Abstract
The phase and mixing state of atmospheric aerosols is a central determinant of their properties and thus their role in atmospheric cycling and climate. Particularly, the hygroscopic response of aerosol particles to relative humidity (RH) variation is a key aspect of their atmospheric life cycle and impacts. Here we applied X-ray microspectroscopy under variable RH conditions to internally mixed aerosol particles from the Amazonian rain forest collected during periods with anthropogenic pollution. Upon hydration, we observed substantial and reproducible changes in particle microstructure, which appear as mainly driven by efflorescence and recrystallization of sulfate salts. Multiple solid and liquid phases were found to coexist, especially in intermediate humidity regimes. We show that X-ray microspectroscopy under variable RH is a valuable technique to analyze the hygroscopic response of individual ambient aerosol particles. Our initial results underline that RH changes can trigger strong particle restructuring, in agreement with previous studies on artificial aerosols.
Citation
@article{Pohlker2014,
author = {Pöhlker, Christopher and Saturno, Jorge and Krüger, Mira L and Förster, Jan-David and Weigand, Markus and Wiedemann, Kenia T and Bechtel, Michael and Artaxo, Paulo and Andreae, Meinrat O},
doi = {10.1002/2014GL059409},
issn = {00948276},
journal = {Geophysical Research Letters},
keywords = {Mixing state,STXM,X-ray microspectroscopy,aerosol microstructure,aerosol mixing and phase state,hydration cycle},
month = {may},
pages = {3681--3689},
title = {Efflorescence upon humidification? X-ray microspectroscopic in-situ observation of changes in aerosol microstructure and phase state upon hydration},
url = {http://doi.wiley.com/10.1002/2014GL059409},
volume = {41},
year = {2014}
}