scholarly journals Heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> with illite and Arizona Test Dust particles

2013 ◽  
Vol 13 (9) ◽  
pp. 24855-24884 ◽  
Author(s):  
M. J. Tang ◽  
G. Schuster ◽  
J. N. Crowley
Keyword(s):  
Relative Humidity ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Heterogeneous Reaction ◽  
Thermal Dissociation ◽  
Dust Particles ◽  
Experimental Uncertainty ◽  
Mineral Surfaces ◽  
Uptake Coefficient ◽  
Flow Tube

Abstract. The heterogeneous reaction of N2O5 with airborne illite and Arizona Test Dust particles was investigated at room temperature and at different relative humidities using an atmospheric pressure aerosol flow tube. N2O5 at concentrations in the range 8 to 24×1012 molecule cm−3 was monitored using thermal-dissociation cavity ring-down spectroscopy at 662 nm. At zero relative humidity a large uptake coefficient of N2O5 to illite was obtained, γ(N2O5) = 0.09, which decreased to 0.04 as relative humidity was increased to 67%. In contrast, the uptake coefficient derived for ATD is much lower (~ 0.006) and, within experimental uncertainty, independent of relative humidity (0–67%). Potential explanations are given for the significant differences between the uptake behaviour for ATD and illite and the results are compared with uptake coefficients for N2O5 on other mineral surfaces.

scholarly journals Heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> with illite and Arizona test dust particles

2014 ◽  
Vol 14 (1) ◽  
pp. 245-254 ◽  
Author(s):  
M. J. Tang ◽  
G. Schuster ◽  
J. N. Crowley
Keyword(s):  
Relative Humidity ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Heterogeneous Reaction ◽  
Thermal Dissociation ◽  
Dust Particles ◽  
Mineral Surfaces ◽  
Uptake Coefficient ◽  
Flow Tube ◽  
Aerosol Flow

Abstract. The heterogeneous reaction of N2O5 with airborne illite and Arizona test dust (ATD) particles was investigated at room temperature and at different relative humidities using an atmospheric pressure aerosol flow tube. N2O5 at concentrations in the range 8 to 24 × 1012 molecule cm−3 was monitored using thermal-dissociation cavity ring-down spectroscopy at 662 nm. At zero relative humidity a large uptake coefficient of N2O5 to illite was obtained, γ(N2O5) = 0.09, which decreased to 0.04 as relative humidity was increased to 67%. In contrast, the uptake coefficient derived for ATD is much lower (~0.006) and displays a weaker (if any) dependence on relative humidity (0–67%). Potential explanations are given for the significant differences between the uptake behaviour for ATD and illite and the results are compared with uptake coefficients for N2O5 on other mineral surfaces.

scholarly journals Uptake of HO<sub>2</sub> radicals onto Arizona test dust particles using an aerosol flow tube

2014 ◽  
Vol 14 (14) ◽  
pp. 7397-7408 ◽  
Author(s):  
P. S. J. Matthews ◽  
M. T. Baeza-Romero ◽  
L. K. Whalley ◽  
D. E. Heard
Keyword(s):  
Atmospheric Pressure ◽  
Room Temperature ◽  
Reaction Times ◽  
Dust Particles ◽  
Partial Saturation ◽  
Flow Tube ◽  
Aerosol Flow ◽  
Uptake Coefficients ◽  
Gas Expansion ◽  
Dust Surface

Abstract. Uptake coefficients for HO2 radicals onto Arizona test dust (ATD) aerosols were measured at room temperature and atmospheric pressure using an aerosol flow tube and the sensitive fluorescence assay by gas expansion (FAGE) technique, enabling HO2 concentrations in the range 3–10 × 108 molecule cm−3 to be investigated. The uptake coefficients were measured as 0.031 ± 0.008 and 0.018 ± 0.006 for the lower and higher HO2 concentrations, respectively, over a range of relative humidities (5–76%). A time dependence for the HO2 uptake onto the ATD aerosols was observed, with larger uptake coefficients observed at shorter reaction times. The combination of time and HO2 concentration dependencies suggest either the partial saturation of the dust surface or that a chemical component of the dust is partially consumed whilst the aerosols are exposed to HO2. A constrained box model is used to show that HO2 uptake to dust surfaces may be an important loss pathway of HO2 in the atmosphere.

