Black Carbon and Aldehyde Sources in Winter

In winter, residential wood combustion is can be a significant source of particulate matter, CO, and other volatile organic compounds (VOCs) in urban areas of the intermountain western US. We report measurements of particle composition, black carbon, CO, NOx, aldehydes and other VOCs from the Yakima Air Wintertime Nitrate Study (YAWNS) that took place in January 2013. Acetonitrile is a good tracer of biomass combustion and was well correlated with black carbon indicating residential wood burning as a dominant source. CO-to-NOx molar ratios were elevated with respect to ratios predicted from mobile source emissions indicating wood combustion as a significant source of CO. During clear sky weather, formaldehyde and acetaldehyde were well correlated with CO, NOx, black carbon and other VOCs suggesting a primary emission source. During persistent overcast periods mixing ratios of primary pollutants were much lower consistent with better ventilation as indicated by ceilometers observations of boundary layer heights. However, aldehydes and particulate nitrate remain elevated suggesting secondary sources, perhaps via cloud processing.