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 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 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 The interaction of N<sub>2</sub>O<sub>5</sub> with mineral dust: aerosol flow tube and Knudsen reactor studies

2007 ◽  
Vol 7 (5) ◽  
pp. 13291-13343
Author(s):  
C. Wagner ◽  
F. Hanisch ◽  
N. Holmes ◽  
H. de Coninck ◽  
G. Schuster ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Reasonable Agreement ◽  
Flow Reactor ◽  
Mineral Dust ◽  
Saharan Dust ◽  
Flow Tube ◽  
Aerosol Flow ◽  
A Value ◽  
Upper Limits ◽  
Efficient Uptake

Abstract. The interaction of mineral dust with N2O5 was investigated using both airborne mineral aerosol (using an aerosol flow reactor with variable relative humidity) and bulk samples (using a Knudsen reactor at zero humidity). Both authentic (Saharan, SDCV) and synthetic dust samples (Arizona test dust, ATD and calcite, CaCO3) were used to derive reactive uptake coefficients (γ). The aerosol experiments (Saharan dust only) indicated efficient uptake, with e.g. a value of γ (SDCV)=(1.3±0.2)×10−2 obtained at zero relative humidity. The values of γ obtained for bulk substrates in the Knudsen reactor studies are upper limits due to assumptions of available surface area, but were in reasonable agreement with the AFT measurements, with: γ(SDCV)=(3.7±1.2)×10−2, γ(ATD)=(2.2±0.8)×10−2 and γ(CaCO3)=(5±2)×10−2. The errors quoted are statistical only. The results are compared to literature values and assessed in terms of their impact on atmospheric N2O5.

scholarly journals The interaction of N<sub>2</sub>O<sub>5</sub> with mineral dust: aerosol flow tube and Knudsen reactor studies

2008 ◽  
Vol 8 (1) ◽  
pp. 91-109 ◽  
Author(s):  
C. Wagner ◽  
F. Hanisch ◽  
N. Holmes ◽  
H. de Coninck ◽  
G. Schuster ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Reasonable Agreement ◽  
Flow Reactor ◽  
Mineral Dust ◽  
Saharan Dust ◽  
Flow Tube ◽  
Aerosol Flow ◽  
A Value ◽  
Upper Limits ◽  
Efficient Uptake

Abstract. The interaction of mineral dust with N2O5 was investigated using both airborne mineral aerosol (using an aerosol flow reactor with variable relative humidity) and bulk samples (using a Knudsen reactor at zero humidity). Both authentic (Saharan, SDCV) and synthetic dust samples (Arizona test dust, ATD and calcite, CaCO3) were used to derive reactive uptake coefficients (γ). The aerosol experiments (Saharan dust only) indicated efficient uptake, with e.g. a value of γ(SDCV)=(1.3±0.2)×10−2 obtained at zero relative humidity. The values of γ obtained for bulk substrates in the Knudsen reactor studies are upper limits due to assumptions of available surface area, but were in reasonable agreement with the AFT measurements, with: γ(SDCV)=(3.7±1.2)×10−2, γ(ATD)=(2.2±0.8)×10−2 and γ(CaCO3=(5±2)×10−2. The errors quoted are statistical only. The results are compared to literature values and assessed in terms of their impact on atmospheric N2O5.

scholarly journals Modelling Atmospheric Mineral Aerosol Chemistry to Predict Heterogeneous Photooxidation of SO<sub>2</sub>

2017 ◽  
Author(s):  
Zechen Yu ◽  
Myoseon Jang ◽  
Jiyeon Park
Keyword(s):  
Mineral Dust ◽  
Uv Light ◽  
Full Range ◽  
Saharan Dust ◽  
Dust Particles ◽  
Oh Radicals ◽  
Desorption Kinetics ◽  
So2 Oxidation ◽  
Photocatalytic Ability ◽  
Sulfate Formation

