosols, the effects of coexisting species on hygroscopicity of nitrate salts remain uncertain. The hygroscopic behaviors of nitrate salt aerosols (NH4NO3, NaNO3, Ca(NO3)2) and their internal mixtures with water-soluble organic acids were determined using a hygroscopicity tandem differential mobility analyzer (HTDMA). The nitrate salt ∕ organic acid mixed aerosols exhibit varying phase behavior and hygroscopic growth depending upon the type of components in the particles. Whereas pure nitrate salt particles show continuous water uptake with increasing relative humidity (RH), the deliquescence transition is still observed for ammonium nitrate particles internally mixed with organic acids such as oxalic acid and succinic acid with a high deliquescence point. The hygroscopicity of submicron aerosols containing sodium nitrate and an organic acid is also characterized by continuous growth, indicating that sodium nitrate tends to exist in a liquid-like state under dry conditions. It is observed that in contrast to the pure components, the water uptake is hindered at low and moderate RH for calcium nitrate particles containing malonic acid or phthalic acid, suggesting the potential effects of mass transfer limitation in highly viscous mixed systems. Our findings improve fundamental understanding of the phase behavior and water uptake of nitrate-salt-containing aerosols in the atmospheric environment.
The nitrate/organic acid mixed aerosols exhibit varying phase behavior and hygroscopic growth depending upon the type of components in the particles. Our results reveal that the coexisting organic acid has considerable impacts on the phase and morphology of nitrate particles in the low and medium RH range, which thus result in obvious enhancement or suppression of water uptake with increasing RH. This new information provided here has important implications for atmospheric chemistry.
The nitrate/organic acid mixed aerosols exhibit varying phase behavior and hygroscopic growth...
