scholarly journals Simulation of Heterogeneous Photooxidation of SO<sub>2</sub> and NO<sub>x</sub> in the presence of Gobi Desert Dust Particles under Ambient Sunlight

2018 ◽  
Author(s):  
Zechen Yu ◽  
Myoseon Jang
Keyword(s):  
Urban Areas ◽  
Mineral Dust ◽  
Kinetic Mechanism ◽  
Buffering Capacity ◽  
Dust Particles ◽  
Gobi Desert ◽  
Heterogeneous Chemistry ◽  
Desert Dust ◽  
Photodegradation Rate ◽  
Nitrate Salts

Abstract. To improve the simulation of the heterogeneous oxidation of SO2 and NOx in the presence of authentic mineral dust particles under ambient environmental conditions, the explicit kinetic mechanism was constructed in Atmospheric Mineral Aerosol Reaction (AMAR) model. The formation of sulfate and nitrate was divided into three phases: gas phase, non-dust aqueous phase and dust phase. Specially, AMAR established the mechanistic role of dust chemical characteristics (e.g., photoactivation, hygroscopicity, and buffering capacity) on heterogeneous chemistry. The photo-activation kinetic process of different dust particles was built into the model by measuring the photodegradation rate constant of an impregnated surrogate (malachite green dye) on a dust filter sample (e.g., Arizona Test dust (ATD) and Gobi Desert dust (GDD)) using an online reflective UV-visible spectrometer. The photoactivation parameters were integrated with the heterogeneous chemistry to predict OH radical formation on dust surfaces. A mathematical equation for the hygroscopicity of dust particles was also included in the AMAR model to process the multiphase partitioning of tracers and in-particle chemistry. The buffering capacity of dust, which is related to the neutralization of dust alkaline carbonates with inorganic acids, was included in the model to dynamically predict the hygroscopicity of aged dust. The AMAR model simulated the formation of sulfate and nitrate using experimental data obtained in the presence of authentic mineral dust under ambient sunlight using a large outdoor smog chamber (UF-APHOR). Overall, both GDD and ATD significantly enhanced the formation of sulfate and nitrate, compared to that in the system without dust particles. However, the influence of GDD on the heterogeneous chemistry was much greater than that of ATD. Based on the model analysis, GDD enhanced the sulfate formation mainly via its high photoactivation capability. In the case of NO2 oxidation, dust-phase nitrate formation is mainly regulated by the buffering capacity of dust. The measured buffering capacity of GDD was two times greater than that of ATD, and consequently, the maximum nitrate concentration with GDD was nearly two times higher than that with ATD. The model also highlights that in urban areas with high NOx concentrations, hygroscopic nitrate salts quickly form via titration of the carbonates in the dust phase, but in the presence of SO2, the nitrate salts are gradually depleted by sulfate.

scholarly journals Simulation of heterogeneous photooxidation of SO<sub>2</sub> and NO<sub><i>x</i></sub> in the presence of Gobi Desert dust particles under ambient sunlight

2018 ◽  
Vol 18 (19) ◽  
pp. 14609-14622 ◽  
Author(s):  
Zechen Yu ◽  
Myoseon Jang
Keyword(s):  
Urban Areas ◽  
Mineral Dust ◽  
Buffering Capacity ◽  
Dust Particles ◽  
Gobi Desert ◽  
Heterogeneous Chemistry ◽  
Desert Dust ◽  
Malachite Green Dye ◽  
Photodegradation Rate ◽  
Nitrate Salts

