Ozone Decomposition on Kaolinite as a Function of Monoterpene Exposure and Relative Humidity

Abstract

Atmospheric processing of mineral aerosol by trace gases results in the formation of surface-adsorbed products that have the capacity to alter the chemical and physical properties of these airborne particulates. To investigate one potential impact of aerosol processing by biogenic volatile organic compounds (BVOCs), we investigated the heterogeneous decomposition of ozone on pure and monoterpene-processed kaolinite. We used a laminar flow reactor to measure O3 reactive uptake coefficients on kaolinite-coated tubes as a function of relative humidity, O3 concentration, and pre-exposure to gaseous limonene and α-pinene. At 26% RH, kaolinite has a near equivalent of a monolayer of adsorbed water, and the ozone steady-state uptake coefficient was γav = 2.9 × 10–9 assuming the BET surface area. Pre-exposing kaolinite to limonene and α-pinene increased O3 uptake coefficients by nearly 2 orders of magnitude to 2.1 × 10–7 and 2.5 × 10–7, respectively. At all humidities studied (10–50% RH), O3 uptake was at least 1...