Characterization of an aerodynamic lens for transmitting particles greater than 1 micrometer in diameter into the Aerodyne aerosol mass spectrometer

Williams, Leah R.; Gonzalez, Lino; Peck, Jay; Trimborn, D.; McInnis, Jennifer P.; Farrar, M. R.; Moore, Kori D.; Jayne, John T.; Robinson, Walter A.; Lewis, David; Onasch, T. B.; Canagaratna, Manjula R.; Trimborn, A.; Timko, Michaël T.; Magoon, Gregory R.; Deng, Rensheng; Tang, Duyu; Blanco, Elena de la Rosa; Prévôt, Andrê S. H.; Smith, Kenneth A.; Worsnop, D. R.

doi:10.5194/amt-6-3271-2013

Cited by 88 publications

(74 citation statements)

References 18 publications

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“…It is well established that an aerodynamic lens can achieve an efficiency close to unity for the size range under examination here (20-600 nm) (Huffman et al, 2005;Williams et al, 2013); therefore, although the lens is uncharacterised, we assumed E 600 nm Lens = 1. It was observed that the vast majority of PSL particles that produced an optical trigger also produced a mass spectrum so that E 600 nm Hit ≈ 1.…”

Section: Instrument Performance Measurementsmentioning

confidence: 99%

Evaluating the influence of laser wavelength and detection stage geometry on optical detection efficiency in a single-particle mass spectrometer

et al. 2016

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Abstract. Single-particle mass spectrometry (SPMS) is a useful tool for the online study of aerosols with the ability to measure size-resolved chemical composition with a temporal resolution relevant to atmospheric processes. In SPMS, optical particle detection is used for the effective temporal alignment of an ablation laser pulse with the presence of a particle in the ion source, and it gives the option of aerodynamic sizing by measuring the offset of particle arrival times between two detection stages. The efficiency of the optical detection stage has a strong influence on the overall instrument performance.A custom detection laser system consisting of a highpowered fibre-coupled Nd:YAG solid-state laser with a collimated beam was implemented in the detection stage of a laser ablation aerosol particle time-of-flight (LAAP-TOF) singleparticle mass spectrometer without major modifications to instrument geometry. The use of a collimated laser beam permitted the construction of a numerical model that predicts the effects of detection laser wavelength, output power, beam focussing characteristics, light collection angle, particle size, and refractive index on the effective detection radius (R) of the detection laser beam. We compare the model predictions with an ambient data set acquired during the Ice in Clouds Experiment -Dust (ICE-D) project.The new laser system resulted in an order-of-magnitude improvement in instrument sensitivity to spherical particles in the size range 500-800 nm compared to a focussed 405 nm laser diode system. The model demonstrates that the limit of detection in terms of particle size is determined by the scattering cross section (C sca ) as predicted by Mie theory. In addition, if light is collected over a narrow collection angle, oscillations in the magnitude of C sca with respect to particle diameter result in a variation in R, resulting in large particlesize-dependent variation in detection efficiency across the particle transmission range. This detection bias is imposed on the aerodynamic size distributions measured by the instrument and accounts for some of the detection bias towards sea salt particles in the ambient data set.

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Section: Instrument Performance Measurementsmentioning

confidence: 99%

Evaluating the influence of laser wavelength and detection stage geometry on optical detection efficiency in a single-particle mass spectrometer

et al. 2016

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“…The version of the instrument used in this study features an aerodynamic lens inlet (model LP2.5 Aeromegt GmbH) for transmission of particles approximately 0.07-2.5 µm in diameter that is similar in design to the high-pressure lens (HPL) described by Williams et al (2013). Divergence of the particle beam is size and shape dependent (Jayne et al, 2000), resulting in a morphological dependence on the fraction of particles that reaches the ionisation region (Huffman et al, 2005), an effect that is particularly important for mea- Laser desorption ionisation takes place in a high vacuum (< 1 × 10 −6 mbar) region some 230 mm from the aerodynamic lens exit, where particles interact with a 8 ns pulse of 193 nm radiation that is fired co-axial but counter-propagate to the particle beam.…”

