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Journal of Aerosol Science
Pergamon Press
Journal of Aerosol Science

Pergamon Press

0021-8502

Journal of Aerosol Science/Journal Journal of Aerosol ScienceSCIISTPEI
正式出版
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    On the reactive coagulation of incipient soot nanoparticles

    Hou, DingyuPascazio, LauraMartin, JacobZhou, Yuxin...
    13页
    查看更多>>摘要：In this work, we studied the coagulation process of two PAH clusters with diameter similar to 2 nm using reactive molecular dynamics (MD) simulations. To describe the coagulation process quantitatively, the distance between the center of mass (COM) of the two PAH clusters, as well as the inter-cluster potential energy and kinetic energy of the COM of the clusters were calculated. Head-on coagulation efficiencies (eta) of two PAH clusters at typical flame temperatures where soot inception is most likely to occur, i. e. , 1500 K-2000 K, were determined based on hundreds of MD simulated trajectories. Our simulation results showed that eta decreases with increasing temperature, which is mainly due to the increased kinetic energy of atoms within the PAH clusters at higher temperature. In addition, introduction of surface sigma-radical site fraction in the range of 0.01 to 0.1 can only moderately improve eta by similar to 10% by forming carbon-carbon bonds between the two coagulating clusters, which suggests eta of incipient soot nanoparticles with surface sigma-radicals in high temperature flame regions is very low even if with reactive coagulation taken into consideration.
      原文链接:
    • NSTL
    • Elsevier

    Effects of agglomerate characteristics on their collision kernels in the free molecular regime

    Qian, WeijiaKronenburg, AndreasLin, YuzhenKarsch, Maximilian...
    17页
    查看更多>>摘要：Collision frequencies of fractal clusters need to be modelled to predict cluster growth due to agglomeration. Here, we utilize Langevin dynamics to accurately capture the movement and collision of fractal agglomerates with various morphologies that are characterized by their size, fractal dimension, lacunarity and shape anisotropy in the free molecular regime. The simulations include rotational and translational movement and potential interactions between the agglomerates. The agglomerates move subject to Brownian motion and the simulations are designed such that collision rates can be directly deduced. Results show that collision radii scale with gyration radius but are also dependent on all the other characteristics. The lacunarity increases the collision radii while shape anisotropy can decrease them. The fractal dimension can increase the collision radii and its effect is dominant. The increasing effect of van der Waals forces on the collision radii is also quantified and found to be independent of the size of the agglomerates. A new linear model is proposed to predict collision radii to within 2.5% accuracy.
      原文链接:
    • NSTL
    • Elsevier

    Examining chemical composition of gas turbine-emitted organic aerosol using positive matrix factorisation (PMF)

    Smith, Liam D.Allan, JamesCoe, HughReyes-Villegas, Ernesto...
    16页
    查看更多>>摘要：In this paper, the characteristics of non-refractory aerosol using an International Civil Aviation Organization (ICAO) compliant sampling system emitted from two gas turbine relevant sources are reported, namely: an in-service turboshaft helicopter engine and a development combustor rig. Positive Matrix Factorisation (PMF) analysis was applied on an Aerosol Mass Spectrometer's (AMS) Unit Mass Resolution (UMR) organic aerosol (OA) data to identify three chemical factors: one unburnt fuel factor (AlkOA; Alkane Organic Aerosol) and two factors formed through oxidative processes: Semi Volatile Oxygenated Organic Aerosol (SV-OOA) and Quenched Organic Aerosol (QOA). The AlkOA factor's mass concentration correlated with Elemental Carbon (EC), an incomplete combustion tracer. The SV-OOA factor's mass concentration correlated with AMSdetected sulphate and Organic Carbon (OC) as characterised by a Sunset semi-continuous Analyser, with a high proportion of the OC converted to CO2 at lower temperatures (<= 475 degrees C) during the OC analysis, suggesting a higher volatility. The QOA factor's mass concentration corresponded with higher quantities of OC converted to CO2 at the highest temperature (870 degrees C) during the OCEC analysis protocol. The QOA factor comprised large quantities of AMS-detected organic mass concentrations (20-50%) for the IP Rig. In addition, issues were seen with the OCEC analyser, and future strategies for operation for sampling from aviation sources are considered. The work characterises the available chemical speciation present in the particulate matter phase within an ICAO compliant nvPM sampling system for in-service and development combustor rigs, and comparisons are made between mass spectra seen within this methodology and in evolved plumes.
      原文链接:
    • NSTL
    • Elsevier

