Effects of Irradiation and Oxidant Concentration on the Multiphase Chemical Reactions of Biomass Burning Aerosol Surrogates with OH and O3

Daniel A. Knopf, Seanna M. Forrester, and Jonathan H. Slade

Biomass burning aerosol (BBA) represent a ubiquitous organic aerosol impacting air quality, health related issues, and climate. Multiphase chemical reaction kinetics, products, and irradiation influence were investigated involving BBA surrogates such as levoglucosan (LEV), nitroguaiacol (NG), abietic acid (AA), and Pahokee peat (PP) acting as a photosensitizer and atmospheric oxidants and radicals such as O3 and OH. Heterogeneous oxidation kinetics between OH and BBA surrogates were determined for OH concentration ~107 – ~1011 molecule cm-3 using chemical ionization mass spectrometry (CIMS). OH reactive uptake occurs according to a Langmuir-Hinshelwood (LH) uptake mechanism and varies from ~1 to ~0.01 as OH concentration increases. Volatilization products were identified using high resolution proton transfer reaction time-of-flight mass spectrometry (HR-PTR-ToF-MS). Photosensitized heterogeneous kinetics between O3 and BBA surrogates were determined in the dark and under visible (VIS) and ultraviolet (UV-A) irradiation and as a function of O3 concentration and irradiation intensity using a novel irradiated rectangular channel flow reactor (I-RCFR) coupled to CIMS. Uptake of O3 by BBA surrogates in the presence of a photosensitizer is significantly enhanced by up to 90%, increasing linearly as irradiation intensity increases, and follows an LH uptake mechanism.

Join today to view and download the full abstract/presentation