Heterogeneous reactivity of carbonyl sulfide on α-Al 2O 3 and γ-Al 2O 3

Abstract

The heterogeneous reactions of trace gases in the atmosphere on atmospheric particles could greatly affect the nitrogen, sulfur, ozone, and photochemical oxidant cycles. The uptake coefficient is an important kinetic parameter for atmospheric models to assess the role of heterogeneous reaction in the global cycles of trace gases. In this study, the heterogeneous uptake coefficients of carbonyl sulfide (OCS) on Al 2O 3 have been measured using a Knudsen cell reactor at 300 K. Hydrogen sulfide (H 2S) and carbon dioxide (CO 2) were found to be the gaseous products. The reaction mechanism of OCS on Al 2O 3 was confirmed based on previous work and this study. The true initial uptake coefficient and steady-state uptake coefficient of OCS on α-Al 2O 3 were (3.8±0.8)×10 −7 and (6.5±2.49)×10 −8, and the corresponding uptake coefficients on γ-Al 2O 3 were (7.0±0.7)×10 −8 and (1.8±0.4)×10 −8, respectively. The annual flux of OCS due to heterogeneous reaction on α-Al 2O 3 was calculated to be 0.11–0.63 Tg yr −1 based on the initial uptake coefficient and the steady-state uptake coefficient. When the fraction of Al 2O 3 in authentic atmospheric particles is taken into account, the annual flux of OCS due to heterogeneous reaction on atmospheric particles in the troposphere should be 0.02–0.10 Tg yr −1.