WARREN FINLAY Pengarang

A portable, four-wavelength, single-cell photoacoustic spectrometer for ambient aerosol absorption D. Al Fischer and Geoffrey D. Smith Department of Chemistry, University of Georgia, Athens, Georgia, USA A B S T R A C T Aerosols directly affect Earth’ s climate by scattering and absorbing solar radiation. Although they are ubiquitous in Earth’ s atmosphere, direct, in situ, wavelength-resolved measurements of aerosol optical properties remain challenging. As a result, the so-called aerosol direct effects are one of the largest uncertainties in predictions of Earth’s future climate, and new instrumentation is needed to provide measurements of the absorption of sunlight by atmospheric particles. We have developed a portable, four-wavelength, single-cell photoacoustic spectrometer for simultaneous measurement of aerosol absorption at 406, 532, 662, and 785 nm, with an additional extinction measurement at 662 nm via a built-in cavity ringdown spectrometer. The instrument, dubbed MultiPAS-IV, is compact, robust, has low power requirements, and utilizes a multipass optical arrangement to achieve typical detection limits of 0.6–0.7 Mm ¡1 for absorption (2s, 2-min average). Tests with nigrosin aerosols show agreement with Mie theory calculations to within 2%, and comparison with a 7-wavelength aethalometer shows good correlation for ambient (Athens, GA, USA) aerosols. We demonstrate the utility of the broad spectral coverage and sensitivity of the MultiPAS-IV for calculating the absorption Angstrom exponent of black carbon (AAE€ BC, median value of 0.70) in ambient aerosols and use this value to derive the brown carbon contributions to absorption at 406 nm (43%) and 532 nm (13%) and its wavelength dependence (AAEBrC D 6.3). Comparative performance of a thermal denuder and a catalytic stripper in sampling laboratory and marine exhaust aerosols Stavros Amanatidisa,b,*, Leonidas Ntziachristosa,b, Panu Karjalainen b, Erkka Saukkob,**, Pauli Simonenb, Niina Kuittinenb, P€aivi Aakko-Saksac, Hilkka Timonend, Topi Ronkk€ o€b, and Jorma Keskinenb aMechanical Engineering Department, Aristotle University, Thessaloniki, Greece; bDepartment of Physics, Tampere University of Technology, Tampere, Finland; cVTT Technical Research Centre of Finland, Espoo, Finland; dFinnish Meteorological Institute, Atmospheric Composition Research, Helsinki, Finland A B S T R A C T The performance of a thermal denuder (thermodenuder—TD) and a fresh catalytic stripper (CS) was assessed by sampling laboratory aerosol, produced by different combinations of sulfuric acid, octacosane, and soot particles, and marine exhaust aerosol produced by a medium-speed marine engine using high sulfur fuels. The intention was to study the efficiency in separating non-volatile particles. No particles could be detected downstream of either device when challenged with neat octacosane particles at high concentration. Both laboratory and marine exhaust aerosol measurements showed that sub-23 nm semi-volatile particles are formed downstream of the thermodenuder when upstream sulfuric acid approached 100 ppbv. Charge measurements revealed that these are formed by re-nucleation rather than incomplete evaporation of upstream aerosol. Sufficient dilution to control upstream sulfates concentration and moderate TD operation temperature (250 C) are both required to eliminate their formation. Use of the CS following an evaporation tube seemed to eliminate the risk for particle re-nucleation, even at a ten-fold higher concentration of semi-volatiles than in case of the TD. Particles detected downstream of the CS due to incomplete evaporation of sulfuric acid and octacosane aerosol, did not exceed 0.01% of upstream concentration. Despite the superior performance of CS in separating non-volatile particles, the TD may still be useful in cases where increased sensitivity over the traditional evaporation tube method is needed and where high sulfur exhaust concentration may fast deplete the catalytic stripper adsorption capacity. Comparison of the relative performance effi ciencies of melt-blown and glass fi ber fi lter media for managing fi ne particles Sungho Hwanga, Jaehoon Rohb,c,d,e, and Wha Me Parkb,c aNational Cancer Control Institute, National Cancer Center, Goyang-si, Gyeonggi-do, South Korea; bThe Institute for Occupational Health, Yonsei University College of Medicine, South Korea; cGraduate School of Public Health, Yonsei University, Seoul, South Korea; dDepartment of Preventive Medicine, College of Medicine, Yonsei University, Seoul, South Korea; eInchen Worker’s Health Center, Incheon, South Korea A B S T R A C T The purpose of this study was to compare the performance efficiency of melt-blown and currently