Abstract
The evolution of organic aerosol (OA) and aerosol size distributions within smoke plumes is uncertain due to the variability in rates of coagulation and OA condensation/evaporation between different smoke plumes and at different locations within a single plume. We use aircraft data from the FIREX-AQ campaign to evaluate differences in evolving aerosol size distributions, OA, and oxygen to carbon ratios (O:C) between and within smoke plumes during the first several hours of aging as a function of smoke concentration. The observations show that the median particle diameter increases faster in smoke of a higher initial OA concentration (>1000¯μg¯m-3), with diameter growth of over 100¯nm in 8¯h - despite generally having a net decrease in OA enhancement ratios - than smoke of a lower initial OA concentration (<100¯μg¯m-3), which had net increases in OA. Observations of OA and O:C suggest that evaporation and/or secondary OA formation was greater in less concentrated smoke prior to the first measurement (5-57¯min after emission). We simulate the size changes due to coagulation and dilution and adjust for OA condensation/evaporation based on the observed changes in OA. We found that coagulation explains the majority of the diameter growth, with OA evaporation/condensation having a relatively minor impact. We found that mixing between the core and edges of the plume generally occurred on timescales of hours, slow enough to maintain differences in aging between core and edge but too fast to ignore the role of mixing for most of our cases.
| Original language | English |
|---|---|
| Pages (from-to) | 12803-12825 |
| Number of pages | 23 |
| Journal | Atmospheric Chemistry and Physics |
| Volume | 22 |
| Issue number | 19 |
| DOIs | |
| State | Published - Sep 30 2022 |
Funding
This research has been supported by the National Science Foundation (grant no. AGS-1950327), the National Aeronautics and Space Administration (grant no. 80NSSC19K1589), the U.S. Department of Energy (grant no. DE-SC0019000), and the National Oceanic and Atmospheric Administration (grant nos. NA17OAR4310001 and NA17OAR4310003). This work is supported by the US NOAA, an Office of Science, Office of Atmospheric Chemistry, Carbon Cycle, and Climate program, under the cooperative agreement awards NA17OAR4310001 and NA17OAR4310003; the US NSF Atmospheric Chemistry program, under grant AGS-1950327; and the US Department of Energy's (DOE) Atmospheric System Research, an Office of Science, Office of Biological and Environmental Research program, under grant DE-SC0019000. This publication was also developed under Assistance Agreement No. R8400008 awarded by the U.S. Environmental Protection Agency (EPA) to Shantanu Jathar. It has not been formally reviewed by EPA. The views expressed in this document are solely those of the authors and do not necessarily reflect those of the Agency. EPA does not endorse any products or commercial services mentioned in this publication. The NASA Langley Aerosol Research Group (LARGE) was supported by the NASA Tropospheric Composition Program. Robert J. Yokelson was supported by NASA 80NSSC19K1589 and NOAA NA16OAR4310100. We thank the pilots and crew of the NASA DC-8 and the FIREX-AQ project scientists: Jim Crawford, Jack Dibb, Carsten Warneke, Shuka Schwarz, and Barry Lefer.
| Funders | Funder number |
|---|---|
| Large Synoptic Survey Telescope | |
| AGS-1950327 | |
| National Aeronautics and Space Administration | 80NSSC19K1589 |
| National Oceanic and Atmospheric Administration | NA17OAR4310001, NA17OAR4310003, NA16OAR4310100 |
| Biological and Environmental Research | DE-SC0019000 |