Abstract. To improve the simulation of the heterogeneous oxidation of SO2 and NOx in the presence of authentic mineral dust particles under ambient environmental conditions, the explicit kinetic mechanisms were constructed in the Atmospheric Mineral Aerosol Reaction (AMAR) model. The formation of sulfate and nitrate was divided into three phases: the gas phase, the non-dust aqueous phase, and the dust phase. In particular, AMAR established the mechanistic role of dust chemical characteristics (e.g., photoactivation, hygroscopicity, and buffering capacity) in heterogeneous chemistry. The photoactivation kinetic process of different dust particles was built into the model by measuring the photodegradation rate constant of an impregnated surrogate (malachite green dye) on a dust filter sample (e.g., Arizona test dust – ATD – and Gobi Desert dust – GDD) using an online reflective UV–visible spectrometer. The photoactivation parameters were integrated with the heterogeneous chemistry to predict the formation of reactive oxygen species on dust surfaces. A mathematical equation for the hygroscopicity of dust particles was also included in the AMAR model to process the multiphase partitioning of trace gases and in-particle chemistry. The buffering capacity of dust, which is related to the neutralization of dust alkaline carbonates with inorganic acids, was included in the model to dynamically predict the hygroscopicity of aged dust. The AMAR model simulated the formation of sulfate and nitrate using experimental data obtained in the presence of authentic mineral dust under ambient sunlight using a large outdoor smog chamber (University of Florida Atmospheric Photochemical Outdoor Reactor, UF-APHOR). Overall, the influence of GDD on the heterogeneous chemistry was much greater than that of ATD. Based on the model analysis, GDD enhanced the sulfate formation mainly via its high photoactivation capability. In the case of NO2 oxidation, dust-phase nitrate formation is mainly regulated by the buffering capacity of dust. The measured buffering capacity of GDD was 2 times greater than that of ATD, and consequently, the maximum nitrate concentration with GDD was nearly 2 times higher than that with ATD. The model also highlights that in urban areas with high NOx concentrations, hygroscopic nitrate salts quickly form via titration of the carbonates in the dust particles, but in the presence of SO2, the nitrate salts are gradually depleted by the formation of sulfate.

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.

scholarly journals Heterogeneous ice nucleation on dust particles sourced from nine deserts worldwide – Part 2: Deposition nucleation and condensation freezing

2019 ◽  
Vol 19 (2) ◽  
pp. 1059-1076 ◽  
Author(s):  
Yvonne Boose ◽  
Philipp Baloh ◽  
Michael Plötze ◽  
Johannes Ofner ◽  
Hinrich Grothe ◽  
...  
Keyword(s):  
Active Sites ◽  
Mineral Dust ◽  
Atmospheric Transport ◽  
Chemical Imaging ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Full Potential ◽  
Nucleation Behavior ◽  
Crystal Water ◽  
Desert Dust

Abstract. Mineral dust particles from deserts are amongst the most common ice nucleating particles in the atmosphere. The mineralogy of desert dust differs depending on the source region and can further fractionate during the dust emission processes. Mineralogy to a large extent explains the ice nucleation behavior of desert aerosol, but not entirely. Apart from pure mineral dust, desert aerosol particles often exhibit a coating or are mixed with small amounts of biological material. Aging on the ground or during atmospheric transport can deactivate nucleation sites, thus strong ice nucleating minerals may not exhibit their full potential. In the partner paper of this work, it was shown that mineralogy determines most but not all of the ice nucleation behavior in the immersion mode found for desert dust. In this study, the influence of semi-volatile organic compounds and the presence of crystal water on the ice nucleation behavior of desert aerosol is investigated. This work focuses on the deposition and condensation ice nucleation modes at temperatures between 238 and 242 K of 18 dust samples sourced from nine deserts worldwide. Chemical imaging of the particles' surface is used to determine the cause of the observed differences in ice nucleation. It is found that, while the ice nucleation ability of the majority of the dust samples is dominated by their quartz and feldspar content, in one carbonaceous sample it is mostly caused by organic matter, potentially cellulose and/or proteins. In contrast, the ice nucleation ability of an airborne Saharan sample is found to be diminished, likely by semi-volatile species covering ice nucleation active sites of the minerals. This study shows that in addition to mineralogy, other factors such as organics and crystal water content can alter the ice nucleation behavior of desert aerosol during atmospheric transport in various ways.

scholarly journals The ice-nucleating ability of quartz immersed in water and its atmospheric importance compared to K-feldspar

2019 ◽  
Author(s):  
Alexander D. Harrison ◽  
Katherine Lever ◽  
Alberto Sanchez-Marroquin ◽  
Mark A. Holden ◽  
Thomas F. Whale ◽  
...  
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Mineral Dust ◽  
Aqueous Suspension ◽  
Ice Nucleation ◽  
Dust Particles ◽  
Plagioclase Feldspar ◽  
Desert Dust ◽  
Site Density ◽  
Cloud Regime

