Chemical characterization of prescribed burn emissions from a mixed forest in Northern Michigan

Abstract

A prescribed burn was conducted in October 2017 at the University of Michigan Biological Station located in Pellston, Michigan. Approximately 0.025 km² of a temperate forest, primarily composed of red and white pine, red oak, bigtooth aspen, and red maple, were burned. The resulting smoke was sampled with a combination of real-time trace gas and aerosol instrumentation aboard the Aerodyne Mobile Laboratory. The resulting data were segmented into six plume periods, and the gas and particle concentration and composition measurements were characterized relative to modified combustion efficiency (MCE), which reflected both smoldering and flaming combustion. Emission factors for C₂H₂, C₂H₆, CH₄, and HCN were inversely related to MCE. The bulk submicron particle composition was characterized as mostly organic by mass (>92%). The majority of the bulk organic mass was within individual biomass burning particles (>93%, by number) in the accumulation mode. Analysis of the mass spectral ion peaks of individual biomass burning particles reveals two noteworthy signatures. First, red pine smoke contained combustion products of eugenol, released during the early stages of lignin combustion. Second, the combustion of northern hardwoods (e.g., oak, aspen, maple) exhibited polycyclic aromatic hydrocarbons peaks corresponding to the combustion of furfural. The results from this study provide a detailed assessment of the composition of smoke emissions from biomass common to the understudied north-central United States.