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Title: Secondary organic aerosol formation in biomass-burning plumes: theoretical analysis of lab studies and ambient plumes

Secondary organic aerosol (SOA) has been shown to form in biomass-burning emissions in laboratory and field studies. However, there is significant variability among studies in mass enhancement, which could be due to differences in fuels, fire conditions, dilution, and/or limitations of laboratory experiments and observations. This study focuses on understanding processes affecting biomass-burning SOA formation in laboratory smog-chamber experiments and in ambient plumes. Vapor wall losses have been demonstrated to be an important factor that can suppress SOA formation in laboratory studies of traditional SOA precursors; however, impacts of vapor wall losses on biomass-burning SOA have not yet been investigated. We use an aerosol-microphysical model that includes representations of volatility and oxidation chemistry to estimate the influence of vapor wall loss on SOA formation observed in the FLAME III smog-chamber studies. Our simulations with base-case assumptions for chemistry and wall loss predict a mean OA mass enhancement (the ratio of final to initial OA mass, corrected for particle-phase wall losses) of 1.8 across all experiments when vapor wall losses are modeled, roughly matching the mean observed enhancement during FLAME III. The mean OA enhancement increases to over 3 when vapor wall losses are turned off, implying that vapor wall losses reduce themore » apparent SOA formation. We find that this decrease in the apparent SOA formation due to vapor wall losses is robust across the ranges of uncertainties in the key model assumptions for wall-loss and mass-transfer coefficients and chemical mechanisms. We then apply similar assumptions regarding SOA formation chemistry and physics to smoke emitted into the atmosphere. In ambient plumes, the plume dilution rate impacts the organic partitioning between the gas and particle phases, which may impact the potential for SOA to form as well as the rate of SOA formation. We add Gaussian dispersion to our aerosol-microphysical model to estimate how SOA formation may vary under different ambient-plume conditions (e.g., fire size, emission mass flux, atmospheric stability). Smoke from small fires, such as typical prescribed burns, dilutes rapidly, which drives evaporation of organic vapor from the particle phase, leading to more effective SOA formation. Emissions from large fires, such as intense wildfires, dilute slowly, suppressing OA evaporation and subsequent SOA formation in the near field. We also demonstrate that different approaches to the calculation of OA enhancement in ambient plumes can lead to different conclusions regarding SOA formation. OA mass enhancement ratios of around 1 calculated using an inert tracer, such as black carbon or CO, have traditionally been interpreted as exhibiting little or no SOA formation; however, we show that SOA formation may have greatly contributed to the mass in these plumes.In comparison of laboratory and plume results, the possible inconsistency of OA enhancement between them could be in part attributed to the effect of chamber walls and plume dilution. Lastly, our results highlight that laboratory and field experiments that focus on the fuel and fire conditions also need to consider the effects of plume dilution or vapor losses to walls.« less
Authors:
ORCiD logo [1] ; ORCiD logo [2] ;  [1] ;  [3] ;  [4] ;  [5] ;  [1] ;  [6]
  1. Colorado State Univ., Fort Collins, CO (United States). Dept. of Atmospheric Science
  2. Colorado State Univ., Fort Collins, CO (United States). Dept. of Mechanical Engineering
  3. Univ. of California, Riverside, CA (United States). College of Engineering, Center for Environmental Research and Technology (CE-CERT), Dept. of Chemical and Environmental Engineering
  4. Univ. of California, Riverside, CA (United States). College of Engineering, Center for Environmental Research and Technology (CE-CERT), Dept. of Chemical and Environmental Engineering
  5. The Ohio State Univ., Columbus, OH (United States). Dept. of Civil, Environmental and Geodetic Engineering
  6. Colorado State Univ., Fort Collins, CO (United States). Dept. of Atmospheric Science; Dalhousie Univ., Halifax, NS (Canada). Dept. of Physics and Atmospheric Science
Publication Date:
Grant/Contract Number:
SC0006035; R833747; R834554
Type:
Accepted Manuscript
Journal Name:
Atmospheric Chemistry and Physics (Online)
Additional Journal Information:
Journal Name: Atmospheric Chemistry and Physics (Online); Journal Volume: 17; Journal Issue: 8; Journal ID: ISSN 1680-7324
Publisher:
European Geosciences Union
Research Org:
Univ. of Colorado, Boulder, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1368356

Bian, Qijing, Jathar, Shantanu H., Kodros, John K., Barsanti, Kelley C., Hatch, Lindsay E., May, Andrew A., Kreidenweis, Sonia M., and Pierce, Jeffrey R.. Secondary organic aerosol formation in biomass-burning plumes: theoretical analysis of lab studies and ambient plumes. United States: N. p., Web. doi:10.5194/acp-17-5459-2017.
