Performance Evaluation of the Electrical Low-Pressure Impactor (Elpi)

Marjamäki, Marko; Keskinen, Jorma; Chen, Da Ren; Pui, David Y.H.

doi:10.1016/s0021-8502(99)00052-x

Cited by 343 publications

(257 citation statements)

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“…It should be noted that number distribution is not calculated from measured currents at any point, but instead a mathematical model of ELPI is used. The complete set of information required to construct the mathematical model of ELPI, can be found from Marjamäki et al (2000Marjamäki et al ( , 2005 and Virtanen et al (2001).…”

Section: Methods For Estimating Particle Densitymentioning

confidence: 99%

Winter and summer time size distributions and densities of traffic-related aerosol particles at a busy highway in Helsinki

et al. 2006

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Abstract. Number concentrations and size distributions of traffic related aerosol particles were measured at a roadside in Helsinki during two winter campaigns (10-26 February 2003, 28 January-12 February 2004 and two summer campaigns (12-27 August 2003, 6-20 August 2004. The measurements were performed simultaneously at distances of 9 m and 65 m from the highway. Total number concentrations were measured by a condensation particle counter (CPC) and particle size distributions by a scanning mobility particle sizer (SMPS) and an electrical low pressure impactor (ELPI). This study concentrates on data that were measured when the wind direction was from the road to the measurement site. The total concentrations in the wintertime were 2-3 times higher than in the summertime and the concentrations were dominated by nucleation mode particles. The particles smaller than 63 nm (aerodynamic diameter) constituted ∼90% of all particles in the wintertime and ∼80% of particles in the summer time. The particle total concentration increased with increasing traffic rate. The effect of traffic rate on particles smaller than 63 nm was stronger than on the larger particles. The particle distributions at the roadside consisted of two distinguishable modes. The geometric mean diameter (GMD) of nucleation mode (Mode 1) was 20.3 nm in summer and 18.9 nm in winter. The GMD of the larger mode consisting mostly of traffic related soot particles (Mode 2) was 72.0 nm in summer and 75.1 nm in winter. The GMD values of the modes did not depend on the traffic rate. The average particle density for each mode was determined by a parallel density fitting method based on the size distribution measurement made by ELPI and SMPS. The average density value for Mode 1 particles Correspondence to: A. Virtanen (annele.virtanen@tut.fi) was 1.0±0.13 g/cm 3 and 1.0±0.07 g/cm 3 both in summer and winter respectively, while the average density value for Mode 2 was 1.5±0.1 g/cm 3 and 1.8±0.3 g/cm 3 for summer and winter, respectively.

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Section: Methods For Estimating Particle Densitymentioning

confidence: 99%

Winter and summer time size distributions and densities of traffic-related aerosol particles at a busy highway in Helsinki

et al. 2006

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“…where a = Marjamäki et al (1999) have determined a somewhat different set of parameters a and b, which they found to be the same for NaCl and dioctyl sebacate aerosols. After charging, the aerosol proceeds through a thirteen stage Berner cascade impactor operating at 100 mTorr and a nominal ow rate of 10 std L/min, where particles are separated according to aerodynamic diameter.…”

Section: Elpimentioning

confidence: 99%

“…The impactors cover the size range of 37 nm to 10.5 l m, with D50% cut points of 37 nm, 63 nm, 119 nm, 187 nm, 283 nm, 433 nm, 698 nm, 1.08 l m, 1.75 l m, 2.67 l m, 4.33 l m, 6.94 l m, and 10.54 l m, respectively, for stages 1-13 (in the text, stages are referred to by their D50% cut points). Calibration of the impactor stage cutoff curves has been discussed by Marjamäki et al (1999). These authors also measure the efciency of the diode charger trap and nd it to be lower than speci ed by the manufacturer for particles larger than 2 l m in diameter; however, this is of little consequence for vehicle tailpipe PM.…”

