AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Oxidative Aging of Organic Aerosol: Role of Carbon Skeleton and Fragmentation Reactions
JAMES HUNTER, Anthony Carrasquillo, Kelly Daumit, Eben Cross, Douglas Worsnop, Jesse Kroll, MIT
Abstract Number: 594 Working Group: Aerosol Chemistry
Abstract The atmospheric aging of organic aerosol involves a complex interplay between oxidation chemistry and gas-particle partitioning. Oxidation may cause molecular fragmentation as well as functionalization, and so the effect of aging may be highly dependent on how fragmentation affects the molecular structure of the precursor. A series of aging experiments has been performed to determine the effect of sustained oxidation on aliphatic hydrocarbon molecules containing 10 to 18 carbon atoms as a function of their structure and vapor pressure. Experiments are performed using a recently-developed chamber aging technique combining long residence times with elevated OH concentrations. Experiments run under high NOx conditions with OH exposures reaching a maximum of approximately 3e11 molecule*seconds/cc, equivalent to several days of exposure to ambient OH concentrations. Linear and cyclic alkane structures of test molecules are specifically chosen and compared to evaluate the effect of fragmentation upon sustained oxidation. Properties such as aerosol mass concentration and oxygen content are reported. Fragmentation reactions of later generation products are hypothesized to limit the aerosol production especially for smaller hydrocarbons. Mass spectrometric measurements of the particle-phase and gas-phase carbon enable a measure of carbon balance, to further constrain the production of gas phase products due to fragmentation processes.