Abstract View
Differential Toxicity of PM2.5 Emissions from Residential Wood Burning due to Varying Combustion Conditions
MARCIA PEDROZA, Greg J. Evans, Arthur W. H. Chan, SOCAAR, University of Toronto
Abstract Number: 501
Working Group: Health-Related Aerosols
Abstract
The contribution of residential wood combustion (RWC) to ambient fine particulate matter (PM2.5) has been reported to be as high as 42% in some North American and European urban areas during the heating season. Wood combustion-generated PM2.5 has been postulated to exert different toxic effects by causing oxidative stress via the generation of reactive oxygen species (referred to as the oxidative potential, OP), among other mechanisms. However, the effects of combustion conditions on the toxicity of the emissions are still poorly understood. In this work, we hypothesize that the toxicity of the PM2.5 from wood burning is affected by varying combustion conditions, such as fuel, ventilation, and temperature. The developed methodology includes fuel combustion in a temperature-controlled quartz tube furnace coupled with online measurements of CO2 and CO concentrations, followed by PM2.5 offline analysis by thermal desorption/gas chromatography-mass spectrometry (TD/GC-MS), and thermo-optical organic carbon/elemental carbon (OC/EC) analysis. As a primary metric for toxicity, we measure the OP of the particles with the dithiothreitol assay (OPDTT), which is especially sensitive to highly oxidized organics. As secondary metrics, we are using OC/EC ratios, and modified combustion efficiency (MCE). Our results do not show significant differences between the OPDTT of the PM2.5 of hardwood and softwood combustion. The OPDTT was found to increase with decreased oxygen concentrations, but enhancing ventilation did not decrease OPDTT, likely due to lower effective temperatures of combustion. There is a moderate positive correlation between the OPDTT and the OC fraction (R2=0.56); both show sharp increases under enhanced ventilation conditions and under oxygen-deficient combustion for all the types of wood tested. The highest OPDTT was obtained under smoldering combustion temperatures. The results presented here will inform best practices of residential wood burning to limit health impacts.