scholarly journals Kinetics and mechanism of the uptake of N<sub>2</sub>O<sub>5</sub> on mineral dust at 298 K

2005 ◽  
Vol 5 (4) ◽  
pp. 5645-5667
Author(s):  
S. Seisel ◽  
C. Börensen ◽  
R. Vogt ◽  
R. Zellner
Keyword(s):  
Steady State ◽  
Mineral Dust ◽  
Heterogeneous Reaction ◽  
Kinetics And Mechanism ◽  
Saharan Dust ◽  
Uptake Coefficient ◽  
Uptake Rates ◽  
Hydrolysis Of ◽  
Dust Surface ◽  
Initial Uptake

Abstract. The heterogeneous reaction of N2O5 with mineral (Saharan) dust has been studied at T=298 K using a combination of Knudsen and DRIFTS cell for kinetic and product investigations, respectively. The initial uptake coefficient has been determined to be γ=(8.0±0.3)·10−2. This uptake slowly saturates into a steady state uptake of γ=(1.3±0.3)10−2 suggesting that reaction of N2O5 with the mineral dust surface and hydrolysis of N2O5 on the surface take place simultaneously. Moreover, the product investigations suggest that N2O5 is irreversibly taken up forming nitrate on the surface. The uptake rates of N2O5 on Saharan dust are large enough to influence the photo-oxidant budget of the atmosphere.

scholarly journals Kinetics and mechanism of the uptake of N<sub>2</sub>O<sub>5</sub> on mineral dust at 298 K

2005 ◽  
Vol 5 (12) ◽  
pp. 3423-3432 ◽  
Author(s):  
S. Seisel ◽  
C. Börensen ◽  
R. Vogt ◽  
R. Zellner
Keyword(s):  
Mineral Dust ◽  
Heterogeneous Reaction ◽  
Recent Model ◽  
Saharan Dust ◽  
Uptake Coefficient ◽  
Model Calculations ◽  
Upper Limits ◽  
Uptake Rates ◽  
Hydrolysis Of ◽  
Dust Surface

Abstract. The heterogeneous reaction of N2O5 with mineral (Saharan) dust has been studied at T=298 K using a combination of Knudsen and DRIFTS cells for kinetic and product investigations, respectively. The initial uptake coefficient has been determined to be γ=(8.0±0.3)·10−2. This uptake slowly saturates into a steady state uptake of γ=(1.3±0.3)·10−2 suggesting that reaction of N2O5 with the mineral dust surface and hydrolysis of N2O5 on the surface take place simultaneously. Both uptake coefficients have been calculated on the basis of the geometric (projected) surface area of the sample and must therefore be regarded as upper limits. In addition, the product investigations show that N2O5 is irreversibly taken up to form nitrate on the surface. Recent model calculations suggest that the uptake rates of N2O5 on Saharan dust which we measured may be large enough to influence the photo-oxidant budget of the atmosphere.

scholarly journals Ozone decomposition on Saharan dust: an experimental investigation

2002 ◽  
Vol 2 (6) ◽  
pp. 1809-1845 ◽  
Author(s):  
F. Hanisch ◽  
J. N. Crowley
Keyword(s):  
Experimental Investigation ◽  
Heterogeneous Reaction ◽  
Exposure Period ◽  
Saharan Dust ◽  
Ozone Decomposition ◽  
Uptake Coefficient ◽  
Conversion Efficiencies ◽  
Dust Surface ◽  
Very High ◽  
Initial Uptake

Abstract. The heterogeneous reaction between O3 and authentic Saharan dust surfaces was investigated in a Knudsen reactor at approx 296 K. O3 was destroyed on the dust surface and O2 was formed with conversion efficiencies of 1.0 and 1.3 molecules O2 per O3 molecule destroyed for unheated and heated samples, respectively. No O3 desorbed from exposed dust samples, showing that the uptake was irreversible. The uptake coefficients for the irreversible destruction of O3 on (unheated) Saharan dust surfaces depended on the O3 concentration and varied between 3.5 x10-4 and 5.5 x10-6 for the initial uptake coefficient (g0 approx 3 x10-5 at 30 ppbv O3 STP) and between 4.8 x10-5 and 2.2 x10-6 for the steady-state uptake coefficient (gss approx 7 x10-6 at 30 ppbv O3 STP). At very high O3 concentrations the surface was deactivated, and O3 uptake ceased after a certain exposure period. Sample re-activation (i.e. de-passivation) was found to occur over periods of hours, after exposure to O3 had ceased, suggesting that re-activation processes play a role both in the laboratory and in the atmosphere.