    SARS-CoV-2 in residential rooms of two self-isolating persons with COVID-19

    Shankar, Sripriya NannuWitanachchi, Chiran T.Morea, Alyssa F.Lednicky, John A....
    12页
    查看更多>>摘要：Individuals with COVID-19 are advised to self-isolate at their residences unless they require hospitalization. Persons sharing a dwelling with someone who has COVID-19 have a substantial risk of being exposed to the virus. However, environmental monitoring for the detection of virus in such settings is limited. We present a pilot study on environmental sampling for SARS-CoV-2 virions in the residential rooms of two volunteers with COVID-19 who self-quarantined. Apart from standard surface swab sampling, based on availability, four air samplers positioned 0.3-2.2 m from the volunteers were used: a Viable Virus Aerosol Sampler (VIVAS), an inline air sampler that traps particles on polytetrafluomethylene (PTFE) filters, a NIOSH 2-stage cyclone sampler (BC-251), and a Sioutas personal cascade impactor sampler (PCIS). The latter two selectively collect particles of specific size ranges. SARS-CoV-2 RNA was detected by real-time Reverse-Transcription quantitative Polymerase Chain Reaction (rRT-qPCR) analyses of particles in one air sample from the mom of volunteer A and in various air and surface samples from that of volunteer B. The one positive sample collected by the NIOSH sampler from volunteer A's room had a quantitation cycle (Cq) of 38.21 for the N-gene, indicating a low amount of airborne virus [5.69E-02 SARS-CoV-2 genome equivalents (GE)/cm(3) of air]. In contrast, air samples and surface samples collected off the mobile phone in volunteer B's mom yielded Cq values ranging from 14.58 to 24.73 and 21.01 to 24.74, respectively, on the first day of sampling, indicating that this volunteer was actively shedding relatively high amounts of SARS-CoV-2 at that time. The SARSCoV-2 GE/cm(3) of air for the air samples collected by the PCIS was in the range 6.84E+04 to 3.04E+05 using the LED-N primer system, the highest being from the stage 4 filter, and similarly, ranged from 2.54E+03 to 1.68E+05 GE/cm(3) in air collected by the NIOSH sampler. Attempts to isolate the virus in cell culture from the samples from volunteer B's room with the aforementioned Cq values were unsuccessful due to out-competition by a co-infecting Human adenovirus B3 (HAdVB3) that killed the Vero E6 cell cultures within 4 days of their inoculation, although Cq values of 34.56-37.32 were measured upon rRT-qPCR analyses of vRNA purified from the cell culture medium. The size distribution of SARS-CoV-2-laden aerosol particles collected from the air of volunteer B's room was >0.25 mu m and >0.1 mu m as recorded by the PCIS and the NIOSH sampler, respectively, suggesting a risk of aerosol transmission since these particles can remain suspended in air for an extended time and travel over long distances. The detection of virus in surface samples also underscores the potential for fomite transmission of SARS-CoV-2 in indoor settings.
      原文链接:
    • NSTL
    • Elsevier

    Tutorial: Guidelines for implementing low-cost sensor networks for aerosol monitoring

    Zimmerman, Naomi
    17页
    查看更多>>摘要：Over the past decade, there has been exponential growth in low-cost air pollution sensing technology. While low-cost sensors can provide a path towards more accessible air quality measurement, there are several guidelines that should be considered prior to deploying a low-cost sensor network. In this tutorial guide, we focus on low-cost aerosol sensors (in this case, PM2.5). The tutorial reviews key guidelines for implementing a low-cost PM sensor network. This article is also associated with a companion web-tutorial (https://nzimmerman-ubc.github.io/lcs-PM-demo/) on downloading and assessing sample low-cost PM sensor data from the PurpleAir network using the new U.S. EPA Fine Particle Sensor Base Testing Guidelines. While this tutorial does not cover every single consideration a researcher or citizen scientist might undertake, it covers the key areas of evaluation and calibration, siting, data reporting, and post-processing. The aim of the tutorial is to improve outcomes for researchers using low-cost PM sensor networks and develop a broader community of practice.
      原文链接:
    • NSTL
    • Elsevier

    Solid particle number emissions of 56 light-duty Euro 5 and Euro 6 vehicles

    Lahde, TeroGiechaskiel, BarouchPavlovic, JelicaSuarez-Bertoa, Ricardo...
    10页
    查看更多>>摘要：Vehicle exhaust solid particle number emissions >23 nm (SPN23) and >10 nm (SPN10) were studied for 56 market light-duty vehicles with over 1000 laboratory tests. The studied vehicletypes were gasoline port-fueled injection (PFI), gasoline direct injection (GDI), GDI with gasoline particulate filter (GPF-GDI), and diesel equipped with particulate filter (DPF) vehicles. GDI and DPF SPN emissions decreased with improving emission standards, while PFI did not. When all SPN data was considered, the emissions of GDI were the highest, followed by PFI, then DPF and GPF-GDI. However, considering the vehicles complying with the recent European regulation (Euro 6c or later), the PFI vehicles had the highest emissions amongst the studied vehicle types, often exceeding the current European SPN23 limit of 6.1011 1/km. although the limit is not applicable to them. In addition, PFI-vehicles had the highest average sub-23 nm fraction of the studied vehicle types at all SPN23 levels. For all of the vehicle types, SPN emissions increased at low ambient temperatures. While for GDI and PFI, the sub-23 nm fraction decreased at low temperatures, for DPF vehicles it increased.
      原文链接:
    • NSTL
    • Elsevier

    Improving quantitative analysis of spark-induced breakdown spectroscopy: Multivariate calibration of metal particles using machine learning