Section: Elpimentioning

confidence: 99%

“…The bounce problem is expected to worsen towards the smaller particle stages owing to the increasing impactor jet velocities (Marjamäki et al 1999). This, too, is consistent with the observation in Figure 1 that the discrepancy between ELPI and SMPS measurements of the PSLs is greater (smaller PSL peak and higher small particle background) for the 240 nm PSLs as compared to the 503 nm size.…”

Section: Pslsmentioning

confidence: 99%

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Size Distributions of Motor Vehicle Exhaust PM: A Comparison Between ELPI and SMPS Measurements

Maricq¹,

Podsiadlik²,

Chase³

2000

Aerosol Science and Technology

176

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ABSTRACT. Particle size measurements using the electrical low pressure impactor (ELPI) and scanning mobility particle sizer (SMPS) are compared from the perspective of characterizing the particulate matter in motor vehicle exhaust. Both steady state vehicle operation and transient drive cycles are considered, and both gasoline and diesel fueled vehicle emissions are compared. Although the ELPI and SMPS measure different physical properties, respectively, the aerodynamic diameter and mobility diameter, the steady state particle size distributions are in close agreement, except for the 37 nm impactor stage of the ELPI which may overestimate particle number by up to a factor of two relative to the SMPS. This has little effect on the volume, or mass, weighted distribution. These, too, are generally in good agreement, though discrepancies appear at large particle size due to multiple charging effects in the SMPS and to electrometer offsets and the small particle loss correction in the ELPI. Selecting particles based on their electrical mobility with the SMPS, and then measuring their aerodynamic diameter with the ELPI, reveals that diesel particulate matter with well-speci ed mobility diameter exhibits a wide range in aerodynamic diameter and, therefore, also in effective density. Over transient drive cycles, the ELPI provides second by second particle distributions, whereas the SMPS must be run in a xed particle size mode and size distributions constructed from repeated tests. The ELPI registers higher instantaneous PM emission rates during transients than the SMPS due to the faster time responses of the ELPI. The time integrated ELPI and SMPS size distributions, however, remain in good agreement. The relative merits of the two instruments for steady state and transient tests are discussed.

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“…Here, they are positively charged to a defined level according to their mobility equivalent diameter (Moisio, 1999;Marjamäki et al, 2000):…”

mentioning

confidence: 99%

Determining the effective density of airborne nanoparticles using multiple charging correction in a tandem DMA/ELPI setup

et al. 2014

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Increasing numbers of workers are exposed to airborne nanoparticles, the health effects of which remain difficult to evaluate. Effective density is considered to be a key characteristic of airborne nanoparticles due to its role in particle deposition in the human respiratory tract and in the conversion of number distributions to mass distributions. Because effective density cannot be measured directly, in this study the electrical mobility and aerodynamic equivalent diameters of airborne nanoparticles were measured simultaneously (tandem DMA/ELPI). Test aerosols consisted of spherical Di-Ethyl-Hexyl-Sebacate nanoparticles produced by nebulization (PALAS AGK 2000). To take into account the presence of multiply-charged particles at the DMA outlet, a theoretical model was developed in which the successive mechanisms undergone by particles are accounted for. Using this model, it is possible to determine the proportion of each population exiting the DMA (p = 1, 2, …5 elementary charges) in each channel of the overall ELPI signal.Thus, particle effective density can be estimated for each population. The results indicate that using the ELPI signal alone could lead to significant misevaluation of particle effective density, with biases up to 150%. However, when the proportion of each population is taken into account, particle effective density is determined within 15% of the theoretical value.3

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Performance Evaluation of the Electrical Low-Pressure Impactor (Elpi)

Cited by 343 publications

References 0 publications

Winter and summer time size distributions and densities of traffic-related aerosol particles at a busy highway in Helsinki

Winter and summer time size distributions and densities of traffic-related aerosol particles at a busy highway in Helsinki

Size Distributions of Motor Vehicle Exhaust PM: A Comparison Between ELPI and SMPS Measurements

Determining the effective density of airborne nanoparticles using multiple charging correction in a tandem DMA/ELPI setup

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