7. In-situ characterization of e-cigarette aerosols by 90 -light scattering of polarized
light
Wilhelm Dunkhorsta, Peter Lipowiczb, Weiling Lib, Casey Huxb, Qiang Wangc, and Wolfgang Kocha
aFraunhofer Institute Toxicology and Experimental Medicine, Department of Aerosol Technology, Hannover, Germany; bAltria Client Services LLC, Center for Research and Technology, Richmond, Virginia, USA; cLancaster Laboratories, c/o Altria Client Services LLC, Richmond, Virginia, USA
A B S T R A C T
The polarization ratio method is used for fast in-situ characterization of unimodal condensed aerosols of e-cigarettes. The method is based on 90 -light scattering of polarized 680 nm laser light by the droplet ensemble inside an optically defined measuring volume. Mass median droplet diameter (MMD) is derived from the ratio of scattered light from horizontally and vertically polarized incident light beams assuming a fixed value of the geometric standard deviation of the aerosol mass distribution. MMD is used to correct for the size dependence of the mass-based scattering signal of vertically polarized light to obtain the mass concentration if the sensor is calibrated once with an aerosol with a fixed MMD. The sensor uses commercially available aerosol photometers, and its application to e-cigarette aerosols was validated with an impactor for MMD and with a filter measurement for mass concentration. Good correlation (r2 > 0.97) for both parameters was observed. Application ranges are mass concentration range 0.5–50 mg/L, MMD 0.2–1.2 mm, 100 ms time resolution, and 0.2–3 L/min flow rate. The usefulness of this simple sensor for e-cigarette aerosol characterization is demonstrated by developing a scaling law between MMD and operating parameters of an e-cigarette, i.e., puff flow rate and mass concentration.
Evaluation of the new capture vaporizer for aerosol mass spectrometers:
Characterization of organic aerosol mass spectra
Weiwei Hu a,b,†, Douglas A. Day a,b, Pedro Campuzano-Jost a,b, Benjamin A. Nault a,b, Taehyun Parkc,
Taehyoung Leec, Philip Croteaud, Manjula R. Canagaratnad, John T. Jayned, Douglas R. Worsnop d,
and Jose L. Jimenez a,b
aCooperative Institute for Research in the Environmental Sciences (CIRES), University of Colorado at Boulder, Boulder, Colorado, USA; bDepartment of Chemistry & Biochemistry, University of Colorado at Boulder, Boulder, Colorado, USA; cDepartment of Environmental Science, Hankuk University of Foreign Studies, Yongin, South Korea; dAerodyne Research, Inc., Billerica, Massachusetts, USA
A B S T R A C T
The Aerosol Mass Spectrometer (AMS) and Aerosol Chemical Speciation Monitor (ACSM) are widely used for quantifying submicron aerosol mass concentration and composition, in particular for organic aerosols (OA). Using the standard vaporizer (SV) installed in almost all commercial instruments, a collection efficiency (CE) correction, varying with aerosol phase and chemical composition, is needed to account for particle bounce losses. Recently, a new “capture vaporizer” (CV) has been shown to achieve CE »1 for ambient aerosols, but its chemical detection properties show some differences from the SV due to the increased residence time of particles and vaporized molecules inside the CV. This study reports on the properties and changes of mass spectra of OA in CV-AMS using both AMS and ACSM for the first time. Compared with SV spectra, larger molecularweight fragments tend to shift toward smaller ions in the CV due to additional thermal decomposition arising from increased residence time and hot surface collisions. Artifact CO C ions (and to a lesser extent, H2O C), when sampling long chain alkane/alkene-like OA (e.g., squalene) in the CV during the laboratory studies, are observed, probably caused by chemical reactions between sampled OA and molybdenum oxides on the vaporizer surfaces (with the carbon derived from the incident OA). No evidence for such CO C enhancement is observed for ambient OA. Tracer ion marker fractions (fm/z D, i.e., the ratio of the organic signal at a given m/z to the total OA signal), which are used to characterize the impact of different sources are still present and usable in the CV. A public, web-based spectral database for mass spectra from CV-AMS has been established.
