How salt lakes affect atmospheric new particle formation: A case study in Western Australia.
New particle formation was studied above salt lakes in-situ using a mobile aerosol chamber set up above the salt crust and organic-enriched layers of seven different salt lakes in Western Australia. This unique setup made it possible to explore the influence of salt lake emissions on atmospheric new particle formation, and to identify interactions of aqueous-phase and gas-phase chemistry. New particle formation was typically observed at enhanced air temperatures and enhanced solar irradiance. Volatile organic compounds were released from the salt lake surfaces, probably from a soil layer enriched in organic compounds from decomposed leaf litter, and accumulated in the chamber air. After oxidation of these organic precursor gases, the reaction products contributed to new particle formation with observed growth rates from 2.7 to 25.4nmh-1. The presence of ferrous and ferric iron and a drop of pH values in the salt lake water just before new particle formation events indicated that organic compounds were also oxidized in the aqueous phase, affecting the new particle formation process in the atmosphere. The contribution of aqueous-phase chemistry to new particle formation is assumed, as a mixture of hundreds of oxidized organic compounds was characterized with several analytical techniques. This chemically diverse composition of the organic aerosol fraction contained sulfur- and nitrogen-containing organic compounds, and halogenated organic compounds. Coarse mode particles were analyzed using electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. Ultra-high resolution mass spectrometry was applied to analyze filter samples. A targeted mass spectral analysis revealed the formation of organosulfates from monoterpene precursors and two known tracers for secondary organic aerosol formation from atmospheric oxidation of 1,8-cineole, which indicates that a complex interplay of aqueous-phase and gas-phase oxidation of monoterpenes contributes to new particle formation in the investigated salt lake environment.
Atmospheric Chemistry, University of Bayreuth, Bayreuth, Germany. Electronic address: katharina.kamilli@uni-bayreuth.de.
K A
KA
Kamilli
Institute of Chemical Technologies and Analytics, TU Wien, Vienna, Austria.
J
J
Ofner
Institute of Earth Science, University of Heidelberg, Germany.
T
T
Krause
Institute of Earth Science, University of Heidelberg, Germany.
T
T
Sattler
Research Unit Analytical BioGeoChemistry, Helmholtz Centre Munich, Oberschleißheim, Germany.
P
P
Schmitt-Kopplin
Institute of Chemical Technologies and Analytics, TU Wien, Vienna, Austria.
E
E
Eitenberger
Institute of Chemical Technologies and Analytics, TU Wien, Vienna, Austria.
G
G
Friedbacher
Institute of Chemical Technologies and Analytics, TU Wien, Vienna, Austria.
B
B
Lendl
Institute of Chemical Technologies and Analytics, TU Wien, Vienna, Austria.
H
H
Lohninger
Institute of Earth Science, University of Heidelberg, Germany.
H F
HF
Schöler
Atmospheric Chemistry, University of Bayreuth, Bayreuth, Germany; Bayreuth Center of Ecology and Environmental Research BayCEER, Bayreuth, Germany.
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A
Held
D000336:Aerosols; D000393:Air Pollutants / Q000032:analysis*; D001315:Australia; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D060106:Lakes / Q000737:chemistry*; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D044367:Phase Transition; D012492:Salts; D013059:Spectrum Analysis, Raman; D055549:Volatile Organic Compounds / Q000032:analysis*
D000336:Aerosols; D000393:Air Pollutants; D052638:Particulate Matter; D012492:Salts; D055549:Volatile Organic Compounds
Aerosol chamber; Interaction of aqueous-phase and gas-phase chemistry; New particle formation; Organic precursor gases; Salt lake emission