Abstract. The photocatalytic ability of airborne mineral dust particles is known to heterogeneously promote SO2 oxidation, but prediction of this phenomenon is not fully taken into account by current models. In this study, the Atmospheric Mineral Aerosol Reaction (AMAR) model was developed to capture the influence of air-suspended mineral dust particles on sulfate formation in various environments. In the model, SO2 oxidation proceeds in three phases including the gas phase, the inorganic-salted aqueous phase (non-dust phase), and the dust phase. Dust chemistry is described as the adsorption-desorption kinetics (gas-particle partitioning) of SO2 and NOx. The reaction of adsorbed SO2 on dust particles occurs via two major paths: autoxidation of SO2 in open air and photocatalytic mechanisms under UV light. The kinetic mechanism of autoxidation was first leveraged using controlled indoor chamber data in the presence of Arizona Test Dust (ATD) particles without UV light, and then extended to photochemistry. With UV light, SO2 photooxidation was promoted by surface oxidants (OH radicals) that are generated via the photocatalysis of semiconducting metal oxides (electron–hole theory) of ATD particles. This photocatalytic rate constant was derived from the integration of the combinational product of the dust absorbance spectrum and wave-dependent actinic flux for the full range of wavelengths of the light source. The predicted concentrations of sulfate and nitrate using the AMAR model agreed well with outdoor chamber data that were produced under natural sunlight. For seven consecutive hours of photooxidation of SO2 in an outdoor chamber, dust chemistry at the low NOx level was attributed to 70 % of total sulfate (60 ppb SO2, 290 μg m−3 ATD, and NOx less than 5 ppb). At high NOx (> 50 ppb of NOx with low hydrocarbons), sulfate formation was also greatly promoted by dust chemistry, but it was significantly suppressed by the competition between NO2 and SO2 that both consume the dust-surface oxidants (OH radicals or ozone). The AMAR model, derived in this study with ATD particles, will provide a platform for predicting sulfate formation in the presence of authentic dust particles (e.g. Gobi and Saharan dust).

scholarly journals Saharan dust levels in Greece and received inhalation doses

2008 ◽  
Vol 8 (3) ◽  
pp. 11967-11996 ◽  
Author(s):  
C. Mitsakou ◽  
G. Kallos ◽  
N. Papantoniou ◽  
C. Spyrou ◽  
S. Solomos ◽  
...  
Keyword(s):  
Urban Areas ◽  
Particle Deposition ◽  
Mineral Dust ◽  
Weather Conditions ◽  
Pm10 Concentration ◽  
Saharan Dust ◽  
Dust Particles ◽  
Annual Number ◽  
Human Respiratory Tract ◽  
Dust Transport

Abstract. The desert of Sahara is one of the major sources of mineral dust on Earth, producing around 2×108 tons/yr. Under certain weather conditions, dust particles from Saharan desert get transported over the Mediterranean Sea and most of Europe. The limiting values set by the directive EC/30/1999 of European Union can easily be exceeded by the transport of desert dust particles in all south European areas and especially urban. In this study, the effects of dust transport on air quality in several Greek urban areas are quantified. PM10 concentration values from stationary monitoring stations are compared to dust concentrations for the 4-year period 2003–2006. The dust concentration values in the Greek areas were estimated by the SKIRON modelling system coupled with embedded algorithms describing the dust cycle. The mean annual dust contribution to daily-averaged PM10 concentration values was found to be around or even greater than 10% in the urban areas throughout the years examined. Natural dust transport may contribute by much more than 20% to the annual number of exceedances – PM10 values greater than EU limits – depending on the specific monitoring location. In a second stage of the study, the inhaled lung dose received by the residents in various Greek locations is calculated. The particle deposition efficiency of mineral dust at the different parts of the human respiratory tract is determined by applying a lung dosimetry numerical model, which incorporates inhalation dynamics and aerosol physical processes. The inhalation dose from mineral dust particles was greater in the upper respiratory system (extrathoracic region) and less significant in the lungs, especially in the sensitive alveolar region. However, in cases of dust episodes, the amounts of mineral dust deposited along the human lung are comparable to those received during exposure in heavily polluted urban or smoking areas.