On the theory of bipolar charging of large aerosol particles
V. I. Tarasov and M. S. Veshchunov
Nuclear Safety Institute (IBRAE), Russian Academy of Sciences, Moscow, Russian Federation
A B S T R A C T
The theory of bipolar charging of aerosol particles is developed for large particles ( 10 mm), taking into consideration the Coulomb field screening effect, which becomes relatively strong under conditions of high ion concentration attained in ionizers, n 107 ¡ 108 cm ¡ 3 . The corresponding generalized kinetic model is based on the diffusion equations for positively and negatively charged ions migrating to the central particle in the collective electrostatic field with the potential obeying the Poisson equation (rather than the Laplace equation, as in the traditional approach). Direct numerical calculations show that the Coulomb field screening becomes especially important for very large particles, which can be eventually charged to the values, several times exceeding those calculated in the traditional approach.
Characterization of the TSI model 3086 differential mobility analyzer
for classifying aerosols down to 1 nm
Mark R. Stolzenburga, Jacob H. T. Scheckmanb, Michel Attouic, Hee-Siew Hanb, and Peter H. McMurrya
aDepartment of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, USA; bTSI Incorporated, Shoreview, Minnesota, USA; cLISA, UMR CNRS 7583, University Paris-Diderot, University Paris-Est Creteil, IPSL, Paris, France
A B S T R A C T
Measurement systems for particle sizing starting at 1 nm are used to bridge the gap between mass spectrometer measurements and traditional aerosol sizing methods, and thus to enable measurement of the complete size distribution from molecules and clusters to large particles. Such a measurement can be made using a scanning mobility particle sizer equipped with a diethylene glycol growth engine (e.g., TSI Model 3777 Nano Enhancer) along with a condensation particle counter, and a differential mobility analyzer (DMA) appropriate for such small sizes. Previous researchers have used high-resolution DMA (HRDMA) and also the TSI Nano-DMA (Model 3085) in such a scanning mobility particle sizer system. In this study, we evaluate the performance of the
recently introduced TSI 1 nm-DMA (Model 3086). The transfer function was characterized using 1 –2 nm monomobile molecular ion standards. The same measurements were repeated on a TSI NanoDMA, with good agreement to previously published values. From the measured transfer function, the resolution of each DMA model was determined as a function of particle size and sheath flow rate. Resolution of the TSI 3086 in the 1 –2 nm range was 10–25% higher than the TSI 3085. Measured resolutions of the TSI 3086 were 10–20% lower than theoretically predicted values, whereas those of the Model 3085 were 0–10% lower.
Investigation of the absorption Angstrom exponent and its relation€ to physicochemical properties for mini-CAST soot
Sandra Tor€ ok€ a, Vilhelm B. Malmborgb, Johan Simonssona, Axel Erikssonb, Johan Martinssonc, Manu Mannazhia, Joakim Pagelsb, and Per-Erik Bengtssona
aDivision of Combustion Physics, Lund University, Lund, Sweden; bDivision of Ergonomics and Aerosol Technology, Lund University, Lund, Sweden; cDivision of Nuclear Physics, Lund University, Lund, Sweden
A B S T R A C T
In this work, a mini-CAST soot generator was used to produce soot with different optical and physicochemical characteristics. Absorption Angstrom exponents (€ AA E) expressing the absorption wavelength dependence were assessed by multiwavelength in-situ and filter-based (aethalometer) laser extinction. The two optical techniques showed good agreement. For the chosen mini-CAST operating conditions, AAEs between 1 and 3.5 were found. Soot with high mass-fractions of organic carbon (OC) and pyrolytic carbon (PC) determined with thermal optical analysis were associated with AAEs significantly higher than 1. Heating to 250 and 500C removed the majority of polycyclic aromatic hydrocarbons. However, the thermal-optical analysis revealed that OC and PC were abundant in the soot with AA E > 2 also after heating the aerosol. Analysis of mass absorption cross section ratios for elemental carbon and OC indicated that elevated AAEs also after heating to 500C could be related to persistent OC and PC components and/or the refractory soot. By comparing the mini-CAST soot optical properties with soot properties derived from in-situ extinction measurements in a premixed flame, mini-CAST soot with a higher AA E could be identified as less mature soot.