scholarly journals Ozone decomposition on Saharan dust: an experimental investigation

2003 ◽  
Vol 3 (1) ◽  
pp. 119-130 ◽  
Author(s):  
F. Hanisch ◽  
J. N. Crowley
Keyword(s):  
Experimental Investigation ◽  
Heterogeneous Reaction ◽  
Exposure Period ◽  
Saharan Dust ◽  
Ozone Decomposition ◽  
Uptake Coefficient ◽  
Conversion Efficiencies ◽  
Dust Surface ◽  
Very High ◽  
Initial Uptake

Abstract. The heterogeneous reaction between O3 and authentic Saharan dust surfaces was investigated in a Knudsen reactor at approx 296 K. O3 was destroyed on the dust surface and O2 was formed with conversion efficiencies of 1.0 and 1.3 molecules O2 per O3 molecule destroyed for unheated and heated samples, respectively. No O3 desorbed from exposed dust samples, showing that the uptake was irreversible. The uptake coefficients for the irreversible destruction of O3 on (unheated) Saharan dust surfaces depended on the O3 concentration and varied between 3.5 x 10-4 and 5.5 x 10-6 for the initial uptake coefficient (g0 approx 3 x 10-5 at 30 ppbv O3 STP) and between 4.8 x 10-5 and 2.2 x 10-6 for the steady-state uptake coefficient (gss approx 7 x10-6 at 30 ppbv O3 STP). At very high O3 concentrations the surface was deactivated, and O3 uptake ceased after a certain exposure period. Sample re-activation (i.e. de-passivation) was found to occur over periods of hours, after exposure to O3 had ceased, suggesting that re-activation processes play a role both in the laboratory and in the atmosphere.

scholarly journals Kinetics and mechanisms of heterogeneous reaction of NO<sub>2</sub> on CaCO<sub>3</sub> surfaces under dry and wet conditions

2009 ◽  
Vol 9 (2) ◽  
pp. 7115-7154
Author(s):  
H. J. Li ◽  
T. Zhu ◽  
D. F. Zhao ◽  
Z. F. Zhang ◽  
Z. M. Chen
Keyword(s):  
Photoelectron Spectroscopy ◽  
Water Solubility ◽  
Mineral Dust ◽  
Heterogeneous Reaction ◽  
Calcium Nitrate ◽  
Adsorbed Water ◽  
Uptake Coefficient ◽  
Dry Conditions ◽  
Diffuse Reflectance Infrared ◽  
Initial Uptake

Abstract. Calcium nitrate (Ca(NO3)2) was observed in mineral dust and could change the hygroscopic and optical properties of mineral dust significantly due to its strong water solubility. The reaction of calcium carbonate (CaCO3) with nitric acid (HNO3) is believed the main reason for the observed Ca(NO3)2 in the mineral dust. In the atmosphere, the concentration of nitrogen dioxide (NO2) is orders of magnitude higher than that of HNO3; however, little is known about the reaction of NO2 with CaCO3. In this study, the heterogeneous reaction of NO2 on the surface of CaCO3 particles was investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) combined with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) under wet and dry conditions. Nitrate formation was observed in both conditions, and nitrite was observed under wet conditions, indicating the reaction of NO2 on the CaCO3 surface produced nitrate and probably nitrous acid (HONO). Relative humidity (RH) influenced both the initial uptake coefficient and the reaction mechanism. With RH<52%, surface –OH was formed through dissociation of the surface adsorbed water via oxygen vacancy, thus determining the reaction order. With RH>52%, a monolayer of water formed on the surface of the CaCO3 particles, which reacted with NO2 as a first order reaction, forming HNO3 and HONO. The initial uptake coefficient γ0 was determined to be (1.66±0.38)×10−7 under dry conditions and up to (0.84±0.44)×10−6 under wet conditions. Considering that NO2 concentrations in the atmosphere are orders of magnitude higher than those of HNO3, the reaction of NO2 on CaCO3 particle should have similar importance as that of HNO3 in the atmosphere and could also be an important source of HONO in the atmosphere.