scholarly journals AVALIAÇÃO DE PRODUTOS OBTIDOS PELA DESIDRATAÇÃO OSMÓTICA DE BANANA SEGUIDA DE SECAGEM

2003 ◽  
Vol 21 (1) ◽  
Author(s):  
PAULO HENRIQUE MACHADO DE SOUSAPAULO HEN MACHADO DE SOUSA ◽  
GERALDO ARRAES MAIA ◽  
MEN DE SÁ MOREIRA DE SOUZA FILHO ◽  
RAIMUNDO WILANE DE FIGUEIREDO ◽  
RENATA TIEKO NASSU ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Storage Stability ◽  
Osmotic Dehydration ◽  
Storage Period ◽  
Sensory Characteristics ◽  
Sensorial Analysis ◽  
Physico Chemical ◽  
Microbiological Stability

Foram obtidos dois produtos de banana por desidratação osmótica, um sob pressão atmosférica e outro sob vácuo, com complemento de secagem em estufa. A estabilidade dos produtos foi estudada, durante 120 dias, mediante análises físico-químicas, microbiológicas e sensoriais. Nesse período, os produtos ficaram armazenados em temperatura ambiente (23,4-34,1oC) e umidade relativa entre 33-81%. Concluiu-se que os produtos mantiveram suas características químicas, físico-químicas e sensoriais, além de estabilidade microbiológica (pouca variação durante o período de armazenamento). Somente a cor dos produtos apresentou variação expressiva. Sugere-se o tratamento utilizando osmose com vácuo seguido de secagem para produção de banana passa. EVALUATION OF PRODUCTS OBTAINED BY THE BANANA’S OSMOTIC DEHYDRATION FOLLOWED OF DRYING Abstract It was obtained two bananas products through osmotic dehydration, one under atmospheric pressure and other under vacuum, with drying complement in stove. The storage stability of these products was studied, during 120 days, through physicalchemical, microbiological and sensorial analysis. In this period, the products were stored at room temperature (23,4-34,1oC) and relative humidity between 33-81%. It was concluded that the obtained products maintained their chemical, physico-chemical and sensory characteristics, beyond microbiological stability (small variations during the storage period). Only the color of the produtcs presented more expressive variations. Therefore it is suggested the treatment using osmosis with vacuum followed by oven drying for the production of banana fig.

scholarly journals The effect of fatty acid surfactants on the uptake of ozone to aqueous halogenide particles

2010 ◽  
Vol 10 (6) ◽  
pp. 15023-15054
Author(s):  
A. Rouvière ◽  
M. Ammann
Keyword(s):  
Atmospheric Pressure ◽  
Phase State ◽  
Saturated Fatty Acids ◽  
Organic Coatings ◽  
Organic Films ◽  
Condensed State ◽  
Uptake Coefficient ◽  
Straight Chain ◽  
Flow Tube ◽  
Aqueous Surface

Abstract. The reactive uptake of ozone to deliquesced potassium iodide aerosol particles coated with linear saturated fatty acids (C9, C12, C15, C18 and C20) as surfactants was studied. The experiments were performed in an aerosol flow tube at 293 K and atmospheric pressure. The uptake coefficient on pure deliquesced KI aerosol was γ=(1.10±0.20)×10−2 at 72–75% relative humidity. In presence of organic coatings, the uptake coefficient decreased significantly for long straight chain surfactants (>C15), while it was only slightly reduced for the short ones (C9, C12). We linked the kinetic results to the monolayer properties of the surfactants, and specifically to the phase state of the monolayer formed (liquid expanded or liquid condensed state). We also investigated the effect of organic films to mixed deliquesced aerosol composed of a variable mixture of KI and NaCl, which allowed determining the resistance exerted to O3 at the aqueous surface by the two longer chained surfactants pentadecanoic acid (C15) and stearic acid (C18). Finally, the effect of two-component coatings, consisting of a mixture of long and short chained surfactants, was also studied.