Capture rate consequences of multispherule aggregate formation in gases— combined roles of direct interception and interspherule momentum “ shielding”
Daniel E. Rosnera and Pushkar Tandonb
aSol Reaction Engineering Group, Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut, USA; bCorning Inc., Corning, New York, USA
A B S T R A C T
Our recent work on the consequences of multispherule cluster aggregate (CA) formation and deposition-rates on much larger solid targets has emphasized the decisive role of “momentumshielding” in determining aggregate “mobility” compared to N isolated spherules in the same gaseous environment—an effect analogous to the drag-reduction advantages experienced by birds electing to move “in formation.” The extent of “momentum shielding” is conveniently quantified via a dimensionless function:
Smom(N;Kn1, aggregate structure), which facilitates predicting the depositionrate consequences of aggregation in aerosol flow systems when the cluster deposition mechanism is dominated by either: (i) isothermal convective-diffusion (C-D),
(ii) thermophoresis (T-P) or: (iii) inertial impaction (I-I). Significantly, isothermal C-D was found to be the only transport-mechanism leading to aggregation-induced reductions in spherule deposition rates on large targets (cf. isolated spherules
present at the same mainstream spherule volume fraction). However, we demonstrate here that, for aggregate deposition on sufficiently small solid targets—e.g., fibrous filter elements with diameters of O(10 mm)—even these reductions, which exceed one decade for N D O(103), can be overcome by the mechanism of “direct-interception” (D-I) associated with nonzero effective aggregate size, without the need to invoke either inertial impaction or thermophoresis. This is especially true for DiffusionLimited (i.e., “open”) CAs (with Df D 1.8) at gas pressures such that the constituent spherules are near the continuum (Kn1 << 1) limit. Our present analysis and numerical illustrations exploit the fact that direct-interception is expected to play a negligible role for the capture of individual (dense) nanospherules (perhaps comparable in size to the prevailing gas molecule mean-free-path) but the
underlying theory, exploited, extended, and illustrated here, was developed with the help of initial capture rate experimental data for much larger diameter (but unaggregated) aerosols on single filter fibers in low Re crossflow. With such small diameter targets, we demonstrate that this “interception” augmentation for large CAs can occur even for the limiting case of rcp Df D 3 aggregates, before the expected onset of CA-inertial effects–i.e., StkN << Stkcrit, where, for Re D O(1), Stkcrit is also O(1). A simple method is also presented for predicting interception-modified spherule deposition rates in the presence of log-normal type aggregate size distributions.
On the time response determination of condensation particle counters
Joonas Enroth a, Juha Kangasluomaa, Frans Korhonena, Susanne Heringb, David Picardc, Greg Lewisb,
Michel Attouia,d, and Tuukka Pet€aj€aa
aDepartment of Physics, University of Helsinki, Helsinki, Finland; bAerosol Dynamics Inc., Berkeley, CA, USA; cLaboratoire de Meteorologie Physique, UMR6016, Observatoire de Physique du Globe de Clermont-Ferrand, CNRS – Universite Clermont Auvergne, Clermont-Ferrand, France; dUniversity Paris Est Creteil, University Paris-Diderot, LISA, UMR CNRS 7583, Paris, France
A B S T R A C T
Condensation particle counter (CPC) technology has continued to evolve, with the introduction of several new instruments over the last several years. An important aspect in the characterization of these instruments is the measurement of their time response. Yet there is no standardly accepted approach for this measurement. Here we evaluate different classically used methods for
determining CPC time response, and present the potential pitfalls associated with these approaches. Further, we introduce a new simple definition for the term response time, e, which is based on the first-order systems response, while providing a practical definition by corresponding to »95% change in concentration. We also present results for various commonly used CPCs, and for
the Airmodus A11 nano Condensation Nucleus Counter (nCNC) system, the TSI 3777 C3772 Nano Enhancer system, and Aerosol Dynamics Inc.’s (ADI) new versatile water condensation particle counter.
