Measurements of Smoke from Chipped and Unchipped Plots

Smoke data were collected from two instrumented plots located on the Francis Marion National Forest in South Carolina during prescribed burns on Feb. 12, 2003. One of the plots had been subjected to mechanical chipping. Particulate matter (PM2.5) data analyzed by gravimetric methods were collected at nine locations on the downwind sides of each plot. In addition, samplers were hung atop approximately 9-m poles at four interior positions within each plot. Perimeter 12-hour PM2.5 concentrations in the burn-only plot were significantly higher than those at the chip-burn plot. Similarly, interior 8-hour PM2.5 concentrations in the burn-only plot were moderately higher than those at the chip-burn plot. When possible cross-contamination was detected at a check site midway between the two plots, we used PB-Piedmont, a smoke model for predicting ground-level smoke movement at night. The modeled smoke, verified by smoke observed at the check site, indicated winds blowing 75 degrees off from winds observed at the Charleston Airport, approximately 50 km southwest of the experimental site.