Experimental Measurements of the Diffusion Coefficient of 212Pb

Su, Yin‐Fong; Newton, G.J.; Cheng, Yung‐Sung; Yeh, Hsu‐Chi

doi:10.1097/00004032-198903000-00005

Cited by 10 publications

(3 citation statements)

References 11 publications

(17 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The deposition efficiency increased with decreasing flow rate, indicating that diffusion is the dominant mechanism for deposition. The particle size of the radon daughters was not given, however it is believed to be within the range of 1-3 nm, with values for diffusion coefficients of between 0.06 and 0.006 cm2/s (Busigin et al, 1981;Su et al, 1989). More recently, we reported aerosol deposition in a human nasal cast using ultrafine particles ranging from 0.005-0.2 p m at constant inspiratory and expiratory flow rates between 4 and 50 L/min Yamada et al, 1988).…”

Section: Introductionmentioning

confidence: 99%

Deposition of Ultrafine Aerosols in a Human Oral Cast

Cheng

Yamada

Yeh

et al. 1990

Aerosol Science and Technology

View full text Add to dashboard Cite

--I'his paper reports experimental measurements of the total deposition of ultrafine aerosols in a human oral airway cast. A clear polyester resin cast of the upper airways of a normal human adult, including the nasal airways, oral cavity, tongue, nasopharynx, and larynx, was made from a postmortem solid cast. Measured pressure drop in the oral airway was slightly lower than in the nasal airway. The measured oral flow resistance was similar to the values reported for human volunteers breathing through the mouth at rest and for spontaneously opening of the month. Aerosol deposition data in the cast for monodisperse NaCl aerosols between 0.2 and 0.005 y m in diameter deposited in the cast were obtained for inspiratory and expiratory flow rates of 4, 20, and 40 L/min. Deposition efficiency increased with decreasing particle size and flow rate indicating that turbulent diffusion was the dominant mechanism for deposition. Higher deposition efficiency was ohsewed for inspiratory flow in the oral airway than for expiratory flow. Oral deposition and nasal deposition for inspiratory flow were similar, but oral deposition was lower for expiratory flow. Deposition efficiency can be expressed as a function of the flow rate and diffusion coefficient of the particle.

show abstract

Section: Introductionmentioning

confidence: 99%

Deposition of Ultrafine Aerosols in a Human Oral Cast

Cheng

Yamada

Yeh

et al. 1990

Aerosol Science and Technology

View full text Add to dashboard Cite

show abstract

“…The residence time in the chamber was controlled by the flow rate through the chamber. Another air stream (0.1 L min-') was delivered to the 2 2 8~h source to entrain the 2 2 0~n gas, which was generated from a 1.1 X lo7 Bq (0.3 mCi) dry 2 2 8~h source (Hursh and Lovaas 1967;Su et al 1989).…”

Section: Deposition Of Thoron Progenymentioning

confidence: 99%

Deposition of Ultrafine Aerosols and Thoron Progeny in Replicas of Nasal Airways of Young Children

Cheng¹,

Smith²,

Yeh³

et al. 1995

Aerosol Science and Technology

View full text Add to dashboard Cite

The deposition efficiencies of ultrafine aerosols and thoron progeny were measured in youth nasal replicas. Clear polyester-resin casts of the upper airways of 1.5-yr-old (Cast GI, 2.5-yr-old (Cast H), and 4-yr-old (Cast I) children were used. These casts were constructed from series of coronal magnetic resonance images of healthy children. The casts extended from the nostril tip to the junction of the nasopharynx and pharynx. These casts were similar in construction to those used in previous studies (Swift et al. 1992;Cheng et al. 1993). Total deposition was measured for monodisperse NaCl or Ag aerosols between 0.0046 and 0.20 p m in diameter a t inspiratory and expiratory flow rates of 3, 7, and 16 L min-' (covering a near-normal range of breathing rates for children of different ages). Deposition efficiency decreased with increasing particle size and flow rate, indicating that diffusion was the main deposition mechanism. Deposition efficiency also decreased with increasing age a t a given flow rate and particle size. At 16 L min -' , the inspiratory deposition efficiencies in Cast G were 33% and 6% for 0.008-and 0.03-pm particles, respectively. Nasal deposition of thoron progeny with a mean diameter of 0.0013 p m was substantially higher (80%-93%) than those of the ultrafine aerosol particles, but still had a similar flow dependence. Both the aerosol and thoron progeny data were used to establish a theoretical equation relating deposition efficiency to the diffusion coefficient (D in cm2 S-') and flow rate (Q in L min-') based on a turbulent diffusion process. Data from all casts can be expressed in a single equation previously developed from an adult nasal cast: E = 1exp( -~D'.'Q -0.'2s). We further demonstrated that the effect of age, including changes to nasal airway size and breathing flow rate, on nasal deposition can be expressed in the parameter "a" of the fitted equation. Based on this information and information on minute volumes for different age groups, we predicted nasal deposition in age groups ranging from 1.5-to 20-yr-old at resting breathing rates. Our results showed that the nasal deposition increases with decreasing age for a given particle size between 0.001 to 0.2 pm. This information will be useful in deriving future population-wide models of respiratory tract dosimetry.

show abstract

“…This gas stream was split into two legs; one leg (0.1 L min-') passed through a 1.11 x lo7 Bq (0.3 mCi) dry '28Th source (Hursh and Lovaas 1967;Su et al 1989) which would carry the ' "Rn gas. The ' "Rn gas was passed through a fiberglass filter to remove decay products.…”

Section: Experimental Apparatus and Proceduresmentioning

confidence: 99%

Neutralization of Thoron Progeny in Gases

Cheng¹,

Yu²,

Tung³

et al. 1994

Health Physics

Self Cite

View full text Add to dashboard Cite

This paper reports charge neutralization phenomena of 212Pb particles in nitrogen or oxygen atmospheres with trace amounts of other gases. Newly produced thoron or radon progeny are positively charged, stable molecular clusters that are subsequently neutralized by several mechanisms. The charged clusters have a smaller diffusion coefficient than neutral clusters of the same size due to the interaction of the charge with the surrounding gas molecules. In this study, we have found that the diffusion coefficients of 212Pb in O2, N2, NH3/O2, NH3/N2, and C6H12/N2 (IPs between 15.58 and 9.8 eV) ranged between 0.015 and 0.030 cm2 s-1. In the case of C6H12/O2, NO2/O2, NO/O2, and dimethylamine/O2 (ionization potential between 9.8 and 8.23 eV), the diffusion coefficients have increased to between 0.046 and 0.69 cm2 s-1. These results are consistent with previous results of 218Po, indicating that charged progeny are neutralized by electron transfer from a gas molecule with a lower ionization potential than lead oxide. We estimate the ionization potential of lead oxide to range between 9.8 and 10.2 eV. 212Pb was also neutralized by an electron scavenging mechanism in NO2/nitrogen.

show abstract

Experimental Measurements of the Diffusion Coefficient of 212Pb

Cited by 10 publications

References 11 publications

Deposition of Ultrafine Aerosols in a Human Oral Cast

Deposition of Ultrafine Aerosols in a Human Oral Cast

Deposition of Ultrafine Aerosols and Thoron Progeny in Replicas of Nasal Airways of Young Children

Neutralization of Thoron Progeny in Gases

Contact Info

Product

Resources

About