scholarly journals Uptake of HO<sub>2</sub> radicals onto Arizona Test Dust aerosols

2014 ◽  
Vol 14 (4) ◽  
pp. 4229-4261 ◽  
Author(s):  
P. S. J. Matthews ◽  
M. T. Baeza-Romero ◽  
L. K. Whalley ◽  
D. E. Heard
Keyword(s):  
Time Dependence ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Reaction Times ◽  
Box Model ◽  
Partial Saturation ◽  
Flow Tube ◽  
Uptake Coefficients ◽  
Gas Expansion ◽  
Dust Surface

Abstract. Uptake coefficients for HO2 radicals onto Arizona Test Dust (ATD) aerosols were measured at room temperature and atmospheric pressure using an aerosol flow tube and the sensitive Fluorescence Assay by Gas Expansion (FAGE) technique, enabling HO2 concentrations in the range 3–10 × 108 molecule cm−3 to be investigated. The uptake coefficients were measured as 0.031 ± 0.008 and 0.018 ± 0.006 for the lower and higher HO2 concentrations, respectively, over a range of relative humidities (5–76%). A time dependence for the HO2 uptake onto the ATD aerosols was observed, with larger uptake coefficients observed at shorter reaction times. The combination of time and HO2 concentration dependencies suggest either the partial saturation of the dust surface or that a chemical component of the dust is partially consumed whilst the aerosols are exposed to HO2. A constrained box model is used to show that HO2 uptake to dust surfaces may be an important loss pathway of HO2 in the atmosphere.

scholarly journals A comprehensive characterisation of Asian dust storm particles: chemical composition, reactivity to SO<sub>2</sub>, and hygroscopic property

2010 ◽  
Vol 10 (4) ◽  
pp. 8899-8925 ◽  
Author(s):  
Q. Ma ◽  
Y. Liu ◽  
C. Liu ◽  
J. Ma ◽  
H. He
Keyword(s):  
Dust Storm ◽  
Heterogeneous Reaction ◽  
Cell Mass ◽  
Asian Dust ◽  
Dust Storms ◽  
Source Distribution ◽  
Dust Particles ◽  
Uptake Coefficient ◽  
Asian Dust Storm ◽  
The Impact

Abstract. Mineral dust comprises of a significant fraction of the globe's aerosol loading. Yet it remains the largest uncertainty in future climate predictions due to the complexity in its components and physico-chemical properties. Multi-analysis methods, including SEM-EDX, FTIR, BET, TPD/mass, and Knudsen cell/mass, were used in the present study to characterise Asian dust storm particles. The morphology, element fraction, source distribution, true uptake coefficient of SO2 and hygroscopic behaviour were studied. The major components of Asian dust storm particles were found to consist of aluminosilicate, SiO2, and CaCO3, which were coated with organic compounds and inorganic nitrate. The dust storm particles have a low reactivity to SO2 (true uptake coefficient of 5.767×10−6) which limits the conversion of SO2 to sulfate during a dust storm period. The low reactivity also demonstrated that the heterogeneous reaction of SO2, in both dry and humid air conditions, had little effect on the hygroscopic behaviour of the dust particles. These results indicate that the impact of dust storms on atmospheric SO2 removal should not be overestimated.

scholarly journals Reactive uptake coefficients for heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> with submicron aerosols of NaCl and natural sea salt

2004 ◽  
Vol 4 (5) ◽  
pp. 1381-1388 ◽  
Author(s):  
D. J. Stewart ◽  
P. T. Griffiths ◽  
R. A. Cox
Keyword(s):  
Relative Humidity ◽  
Flow Reactor ◽  
Heterogeneous Reaction ◽  
Sea Salt ◽  
Uptake Coefficient ◽  
A Value ◽  
Reactive Uptake Coefficient ◽  
Uptake Coefficients ◽  
Kinetics Of Uptake ◽  
Kinetics Of

