Time Evolution of Biomass Burning Plumes Observed in BBOP
Authors
Larry Kleinman — Brookhaven National Laboratory
Jian Wang — Washington University in St. Louis
Stephen R. Springston — Brookhaven National Laboratory
Manvendra K. Dubey — Los Alamos National Laboratory
Timothy B Onasch — Aerodyne Research, Inc.
Arthur J Sedlacek — Brookhaven National Laboratory
Rahul Zaveri — Pacific Northwest National Laboratory
Qi Zhang — University of California, Davis
John E Shilling — Pacific Northwest National Laboratory
Duli Chand — Pacific Northwest National Laboratory
Ed Fortner — Aerodyne Research, Inc.
Fan Mei — Pacific Northwest National Laboratory
Peter R. Buseck — Arizona State University
Robert James Yokelson — University of Montana
Kouji Adachi — Meteorological Research Institute
Category
Secondary Organic Aerosol
Description
The Biomass Burn Operational Project (BBOP) was conducted between the beginning of July, 2013 and the end of October, 2013. This period overlapped the wildland fire season in the Pacific Northwest from July to mid September, and in October, overlapped the season for prescribed agricultural burns in the lower Mississippi River Valley. Urban plumes from 7 cities in the NW and SE U.S. provided a contrasting set of observations. An extended aircraft deployment using the DOE G-1 was made possible by the fortuitous citing of the planes home base within 2 hours flight time of regions with an historically high incidence of wildland fires. Flight patterns were designed so as to sample plumes as close to a fire as air traffic regulations allowed, followed by one or two sets of three to six transects covering a transport time of two to four hours. Average values of aerosol parameters are calculated for each plume transect with CO used as an inert tracer to account for dilution. It is found from SP-AMS measurements that near source smoke from wildland fires is approximately 95% organic. Downwind of the fires, OA increase by ~ 20% to 100%, with much of the increase occurring within the first hour. There is a corresponding increase in scattering which causes single scattering albedo to increase. Aerosol sulfate remains constant with downwind distance suggesting that it is a primary pollutant or formed before our closest transect. Nitrate appears to have a primary and secondary source and usually has a downwind fractional change greater than that of OA. A comparison of sulfate and nitrate with ammonium shows instances with a stoichiometry that would be obtained if all of the nitrate were neutralized but none of the sulfate. The wildland fires have a relatively narrow range of modified combustion efficiencies, centered on 0.9, at which point there are emission changes associated with smoldering vs. flaming combustion, perhaps accounting for fire to fire variability in SOA, nitrate, and ozone production. Changes to the aerosol size distribution in the size range 15 to 300 nm are investigated with a box model that incorporates dilution, condensation and coagulation. Results are compared with size resolved observations from a FIMS. Changes in the ratio of OA to CO are used to constrain gas to particle condensation.
