AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
How Do Atmospheric Mineral Dust Particles Promote the Formation of Sulfate?
JIYEON PARK, Myoseon Jang, University of Florida
Abstract Number: 359 Working Group: Aerosol Chemistry
Abstract Mineral dust particles are one of the largest contributors to aerosol mass loading in the atmosphere. The surfaces of mineral dust particles can act as sinks for criteria air pollutants, such as sulfur dioxide (SO2) and NOx. Mineral dust particles can heterogeneously catalyze the oxidation of SO2 ramping to the formation of sulfate. However, there is little knowledge about the mechanisms of photocatalytic oxidation of SO2 on the surface of mineral dust particles. In this study, we investigated the kinetics and mechanisms of SO2 oxidation on the surface of Gobi desert dust (GDD) and Arizona test dust (ATD) particles using a 2-m3 indoor photo-irradiation chamber. Metal oxides in mineral dust particles acts as a semiconductor to form an electron-hole pair, which can react with the water molecules adsorbed on the surface of dust particles and produce OH radicals. These OH radicals contribute to oxidation of the SO2 or sulfite ions. In general, the catalytic ability of GDD is higher than that of ATD because the mineral oxide fraction of GDD particles is higher than that in ATD particles. The rate constant for heterogeneous oxidation of SO2 is determined using the sulfate concentrations measured with a particle into liquid sampler coupled with ion chromatography (PILS-IC) over the course of chamber experiment. The rate constants of heterogeneous oxidation of GDD are measured under varying humidity, ozone and NOx and compared with those from ATD. The hygroscopic properties of fresh dust particles were compared to those of aged dust particles using a Fourier transform infrared spectroscopy (FTIR). To study the chemical reactions between sulfuric acid and alkaline carbonates on dust particles, aerosol acidity ([H+]C-RUV, mol L-1 by aerosol volume) was measured using a colorimetry integrated with a reflectance UV-Visible spectrometer (C-RUV).