    Li, HanyangMazzei, LeonardoWallis, Christopher D.Wexler, Anthony S....
    13页
    查看更多>>摘要：We have recently developed a low-cost spark-induced breakdown spectroscopy (SIBS) instrument for in-situ analysis of toxic metal aerosol particles that we call TARTA (toxic-metal aerosol real time analyzer). In this work, we applied machine learning methods to improve the quantitative analysis of elemental mass concentrations measured by this instrument. Specifically, we applied least absolute shrinkage and selection operator (LASSO), partial least squares (PLS) regression, principal component regression (PCR), and support vector regression (SVR) to develop multivariate calibration models for 13 metals (e.g., Cr, Cu, Mn, Fe, Zn, Co, Al, K, Be, Hg, Cd, Pb, and Ni), some of which are included on the US EPA hazardous air pollutants (HAPS) list. The calibration performance, adjusted coefficient of determination (R2) and normalized root mean square error (RMSE), and limit of detection (LOD) of the proposed models were compared to those of univariate calibration models for each analyte. Our results suggest that machine learning models tend to have better prediction accuracy and lower LODs than conventional univariate calibration, of which the LASSO approach performs the best with R2 > 0.8 and LODs of 40-170 ng m- 3 at a sampling time of 30 min and a flow rate of 15 l min-1. We then assessed the applicability of the LASSO model for quantifying elemental concentrations in mixtures of these metals, serving as independent validation datasets. Ultimately, the LASSO model developed in this work is a very promising machine learning approach for quantifying mass concentration of metals in aerosol particles using TARTA.
      原文链接:
    • NSTL
    • Elsevier

    Characterization techniques for heterogeneous nucleation from the gas phase

    Winkler, Paul M.Wagner, Paul E.
    12页
    查看更多>>摘要：Heterogeneous nucleation constitutes the initial step in the formation of new aerosol particles that evolve on the surface of pre-existing (seed) particles. To this end the interaction of vapor and seed particle plays a critical role which is governed by the seed particle's size, composition, solubility, electrical charge state as well as the chemical nature of the vapor and the wetting properties of the condensing liquid with the underlying surface. Despite being a process on the nanoscale under most conditions of relevance the effect of heterogeneous nucleation has global implications via the formation of clouds, and is technically utilized in condensation particle counters for the detection of nanoparticles. Proper techniques for the characterization of heterogeneous nucleation thus serve a better fundamental understanding and improve the detectability of nanoparticles. Here we review state-of-the-art experimental and theoretical techniques allowing quantitative analysis of heterogeneous nucleation and providing insight to properties of nucleating clusters. Building upon current knowledge we identify and discuss open questions in the field motivating prospective future research.
      原文链接:
    • NSTL
    • Elsevier

    Microstructural transition of nanoparticle deposits from multiple dendrites to compact layer

    Kim, JeonggeonShin, JuhwanLee, Donggeun
    16页
    查看更多>>摘要：Nanoparticle deposit has various microstructures from multiple dendrites to mesopomus compact structures depending on deposition conditions, and the required microstructures are different depending on its applications. There have been recent reports that the overall porosity of deposit can be predicted by a function of diffusive Knudsen number (Kn(D)) and dimensionless translational energy (chi(F)) of the particle. Unlike compact structures, however, dendritic structures consisting of multiple dendrites cannot be characterized solely by overall porosity and their formation mechanism is not known. In this study, various structures of deposit were produced in a wide range of deposition conditions (Kn(D): 10(-1.5)-10(1.5) ; chi(F): 10(-3)-10(3)) using off-lattice Monte Carlo simulation, and the unique characteristics of the deposit could be visualized by presenting local fractional accumulations of pores as color-filled contours. Furthermore, a spatial autocorrelation was calculated for the contour plot in order to find a quantitative footprint of structural features of nanoparticle deposits, in compact vs dendritic structures. As a result, we successfully identified the dendritic-to-compact structural transition in a quantitative manner, for the first time. Lastly considering the deposition behavior of particles, we developed a new model capable of a priori prediction of the specific deposit structure among compact, dendritic, and transition structures, given the deposition condition in terms of Kn(D) and chi(F).
      原文链接:
    • NSTL
    • Elsevier

    Temperature and pressure effects on the performance of the portable TSI 3007 condensation particle counter: Implications on ground and aerial observations

    Bezantakos, S.Biskos, G.
    9页
    查看更多>>摘要：One of the most commonly employed instruments in the category of handheld condensation particle counters (CPCs) is the TSI 3007, which employs a simplified system for achieving a temperature difference between its saturator and its condenser in view of increasing portability, energy efficiency and autonomy. As a result, particle growth and consequently the detection efficiency of the instrument can be affected by the measurement conditions. In this work we measure the detection efficiency of the TSI 3007 CPC under temperatures and pressures that differ from standard conditions. Our results show that the performance of the CPC has a strong temperature dependence in the range of 5-30 degrees C, whereas it is not affected by ambient pressure when this varies between 0.7 and 1.0 atm. The temperature dependent detection efficiency of the instrument becomes significant at sizes below 20 nm. Recording the temperature at which this CPC is operated is therefore strongly advised, especially when required to determine the number concentration of sub-20 nm aerosol particles.
      原文链接:
    • NSTL
    • Elsevier