Abstract. The kinetics of uptake of gaseous N2O5 on submicron aerosols containing NaCl and natural sea salt have been investigated in a flow reactor as a function of relative humidity (RH) in the range 30-80% at 295±2K and a total pressure of 1bar. The measured uptake coefficients, γ, were larger on the aerosols containing sea salt compared to those of pure NaCl, and in both cases increased with increasing RH. These observations are explained in terms of the variation in the size of the salt droplets, which leads to a limitation in the uptake rate into small particles. After correction for this effect the uptake coefficients are independent of relative humidity, and agree with those measured previously on larger droplets. A value of γ=0.025 is recommended for the reactive uptake coefficient for N2O5 on deliquesced sea salt droplets at 298K and RH>40%.

scholarly journals Formation of secondary organic aerosols from the ozonolysis of dihydrofurans

2016 ◽  
Author(s):  
Yolanda Díaz de Mera ◽  
Alfonso Aranda ◽  
Larisa Bracco ◽  
Diana Rodriguez ◽  
Ana Rodriguez
Keyword(s):  
Relative Humidity ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Particle Number ◽  
Secondary Organic Aerosols ◽  
Organic Aerosols ◽  
Organic Aerosol ◽  
Reaction Conditions ◽  
Criegee Intermediates ◽  
Computational Calculations

Abstract. In this work we report the study of the ozonolysis of 2,5-dihydrofuran and 2,3-dihydrofuran and the reaction conditions leading to the formation of secondary organic aerosols. The reactions have been carried out in a Teflon chamber filled with synthetic air mixtures at atmospheric pressure and room temperature. The ozonolysis only produced particles in the presence of SO2. Water vapour has no effect on the production of secondary organic aerosol in the case of 2,5-dihydrofuran while it reduces the particle number and particle mass concentrations from the 2,3-dihydrofuran ozonolysis. The water and SO2 rate constants ratio for the 2,3-dihydrofuran Criegee intermediate was derived from the SOA yields in experiments with different relative humidity values, kH2O/kSO2 = (9.8 &amp;pm; 3.7) ×10−5. The experimental results show that SO3 is not an intermediate in the formation or growth of new particles in contrast to the data reported for other Criegee intermediates/SO2 reactions. For the studied reactions, SO2 behaves as a catalyst in the production of condensable products. Computational calculations show that the stabilised Criegee intermediates from the ozonolysis reaction of both 2,5-dihydrofuran and 2,3-dihydrofuran may react with SO2 resulting in the regeneration of SO2 and the formation of organic acids.

scholarly journals Reactive uptake coefficients for heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> with submicron aerosols of NaCl and natural sea salt

2004 ◽  
Vol 4 (1) ◽  
pp. 569-590 ◽  
Author(s):  
D. J. Stewart ◽  
R. A. Cox
Keyword(s):  
Relative Humidity ◽  
Flow Reactor ◽  
Heterogeneous Reaction ◽  
Sea Salt ◽  
Uptake Coefficient ◽  
A Value ◽  
Reactive Uptake Coefficient ◽  
Uptake Coefficients ◽  
Kinetics Of Uptake ◽  
Kinetics Of

Abstract. The kinetics of uptake of gaseous N2O5 on submicron aerosols containing NaCl and natural sea salt has been investigated in a flow reactor as a function of relative humidity (RH) in the range 30-80% at 295+/-2 K and a total pressure of 1 bar. The measured uptake coefficients, γ, were larger on the aerosols containing sea salt compared to those of pure NaCl, and in both cases increased with increasing RH. These observations are explained in terms of the variation in water content and hence size of the salt droplets, which leads to a limitation in the uptake rate into small particles. After correction for this effect the uptake coefficients are independent of relative humidity, and agree with those measured previously on larger droplets. A value of γ=0.025 is recommended for the reactive uptake coefficient for N2O5 on deliquesced sea salt droplets at 298 K and RH>40%.

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