scholarly journals Technical Note: Use of a beam width probe in an Aerosol Mass Spectrometer to monitor particle collection efficiency in the field

2007 ◽  
Vol 7 (2) ◽  
pp. 549-556 ◽  
Author(s):  
D. Salcedo ◽  
T. B. Onasch ◽  
M. R. Canagaratna ◽  
K. Dzepina ◽  
J. A. Huffman ◽  
...  
Keyword(s):  
Particle Size ◽  
Mexico City ◽  
Particle Shape ◽  
Collection Efficiency ◽  
Beam Width ◽  
Particle Beam ◽  
Aerosol Mass ◽  
Inorganic Species ◽  
Shape And Size ◽  
Beam Broadening

Abstract. Two Aerodyne Aerosol Mass Spectrometers (Q-AMS) were deployed in Mexico City, during the Mexico City Metropolitan Area field study (MCMA-2003) from 29 March–4 May 2003 to investigate particle concentrations, sources, and processes. We report the use of a particle beam width probe (BWP) in the field to quantify potential losses of particles due to beam broadening inside the AMS caused by particle shape (nonsphericity) and particle size. Data from this probe show that no significant mass of particles was lost due to excessive beam broadening; i.e. the shape- and size-related collection efficiency (Es) of the AMS during this campaign was approximately one. Comparison of the BWP data from MCMA-2003 with other campaigns shows that the same conclusion holds for several other urban, rural and remotes sites. This means that the aerodynamic lens in the AMS is capable of efficiently focusing ambient particles into a well defined beam and onto the AMS vaporizer for particles sampled in a wide variety of environments. All the species measured by the AMS during MCMA-2003 have similar attenuation profiles which suggests that the particles that dominate the mass concentration were internally mixed most of the time. Only for the smaller particles (especially below 300 nm), organic and inorganic species show different attenuation versus particle size which is likely due to partial external mixing of these components. Changes observed in the focusing of the particle beam in time can be attributed, in part, to changes in particle shape (i.e. due to relative humidity) and size of the particles sampled. However, the relationships between composition, atmospheric conditions, and particle shape and size appear to be very complex and are not yet completely understood.

scholarly journals Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry – Part I: quantification, shape-related collection efficiency, and comparison with collocated instruments

2005 ◽  
Vol 5 (3) ◽  
pp. 4143-4182 ◽  
Author(s):  
D. Salcedo ◽  
K. Dzepina ◽  
T. B. Onasch ◽  
M. R. Canagaratna ◽  
Q. Zhang ◽  
...  
Keyword(s):  
Mexico City ◽  
Mass Concentration ◽  
Collection Efficiency ◽  
Beam Width ◽  
Soil Mass ◽  
Emission Spectrometry ◽  
Ambient Aerosols ◽  
Pixe Analysis ◽  
Aerosol Mass ◽  
Beam Broadening

Abstract. An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite, while another was deployed in the Aerodyne Mobile Laboratory (AML) during the Mexico City Metropolitan Area field study (MCMA-2003) from 31 March–4 May 2003 to investigate particle concentrations, sources, and processes. This is the first of a series of papers reporting the AMS results from this campaign. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 µm (NR-PM1) with high time and size-resolution. For the first time, we report field results from a beam width probe, which was used to study the shape and mixing state of the particles and to quantify potential losses of irregular particles due to beam broadening inside the AMS. Data from this probe show that no significant amount of irregular particles was lost due to excessive beam broadening. A comparison of the CENICA and AML AMSs measurements is presented, being the first published intercomparison between two quadrupole AMSs. The speciation, and mass concentrations reported by the two AMSs compared relatively well. The differences found are likely due to the different inlets used in both instruments. In order to account for the refractory material in the aerosol, we also present measurements of Black Carbon (BC) using an aethalometer and an estimate of the aerosol soil component obtained from Proton-Induced X-ray Emission Spectrometry (PIXE) analysis of impactor substrates. Comparisons of AMS + BC + soil mass concentration with other collocated particle instruments (a LASAIR Optical Particle Counter, a Tapered Element Oscillating Microbalance (TEOM) and a DustTrak Aerosol Monitor) are also presented. The comparisons show that the AMS + BC + soil mass concentration during MCMA-2003 is a good approximation to the total PM2.5 mass concentration.

