PCDD/F emissions from forest fire simulations

Polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/F) emissions from combustion of forest biomass were sampled to obtain an estimated emission factor for forest fires. An equal composition of live shoot and litter biomass from Oregon and North Carolina was burned in an enclosed monitored facility, and emissions were sampled with a modified ambient air sampling method. Seven tests resulted in an average PCDD/F toxic equivalency (TEQ) emission of 19 ng/kg burned, a value close to previous indirect estimates. Emissions from the Oregon biomass averaged 25 ng TEQ/kg burned (range: 14–47) and those from the North Carolina biomass averaged 15 ng TEQ/kg burned (range: 1–56). Source-specific distinctions in isomer patterns and homologue profiles, however, suggest that the type of biomass has a significant effect on the composition of the resulting PCDD/F emissions. The mass-specific emissions are about 20 times higher than the concentration of the extracted biomass, suggesting that PCDD/F emissions are not simply a result of vaporization of cuticle-bound PCDD/F but are formed predominantly during the biomass combustion.