Bian, Qijing, Jathar, Shantanu H., Kodros, John K., Barsanti, Kelley C., Hatch, Lindsay E., May, Andrew A., Kreidenweis, Sonia M., & Pierce, Jeffrey R.. Secondary organic aerosol formation in biomass-burning plumes: theoretical analysis of lab studies and ambient plumes. United States. doi:10.5194/acp-17-5459-2017.
Bian, Qijing, Jathar, Shantanu H., Kodros, John K., Barsanti, Kelley C., Hatch, Lindsay E., May, Andrew A., Kreidenweis, Sonia M., and Pierce, Jeffrey R.. 2017. "Secondary organic aerosol formation in biomass-burning plumes: theoretical analysis of lab studies and ambient plumes". United States. doi:10.5194/acp-17-5459-2017. https://www.osti.gov/servlets/purl/1368356.
@article{osti_1368356,
title = {Secondary organic aerosol formation in biomass-burning plumes: theoretical analysis of lab studies and ambient plumes},
author = {Bian, Qijing and Jathar, Shantanu H. and Kodros, John K. and Barsanti, Kelley C. and Hatch, Lindsay E. and May, Andrew A. and Kreidenweis, Sonia M. and Pierce, Jeffrey R.},
abstractNote = {Secondary organic aerosol (SOA) has been shown to form in biomass-burning emissions in laboratory and field studies. However, there is significant variability among studies in mass enhancement, which could be due to differences in fuels, fire conditions, dilution, and/or limitations of laboratory experiments and observations. This study focuses on understanding processes affecting biomass-burning SOA formation in laboratory smog-chamber experiments and in ambient plumes. Vapor wall losses have been demonstrated to be an important factor that can suppress SOA formation in laboratory studies of traditional SOA precursors; however, impacts of vapor wall losses on biomass-burning SOA have not yet been investigated. We use an aerosol-microphysical model that includes representations of volatility and oxidation chemistry to estimate the influence of vapor wall loss on SOA formation observed in the FLAME III smog-chamber studies. Our simulations with base-case assumptions for chemistry and wall loss predict a mean OA mass enhancement (the ratio of final to initial OA mass, corrected for particle-phase wall losses) of 1.8 across all experiments when vapor wall losses are modeled, roughly matching the mean observed enhancement during FLAME III. The mean OA enhancement increases to over 3 when vapor wall losses are turned off, implying that vapor wall losses reduce the apparent SOA formation. We find that this decrease in the apparent SOA formation due to vapor wall losses is robust across the ranges of uncertainties in the key model assumptions for wall-loss and mass-transfer coefficients and chemical mechanisms. We then apply similar assumptions regarding SOA formation chemistry and physics to smoke emitted into the atmosphere. In ambient plumes, the plume dilution rate impacts the organic partitioning between the gas and particle phases, which may impact the potential for SOA to form as well as the rate of SOA formation. We add Gaussian dispersion to our aerosol-microphysical model to estimate how SOA formation may vary under different ambient-plume conditions (e.g., fire size, emission mass flux, atmospheric stability). Smoke from small fires, such as typical prescribed burns, dilutes rapidly, which drives evaporation of organic vapor from the particle phase, leading to more effective SOA formation. Emissions from large fires, such as intense wildfires, dilute slowly, suppressing OA evaporation and subsequent SOA formation in the near field. We also demonstrate that different approaches to the calculation of OA enhancement in ambient plumes can lead to different conclusions regarding SOA formation. OA mass enhancement ratios of around 1 calculated using an inert tracer, such as black carbon or CO, have traditionally been interpreted as exhibiting little or no SOA formation; however, we show that SOA formation may have greatly contributed to the mass in these plumes.In comparison of laboratory and plume results, the possible inconsistency of OA enhancement between them could be in part attributed to the effect of chamber walls and plume dilution. Lastly, our results highlight that laboratory and field experiments that focus on the fuel and fire conditions also need to consider the effects of plume dilution or vapor losses to walls.},
doi = {10.5194/acp-17-5459-2017},
journal = {Atmospheric Chemistry and Physics (Online)},
number = 8,
volume = 17,
place = {United States},
year = {2017},
month = {4}
}