AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
A Dual-Chamber Enhancement (DUCE) Method for Quantifying Secondary Organic Aerosol from Biomass Burning Emissions
DANIEL S. TKACIK, Ellis Shipley Robinson, Rawad Saleh, Adam Ahern, Albert A. Presto, Ryan Sullivan, Neil Donahue, Allen Robinson, Carnegie Mellon University
Abstract Number: 350 Working Group: Aerosol Chemistry
Abstract Biomass burning emissions are a large contributor to the global budget of gas- and particle-phase material in the atmosphere, and thus play an important role in atmospheric chemistry, human health, and climate. Current estimates on secondary organic aerosol (SOA) formation from these emissions are highly uncertain. A few biomass burning SOA studies have been conducted, but a challenge is the physiochemical makeup of these emissions is highly variable and depends on characteristics like burn and fuel conditions that are difficult to characterize. Smog chamber experiments typically consist of exposing emissions from a single biomass burn to one type of perturbation (ie: photo-oxidation), so the specific environmental conditions that promote or hinder SOA formation across all burn types are difficult to decipher.
In this study, a dual-chamber experimental setup was used to perturb biomass burning emissions using three different perturbations: high-NOx photo-oxidation, low-NOx photo-oxidation, and dark ozonolysis. During an experiment, dilute emissions from the same biomass burn were injected into two identical Teflon smog chambers. Each chamber was then subjected to a different perturbation using UV lamps (for photo-oxidation), nitrous acid (HONO, for high-NOx conditions), or ozone. Organic aerosol (OA) mass enhancements were derived for each chamber and used to calculate a dual-chamber enhancement (DUCE), a metric that describes the relative behavior of the emissions in response to different perturbations. In the high-NOx photo-oxidation vs. low-NOx photo-oxidation experiments, the high-NOx chamber showed lower OA mass enhancements in half of the experiments (n=4), regardless of fuel type, suggesting that NOx may play a role in hindering SOA formation in biomass burning emissions. In dark ozonolysis vs. low-NOx photo-oxidation experiments, the emissions subjected to dark ozonolysis showed higher OA mass enhancements in almost all experiments (n=7), suggesting that ozone may play an important role in SOA formation from biomass burning emissions.