The heterogeneous chemical kinetics of N<sub>2</sub>O<sub>5</sub> on CaCO<sub>3</sub> and other atmospheric mineral dust surrogates

Abstract

Abstract.Uptake experiments of N 2 O 5 on several mineral dust powder samples were carried out under continuous molecular flow conditions at 298±2 K. At [N 2 O 5 ] 0 =(4.0±1.0)×10 11 cm −3 we have found γ ss values ranging from (3.5±1.1)×10 −2 for CaCO 3 to (0.20±0.05) for Saharan Dust with γ ss decreasing as [N 2 O 5 ] 0 increased. The uptake coefficients reported in this work are to be regarded as upper limiting values owing to the fact that they are based on the geometric (projected) surface area of the mineral dust sample. We have observed delayed production of HNO 3 upon uptake of N 2 O 5 for every investigated sample owing to hydrolysis of N 2 O 5 with surface-adsorbed H 2 O. Arizona Test Dust and Kaolinite turned out to be the samples that generated the largest amount of gas phase HNO 3 with respect to N 2 O 5 taken up. In contrast, the yield of HNO 3 for Saharan Dust and CaCO 3 is lower. On CaCO 3 the disappearance of N 2 O 5 was also accompanied by the formation of CO 2 . For CaCO 3 sample masses ranging from 0.33 to 2.0 g, the yield of CO 2 was approximately 42-50% with respect to the total number of N 2 O 5 molecules taken up. The reaction of N 2 O 5 with mineral dust and the subsequent production of gas phase HNO 3 lead to a decrease in [NO x ] which may have a significant effect on global ozone.

Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars

“…The presence of carbonic acid has been confirmed in numerous other studies on the CaCO 3 surface in the presence of H 2 O vapor (41,45,46). When an O 3 molecule collides with the aerosol surface, it may scatter back into the gas phase or adsorb across the hydration layer depending on the hydration shell thickness (Fig.…”

“…Atmospheric relative humidity levels between 20-90% (∼5-20 Torr water vapor pressure in the atmosphere) promote the formation of thin water films on particle surfaces (40). In the case of metal oxides (CaO, MgO, and Fe 2 O 3 ) and carbonates (CaCO 3 and MgCO 3 ), dissociation of water molecules at the interfaces is energetically favorable because hydroxylated surfaces are more stable than metal-terminated surfaces under ambient conditions (15,41,42). Recent experiments and molecular dynamic simulations have shown the free energy of adsorption of water on calcite surfaces (43,44) to be as low as −10.6 kcal mol −1 .…”

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

“…The kinetics of the uptake of N 2 O 5 onto desert dust particles and their surrogates (e.g., Arizona Test Dust, illite) has been reported by several previous studies (Karagulian et al, 2006;Mogili et al, 2006;Seisel et al, 2005;Tang et al, 2010Tang et al, , 2012Tang et al, , 2014Wagner et al, 2008Wagner et al, , 2009). In addition, Seisel et al (2005) observed the formation of nitrate on mineral dust particles due to the uptake of N 2 O 5 using diffuse reflectance FTIR (Fourier transform infrared spectroscopy), and Tang et al (2012) further confirmed that the yield of nitrate is ∼ 2 (as expected from Reaction R1) within the experimental uncertainty, and that the formation of NO 2 is negligible.…”

Interaction of NO<sub>2</sub> with TiO<sub>2</sub> surface under UV irradiation: measurements of the uptake coefficient

“…Titanium dioxide, although being a minor component of mineral dust particles (Karagulian et al, 2006), was shown recently to be responsible for the photochemical reactivity of atmospheric mineral aerosols (Ndour et al, 2008). Thus the information on the photoinitiated uptake of atmospheric trace gases to TiO 2 surface is of great importance for the modelling of the day time chemistry of the atmosphere.…”