The reaction of ClONO₂ with HCl on aluminum oxide

Abstract

Abstract. The chlorine activation reaction C1ONO2 + HC1 • HNO3 + C12 was investigated in the laboratory on hydroxylated a-alumina surfaces under reactant partial pressure, humidity, and temperature conditions coveting those which are encountered at mid-latitudes in the lower stratosphere. The measured reaction probability is T ~ 0.02. This result has implications with regard to the stratospheric impact of launch vehicles utilizing solid-fuel rocket motors (SRMs), such as the Space Shuttle. The exhaust from SRMs consists of alumina particles and of HC1 and other vapors. The reaction probability measured in this work suggests that the ozone depletion potential of SRMs may be higher than that predicted on the basis of the chlorine emissions alone, especially at mid-latitudes in the lower stratosphere, where catalytic chlorine activation by background sulfuric acid aerosols is very inefficient. The reaction probability on Pyrex glass was found to be similar to that on a-alumina.The reaction mechanism appears to be determined by the water layers adsorbed on the surface, rather than by the detailed nature of the refractory surface itself.

Heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> with airborne TiO<sub>2</sub> particles and its implication for stratospheric particle injection

“…Therefore, the heterogeneous reactions of TiO 2 with chlorine containing trace gases (e.g., ClONO 2 , HOCl, and HCl) in the stratosphere need to be investigated before we can fully assess the impact of TiO 2 on stratospheric ozone. One previous study (Molina et al, 1997) investigated the uptake of ClONO 2 (1-10 × 10 −7 Torr) onto aluminum oxide and Pyrex glass in the presence of HCl (1-10 × 10 −6 Torr) at 210-220 K, and suggested that this process is very efficient, with an uptake coefficient of 0.02, which is > 10 times larger than that onto stratospheric sulfuric acid aerosols. In addition, the uptake of N 2 O 5 onto HCldoped sulfuric acid and SiO 2 (Raff et al, 2009) leads to the formation of ClNO 2 , whose photolysis will release Cl atoms and therefore represent a pathway for chlorine activation (Ghosh et al, 2012).…”

In situ measurement of the aerosol size distribution in stratospheric solid rocket motor exhaust plumes

“…Until recently, there has been little data on which to base such a model. Molina et al [1997] measured the rate of the chlorine activation reaction C1ONO2 + HC1 --> HNO3 + C12 on alumina surface and noted that the reaction was fast enough so as to raise the possibility that AAGTO might be reduced by chlorine activation on SRM alumina surface as much, or more than, the reduction from SRM chlorine loading alone. Jackman et al [1998] coupled the Goddard Space Flight Center two-dimensional photochemistry and transport model, the chlorine activation rates reported by Molina et al [ 1997], and various models of the size distribution of alumina to Copyright 1999 by the American Geophysical Union.…”

Long-term impacts of aerosols on precipitation and lightning over the Pearl River Delta megacity area in China

“…Several major field campaigns of air quality studies, such as the Program of Regional Integrated Experiments of Air Quality in the Pearl River Delta (PRIDE-PRD) 2004 and 2008 , have been conducted in this region to monitor the pollution situation and characterize the chemical and meteorological conditions responsible for accumulations of gaseous and PM pollutants of primary and secondary origins. In addition to their effects on visibility, human health, and weather and regional climate, pollution aerosols profoundly impact atmospheric chemistry via multiphase processes (Molina et al, 1997;Zhang et al, 1996).…”