Investigation of brown carbon formation due to the drying of ambient aerosol in eastern United States
Abstract
Brown carbon (BrC) is the term used to describe a chemically-diverse array of light-absorbing organic compounds found in atmospheric particles. Due to its light-absorbing properties, BrC has significant relevance for radiative forcing by particles and thus climate. BrC in particles can be emitted directly, especially from biomass burning, or formed in the atmosphere from reactions of VOCs. Recent laboratory studies suggest the formation of BrC due to the drying of aqueous particles containing dissolved organic compounds like glyoxal and methylglyoxal. Since ambient aerosol undergoes cycles of drying and humidification during its lifetime, formation of BrC during these drying cycles may have implications for the overall BrC budget, and thus positive radiative forcing in the atmosphere. This phenomenon; however, has never been observed in ambient particles. In this work, we investigated the formation of BrC due to the drying of ambient aerosol at a site in the eastern United States. Ambient aerosol sampled during the summertime is alternated through ambient and dry channels. In the ambient channel the aerosol passes through unperturbed, while in the dry channel the sample passes through a diffusion dryer maintaining a relative humidity of 40%. The aerosol is then sampled in near-real-time with a Particle-into-Liquid Sampler (PILS) coupled to a Liquid Waveguide Capillary Cell - UV spectrometer, and to a total organic carbon analyzer. Our previous work showed that this site is heavily influenced by biogenic SOA formation during the summer. Results from our current campaign suggest no BrC formation occurs due to the drying of ambient particles. This result is consistent across several weeks of measurements, including a wide range of ambient relative humidity conditions and organic aerosol loadings.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A52C..03P
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0320 Cloud physics and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0368 Troposphere: constituent transport and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES