Papers by Mark Stolzenburg
Journal of Aerosol Science, Nov 1, 2021
Abstract The measurement of airborne particles with sizes below 3 nm is critical, as it helps the... more Abstract The measurement of airborne particles with sizes below 3 nm is critical, as it helps the understanding of atmospheric nucleation and elucidates important particle synthesis mechanisms in the gas phase. Condensation particle counters (CPCs) have been widely used to measure the concentration of aerosols. However, it is challenging for the CPCs to measure particles below 3 nm due to the insufficient activation of these particles via vapor condensation. Methods have been proposed to increase the saturation ratio of the condensing vapor to promote the detection efficiency of sub-3 nm particles in the CPCs. Different working fluids also make a considerable impact on particle detection. Given the various types of parameters and the wide range of values these parameters can take, modeling studies are needed in searching for the optimal operating conditions of a CPC. In this work, we simulated the sub-3 nm particle activation and growth in a laminar flow CPC using COMSOL Multiphysics®, which has the advantages of simulating complex flow conditions and interfacing with post-processing software such as MATLAB. Our simulation incorporates the influence of temperature-dependent air and working fluid properties on particle activation and the impact of latent heat and non-continuum effects on droplet growth. Following the method introduced by Iida, Stolzenburg and McMurry (2009), particle activation is optimized for a given working fluid and condenser temperature by adjusting the saturator temperature to achieve a homogeneous nucleation rate of 1 s−1. The results, characterized by Dkel,0 (largest particle size that cannot be activated) and Dkel,50 (particle size activated with 50% efficiency), were compared against the analytical Graetz model used in Stolzenburg (1988). Our COMSOL simulations show that glycerine, diethylene glycol, ethylene glycol, 2-aminoethanol, and dimethyl phthalate are the best five working fluids achieving the smallest Dkel,50 among 45 commonly used solvents. The Dkel,50 values simulated by COMSOL under a condenser temperature of 10 °C for the five working fluids are 1.56, 1.88, 1.92, 1.98, and 2.10 nm, respectively, while the values simulated by the analytical Graetz solution differ slightly from 0.4% to 0.7%. The results demonstrate excellent agreement between these two simulation methods. For the five best working fluids activating the same 2.1 nm particles, the droplets can grow to sizes detectable by a second-stage CPC. The sensitivity of the COMSOL solution to the inlet condition and the form of convective diffusion equations is investigated. We also discussed the effect of CPC operating conditions, such as the condenser geometry and flow conditions, on particle activation for optimizing the performance of the CPC in detecting sub-3 nm particles.
Aerosol Science and Technology, Apr 19, 2018
Aerosol mobility size spectrometers are commonly used to measure size distributions of submicrome... more Aerosol mobility size spectrometers are commonly used to measure size distributions of submicrometer aerosol particles. Commonly used data inversion algorithms for these instruments assume that the measured mobility distribution is broad relative to the DMA transfer function. This article theoretically examines errors that are incurred for input distributions of any width with an emphasis on those with mobility widths comparable to that of the DMA's transfer function. Our analysis is valid in the limit of slow scan rates, and is applicable to the interpretation of measurements such as those obtained with tandem differential mobility analyzers as well as broader distributions. The analysis leads to expressions that show the relationship between the inverted number concentration, mean size, and standard deviation and true values of those parameters. For narrow distributions (e.g., for a mobility distribution produced by a DMA with a 1:10 aerosol:sheath air flow ratio) under typical operating conditions, number concentrations and mean mobility obtained with inversion algorithms are accurate to within 0.5% and 1.0%, respectively. This corresponds to mean diameter retrieval errors of 1.0% for large particles and 0.5% for small (kinetic regime) particles. The widths (i.e., relative mobility variance) of the inverted distributions, however, significantly exceed the true values. EDITOR Jingkun Jiang The inversion algorithm described by Collins et al. (2002) eliminates this error by finely discretizing the mobility distribution function, thereby allowing variations within the DMA mobility window. The inversion technique described by Twomey (1975) is used to determine the size distribution; to our knowledge, this approach is not widely used by aerosol scientists.
