AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Volatility-Resolved Measurements of the Amount and Oxidation State of Gas-Phase and Particulate Organic Compounds in a Forested Environment
JAMES HUNTER, Eben Cross, Anthony Carrasquillo, Patrick Hayes, Pedro Campuzano-Jost, Douglas Day, Brett Palm, LaxmiNarasimha Yatavelli, Harald Stark, Samantha Thompson, Jose-Luis Jimenez, Scott Herndon, Douglas Worsnop, Jesse Kroll, MIT
Abstract Number: 285 Working Group: Aerosol Chemistry
Abstract The volatility and degree of oxidation of organic aerosol can significantly alter its impacts on air quality, climate and human health. Much remains to be understood about these key properties and how they evolve over the full life cycle of aerosol particles, including initial formation through emission or oxidation processes. Here we describe measurements of organic volatility and oxidation state in a ponderosa pine forest in the Colorado Rocky Mountains during the BEACHON-RoMBAS campaign. Measurements of intermediate and semivolatile organic compounds (IVOCs and SVOCs) using a cryogenic preconcentration-electron impact mass spectrometry (CP-EI) technique are combined with organic acid measurements from the MOVi-CIMS and aerosol volatility measurements from a thermo-denuder HR-AMS system to yield organic composition over 19 orders of magnitude in volatility (from logC* = -9 to +8). In addition to organic aerosol, this volatility range includes gas-phase biogenic emissions that act as aerosol precursors (i.e. mono and sesquiterpenes) as well as a complex mixture of gas-phase oxidation products. This data is mapped into a 2D volatility basis set, enabling the entire relevant range of volatility and oxidation state to be viewed simultaneously. This approach allows possible pathways to be proposed and visualized for carbon originating in the gas phase to lead to the observed distribution of condensed and gas-phase oxidation products. Further constraints are placed on these complex, dynamic processes by tracking changes in the VBS distribution at different times of day, and by comparison with key laboratory oxidation experiments.