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Abt. Schütz
Abstract:
The phase andmixing 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-raymicrospectroscopy under variable RH conditions to internallymixed 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.