Atmospheric Environment, Apr 1, 2002
The southeastern aerosol and visibility study (SEAVS) was conducted in Great Smoky Mountains Nati... more The southeastern aerosol and visibility study (SEAVS) was conducted in Great Smoky Mountains National Park in summer 1995 to investigate variations in ambient aerosol size distributions and their effect on visibility. In this paper, we compare dry aerosol size distribution parameters from a MOUDI impactor and two different optical particle counters (OPCs). Size distributions from the various instruments are expressed in a common measure of size, specifically, optical and aerodynamic diameters are converted to a dry, geometric diameter basis. Comparisons of the real part of particle refractive index obtained directly from light scattering measurements and inferred from aerosol composition measurements are also shown. Real refractive indices from direct measurements and those computed from measured fine aerosol chemical composition were generally within 70.02. Maximum differences in estimated accumulation mode integrated volume concentrations from all instruments were within B22%. Accumulation mode integrated number concentrations and geometric standard deviations from the two OPCs agreed within B30% and B3%, respectively. Differences between MOUDI-and OPC-derived accumulation mode number concentrations and geometric standard deviations were B20% and B8%, respectively. The average geometric volume mean diameters derived from the three instruments agreed within 15% or less. The volume median diameters obtained by fitting the CSU number concentration data to a lognormal function were typically the smallest. We show that these discrepancies can be related to the differences and biases in the measurement and data analysis techniques.
Aerosol Science and Technology, Aug 28, 2008
An ultrafine, water-based condensation particle counter (U-WCPC, TSI Model 3786) has been compare... more An ultrafine, water-based condensation particle counter (U-WCPC, TSI Model 3786) has been compared to a butanol-based ultrafine counter (U-BCPC, TSI Model 3025) for measurement of atmospheric and freeway-tunnel aerosols. The U-WCPC utilizes a warm, wet-walled growth tube to activate and grow particles through water condensation in a laminar-flow. It has an aerosol sampling rate of 0.3 L/min, and a nominal detection limit near 3 nm. Several field comparisons were made to the butanol-based instrument with the same nominal detection limit. For measurements of size-selected aerosols with diameters of 5 nm and larger the two instruments generally agreed, with a mean response within 5%. At 3 nm particle size differences were observed, and these differences varied with the data set. Measurements of ambient aerosol in Boulder, Colorado showed higher counting efficiency at 3 nm with the U-BCPC, while in a California freeway tunnel the opposite trend was observed, with higher counting efficiencies at 3 nm observed by the U-WCPC. For direct measurement of atmospheric aerosols, the two types of instruments yielded equivalent concentrations, independent of particle number concentration.
Journal of Aerosol Science, Jun 1, 1998
Ph.D. thesis, University of Minnesota) has shown that for particles smaller than about 15 nm, pul... more Ph.D. thesis, University of Minnesota) has shown that for particles smaller than about 15 nm, pulse heights produced by the optical detector in a white-light ultrafine condensation nucleus counter (UCNC; Stolzenburg and McMurry (1991) Aerosol. Sci. ¹echnol. 14, 48-65) decrease with initial particle size. We have previously reported on the use of pulse heights from this instrument to determine the concentrations of freshly nucleated atmospheric nanoparticles in the 3-4 nm diameter range (
Aerosol Science and Technology, 1998
... 6 Temperature 6 Valve O-Probe \ ... One critical orifice fixes the com-bined flow of the OPC ... more ... 6 Temperature 6 Valve O-Probe \ ... One critical orifice fixes the com-bined flow of the OPC and CNC. The flow split between the counters is adjusted by a manual regulating valve in the exit flow leg from the OPC. The HF-DMA sheath air exit flow is set by a second critical orifice. ...
Lawrence Berkeley National Laboratory, Sep 1, 2001
The goal of this project is to develop a physically-based, semi-empirical model that describes th... more The goal of this project is to develop a physically-based, semi-empirical model that describes the concentration of indoor concentration of PM-2.5 (particle mass that is less than 2.5 microns in diameter) and its sulfate, nitrate, organic and black carbon constituents, derived from outdoor sources. We have established the methodology and experimental plan for building the model. Experimental measurements in residential style houses, in Richmond and Fresno, California, are being conducted to provide parameters for and evaluation of this model. The model will be used to improve estimates of human exposures to PM-2.5 of outdoor origin. The objectives of this study are to perform measurement and modeling tasks that produce a tested, semi-mechanistic description of chemical species-specific and residential PM-2.5 arising from the combination of outdoor PM and gas phase sources (HNO 3 and NH 3), and indoor gas phase (e.g. NH 3) sources. We specifically address how indoor PM is affected by differences between indoor and outdoor temperature and relative humidity. In addition, we are interested in losses of particles within the building and as they migrate through the building shell. The resulting model will be general enough to predict probability distributions for species-specific indoor concentrations of PM-2.5 based on outdoor PM, and gas phase species concentrations, meteorological conditions, building construction characteristics, and HVAC operating conditions. Controlled intensive experiments were conducted at a suburban research house located in Clovis, California. The experiments utilized a large suite of instruments including conventional aerosol, meteorological and house characterization devices. In addition, two new instruments were developed providing high time resolution for the important particulate species of nitrate, sulfate, and carbon as well as important gaseous species including ammonia and nitric acid. Important initial observations include the result that, with rare exceptions, there is virtually no nitrate found inside the house. This nitrate appears to dissociate into ammonia and nitric acid with the nitric acid quickly depositing out. Initial model development has included work on characterizing penetration and deposition rates, the dynamic behavior of the indoor/outdoor ratio, and predicting infiltration rates. Results from the exploration of the indoor/outdoor ratio show that the traditional assumption of steady state conditions does not hold in general. Many values of the indoor/outdoor ratio exist for any single value of the infiltration rate. Successful prediction of the infiltration rate from measured driving variables is important for extending the results from the Clovis house to the larger housing stock.
Aerosol Science and Technology, Sep 1, 2012
ABSTRACT Conventional Differential Mobility Analyzers (DMAs) for classification of aerosol partic... more ABSTRACT Conventional Differential Mobility Analyzers (DMAs) for classification of aerosol particles have one polydisperse-particle inlet and one monodisperse-particle outlet. As a result, when they are used as particle classifiers in aerosol-mobility spectrometers it is needed to scan through different operating conditions, thereby requiring a significant amount of time (i.e., of the order of a minute) for a single mobility distribution measurement. DMAs with multiple outlets can significantly reduce this scanning time because particles of different mobility can be classified and detected simultaneously. In addition, depending on the relative location of the first and the last outlet from the inlet, one can increase the dynamic mobility range of the selected particles in a single particle mobility distribution measurement. In this paper we derive analytical expressions for estimating the transfer function and the resolution of DMAs with multiple monodisperse outlets. Starting with the simple consideration of non-diffusing particles, we extend our analysis for diffusing particles and provide expressions of different complexity and accuracy. The theoretical framework provided in this paper can be employed to optimize the design of DMAs with more than one monodisperse-particle outlet, and to analyze the measurements when such DMAs are used in aerosol mobility spectrometers.
Journal of Aerosol Science, Feb 1, 2012
Aerosol Science and Technology, 1995
An on-line, semicontinuous method for the determination of size and effective density (g/cm3) of ... more An on-line, semicontinuous method for the determination of size and effective density (g/cm3) of particles in the 3-50 nm size range was evaluated using laboratory test aerosols. The method, called double size spectrometry, sizes particles twice, first by electrical mobility, and then by aerodynamic behavior. The first measure gives the geometric diameter for spherical particles. The second measure depends on single particle density. The double size spectrometer uses a differential mobility analyzer and hypersonic impactor in series. The mobility analyzer outputs singly-charged particles of a uniform diameter that are resized by the impactor. The impactor flow is supersonic; the critical aerodynamic capture diameter is varied by adjusting the orifice-to-plate separation; and particle capture is measured on-line by an electrometer. Theoretically, the response is described by a particle Stokes number. Experiments with 10-40 nm particles of dioctylsebacate and a perfluorocarbon vacuum oil gave critical Stokes number for capture near 1. The measured density ratio was 1.9, compared with the bulk material density ratio of 2.0. Experiments with 3-14 nm spark generated silver and copper aerosols differed, with apparent aerosol densities lower than the bulk values by factors of 2.5-3.6.
Air & waste, Feb 1, 1994
ABSTRACT Contributions of the major fine particle species to light scattering were evaluated usin... more ABSTRACT Contributions of the major fine particle species to light scattering were evaluated using Mie theory from measurements of sizeresolved chemistry and particle hygroscopicity obtained during the 1990 NGS Visibility Study at Hopi Point, Grand Canyon, from January 9, 1990 through March 31, 1990. It was found that scattering efficiencies of participate carbon mass ranged from 1.5 to 8 m per gram of carbon particle mass (assumed equal to 1.4 times carbon mass), with an average value of 5.4 ± 1.5 m/g. Sulfur size distributions, which are available for the entire 80-day study, show that sulfate scattering efficiencies depend on both relative humidity and on median particle size, and that “dry” (RH 0.3 μm were only found during periods of high relative humidity, but not all high humidity periods had large sulfur mass median diameters. Sulfate scattering efficiencies for >60 percent RH were smaller for instances of direct transport of
Journal of Geophysical Research, Dec 2, 2006
This paper investigates the role of ion-induced nucleation (IIN) in new particle formation events... more This paper investigates the role of ion-induced nucleation (IIN) in new particle formation events observed near ground level at a sampling site located near Boulder, Colorado (14 March 2004 to 27 October 2005). Measurements of mobility distributions of small and intermediate ions (0.4-6.3 nm), size distributions of total particles (3 nm to 5 mm), and charged fractions (2.5-25 nm) were carried out. The relative contributions of neutral nucleation and IIN were inferred using both qualitative and quantitative analyses. First, a simple theoretical analysis is performed to show what can be learned about the initial charge state of the nucleated particles from charged fractions measured after they had grown to 3.0-5.5 nm. We found that for much of our data the charge fractions of freshly nucleated particles below 5 nm were significantly below stationary-state values, and that this tendency increased with decreasing size, indicating that neutral nucleation was dominant. However, the data also show that there were occasionally asymmetries between negative and positive charge fractions that we could not explain unless positive or negative IIN occurred to some extent. A quantitative analysis is then performed to estimate the fractional contribution of positive and negative IIN to new particle formation rates for each nucleation event observed during this period. The results show the average contribution of IIN is about 0.5% for both polarities indicating that IIN was a relatively insignificant contributor to new particle formation in this study. This result is consistent with the direct mass spectrometric measurements of sulfuric acid ion cluster compositions and concentrations performed at the same measurement site.
Aerosol Science and Technology, May 1, 2005
A new method is presented for the enlargement of particle size through condensation of water vapo... more A new method is presented for the enlargement of particle size through condensation of water vapor in a laminar, thermally diffusive flow. The method involves the introduction of an air flow at temperature T i into a wet-walled tube at a temperature T w > T i. This approach yields higher supersaturation values than either mixing or cold-walled condensers when operating between the same temperature extremes. Model results for the saturation profiles within the condensing region show that the peak supersaturations are reached along the centerline of the flow, and that the activation efficiency curves are steeper for large temperature differences when the cutpoint diameter is smaller. Experiments conducted with three types of aerosol, oleic acid (a water-insoluble oil), a mixture of oxalic acid and sulfate, and with ambient laboratory aerosol confirmed that condensational growth is achieved with this approach, although experimental cutpoints are somewhat higher than predicted for wettable particles.
Journal of Aerosol Science, 1988
A unique ultrafine aerosol condensation nucleus counter (UFACNC) was used to test the performance... more A unique ultrafine aerosol condensation nucleus counter (UFACNC) was used to test the performance of two commercially available membrane filters. Details of this instrument have been discussed in previous publications (Stolzenburg and McMurry, 1986). Simultaneous ...
Atmospheric environment, 1987
The theory for penetration of'sticky'gaseous molecules through cylindrical tubcsin faminar flow i... more The theory for penetration of'sticky'gaseous molecules through cylindrical tubcsin faminar flow is prcrented and implications of the theory for measurements of mass accommodation coefficients are discussed. For thecase wlmre the inner tube waffs are coated with a liquid, a criterion is developed which can be used to determine whether reuvaporation is likely to contribute significantly to measured penetration values. This criterion can be useful in designing experiments. It is concluded that faminar flow penetration rn~u~~ts can be useful for measuring very smaff mass accommodation coefficients (< IO-'). The theory can also be used to design diiTusion denuders when accommodation coeflicients are known.
Journal of Geophysical Research, 2005
During the Atlanta ANARChE Study of July and August 2002, atmospheric aerosol size distributions ... more During the Atlanta ANARChE Study of July and August 2002, atmospheric aerosol size distributions from 3 to 2000 nm were measured continuously with 5-min resolution. Sulfuric acid vapor concentrations were also measured. During regional nucleation events these data showed the presence of a nucleation mode that grew at rates ranging from 3 to 20 nm h À1. In this paper we compare these measured modal growth rates with calculated rates that account for sulfuric acid condensation, intramodal coagulation of nucleation mode particles, and extramodal coagulation of nucleation mode particles with preexisting particles. Data collected during six time intervals were amenable to analysis. Calculated and measured growth rates were in reasonable agreement for the four events that involved growth below 40 nm (ratios of measured to calculated growth rates = 1.0, 2.1, 0.68, 0.60). Two of the three afternoon events involved growth above 40 nm, and in these cases, measured rates substantially exceeded calculated rates by factors of four to five, suggesting that our model did not account for all growth processes. We also compared observed rates of change in nucleation mode number concentration with calculated coagulation rates during these six time intervals. During the sub-40 nm growth events, particle concentrations changed at rates that were significantly below calculated coagulation rates. In two of these cases, particle concentrations increased during the growth period, suggesting that a source of particles was present. Measured size distributions suggest that particle production by nucleation continued during these events and contributed to this discrepancy. Concentrations during the super-40 nm events decreased at rates that exceeded calculated coagulation rates.
Aerosol Science and Technology, 1991
... An Ultrafine Aerosol Condensation Nucleus Counter Mark R. Stolzenburg a &amp;amp; Peter H... more ... An Ultrafine Aerosol Condensation Nucleus Counter Mark R. Stolzenburg a &amp;amp; Peter H. McMurry a a Particle Technology Laboratory, Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, MN, 55455 ... Counter ...
Atmospheric Environment, Dec 1, 2002
Corrigendum to ''On-road measurement of fine particle and nitrogen oxide emissions from light-and... more Corrigendum to ''On-road measurement of fine particle and nitrogen oxide emissions from light-and heavy-duty motor vehicles'' [Atmospheric Environment 33 (18) (1999)
Nanotechnology, Jun 26, 2006
Carbon nanofibres aerosolized by the agitation of as-produced commercial powder have been charact... more Carbon nanofibres aerosolized by the agitation of as-produced commercial powder have been characterized in situ by using the differential mobility analyser-aerosol particle mass analyser (DMA-APM) method to determine their structural properties such as the effective density and fractal dimension for toxicology study. The effective density of the aerosolized carbon nanofibres decreased from 1.2 to 0.4 g cm(-3) as the mobility diameters increased from 100 to 700 nm, indicating that the carbon nanofibres had open structures with an overall void that increased with increasing diameter, due to increased agglomeration of the nanofibres. This was confirmed by transmission electron microscopy (TEM) observation, showing that 100 nm mobility diameter nanofibres were predominantly single fibres, while doubly or triply attached fibres were seen at mobility diameters of 200 and 400 nm. Effective densities calculated using Cox&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s theory were in reasonable agreement with experimental values. The mass fractal dimension of the carbon nanofibres was found to be 2.38 over the size range measured and higher than that of single-walled carbon nanotubes (SWCNTs), suggesting that the carbon nanofibres have more compact structure than SWCNTs.
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Papers by Mark Stolzenburg