Earl O. Knutson

Total Deposition of Ultrafine Hydrophobic and Hygroscopic Aerosols in the Human Respiratory System

The deposition of ultrafine particles in the human respiratory system was studied under a variety of steady breathing conditions. The monodisperse aerosols tested were hydrophobic kerosene heater, aluminosilicate, and hygroscopic NaCl in the size range of 0.03 to 0.4 μm in diameter. The results for all aerosols show that particle deposition increases with an increase in tidal volume, but with a decrease in breathing frequency. Also, deposition during breath holding increases nearly exponentially with an increase in time. However, particle deposition as a function of particle size is different between hydrophobic and hygroscopic aerosols in the size range tested. The hydrophobic aerosols increase with a decrease in particle size, while hygroscopic aerosols show minimum value in the size range of 0.06 to 0.09 μm. The hydrophobic kerosene heater and aluminosilicate particle deposition confirms the recent theoretical calculations of Yeh and Schum (1980), Yu and Diu (1982), and Yu and Hu (1983). The NaCl parti...

History of diffusion batteries in aerosol measurements

The starting point for this account is 1900 when J. S. E. Townsend conceived the diffusion battery technique and demonstrated it by measuring the diffusion coefficient of ions in various gases. Application to aerosols, however, awaited developments in the fundamental physics of airborne particles. A key step was Einsteins derivation in 1905 of the equation relating the random displacement of airborne (or liquid-borne) particles to their mobility. Cunningham and Millikan found an accurate expression relating mobility to particle size. By 1914, R. A. Millikan and his colleague, H. Fletcher, had tested Einsteins theory by experiment with gas-borne particles and found that it was correct. Thus, aerosol particles could be expected to obey the same diffusion equations as gas-borne ions. In 1935 Nolan and Guerini described a parallel-plate diffusion battery and used it to measure the size of Aitkin particles. Two years later, Radushkevich used a cylindrical tube battery to measure the size of a laboratory aero...

Indoor Outdoor Aerosol Measurements for Two Residential Buildings in New Jersey

Indoor /outdoor aerosols were studied in two residential homes in New Jersey by making hourly measurements of the concentration and particle size for 2 week intervals in the wintertime. Indoor particle concentrations ranged from 104 to 107 cm−3 and were highly dependent on household activities, including cooking, cigarette smoking, and use of a fireplace and a kerosene space heater. Besides producing large amounts of particles, the kerosene space heater also produced concentrations of carbon dioxide, up to 3000 ppm, and carbon monoxide, up to 9 ppm. The ratio of indoor/outdoor aerosol concentrations varied from 0.2 to 41 (correlation coefficients < 0.3), consistent with the low air infiltration rate measured (0.3–0.5 air changes/h). The results indicate that indoor particles were mainly from indoor origins. In addition, radon progeny particle-size distributions were calculated by applying the attachment theory to the measured aerosol size distribution. This mode was found to range from 0.04 to 0.1 μm, a r...

Radon daughter plateout--I. Measurements.

Radon daughter plateout (surface deposition) was measured directly in 1.9 and 20-m3 chambers. To test the effect of different parameters on plateout, measurements were made over a wide range of particle concentrations and sizes. The results indicate that plateout is strongly dependent on particle concentration. The ratio of surface-deposited activity to total daughter activity in the chamber varied from 4% at particle concentrations greater than 10(5)/cm3 to 86% for particle concentrations less than 10(3)/cm3. Comparison for the experimental data with a theoretical model shows that the theory overestimates plateout and underestimates the airborne concentration by factors of about 3.5 and 3.3, respectively.