scholarly journals Uptake of NO<sub>3</sub> and N<sub>2</sub>O<sub>5</sub> to Saharan dust, ambient urban aerosol and soot: a relative rate study

2010 ◽  
Vol 10 (6) ◽  
pp. 2965-2974 ◽  
Author(s):  
M. J. Tang ◽  
J. Thieser ◽  
G. Schuster ◽  
J. N. Crowley
Keyword(s):  
Mineral Dust ◽  
Relative Rate ◽  
Simultaneous Detection ◽  
Saharan Dust ◽  
Uptake Coefficient ◽  
Ambient Aerosols ◽  
Mixing Ratios ◽  
A Value ◽  
Rate Study ◽  
Absolute Basis

Abstract. The uptake of NO3 and N2O5 to Saharan dust, ambient aerosols and soot was investigated using a novel and simple relative rate method with simultaneous detection of both NO3 and N2O5. The use of cavity ring down spectroscopy to detect both trace gases enabled the measurements to be carried out at low mixing ratios (<500 pptv or 1×1010 molecule cm−3). The uptake coefficient ratio, γ(NO3)/γ(N2O5), was determined to be 0.9±0.4 for Saharan dust, independent of relative humidity, NO3 or N2O5 mixing ratio and exposure time. Ambient (urban) aerosols showed a very limited capacity to take up N2O5 but were reactive towards NO3 with γ(NO3)/γ(N2O5)>15. A value of γ(NO3)/γ(N2O5)~1.5–3 was obtained when using candle generated soot. The relative rate obtained for Saharan dust can be placed on an absolute basis using our recently determined value of γ(N2O5)=1×10−2 to give γ(NO3)=9×10−3, which is significantly smaller than the single previous value. With the present uptake coefficient, reaction of NO3 with mineral dust will generally not contribute significantly to its NO3 loss in the boundary atmosphere or to the nitration of mineral dust.

scholarly journals The uptake of SO<sub>2</sub> on Saharan dust: a flow tube study

2005 ◽  
Vol 5 (10) ◽  
pp. 2679-2689 ◽  
Author(s):  
J. W. Adams ◽  
D. Rodriguez ◽  
R. A. Cox
Keyword(s):  
Gas Phase ◽  
Mineral Dust ◽  
Unit Area ◽  
Surface Reactivity ◽  
Saharan Dust ◽  
Bet Surface Area ◽  
Flow Tube ◽  
Wall Flow ◽  
Phase Water ◽  
Initial Uptake

Abstract. The uptake of SO2 onto Saharan mineral dust from the Cape Verde Islands was investigated using a coated wall flow tube coupled to a mass spectrometer. The rate of loss of SO2 to the dust coating was measured and uptake coefficients were determined using the measured BET surface area of the sample. The uptake of SO2, with an initial concentration between (2-40)x1010molecule cm-3 (0.62-12 µTorr), was found to be strongly time dependent over the first few hundred seconds of an experiment, with an initial uptake γ0,BET of (6.6±0.8)x10-5 (298 K), declining at longer times. The amount of SO2 adsorbed on the dust samples was measured over a range of SO2 concentrations and mineral dust loadings. The uptake of SO2 was found to be up to 98% irreversible over the timescale of these investigations. Experiments were also performed at 258 K, at a relative humidity of 27% and at 298 K in the presence of ozone. The initial uptake and the amount of SO2 taken up per unit area of BET dust surface was the same within error, irrespective of the conditions used; however the presence of ozone reduced the amount of SO2 released back into the gas-phase per unit area once exposure of the surface ended. Multiple uptakes to the same surface revealed a loss of surface reactivity, which did not return if the samples were exposed to gas-phase water, or left under vacuum overnight. A mechanism which accounts for the observed uptake behaviour is proposed and numerically modelled, allowing quantitative estimates of the rate and amount of SO2 removal in the atmosphere to be estimated. Removal of SO2 by mineral dust is predicted to be significant at high dust loadings.

