Ozone Tendency in Biomass Burning Plumes: Influence of Biogenic and Anthropogenic Emissions Downwind of Forest Fires

Abstract:

Forest fires emit pollutants that can influence downwind surface concentrations of ozone, with potential implications for exceeding air quality regulations. The influence of emissions from biogenic and anthropogenic sources that are mixed into a biomass burning plume as it travels downwind is not well understood. Using the GEOS-Chem atmospheric chemistry transport model and a novel method to track the centre of biomass burning plumes, we identify the chemical reactions that determine ozone production and loss along the plume trajectory. Using a series of sensitivity runs, we quantify the role of biogenic and anthropogenic emissions on the importance of individual chemical reactions. We illustrate the method using data collected during the BORTAS aircraft campaign over eastern Canada during summer 2011. We focus on two contrasting plume trajectories originating from the same multi-day fire in Ontario. The first plume trajectory on 16th July 2011 travels eastward from the fire and eventually mixes with anthropogenic emissions travelling up the east coast of the United States before outflow over the North Atlantic. The second plume trajectory we follow is three days later and travels eastward with a strong northeast component away from large anthropogenic sources. Both trajectories are influenced by downwind biogenic emissions. We generate a chemical reaction narrative for each plume trajectory, allowing is to quantify how mixing pyrogenic, biogenic and anthropogenic emissions influences downwind ozone photochemistry.