Section: Laap-tof Single-particle Mass Spectrometermentioning

confidence: 99%

Online differentiation of mineral phase in aerosol particles by ion formation mechanism using a LAAP-TOF single-particle mass spectrometer

et al. 2018

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Abstract. Mineralogy of silicate mineral dust has a strong influence on climate and ecosystems due to variation in physiochemical properties that result from differences in composition and crystal structure (mineral phase). Traditional offline methods of analysing mineral phase are labour intensive and the temporal resolution of the data is much longer than many atmospheric processes. Single-particle mass spectrometry (SPMS) is an established technique for the online size-resolved measurement of particle composition by laser desorption ionisation (LDI) followed by time-of-flight mass spectrometry (TOF-MS). Although non-quantitative, the technique is able to identify the presence of silicate minerals in airborne dust particles from markers of alkali metals and silicate molecular ions in the mass spectra. However, the differentiation of mineral phase in silicate particles by traditional mass spectral peak area measurements is not possible. This is because instrument function and matrix effects in the ionisation process result in variations in instrument response that are greater than the differences in composition between common mineral phases.In this study, we introduce a novel technique that enables the differentiation of mineral phase in silicate mineral particles by ion formation mechanism measured from subtle changes in ion arrival times at the TOF-MS detector. Using a combination of peak area and peak centroid measurements, we show that the arrangement of the interstitial alkali metals in the crystal structure, an important property in silicate mineralogy, influences the ion arrival times of elemental and molecular ion species in the negative ion mass spectra. A classification scheme is presented that allowed for the differentiation of illite-smectite, kaolinite and feldspar minerals on a single-particle basis. Online analysis of mineral dust aerosol generated from clay mineral standards produced mineral fractions that are in agreement with bulk measurements reported by traditional XRD (X-ray diffraction) analysis.

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“…The hourly near-surface CO, SO (Williams et al, 2013). The positive matrix factorization (PMF) technique is utilized with constraints implemented in SoFi (Canonaco et al, 2013) to analyze the sources of OA and five components are separated by their mass spectra and time series.…”

Section: Pollutant Measurementsmentioning

confidence: 99%

Impacts of meteorological uncertainties on the haze formation in Beijing–Tianjin–Hebei (BTH) during wintertime: a case study

Bei

Elser

et al. 2017

Atmos. Chem. Phys.

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Abstract. In the present study, a persistent heavy haze episode from 13 to 20 January 2014 in Beijing-TianjinHebei (BTH) is simulated using the WRF-CHEM model through ensemble simulations to investigate impacts of meteorological uncertainties on the haze formation. Model results show that uncertainties in meteorological conditions substantially influence the aerosol constituent simulations at an observation site in Beijing, and the ratio of the ensemble spread to the ensemble mean (RESM) exceeds 50 %. The ensemble mean generally preforms well in reproducing the fine particles' (PM 2.5 ) temporal variations and spatial distributions against measurements in BTH. The meteorological uncertainties do not alter the PM 2.5 distribution pattern in BTH principally or dominate the haze formation and development, but remarkably affect the simulated PM 2.5 level, and the RESM for the simulated PM 2.5 concentrations can be up to 30 % at the regional scale. In addition, the rather large RESM in PM 2.5 simulations at the city scale also causes difficulties in evaluation of the control strategies. Therefore, our results suggest that the ensemble simulation is imperative to take into account the impact of the meteorological uncertainties on the haze prediction.

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Characterization of an aerodynamic lens for transmitting particles greater than 1 micrometer in diameter into the Aerodyne aerosol mass spectrometer

Cited by 88 publications

References 18 publications

Evaluating the influence of laser wavelength and detection stage geometry on optical detection efficiency in a single-particle mass spectrometer

Evaluating the influence of laser wavelength and detection stage geometry on optical detection efficiency in a single-particle mass spectrometer

Online differentiation of mineral phase in aerosol particles by ion formation mechanism using a LAAP-TOF single-particle mass spectrometer

Impacts of meteorological uncertainties on the haze formation in Beijing–Tianjin–Hebei (BTH) during wintertime: a case study

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