Kinetics and mechanism of the heterogeneous reaction of N2O5 with mineral dust particles

2012 ◽  
Vol 14 (24) ◽  
pp. 8551 ◽  
Author(s):  
M. J. Tang ◽  
J. Thieser ◽  
G. Schuster ◽  
J. N. Crowley
Keyword(s):  
Mineral Dust ◽  
Heterogeneous Reaction ◽  
Kinetics And Mechanism ◽  
Dust Particles

scholarly journals Uptake of NO<sub>3</sub> and N<sub>2</sub>O<sub>5</sub> to Saharan dust, ambient urban aerosol and soot: a relative rate study

2010 ◽  
Vol 10 (1) ◽  
pp. 391-415
Author(s):  
M. J. Tang ◽  
J. Thieser ◽  
G. Schuster ◽  
J. N. Crowley
Keyword(s):  
Mineral Dust ◽  
Relative Rate ◽  
Simultaneous Detection ◽  
Saharan Dust ◽  
Uptake Coefficient ◽  
Ambient Aerosols ◽  
Mixing Ratios ◽  
A Value ◽  
Rate Study ◽  
Absolute Basis

Abstract. The uptake of NO3 and N2O5 to Saharan dust, ambient aerosols and soot was investigated using a novel and simple relative rate method with simultaneous detection of both NO3 and N2O5. The use of cavity ring down spectroscopy to detect both trace gases enabled the measurements to be carried out at low mixing ratios (<500 pptv or 1×1010 molecule cm-3). The uptake coefficient ratio, γ(3)/γ(N2O5), was determined to be 0.9±0.4 for Saharan dust, independent of relative humidity, NO3 or N2O5 mixing ratio and exposure time. Ambient (urban) aerosols showed a very limited capacity to take up N2O5 but were reactive towards 3 with γ(NO3)/γ(N2O5)>15. A value of γ(NO3)/γ(N2O5)≈1.5–3 was obtained when using candle generated soot. The relative rate obtained for Saharan dust can be placed on an absolute basis using our recently determined value of γ(N2O5)=1×10−2 to give γ(NO3)=9×10-3, which is significantly smaller than the single previous value. With the present uptake coefficient, reaction of NO3 with mineral dust will generally not contribute significantly to its NO3 loss in the boundary atmosphere or to the nitration of mineral dust.

scholarly journals Kinetics and mechanisms of heterogeneous reaction of NO<sub>2</sub> on CaCO<sub>3</sub> surfaces under dry and wet conditions

2010 ◽  
Vol 10 (2) ◽  
pp. 463-474 ◽  
Author(s):  
H. J. Li ◽  
T. Zhu ◽  
D. F. Zhao ◽  
Z. F. Zhang ◽  
Z. M. Chen
Keyword(s):  
Photoelectron Spectroscopy ◽  
Heterogeneous Reaction ◽  
Adsorbed Water ◽  
Uptake Coefficient ◽  
Liquid Reaction ◽  
Dry Conditions ◽  
Caco3 Particle ◽  
Condensed Water ◽  
Diffuse Reflectance Infrared ◽  
Initial Uptake

Abstract. With increasing NO2 concentration in the troposphere, the importance of NO2 reaction with mineral dust in the atmosphere needs to be evaluated. Until now, little is known about the reaction of NO2 with CaCO3. In this study, the heterogeneous reaction of NO2 on the surface of CaCO3 particles was investigated at 296 K and NO2 concentrations between 4.58×1015 molecules cm−3 to 1.68×1016 molecules cm−3, using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) combined with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), under wet and dry conditions. Nitrate formation was observed under both conditions, while nitrite was observed under wet conditions, indicating the reaction of NO2 on the CaCO3 surface produced nitrate and probably nitrous acid (HONO). Relative humidity (RH) influences both the initial uptake coefficient and the reaction mechanism. At low RH, surface −OH is formed through dissociation of the surface adsorbed water via oxygen vacancy, thus determining the reaction order. As RH increases, water starts to condense on the surface and the gas-liquid reaction of NO2 with the condensed water begins. With high enough RH (>52% in our experiment), the gas-liquid reaction of NO2 with condensed water becomes dominant, forming HNO3 and HONO. The initial uptake coefficient γ0 was determined to be (4.25±1.18)×10−9 under dry conditions and up to (6.56±0.34)×10−8 under wet conditions. These results suggest that the reaction of NO2 on CaCO3 particle is unable to compete with that of HNO3 in the atmosphere. Further studies at lower NO2 concentrations and with a more accurate assessment of the surface area for calculating the uptake coefficient of the reaction of NO2 on CaCO3 particle and to examine its importance as a source of HONO in the atmosphere are needed.

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