Mixing State and Composition of Aerosol Particles Collected During the GoAmazon2014/15, HI-SCALE, and ACE-ENA Field Campaigns
Abstract
Aerosol mixing state has an influence over uncertain climate relevant atmospheric phenomena such as aerosol radiative and cloud nucleating properties. To better understand these effects, a combination of scanning transmission x-ray microscopy/near-edge x-ray fine structure spectroscopy and scanning electron microscopy/energy-dispersive x-ray spectroscopy was used to investigate particles collected during several field campaigns. Elemental mass fractions including light (C, N, and O) and heavy (Z>11) elements were determined on a per-particle basis for particles from the GoAmazon2014/15 campaign. Quantitative mixing state parameters such as particle diversity (Di) and mixing state index (χ) were then calculated. Cluster analysis for the GoAmazon data set identified 12 particle types across the three sites, with a larger variety of particle types appearing at more anthropogenically influenced sites. A positive correlation between Di and particle size was observed, with particles < 0.5 μm having a Di of 2.4 and > 0.5 μm particles having a Di of 3.6. These Di values likely correspond to fresh and aged aerosols, respectively.
Viscous organic aerosols from the Atmospheric Research and Measurements site in the Southern Great Plains of the central United States were studied as part of the Holistic Interactions of Shallow Clouds, Aerosols, and Land Ecosystems (HI-SCALE) campaign. These aerosols, dubbed airborne soil organic particles (ASOPs), have been shown to be a source of brown carbon and to originate from rainfall impaction upon soil. Unique features within NEXAFS spectra have also been identified which serve to differentiate ASOPs from tar balls such as a lower COOH/C=C peak ratio. Lastly, ground site particles were collected from the Azores, an archipelago in the North Atlantic Ocean about 1400 km west of Portugal, as part of the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) campaign. Anthropogenic influence from North America on particle composition has been observed due to periodic long-range transport events. Samples influenced by these events contained particles with elevated soot and organic content. Contrasting these sampling periods with those dominated by short-range transport helps to better quantify the cloud condensation nuclei (CCN) budget in the ENA region.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A53M2941F
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0317 Chemical kinetic and photochemical properties;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0320 Cloud physics and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES