Chemical Characterization of Fine Particle Emissions from the Wood Stove Combustion of Prevalent United States Tree Species

Abstract

Residential wood combustion is an important contributor to ambient fine particle levels in the United States. About one-half to two-thirds of the residential wood combustion in the United States occurs in wood stoves as opposed to fireplaces. Thus, any differences between these two sources must be accounted for in chemical mass balance receptor models which attempt to determine the contribution of wood smoke sources to ambient fine particle samples. To fully characterize the fine particle emissions from wood stoves and compare the emissions profiles to those determined from previous fireplace experiments, a series of source tests were conducted on the burning of the most prevalent U.S. tree species in wood stoves. The catalyst-equipped wood stove chosen for these tests was operated under both noncatalytic and catalytic conditions to assess the effects of the catalyst on fine particle emissions. Analysis of the wood smoke includes fine particle mass emission factors, organic and elemental carbon content, ionic and elemental composition, and detailed organic speciation by GC/MS. Between 60 and 90% of the fine particle mass emissions were attributed to measured chemical species. The fine particle emissions from wood stoves show the same general patterns as those from the fireplace combustion of the same tree species; important differences between hardwood and softwood combustion are seen among the substituted phenols and diterpenoids, and levoglucosan is the most abundant individual organic compound emitted. However, fine particle mass emission factors from wood stoves are significantly lower than those from fireplaces. The elemental carbon content of the fine particle mass is generally higher in wood stove smoke than in fire- place smoke, and is even higher when the catalyst was employed. Furthermore, a greater fraction of the organic compounds is identifiable by GC/MS methods in the wood stove smoke vs. the fireplace smoke. These results suggest that differences in the source profiles between wood stove and fireplace combustion merit consideration in source apportionment calculations using organic compounds as tracers.