AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Assessing the Contribution of NO3 Radical Chemistry to Nanoparticle Composition in the Boreal Atmosphere
DANIELLE C. DRAPER, Michael Lawler, Theo Kurten, James Smith, University of California, Irvine
Abstract Number: 364 Working Group: Aerosol Chemistry
Abstract Products consistent with NO3 radical-initiated oxidation of monoterpenes have been observed in nanoparticles measured at the SMEAR II station in Hyytiӓlä, Finland, using the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). Several organic nitrates, detected as molecular ions and as thermally decomposed fragments, displayed a striking diurnal profile, peaking at night and comprising a significant fraction of total compounds measured by the TDCIMS. These same ions have also been measured by the TDCIMS during monoterpene and NOy-containing chamber experiments. Products identified are consistent with first-generation oxidation products, which are assumed to be semivolatile and thus surprising to contribute strongly to nanoparticle composition under ambient conditions. Observed time series are assessed with kinetics and partitioning modeling approaches, using vapor pressures estimated using the SIMPOL group contribution method, as well as using the quantum chemical software COSMOtherm to obtain closure between our measurements and known partitioning theory. This work adds to the growing body of literature that suggests NO3 oxidation of monoterpenes is a strong contributor to SOA formation in forested environments. Furthermore, it emphasizes the potential importance of this chemistry in the growth of atmospheric nanoparticles.