scholarly journals Collection efficiency of the soot-particle aerosol mass spectrometer (SP-AMS) for internally mixed particulate black carbon

2014 ◽  
Vol 7 (12) ◽  
pp. 4507-4516 ◽  
Author(s):  
M. D. Willis ◽  
A. K. Y. Lee ◽  
T. B. Onasch ◽  
E. C. Fortner ◽  
L. R. Williams ◽  
...  
Keyword(s):  
Laser Beam ◽  
Black Carbon ◽  
Mass Spectrometer ◽  
Soot Particle ◽  
Collection Efficiency ◽  
Particle Beam ◽  
Aerosol Mass Spectrometer ◽  
Coated Particles ◽  
Aerosol Mass ◽  
Wide Range

Abstract. The soot-particle aerosol mass spectrometer (SP-AMS) uses an intra-cavity infrared laser to vaporize refractory black carbon (rBC) containing particles, making the particle beam–laser beam overlap critical in determining the collection efficiency (CE) for rBC and associated non-refractory particulate matter (NR-PM). This work evaluates the ability of the SP-AMS to quantify rBC and NR-PM mass in internally mixed particles with different thicknesses of organic coating. Using apparent relative ionization efficiencies for uncoated and thickly coated rBC particles, we report measurements of SP-AMS sensitivity to NR-PM and rBC, for Regal Black, the recommended particulate calibration material. Beam width probe (BWP) measurements are used to illustrate an increase in sensitivity for highly coated particles due to narrowing of the particle beam, which enhances the CE of the SP-AMS by increasing the laser beam–particle beam overlap. Assuming complete overlap for thick coatings, we estimate CE for bare Regal Black particles of 0.6 ± 0.1, which suggests that previously measured SP-AMS sensitivities to Regal Black were underestimated by up to a factor of 2. The efficacy of the BWP measurements is highlighted by studies at a busy road in downtown Toronto and at a non-roadside location, which show particle beam widths similar to, but greater than that of bare Regal Black and coated Regal Black, respectively. Further BWP measurements at field locations will help to constrain the range of CE for fresh and aged rBC-containing particles. The ability of the SP-AMS to quantitatively assess the composition of internally mixed particles is validated through measurements of laboratory-generated organic coated particles, which demonstrate that the SP-AMS can quantify rBC and NR-PM over a wide range of particle compositions and rBC core sizes.

scholarly journals Evaluation of the new capture vapourizer for aerosol mass spectrometers (AMS) through laboratory studies of inorganic species

2017 ◽  
Vol 10 (8) ◽  
pp. 2897-2921 ◽  
Author(s):  
Weiwei Hu ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
Philip Croteau ◽  
Manjula R. Canagaratna ◽  
...  
Keyword(s):  
Collection Efficiency ◽  
Submicron Particles ◽  
Size Distributions ◽  
Volatile Species ◽  
Pure Species ◽  
Mass Spectrometers ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Inorganic Species ◽  
Multiple Collisions

Abstract. Aerosol mass spectrometers (AMSs) and Aerosol Chemical Speciation Monitors (ACSMs) commercialized by Aerodyne are widely used to measure the non-refractory species in submicron particles. With the standard vapourizer (SV) that is installed in all commercial instruments to date, the quantification of ambient aerosol mass concentration requires the use of the collection efficiency (CE) to correct for the loss of particles due to bounce. A new capture vapourizer (CV) has been designed to reduce the need for a bounce-related CE correction. Two high-resolution AMS instruments, one with a SV and one with a CV, were operated side by side in the laboratory. Four standard species, NH4NO3, NaNO3, (NH4)2SO4 and NH4Cl, which typically constitute the majority of the mass of ambient submicron inorganic species, are studied. The effect of vapourizer temperature (Tv ∼ 200–800 °C) on the detected fragments, CE and size distributions are investigated. A Tv of 500–550 °C for the CV is recommended. In the CV, CE was identical (around unity) for more volatile species (e.g. NH4NO3) and comparable to or higher than the SV for less-volatile species (e.g. (NH4)2SO4), demonstrating an improvement in CE for laboratory inorganic species in the CV. The detected relative intensities of fragments of NO3 and SO4 species observed with the CV are different from those observed with the SV, and are consistent with additional thermal decomposition arising from the increased residence time and multiple collisions. Increased residence times with the CV also lead to broader particle size distribution measurements than with the SV. A method for estimating whether pure species will be detected in AMS sizing mode is proposed. Production of CO2(g) from sampled nitrate on the vapourizer surface, which has been reported for the SV, is negligible for the CV for NH4NO3 and comparable to the SV for NaNO3. . We observe an extremely consistent fragmentation for ammonium compared to very large changes for the associated anions. Together with other evidence, this indicates that it is unlikely that a major fraction of inorganic species vapourizes as intact salts in the AMS.

