Detailed airborne measure ments of smoke plumes from seven prescribed burns of forest biomass residues leftover from timber harvests in Washington and Oregon are described. Measurements of particle size distributions in the plumes at 3.3 km downwind of the burns showed a prominent peak in the mass concentration for particles 0.25-0.30 µm in diameter. The total mass of particles in the plume was dominated, however, by supermicron-sized particles. The particle number distributions were dominated by large numbers of Aitken nuclei (median number diameter 0.15 µm).
Based on numerous airborne measurements from six burns, the following average emission factors were determined using the carbon balance method: for total suspended particulates 1.2 ± 0.4 percent, for particles < 43 µm in diameter 0.6± 0.3 percent, and for particles < 0.2 µm in diameter 0.4 ± 0.2 percent. Particle mass fluxes for total suspended particulates, particles < 43 µm diameter, and particles < 2 µm diameter ranged from 0.1 to 2.4 kg · s-1, 0.1 to 1.1 kg · s -1, and 0.1 to 0.8 kg · s-1, respectively, for the smaller Oregon burns and from 1.1 to 11.7 kg · s-1, 0.6 to 7.0 kg · s-1, and 0.4 to 14.1 kg · s-1, respectively, for the larger Washington burns.
Other samples collected in conjunction with the airborne work included those for trace gas analysis, particulate matter for trace element analysis, and gas concentration measurements for carbon-mass analysis (oxides of nitrogen, ozone, and hydrocarbons). Mass concentration-to-light scattering coefficient algorithms and ratios, which can be used to convert integrating nephelometer response to mass concentration units, are also reported.
Radke, Lawrence F.; Lyons, Jamie H.; Hobbs, Peter V.; Hegg, Dean A.; Sandberg, David V.; Ward, Darold E. 1990. Airborne monitoring and smoke characterization of prescribed fires on forest lands in western Washington and Oregon. Gen. Tech. Rep. PNW-GTR-251. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 81 p