used glass fiber filter media under the same environmental conditions. To evaluate filter efficiency, filter class was determined according to ISO and European standards (EN 1822-1:2009) using an automated filter tester (0.3 mm size), taking into account particle filtration, fractional efficiency for negative pressure devices, and consumption of electrical power. The average fractional efficiency, quality factor (QF), fractional efficiency by dust loading amount, pressure by dust loading amount, and QF by dust loading amount were higher in the case of melt-blown media than in the case of glass fiber filters. The fractional efficiency of hydrocharged melt-blown filters was higher than that of uncharged media. Based on performance efficiency, melt-blown filters are more effective high efficiency particulate air filters than glass fiber media. Computational simulation of the dynamics of secondary organic aerosol formation in an environmental chamber A. M. Sunol, S. M. Charan, and J. H. Seinfeld Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA A B S T R A C T A key atmospheric process that is studied in laboratory chambers is the oxidation of volatile organic compounds to form low volatility products that condense on existing atmospheric particles (or nucleate) to form organic aerosol, so-called secondary organic aerosol. The laboratory chamber operates as a chemical reactor, in which a number of chemical and physical processes take place: gas-phase chemistry, transport of vapor oxidation products to suspended particles followed by uptake into the particles, deposition of vapors on the walls of the chamber, deposition of particles on the walls of the chamber, and coagulation of suspended particles. Understanding the complex interplay among these simultaneous physicochemical processes is necessary in order to interpret the results of chamber experiments. Here we develop and utilize a comprehensive computational model for dynamics of vapors and particles in a laboratory chamber and analyze chamber behavior over a range of physicochemical conditions. Continuous fl ow hygroscopicity-resolved relaxed eddy accumulation (Hy-Res REA) method of measuring size-resolved sodium chloride particle fl uxes N. Meskhidze a, T. M. Royaltya, B. N. Phillipsa, K. W. Dawsona, M. D. Petters a, R. Reedb, J. P. Weinsteinc, D. A. Hookc, and R. W. Wienerc aDepartment of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina, USA; bDepartment of Applied Ecology, North Carolina State University, Raleigh, North Carolina, USA; cNational Exposure Research Laboratory, US EPA, Research Triangle Park, North Carolina, USA A B S T R A C T The accurate representation of aerosols in climate models requires direct ambient measurement of the size- and composition-dependent particle production fluxes. Here, we present the design, testing, and analysis of data collected through the first instrument capable of measuring hygroscopicity-based, size-resolved particle fluxes using a continuous-flow Hygroscopicity-Resolved Relaxed Eddy Accumulation (Hy-Res REA) technique. The Hy-Res REA system used in this study includes a 3D sonic anemometer, two fast-response solenoid valves, two condensation particle counters, a scanning mobility particle sizer, and a hygroscopicity tandem differential mobility analyzer. The different components of the instrument were tested inside the US Environmental Protection Agency’s Aerosol Test Facility for sodium chloride and ammonium sulfate particle fluxes. The new REA system design does not require particle accumulation, and therefore avoids the diffusional wall losses associated with long residence times of particles inside the air collectors of traditional REA devices. A linear relationship was found between the sodium chloride particle fluxes measured by eddy covariance and REA techniques. The particle detection limit of the Hy-Res REA flux system is estimated to be »3 £ 105 m ¡2 s ¡1 . The estimated sodium chloride particle classification limit, for the mixture of sodium chloride and ammonium sulfate particles of comparable concentrations, is »6 £ 106 m ¡2 s ¡1 . Deposition of micrometer-sized aerosol particles in neonatal nasal airway replicas S. Taverninia, T. K. Church b, D. A. Lewis b, M. Nogac, A. R. Martina, and W. H. Finlay a aDepartment of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada; bChiesi Limited, Chippenham, Wiltshire, United Kingdom; cDepartment of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, Alberta, Canada A B S T R A C T The nasal aerosol filtration properties of infants 0–3 months old have been quantified through in vitro measurements. Computed tomography (CT) scan data was obtained of seven individuals with ages of 5–79 days. Nasal airway replicas based on these images were manufactured using rapid prototyping. Deposition in the replicas was measured using an electrical low pressure impactor (ELPI) to measure the concentration of aerosol particles in the inertial regime. Comparing the difference in concentration when sampling through the model versus sampling through a blank line gave the deposition fraction. Deposition was measured for particles with aerodynamic diameters between 0.53 and 5.54 mm. Nonlinear least squares curve fitting was performed to collapse intersubject variability and represent the data with a single curve. To achieve satisfactory intersubject variability collapse, a non-dimensional pressure drop, the Euler number (Eu), was required in addition to the Reynolds number (Re) and the particle Stokes number (Stk) where the dimensionless parameters are evaluated with a length scale, D, defined as the airway volume divided by the airway surface area. The equation describing the deposition fraction, h, is h D 1- (14590 / (14590 C Stk1.2201Re1.7742Eu1.5772))0.3687. An analysis of the expected intersubject variability in in vivo deposition was also performed, yielding a method for predicting variance in neonatal nasal airway deposition. Dihydroxyacetone levels in electronic cigarettes: Wick temperature and toxin formation Shawna Vreekea, Tetiana Korzuna, Wentai Luob, R. Paul Jensena, David H. Peytona, and Robert M. Strongina aDepartment of Chemistry, Portland State University, Portland, Oregon, USA; bDepartment of Civil and Environmental Engineering, Portland State University, Portland, Oregon, USA A B S T R A C T Recently, we reported the presence of dihydroxyacetone (DHA), the active ingredient in sunless tanners, in the aerosol of an electronic cigarette. DHA has been shown to react with DNA in vitro. The FDA restricts the use of DHA to external application only. It states that it should not be inhaled, ingested, or come into contact with any areas containing mucous membranes, due to unknown risk. Herein, the quantification of DHA in the aerosols of three brands of e-cigarettes has been carried out. These included two devices with horizontal heating coil configurations as well as one with a sub-ohm resistance vertical heating coil. In order to understand and begin to address the origin of DHA and related aerosol products, the wicking properties of the three e-cigarettes were compared. DHA levels were analyzed by a combination of GS/MS and 1 H NMR. DHA was found in all three ecigarettes, with substantially less in the sub-ohm, vertical coil device as compared to the horizontal coil devices (e.g., 0.088 mg/puff vs. 2.29 mg/puff, respectively). Correspondingly, the temperature of the wet layer of the wick for the vertical coil was relatively stable, compared to the wicks for the horizontal coils, upon increasing battery power output. This result is in agreement with prior studies of e-cigarette wicking efficiency and aerosol toxin formation. The temperature measurements reported are a simple means for comparing devices with different design properties during operation. Fate of pyrazines in the fl avored liquids of e-cigarettes Rachel El-Hagea,b, Ahmad El-Hellania,b, Rola Salmanb,c, Soha Talihb,c, Alan Shihadehb,c, and Najat Aoun Salibaa,b aChemistry Department, Faculty of Arts and Sciences, American University of Beirut, Beirut, Lebanon; bCenter for the Study of Tobacco Products, Virginia Commonwealth University, Richmond, Virginia, USA; cMechanical Engineering Department, Faculty of Engineering and Architecture, American University of Beirut, Beirut, Lebanon A B S T R A C T Popularity of electronic cigarettes (ECIGs) has increased tremendously among young people, in part due to flavoring additives in ECIG liquids. Pyrazines are an important class of these additives, and their presence in tobacco cigarettes has been correlated with increased acceptability of smoking among smokers and bystanders. Pyrazine use by the tobacco industry is therefore thought to encourage smoking. However, the extent of transfer of pyrazines present in the liquid to aerosols upon vaping remains unclear. We present a simple analytical method to quantify six pyrazine derivatives in liquids and aerosols of ECIGs that allows the isolation of pyrazines from interfering compounds, like nicotine. Standard pyrazine solutions and commercial ECIG samples of different brands and flavors were tested for their pyrazine content in the liquids and in the generated aerosols from these solutions. Testing on ECIG commercial liquids revealed a heterogeneous distribution in the levels and types of pyrazines, with acetyl and alkyl pyrazines present in more than 70% of the samples. This method confirmed that pyrazine additives are common in ECIG and that labels do not usually reflect the type and quantity of pyrazines in the liquid. Pyrazines were not correlated with the nicotine content or the brand of the liquid. The aerosols showed similar pyrazine profiles to their corresponding liquids. The efficiency of transfer of pyrazines into the particle phase was approximately 46%. Therefore, addition of pyrazines to ECIGs should be regulated, because they act synergistically with nicotine to increase product appeal, ease smoking initiation, and discourage cessation. Impact of power level and refi ll liquid composition on the aerosol output and particle size distribution generated by a new-generation e-cigarette device J er emie Pourcheza, Sandrine Parisseb,c, Gwendoline Sarrya, Sophie Perinel-Rageyb,d, Jean-Michel Vergnonb,e, Anthony Clotagatideb,c, and Nathalie Prevot^ b,c aUniv Lyon, IMT Mines Saint-Etienne, Centre CIS, INSERM, SainBioSE, Saint-Etienne, France; bUniv Lyon, Univ Jean Monnet, INSERM, SainBioSE, Saint-Etienne, France; cDepartment of Nuclear Medicine, CHU Saint-Etienne, Saint-Etienne, France; dMedical-Surgical Intensive Care Unit, CHU Saint-Etienne, Saint-Etienne, France; eDepartment of Chest Diseases and Thoracic Oncology, CHU Saint-Etienne, Saint-Etienne, France A B S T R A C T The new high-power Electronic Nicotine Delivery System (ENDS) can generate aerosols with higher nicotine concentrations than older ENDS. Aerosol particle sizes affect deposition patterns and then plasma nicotine levels in vapers. Consequently, understanding the factors influencing particle size distribution of high-power ENDS is relevant to assess their performance in terms of nicotine delivery. The particle size distribution and the aerosol output (aerosol mass) were measured using cascade impactors. The effects of the refill liquid composition (80% PG/20% VG vs. 80% VG/20% PG; PG refers to propylene glycol and VG to vegetable glycerin) and the power level of the battery (from 7 W to 22 W) were investigated. The aerosol output increases significantly with the power level following a logarithmic law. The PG/VG ratio also has an impact on the aerosol output. The higher the VG content in the refill liquid, the higher is the aerosol output. Besides, particle size distribution is positively related to the power level, following linear correlations between the mass median aerodynamic diameter (MMAD) and the power level in the range of 7–22 W. A moderate impact of the PG/VG ratio on size distribution is equally observed. Changes in the power level allow the transition between a dominant mode with MMAD from 613 nm to 949 nm. We demonstrated that the power level can strongly change the aerodynamic properties of high-power ENDS, especially at high voltage. Associated with the aerosol nicotine level assessment, MMAD could be determined as a means for comparing ENDS devices and nicotine delivery Infl uence of surfactants on growth of individual aqueous coarse mode aerosol particles Amanda A. Frossard a,*, Wayne Lia, Violaine Gerardb, Barbara Noziereb, and Ronald C. Cohena aDepartment of Chemistry, University of California Berkeley, Berkeley, CA, USA; bInstitut de Recherches sur la Catalyse et l’Environnement de Lyon (IRCELYON), CNRS, Universite Lyon 1, Villeurbanne, France A B S T R A C T Understanding the links between a erosol and cloud and radiative properties remains alarge uncertaintyin predicting Earth’s changing energy budget. Surfactants are observed in ambient atmospheric aerosol particles, and their effect on cloud droplet growth is a mechanism that was, until recently, neglected in model calculations of particle activation and droplet growth. In this study, coarse mode aqueous aerosol particles were created containing the surfactant Igepal CA-630 and NaCl. The evaporation and condensation of these individual aqueous particles were investigated using an aerosol optical trap combined with Raman spectroscopy. For a relative humidity (RH) change from 70% to 80%, droplets containing both Igepal and NaCl at atmospheric concentrations exhibited on average more than 4% larger changes in droplet radii, compared to droplets containing NaCl only. This indicates enhanced water uptake in the presence of surfactants, but this result is unexpected based on the standard calculation of the effect of surfactants, using surface tension reduction and/or hygroscopicity changes, for particles of this size. One implication of these results is that in periods with increasing RH, surfactant-containing aqueous particles may grow larger than similarly sized aqueous NaCl particles without surfactants, thus shifting atmospheric particle size distributions, influencing particle growth, and affecting aerosol loading, visibility,and radiative forcing.