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Abstract. Secondary organic aerosol (SOA) constitutes a largefraction of atmospheric aerosol. To assess its impacts on climate and airpollution, knowledge of the number of phases in internal mixtures ofdifferent SOA types is required. Atmospheric models often assume thatdifferent SOA types form a single phase when mixed. Here, we present visualobservations of the number of phases formed after mixing differentanthropogenic and biogenic SOA types. Mixing SOA types generated inenvironmental chambers with oxygen-to-carbon (O/C) ratios between 0.34 and 1.05, we found 6 out of 15 mixtures of two SOA types to result in two phase particles. We demonstrate that the number of phases depends on thedifference in the average O/C ratio between the two SOA types (Δ(O/C)). Using a threshold Δ(O/C) of 0.47, we can predict the phasebehavior of over 90 % of our mixtures, with one- and two-phase particlespredicted for Δ(O/C)<0.47 and Δ(O/C)≥0.47,respectively. This threshold ΔO/C value provides a simple parameterto predict whether mixtures of fresh and aged SOA form one- or two-phase particles in the atmosphere. In addition, we show that phase-separated SOAparticles form when mixtures of volatile organic compounds emitted from realtrees are oxidized.
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α-Pinene-Derived organic coatings on acidic sulfate aerosol impacts secondary organic aerosol formation from isoprene in a box model
- Award ID(s):
- 1703535
- PAR ID:
- 10226176
- Date Published:
- Journal Name:
- Atmospheric Environment
- Volume:
- 213
- Issue:
- C
- ISSN:
- 1352-2310
- Page Range / eLocation ID:
- 456 to 462
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic aerosolAbstract. Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 decades, during which time a large body of research has emerged from laboratory, field, and modeling studies. NO3-BVOC reactions influence air quality, climate and visibility through regional and global budgets for reactive nitrogen (particularly organic nitrates), ozone, and organic aerosol. Despite its long history of research and the significance of this topic in atmospheric chemistry, a number of important uncertainties remain. These include an incomplete understanding of the rates, mechanisms, and organic aerosol yields for NO3-BVOC reactions, lack of constraints on the role of heterogeneous oxidative processes associated with the NO3 radical, the difficulty of characterizing the spatial distributions of BVOC and NO3 within the poorly mixed nocturnal atmosphere, and the challenge of constructing appropriate boundary layer schemes and non-photochemical mechanisms for use in state-of-the-art chemical transport and chemistry–climate models. This review is the result of a workshop of the same title held at the Georgia Institute of Technology in June 2015. The first half of the review summarizes the current literature on NO3-BVOC chemistry, with a particular focus on recent advances in instrumentation and models, and in organic nitrate and secondary organic aerosol (SOA) formation chemistry. Building on this current understanding, the second half of the review outlines impacts of NO3-BVOC chemistry on air quality and climate, and suggests critical research needs to better constrain this interaction to improve the predictive capabilities of atmospheric models.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.atmosenv.2019.06.005