Dominant environmental parameters for dust deposition and resuspension
in desert climates
Benjamin Figgisa,b, Bing Guoc, Wasim Javedc, Said Ahzia, and Yves Remondb
aQatar Environment & Energy Research Institute, Hamad Bin Khalifa University (HBKU), Doha, Qatar; bICube Laboratory, Universite de Strasbourg–CNRS, Strasbourg, France; cDepartment of Mechanical Engineering, Texas A&M University at Qatar, Doha, Qatar
A B S T R A C T
Field studies of dry deposition usually measure dust accumulation over periods of days or weeks. However, long measurement periods obscure the effects of meteorological conditions on the deposition rate. Previously we developed an “outdoor soiling microscope” (OSM) in order to measure dust deposition and detachment every 10 min in the field. In this study a greased/ ungreased pair of OSMs was deployed for 51 days in the desert climate of Doha, Qatar. Stepwise regression analysis was performed to quantify the explanatory power of meteorological parameters on dust deposition and detachment rates. It was found that wind speed dominated deposition and rebound of dust particles, and produced a distinctive “threshold” response in deposition. The dry deposition results were highly consistent with a model by Kim et al. (2000) derived from outdoor experiments. By comparison, relative humidity and particulate matter concentration had less influence on dust flux rates..
Tailpipe emission characteristics of PM2.5 from selected on-road China III
and China IV diesel vehicles
Chunyan Maa,b, Tao Zhuangb, Zengyi Zhanga, Jin Wanga, Fan Yanga, Chen Qiaoa, and Mingming Luc
aSchool of Civil Engineering, Beijing Jiaotong University, Beijing, China; bJinan Environmental Research Academy, Jinan, Shandong Province, China; cDepartment of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, Ohio, USA
A B S T R A C T
Eighteen China III and IV diesel vehicles, including light-duty diesel trucks (LDDTs), medium-duty diesel trucks (MDDTs), heavy-duty diesel trucks (HDDTs) and buses, were tested with real-world measurements using a portable emission measurement system (PEMS). The emission factors (EFs), chemical components and surface morphology of emitted particles from these vehicles were characterized. Measured features included organic carbon (OC), elemental carbon (EC), water soluble ions (WSIs) and trace elements of PM2.5. The modelling system MOtor Vehicle Emission Simulator (MOVES) was also employed to estimate the PM2.5 EFs from these vehicles. Carbonaceous content made up 35.8–110.8% of PM2.5, the largest contribution of all the determined chemical components; WSIs and elements accounted for less than 10%. The average PM2.5 EFs of MDDTs and HDDTs were 0.389 g ¢km ¡1 and 0.115 g ¢km ¡1 , respectively, approximately one order of magnitude higher than that of LDDTs. The PM2.5 EFs of China III buses were much lower than those of China III MDDTs and HDDTs, indicating that the inspection maintenance program (I/M) system was carried out effectively on public diesel vehicles. Moreover, the chemical composition of 9.2–56.2% of the PM2.5 mass emitted from China IV diesel trucks could not be identified in the present study. It was possible this unidentified mass was particle bound water, but this hypothesis should be confirmed with further measurements. The SEM images of PM2.5 samples presented a loose floc structure. In addition, the trends of variation of estimated PM2.5 EFs derived from the MOVES simulation were essentially consistent with those of tested values.