scholarly journals Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with Aerosol Mass Spectrometry: results from the CENICA Supersite

2006 ◽  
Vol 6 (4) ◽  
pp. 925-946 ◽  
Author(s):  
D. Salcedo ◽  
T. B. Onasch ◽  
K. Dzepina ◽  
M. R. Canagaratna ◽  
Q. Zhang ◽  
...  
Keyword(s):  
Mexico City ◽  
Mass Concentration ◽  
Inorganic Compounds ◽  
Regional Scale ◽  
Soil Mass ◽  
Emission Spectrometry ◽  
Size Distributions ◽  
Pixe Analysis ◽  
Aerosol Mass ◽  
Inorganic Species

Abstract. An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite, during the Mexico City Metropolitan Area field study (MCMA-2003) from 31 March-4 May 2003 to investigate particle concentrations, sources, and processes. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 µm (NR-PM1) with high time and size-resolution. In order to account for the refractory material in the aerosol, we also present estimates of Black Carbon (BC) using an aethalometer and an estimate of the aerosol soil component obtained from Proton-Induced X-ray Emission Spectrometry (PIXE) analysis of impactor substrates. Comparisons of AMS + BC + soil mass concentration with other collocated particle instruments (a LASAIR Optical Particle Counter, a PM2.5 Tapered Element Oscillating Microbalance (TEOM), and a PM2.5 DustTrak Aerosol Monitor) show that the AMS + BC + soil mass concentration is consistent with the total PM2.5 mass concentration during MCMA-2003 within the combined uncertainties. In Mexico City, the organic fraction of the estimated PM2.5 at CENICA represents, on average, 54.6% (standard deviation σ=10%) of the mass, with the rest consisting of inorganic compounds (mainly ammonium nitrate and sulfate/ammonium salts), BC, and soil. Inorganic compounds represent 27.5% of PM2.5 (σ=10%); BC mass concentration is about 11% (σ=4%); while soil represents about 6.9% (σ=4%). Size distributions are presented for the AMS species; they show an accumulation mode that contains mainly oxygenated organic and secondary inorganic compounds. The organic size distributions also contain a small organic particle mode that is likely indicative of fresh traffic emissions; small particle modes exist for the inorganic species as well. Evidence suggests that the organic and inorganic species are not always internally mixed, especially in the small modes. The aerosol seems to be neutralized most of the time; however, there were some periods when there was not enough ammonium to completely neutralize the nitrate, chloride and sulfate present. The diurnal cycle and size distributions of nitrate suggest local photochemical production. On the other hand, sulfate appears to be produced on a regional scale. There are indications of new particle formation and growth events when concentrations of SO2 were high. Although the sources of chloride are not clear, this species seems to condense as ammonium chloride early in the morning and to evaporate as the temperature increases and RH decreases. The total and speciated mass concentrations and diurnal cycles measured during MCMA-2003 are similar to measurements during a previous field campaign at a nearby location.

scholarly journals Collection efficiency of the Soot-Particle Aerosol Mass Spectrometer (SP-AMS) for internally mixed particulate black carbon

2014 ◽  
Vol 7 (5) ◽  
pp. 5223-5249 ◽  
Author(s):  
M. D. Willis ◽  
A. K. Y. Lee ◽  
T. B. Onasch ◽  
E. C. Fortner ◽  
L. R. Williams ◽  
...  
Keyword(s):  
Laser Beam ◽  
Black Carbon ◽  
Mass Spectrometer ◽  
Soot Particle ◽  
Collection Efficiency ◽  
Particle Beam ◽  
Aerosol Mass Spectrometer ◽  
Coated Particles ◽  
Aerosol Mass ◽  
Wide Range

