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Abstract Furans are a major class of volatile organic compounds emitted from biomass burning. Their high reactivity with atmospheric oxidants leads to the formation of secondary organic aerosol (SOA), including secondary brown carbon (BrC) that can affect global climate via interactions with solar radiation. Here, we investigate the optical properties and chemical composition of SOA generated via photooxidation of furfural, 2‐methylfuran, and 3‐methylfuran under dry (RH < 5%) and humid (RH ∼ 50%) conditions in the presence of nitrogen oxides (NOx) and ammonium sulfate seed aerosol. Dry furfural oxidation has the greatest BrC formation, including reduced nitrogen‐containing organic compounds (NOCs) in SOA, which are dominated by amines and amides formed from reactions between carbonyls and ammonia/ammonium. Based on the products detected, we propose novel formation pathways of NOCs in furfural photooxidation, which can contribute to BrC via accretion reactions during the photochemical aging of biomass burning plumes.
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Secondary brown carbon from photooxidation of 1-methylnaphthalene and longifolene
An improved understanding of the optical properties of secondary organic aerosol (SOA) particles is needed to better predict their climate impacts. Here, SOA was produced by reacting 1-methylnaphthalene or longifolene with hydroxyl radicals (OH) under variable ammonia (NH3), nitrogen oxide (NOx), and relative humidity (RH) conditions. In the presence of NH3 and NOx, longifolene-derived aerosols had relatively high single scattering albedo (SSA) values and low absorption coefficients at 375 nm independent of RH, suggesting that the longifolene SOA is mostly scattering. In 1-methylnaphthalene experiments, the resulting SSA and SOA mass absorption coefficient (MACorg) values suggest the formation of light-absorbing SOA, and the addition of high NOx and high NH3 enhanced the SOA absorption. Under intermediate-NOx dry conditions, the MACorg values increased from 0.13 m2 g−1 in NH3-free conditions to 0.28 m2 g−1 in high-NH3 conditions. Under high-NH3 conditions, the MACorg value further increased to 0.36 m2 g−1 with an increase in RH. Under dry high-NOx conditions, the MACorg value increased from 0.42 to 0.67 m2 g−1 with the addition of NH3, while with elevated RH, the MACorg value reached 0.70 m2 g−1. The time series of MACorg showed increasing trends only in the presence of NH3. Composition analysis of SOA suggests that organonitrates, nitroorganics, and other nitrogen-containing organic compounds (NOCs) are potential chromophores in the 1-methylnaphthalene SOA. Significant formation of NOCs was observed in the presence of high-NOx and NH3 and was enhanced under elevated RH. The data have been collected in an environmental chamber, oxidizing 30-100 ppbv of 1-methylnaphthalene and 70-100 ppbv of longifolene under different levels of nitrogen oxides, ammonia, and relative humidity. Microphysical properties (size distribution and absorption and scattering coefficients) of SOA along with its composition were monitored throughout the experiment. Submitted data include the time series of the calculated mass absorption coefficient and single scattering albedo at 375 nm, derived real and imaginary components of the refractive index, organic nitrate to organic ratio, and organic and nitrate mass concentrations. The data have been analyzed using Wavemetrics Igor Pro, specifically the software written specifically to analyze the data obtained from Aerodyne's aerosol mass spectrometers (i.e., Squirrel and Pika). Other calculations were also carried out in Igor Pro. More details are provided in the related manuscripts. Please see README file.
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- Award ID(s):
- 1454374
- PAR ID:
- 10336631
- Publisher / Repository:
- Dryad
- Date Published:
- Edition / Version:
- 5
- Subject(s) / Keyword(s):
- 1-methylnaphthalene photooxidation Secondary brown carbon ammonia nitrogen oxide optical properties longifolene FOS: Earth and related environmental sciences
- Format(s):
- Medium: X Size: 72022 bytes
- Size(s):
- 72022 bytes
- Sponsoring Org:
- National Science Foundation
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