AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Comprehensive Measurements of Gas- and Particle-phase Organic Carbon Formed in the Multigenerational Oxidation of Biogenic Hydrocarbons
GABRIEL ISAACMAN-VANWERTZ, Jonathan Franklin, Rachel O'Brien, Christopher Lim, Paola Massoli, Andrew Lambe, John B. Nowak, Timothy Onasch, Manjula Canagaratna, Joseph Roscioli, Scott Herndon, John Jayne, Douglas Worsnop, Luping Su, Daniel Knopf, Pawel Misztal, Caleb Arata, Allen H. Goldstein, Jesse Kroll, MIT
Abstract Number: 308 Working Group: Aerosol Chemistry
Abstract Atmospheric oxidation processes quickly transform emitted organic compounds into a multiphase, chemically dynamic system of organic aerosol and gas-phase products. Particle-phase mass serves as a temporary sink for carbon that can impact the distribution of products and oxidation reactions, but the low-volatility gases that condense to form organic aerosol and exchange with particle-phase mass are difficult to measure. Consequently, attempts to understand the evolution of carbon through atmospheric oxidation has in nearly all cases resulted in a large fraction of “missing” or unidentified carbon. We present here results from laboratory oxidation experiments in which a large suite of state-of-the-art mass spectrometric and spectroscopic instrumentation was employed to measure organic compounds across nearly all volatilities and chemical functionalities typically observed in the atmosphere. Photochemical oxidation of common biogenic emissions was studied, spanning hours to days of simulated atmospheric aging, with a focus here on α-pinene. New chemical ionization mass spectrometric instruments allowed for the quantification of low-volatility gases formed through these processes, and characterization of their role in aerosol growth. Through systematic variation of reaction conditions (e.g. with and without seed aerosol) coupled with measurements of low-volatility compounds, we explore the importance of measurement artifacts, especially vapor deposition to surfaces, on typical measurements and laboratory experiments. By observing all carbon through multiple generations of oxidation, we examine the transitions between particles and lower-volatility gases with unprecedented detail and place them in the context of current simplified (i.e. two-dimensional) model frameworks, providing a more complete understanding of the evolution of organics in the atmosphere as well as an updated assessment of the capabilities and limitations of current atmospheric instrumentation.