Impacts of Nucleating Aerosol on Florida Storms. Part I: Mesoscale Simulations

2006 ◽  
Vol 63 (7) ◽  
pp. 1752-1775 ◽  
Author(s):  
Susan C. van den Heever ◽  
Gustavo G. Carrió ◽  
William R. Cotton ◽  
Paul J. DeMott ◽  
Anthony J. Prenni
Keyword(s):  
Hydrological Cycle ◽  
Cloud Condensation Nuclei ◽  
Supercooled Liquid ◽  
Atmospheric Modeling ◽  
Saharan Dust ◽  
Regional Study ◽  
Surface Precipitation ◽  
Convective Storms ◽  
Mixing Ratios ◽  
High Concentrations

Abstract Toward the end of the Cirrus Regional Study of Tropical Anvils and Cirrus Layer–Florida Area Cirrus Experiment (CRYSTAL–FACE) field campaign held during July 2002, high concentrations of Saharan dust, which can serve as cloud condensation nuclei (CCN), giant CCN (GCCN), and ice-forming nuclei (IFN) were observed over the peninsula of Florida. To investigate the impacts of enhanced aerosol concentrations on the characteristics of convective storms and their subsequent anvil development, sensitivity tests are conducted using the Regional Atmospheric Modeling System (RAMS) model, in which the initialization profiles of CCN, GCCN, and IFN concentrations are varied. These variations are found to have significant effects on the storm dynamics and microphysical processes, as well as on the surface precipitation. Updrafts are consistently stronger as the aerosol concentrations are increased. The anvils cover a smaller area but are better organized and have larger condensate mixing ratio maxima in the cases with greater aerosol concentrations. Cloud water mass tends to increase with increasing aerosol concentrations, with enhanced GCCN concentrations having the most significant influence. Increasing either the GCCN or IFN concentrations produces the most rainfall at the surface whereas enhanced CCN concentrations reduce surface rainfall. Higher IFN concentrations produce ice at warmer temperatures and deeper anvils, but simultaneously increasing the concentrations of CCN and GCCN leads to more supercooled liquid water available for freezing and greater ice mixing ratios. Graupel mixing ratios decrease and hail mixing ratios increase with increasing aerosol concentrations. Higher concentrations of GCCN and IFN result in greater accumulated surface precipitation initially. By the end of the simulation period, however, the accumulated precipitation is the greatest for the case in which the aerosol concentrations are lowest. Such changes in the dynamical and microphysical characteristics of convective storms as a result of the variations in aerosol concentrations have potential climate consequences, both through cloud radiative effects and the hydrological cycle. The impacts of varying CCN, GCCN, and IFN concentrations on the anvils will be discussed more fully in Part II.

Saharan Dust Records and Its Impact in the European Alps

2021 ◽  
Author(s):  
Marion Greilinger ◽  
Anne Kasper-Giebl
Keyword(s):  
Mineral Dust ◽  
Cloud Condensation Nuclei ◽  
Ice Cores ◽  
Atmospheric Particulate Matter ◽  
Saharan Dust ◽  
Cloud Formation ◽  
Dust Particles ◽  
European Alps ◽  
Airborne Dust ◽  
Dust Events

Mineral dust is one of the main natural sources of atmospheric particulate matter, with the Sahara being one of the most important source regions for the occurrence and deposition of mineral dust in Europe. The occurrence of dust events in the European Alps is documented via measurements of airborne dust and its deposits onto the glaciers. Dust events occur mainly in spring, summer, and early autumn. Dust layers are investigated in ice cores spanning the last millennium as well as in annual snow packs. They strongly affect the overall flux of dust-related compounds (e.g., calcium and magnesium), provide an alkaline input to wet deposition chemistry, and change the microbial abundance and diversity of the snow pack. Still airborne mineral dust particles can act as ice nuclei and cloud condensation nuclei, influencing the formation of cloud droplets and hence cloud formation and precipitation. Dust deposits on the snow lead to a darkening of the surface, referred to as “surface albedo reduction,” which influences the timing of the snowmelt and reduces the annual mass balance of glaciers, showing a direct link to glacier retreat as observed presently in a warming climate.

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