Insights into Chemical Transport and Oxidative Processing in the Arctic Springtime

Tuesday, 15 December 2015: 15:10
3010 (Moscone West)
Eric C Apel1, Rebecca S Hornbrook2, Frank M Flocke2, Samuel R Hall2, Alan J Hills3, Denise Montzka2, John Joseph Orlando2, Andrew A Turnipseed4, Kirk Ullmann2, Andrew John Weinheimer2, Lee Mauldin5, Daniel D Riemer6, Paul B Shepson7, Barkley C Sive8, Ralf M Staebler9 and Nicola J Blake10, (1)University Corporation for Atmospheric Research, Boulder, CO, United States, (2)National Center for Atmospheric Research, Boulder, CO, United States, (3)NCAR, Boulder, CO, United States, (4)2B Technologies, Boulder, CO, United States, (5)University of Colorado at Boulder, Boulder, CO, United States, (6)Self Employed, Washington, DC, United States, (7)Purdue University, West Lafayette, IN, United States, (8)National Park Service Lakewood, Air Resources Division, Lakewood, CO, United States, (9)Environment Canada Toronto, Toronto, ON, Canada, (10)University of California Irvine, Irvine, CA, United States
Gas-phase volatile organic compounds (VOCs) were measured at several levels between the snow surface and 6 m in the Arctic boundary layer in Barrow, Alaska for the OASIS-2009 field campaign during March and April 2009, as part of the International Polar Year (IPY). Nonmethane hydrocarbons (NMHCs) from C4-C8 and oxygenated VOCs, including alcohols, aldehydes and ketones were quantified multiple times per hour, day and night during the campaign using in-situ fast gas chromatography-mass spectrometry (fast-GC/MS). Samples were also collected in canisters two to three times daily and subsequently analyzed for C2-C8 NMHCs. The NMHCs and aldehydes all showed decreasing mixing ratios with time during the experiment whereas acetone and MEK showed increases. These results are interpreted in the context of a box model and a 3D chemical transport model. After adjusting for seasonal trends in the VOCs, acetone, MEK and 2-pentanone were all negatively correlated with O3, while NMHCs, methanol, ethanol, acetaldehyde, propanal and butanal were all positively correlated with O3. Several ozone depletion events (ODEs) during the study provided an opportunity to investigate the large perturbations due to halogen chemistry on the production and loss of VOCs in the air masses at the sampling site. Notably, aldehyde mixing ratios dropped below the detection limit of the instrument (< 3 pptv) during the ODEs. The NCAR Master Mechanism (MM) (0-D box model), which was updated to include halogen chemistry, was able to reproduce the bromine explosion and showed consistency with key observations including the aldehyde data. Further, no clear positive or negative air-snow flux could be identified for any of the VOCs observed by fast-GC/MS during the study.