Abstract. The soot-particle aerosol mass spectrometer (SP-AMS) uses an intra-cavity infrared laser to vaporize refractory black carbon (rBC) containing particles, making the particle beam–laser beam overlap critical in determining the collection efficiency (CE) for rBC and associated non-refractory particulate matter (NR-PM). This work evaluates the ability of the SP-AMS to quantify rBC and NR-PM mass in internally mixed particles with different thicknesses of organic coating. Using apparent relative ionization efficiencies for uncoated and thickly coated rBC particles, we report measurements of SP-AMS sensitivity to NR-PM and rBC, for Regal Black, the recommended particulate calibration material. Beam width probe (BWP) measurements are used to illustrate an increase in sensitivity for highly coated particles due to narrowing of the particle beam, which enhances the CE of the SP-AMS by increasing the laser beam–particle beam overlap. Assuming complete overlap for thick coatings, we estimate CE for bare Regal Black particles of 0.6 ± 0.1, which suggests that previously measured SP-AMS sensitivities to Regal Black were underestimated by up to a factor of two. The efficacy of the BWP measurements is highlighted by studies at a busy road in downtown Toronto and at a non-roadside location, which show particle beam widths similar to, but greater than that of bare Regal Black and coated Regal Black, respectively. Further BWP measurements at field locations will help to constrain the range of CE for fresh and aged rBC-containing particles. The ability of the SP-AMS to quantitatively assess the composition of internally mixed particles is validated through measurements of laboratory-generated organic coated particles, which demonstrate that the SP-AMS can quantify rBC and NR-PM over a wide range of particle compositions and rBC core sizes.

Particle Shape and Size Effects on Slurry Erosion of AISI 5117 Steels

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
M. A. Al-Bukhaiti ◽  
A. Abouel-Kasem ◽  
K. M. Emara ◽  
S. M. Ahmed
Keyword(s):  
Silicon Carbide ◽  
Particle Size ◽  
Aspect Ratio ◽  
Size Effects ◽  
Particle Shape ◽  
Impact Angle ◽  
Carbon Steels ◽  
Silica Sand ◽  
Slurry Erosion ◽  
Shape And Size

Solid particle shape and size effects on the slurry erosion behavior of AISI 5117 carbon steels are investigated, using whirling-arm ring for two different erodent particles, namely, silica sand (SiO2) and silicon carbide (SiC). From this work, it was found that aspect ratio and circularity factor (CF) increase for silica sand and decrease for silicon carbide with increasing size. The erosion rate increased with the increase of particle size for the two types of erodent particles and its value was greater in the case of silicon carbide particles. At the same test conditions, it has been noticed that the particle size plays the major role in the slurry erosion of 5117 steels in comparison with the aspect ratio and circularity factor. Microcutting and plowing with serrated wear tracks were observed for coarse SiC particles having irregular and angular shape. But, for coarse SiO2 particles which had a rounded shape, the main mechanism was plowing with plain and smooth wear tracks for an impact angle of 30 deg. Indentations and material extrusion prevailed for the coarse size of the two erodents for an impact angle of 90 deg.

scholarly journals Evaluation of the new capture vaporizer for Aerosol Mass Spectrometers (AMS) through laboratory studies of inorganic species

2016 ◽  
Author(s):  
Weiwei Hu ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
Philip Croteau ◽  
Manjula R. Canagaratna ◽  
...  
Keyword(s):  
Collection Efficiency ◽  
Submicron Particles ◽  
Size Distributions ◽  
Laboratory Studies ◽  
Volatile Species ◽  
Pure Species ◽  
Mass Spectrometers ◽  
Aerosol Mass ◽  
Aerosol Mass Concentration ◽  
Inorganic Species