Indoor radon progeny aerosol size measurements in Urban, Suburban, and rural regions

By using direct and indirect methods, we conducted size distribution measurements of radon progeny particles in a variety of indoor environments in urban, suburban, and rural areas. The radon progeny particle size distribution owing to indoor activities has two definable source categories: (1) gas combustion from stoves and kerosene heaters–particles were found to be smaller than 0.1 μm in diameter, mostly in the range 0.02–0.08 μm; and (2) cigarette smoking and food frying—particles were found to be larger, in the size range 0.1–0.2 μm. The radon progeny particle size distribution, without significant indoor activities, such as cooking, was found to be larger in rural areas than in urban or suburban areas. The modal diameters of the size spectra in the rural areas were two to three times larger than those in urban or suburban areas, around 0.3–0.4 vs. 0.1–0.2 μm. Results obtained by applying the attachment theory to the measured number-weighted size spectra from an electrical aerosol size analyzer suppor...

Random and Systematic Errors in the Graded Screen Technique for Measuring the Diffusion Coefficient of Radon Decay Products

Measurement data for the diffusion coefficient of radon progeny from a 1985 experiment was reexamined to give an updated report on the results of the experiment, and to identify and quantify random and systematic errors in the measurement method. The measurement technique used in the 1985 experiment was an early version of a sampler subsequently named the graded screen array (GSA). In this reexamination, the baseline value of the diffusion coefficient of 218Po from repeated sampling with the GSA was found to be 0.0523 ± 0.0086 [1 standard deviation (SD)] cm2 s−1. The SD was found to be consistent with the propagated random errors associated with adjusting the sampling flow rate, combined with those due to small-number statistics in measuring radioactivity. It was not possible to determine the width of the distribution; narrow distributions fit the data just as well as wide ones. Corrections were made to avoid systematic errors due to inlet losses and recoil losses. The former was significant but the latte...

The Graded Screen Technique for Measuring the Diffusion Coefficient of Radon Decay Products

ABSTRACT The main focus of this paper is the graded screen array (GSA) sampler, a specialized diffusion battery developed modified at our Laboratory to measure the size distribution of unattached 218Po, a naturally occurring “atomic aerosol,” implicated in causing lung cancer. The GSA, as used in this study, consists of four stainless steel wire screens with increasing mesh count, each positioned on a circular mount. For sampling, the four mounted screens are stacked into a holder and air is drawn through them in the direction of increasing mesh count. A backup filter is placed behind the fourth screen. After sampling, the alpha radioactivity on each screen, and on the backup filter, is measured by standard methods. Size distributions are retrieved from these data using both the Nelder-Mead downhill simplex method and the expectation-maximization algorithm. To illustrate the usefulness of the GSA sampler, size distributions from 218Po samples taken from the radon chamber at Clarkson University, Potsdam, N...

Thoron versus Radon: Comparison of Measured Progeny Aerosol Size Distributions

A review of the literature showed that measurements of the comparative size of radon and thoron progeny have yielded mixed results. On the other hand, a theoretical analysis showed that differences might be expected in certain circumstances. Therefore, we reviewed our archived and recent measurements of radon progeny particle size to see if information on thoron progeny particle size can be extracted. The data reviewed include tests done in our 20 m3 radon test chamber and in three single-family houses in New Jersey. To determine if there were significant differences in the radon and thoron progeny particle size, a Monte Carlo error analysis was carried out on these test data. From these studies we conclude that the difference between radon and thoron progeny particle size is too small to be measured.

Application of the expectation-maximization algorithm to the processingof cascade impactor data: the method of lognormal components

Abstract If the expectation-maximization algorithm (E-M) is applied directly toextract particle size distributions from cascade impactor data, the resulting distributions are likely to reflect the jagged structure of the kernel functions.Therefore, the algorithm must be modified to incorporate a smoothing procedure or a smoothness constraint. One such method is described in this paper, and it replaces the discrete particle sizes used in E-M by a set of lognormal distributions. The method was applied to a Berner impactor data set from the literature with good results.

The scan time effect on the particle size distribution measurement in the scanning mobility particle sizer system

The scan time effect in the scanning mobility particle sizer was confirmed. The magnitude of this effect was shown in a typical situation. The cause of this scan time effect is the mixing process described by Russell et al. (1995). In that case, the result obtained at the longer scan time is the more accurate one.