Abstract. Mineral dust particles are thought to be an important type of ice-nucleating particle (INP) in the mixed-phase cloud regime around the globe. While K-feldspar has been identified as being a particularly important component of mineral dust for ice nucleation, it has been shown that quartz is also relatively ice nucleation active. Given quartz typically makes up a substantial proportion of atmospheric desert dust it could potentially be important for cloud glaciation. Here, we survey the ice-nucleating ability of 10 α-quartz samples (the most common quartz polymorph) when immersed in microlitre supercooled water droplets. Despite all samples being α-quartz, the temperature at which they induce freezing varies by around 12 °C for a constant active site density. We find that some quartz samples are very sensitive to ageing in both aqueous suspension and air, resulting in a loss of ice-nucleating activity, while other samples are insensitive to exposure to air and water over many months. The sensitivity to water and air is perhaps surprising as quartz is thought of as a chemically resistant material, but this observation suggests that the active sites responsible for nucleation are less stable than the bulk of the material. We find that the quartz group of minerals are generally less active than K-feldspars, although the most active quartz samples are of a similar activity to some K-feldspars. We also find that the quartz samples are generally more active than the plagioclase feldspar group of minerals and the albite end-member has an intermediate activity. Using both the new and literature data, active site density parameterisations have been proposed for quartz, K-feldspar, plagioclase and albite. Combining these parameterisations with the typical atmospheric abundance of each mineral and comparing the results with atmospheric ice-nucleating particle concentrations, supports previous work that suggests that K-feldspar dominates, rather than quartz (or other minerals), the ice nucleation particle population in desert dust aerosol.

scholarly journals Saharan dust levels in Greece and received inhalation doses

2008 ◽  
Vol 8 (23) ◽  
pp. 7181-7192 ◽  
Author(s):  
C. Mitsakou ◽  
G. Kallos ◽  
N. Papantoniou ◽  
C. Spyrou ◽  
S. Solomos ◽  
...  
Keyword(s):  
Urban Areas ◽  
Particle Deposition ◽  
Mineral Dust ◽  
Pm10 Concentration ◽  
Saharan Dust ◽  
Anthropogenic Sources ◽  
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 the south European Region and especially in urban areas, where there is also significant contribution from anthropogenic sources. 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 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.

scholarly journals Size-segregated fluxes of mineral dust from a desert area of northern China by eddy covariance

2007 ◽  
Vol 7 (1) ◽  
pp. 2133-2168
Author(s):  
G. Fratini ◽  
P. Ciccioli ◽  
A. Febo ◽  
A. Forgione ◽  
R. Valentini
Keyword(s):  
Eddy Covariance ◽  
Mineral Dust ◽  
Northern China ◽  
Dust Particles ◽  
Storm Event ◽  
Gobi Desert ◽  
Storm Events ◽  
Particle Volume ◽  
Intense Storm ◽  
Desert Areas

Abstract. Mineral dust emission accounts for a substantial portion of particles present in the troposphere. It is emitted most from desert areas, mainly through intense storm episodes. The aim of this work was to quantify size-segregated fluxes of mineral dust particles emitted during storm events occurring in desert areas of northern China (Alashan desert, Inner Mongolia), known to act as one of the strongest sources of mineral dust particles in the Asian continent. Long-range transport of mineral dust emitted in this area is responsible for the high particle concentrations reached in densely populated areas, including the city of Beijing. Based on a theoretical analysis, an eddy covariance system was built to get size-segregated fluxes of mineral dust particles with optical diameters ranging between 0.26 and 7.00 μm. The system was optimised to measure fluxes under intense storm event conditions. It was tested in two sites located in the Chinese portion of the Gobi desert. During the field campaign, an intense storm event was recorded in one of them. Data obtained during this event indicate that particle number fluxes were dominated by the finer fraction, whereas in terms of volume, coarser particle accounted for the largest portion. It was found that during the storm event, ratios of size-segregated particle volume fluxes remained substantially constant and a simple parameterization of particle emission from total volume fluxes was possible. A strong correlation was also found between particle volume fluxes and the friction velocity. This relationship is extremely useful to investigate mechanisms of particle formation by wind erosion.

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