Abstract. Aerosol mass spectrometers (AMS) and Aerosol Chemical Speciation Monitors (ACSM) commercialized by Aerodyne Research Inc. are used widely to measure the mass concentrations and size distributions of non-refractory species in submicron-particles. With the "standard" vaporizer (SV) that is installed in all commercial instruments to date, the quantification of ambient aerosol mass concentration requires the use of a collection efficiency (CE) for correcting the loss of particles due to bounce on the SV. However, CE depends on aerosol phase, and thus can vary with location, airmass, and season of sampling. Although a composition-dependent parameterization of CE in the SV for ambient data has been successful, CE still contributes most of the estimated uncertainty to reported concentrations, and is also an important uncertainty in laboratory studies. To address this limitation, a new "capture" vaporizer (CV) has been designed to reduce or eliminate particle bounce and thus the need for a CE correction. To test the performance of the CV, two high-resolution AMS instruments, one with a SV and one with a CV were operated side by side in the laboratory. Four standard species NH4NO3, NaNO3, (NH4)2SO4 and NH4Cl, which typically constitute the majority of the mass of ambient submicron inorganic species, are studied. The effect of vaporizer temperature (Tv ~ 200–800 ℃) on the detected fragments, CE and size distributions are investigated. A Tv of 500–550 ℃ for the CV is recommended based on the observed performance. In the CV, CE was identical (around unity) for more volatile species and comparable or higher compared to the SV for less volatile species, demonstrating a substantial improvement in CE of inorganic species in the CV. The detected fragments of NO3 and SO4 species observed with the CV are different than those observed with the SV, suggesting additional thermal decomposition arising from the increased residence time and hot surface collisions. Longer particle detection times lead to broadened particle size distribution measurements made with the AMS. The degradation of CV size distributions due to this broadening is significant for laboratory studies using monodisperse particles, but minor for field studies since ambient distributions are typically quite broad. A method for estimating whether pure species will be detected in AMS sizing mode is proposed. Production of CO2(g) from sampled nitrate on the vaporizer surface, which has been reported for the SV, is negligible for the CV for NH4NO3 and comparable to the SV for NaNO3. Adjusting the alignment of aerodynamic lens to focus particles on the edge of the CV results in higher resolution size distributions, which can be useful in some laboratory experiments. We observe an extremely consistent detection of ammonium from different inorganic ammonium salts, independent of the vaporizer types and/or the Tv. This contradicts a recent suggestion by Murphy (2016) that inorganic species evaporate as intact salts in the AMS.

Design, Modeling, Optimization, and Experimental Tests of a Particle Beam Width Probe for the Aerodyne Aerosol Mass Spectrometer

2005 ◽  
Vol 39 (12) ◽  
pp. 1143-1163 ◽  
Author(s):  
J. Alex Huffman ◽  
John T. Jayne ◽  
Frank Drewnick ◽  
Allison C. Aiken ◽  
Timothy Onasch ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Experimental Tests ◽  
Beam Width ◽  
Particle Beam ◽  
Aerosol Mass Spectrometer ◽  
Aerosol Mass

ANALYSIS OF AIRBORNE PARTICULATE MATTER COLLECTED AFTER AN ERUPTION EPISODE OF THE POPOCATÉPETL VOLCANO

2003 ◽  
Vol 13 (03n04) ◽  
pp. 133-139 ◽  
Author(s):  
F. ALDAPE ◽  
J. FLORES M.
Keyword(s):  
Particle Size ◽  
Particulate Matter ◽  
Mexico City ◽  
Airborne Particulate Matter ◽  
Airborne Particulate ◽  
Size Fractions ◽  
Particle Size Fractions ◽  
Two Samples ◽  
Popocatépetl Volcano ◽  
Popocatepetl Volcano

Samples of airborne particulate matter were collected in four sites along an east-west line from the Popocatépetl volcano after the eruption episode of June 30, 1997. The Popocatépetl volcano, with variable activity since it was known, is currently under low but continuous activity prolonged for almost one decade, with occasional moderate eruption episodes producing mainly fumes, ashes and volcanic dusts. The main objective of this study is to determine whether or not some elements have increased their presence in the atmosphere as a result of the volcanic activity, and also if some others, not usually found in urban aerosols, have appeared because of the same reason. In addition, the information obtained will be a source of scientific data for health risk assessment of the population exposed to volcanic emanations. The sample collection was performed on alternate days from July 10 to August 13 1997 in Puebla and Atlixco in Puebla State. Tlalpan within Mexico City, and Salazar in the State of Mexico. Two samples a day were taken in two periods: 7-19 h and 19-7 h. The samplers separated particles into two particle size fractions. PM25 and PM15. Elemental concentrations were determined by PIXE and the results obtained showed increased concentrations of mainly Ti and Fe in all sampling sites, thus indicating a long range transportation of volcanic dusts in both particle size fractions. Concentrations of Ti were found clearly above the average values of urban areas such as Mexico City, and although this element can be considered of low toxicity, the biological, metabolic and toxic effects on human beings are still under investigation.

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