Equilibrium factor measurement

The equilibrium factor measures the affinity of the adsorbent for a particular component relative to the same component in the fluid phase whereas the binary separation factor measures the relative preference of the adsorbent for two different competing adsorbates. If the equilibrium obeys the multicomponent Langmuir model ... 

The atomic temperature factor, or B factor, measures the dynamic disorder caused by the temperature-dependent vibration of the atom, as well as the static disorder resulting from subtle structural differences in different unit cells throughout the crystal. For a B factor of 15 A2, displacement of an atom from its equilibrium position is approximately 0.44 A, and it is as much as 0.87 A for a B factor of 60 A2. It is very important to inspect the B factors during any structural analysis a B factor of less than 30 A2 for a particular atom usually indicates confidence in its atomic position, but a B factor of higher than 60 A2 likely indicates that the atom is disordered. 

This inverse relationship between equilibrium factor and "unattached" fraction and their relationship to the resulting dose is important in considering how to most efficiently and effectively monitor for exposure. This inverse relationship suggests that it is sufficient to determine the radon concentration. However, it is not clear how precisely this relationship holds and if the dose models are sufficiently accurate to fully support the use of only radon measurements to estimate population exposure and dose. 

From the measured indoor Rn-222 concentration during the heating season, measurements of equilibrium factors and assessments of the seasonal variations, it is possible to assess population averaged indoor concentrations of Rn-222 progeny in Norwegian dwellings. 

Here we have only discussed the concentration of the radon gas. This is because the measurements have been made of this nuclide. However, the health effects are referred to the short-lived decay products. The equilibrium factor depends on the ventilation rate and the particle concentrations. 

Figure 1. Variations in the hourly mean alpha-energy concentration during an integrating radon gas measurement of three weeks The alpha-energy concentration calculated from the radon level (4860 Bq/m3) and the typical equilibrium factor (0.45) is also given.

An equilibrium factor of 0.35, derived from measurements made during the local surveys, has been assumed to typify conditions in UK dwellings. This value has been used to convert the average radon concentrations measured in the national survey to potential alpha-energy concentration of radon decay-products. On average, persons in the UK spend 75% of their time in their homes and 15% of their time elsewhere indoors (Brown, 1983). The occupancy factor of 0.75, together with an equilibrium factor of 0.35, results in an annual exposure of 1.3 10"5 J h m"3 (0.0037 Working Level Months,... 

The paper summerizes the experimental data on the equilibrium factor, F, the free fraction, fp, the attachment rate to the room air aerosol, X, the recoil factor,, and the plateout rates of the free, qf, and the attached, q3, radon daughters, determined in eight rooms of different houses. In each room several measurements were carried out at different times, with different aerosol sources (cigarette smoke, stove heating etc.) and under low (v<0.3 It1) and moderate (0.3[Pg.288]

The mean value of the equilibrium factor F measured in houses without aerosol sources was 0.3 t 0.1 and increased up to 0.3 by additional aerosol particles in the room air. The fraction of the free radon daughters had values between fp = 0.06-0.13 with a mean value near 0.1. Only additional aerosol sources led to a decrease of f - values below 0.05. 

The concentrations of radon (cj) and the free (c f, c2f ) and on aerosol attached (cja, cja, cja radon daughters vi/ere measured and with these data the equilibrium factor F and the free fraction of the radon daughters fp were calculated. The room parameters (e, v) and the parameters of radon daughter transport processes (X, qf, q3, ri) were evaluated by means of equations (3), (4), (8), (9), (10) and (11) using the measured data. 

Table lb. The equilibrium factor (F), the free fraction (fp), the attachment parameters (X,0,d), the plateout rates (qf, qa) and the recoil factor (r ), calculated from the measured data of Table la (lo i/ ventilation). 

The fraction of unattached daughters (fp), the equilibrium factor (F) and the activity median diameter (AMD) are plotted in Figure 6 for all the measurements. The AMD is derived from the aerosol measurements. These three parameters are important in the dosimetric models. At the top of Figure 6 the effective dose equivalent is plotted, computed with two models called the J-E (Jacobi-Eisfeld) and J-B (James-Birchall) models in the NEA-report (1983, table 2.9, linear interpolation between AMD=0.1 and 0.2 ym). The figure also shows the effective dose equivalent calculated from the equilibrium equivalent radon concentrations with the NEA dose conversion factor (NEA,1983, table 2.11). 

In Figure 8 the doses per unit radon concentration are plotted as a function of the measured ventilation rate. The NEA conversion factor for low and moderate ventilation (NEA,1983, table 2.10) is multiplied by the appropriate equilibrium factor. In the figure no influence of the ventilation rate on the doses is found. 

Figure 7. Effective dose equivalent per hour and per unit radon concentration (AJ-B, 7 J-E) as a function of the equilibrium factor. The full lines are calculated with the mean values of the 72 measurements (Xa -. 37/h, XVent . 41/h, P -. 53, A.M.D. —. 15 lJm) and changing attachment rates.

Equilibrium factors were estimated from simultaneous measurements of radon gas and daughters when available. A default equilibrium factor of 0.3 was used when simultaneous gas and daughter values were not available. The default equilibrium factor is based on reported data for Salt Lake City (EPA, 1974) and on data obtained in Edgemont, South Dakota (Jackson et al., 1985), for climatic conditions similar to those in Salt Lake City. 

Before standards for indoor exposure to radon can be formally established, work is necessary to determine whether remedies are feasible and what is likely to be involved. Meanwhile, the Royal Commission on Environmental Pollution (RCEP) in the UK has considered standards for indoor exposure to radon decay products (RCEP, 1984). For existing dwellings, the RCEP has recommended an action level of 25 mSv in a year and that priority should be given to devising effective remedial measures. An effective dose equivalent of 25 mSv per year is taken to correspond to an average radon concentration of about 900 Bq m 3 or an average radon decay-product concentration of about 120 mWL, with the assumption of an equilibrium factor of 0.5 and an occupancy factor of 0.83. 

Calculated from the rate of decomposition (Table XI.4) of /-butyl bromide and the equilibrium constant measured by G. B. Kistiakowsky and C. H. Stauffer, J. Am. Chem. Soc., 69, 165 (1937). Log A eq (mole/liter) = —18,000/4.5757 + 6.16. Values in parentheses are from the rate constants of K and S. The values for the frequency factor seem discordant with the value of the chloride. 

The apparatus used to determine separation factors for an adsorbed monolayer was similar to that used by Cunningham, Chapin, and Johnston 4,5) but was modified to minimize the dead space and ensure good thermal equilibrium between the feed gas and the adsorbent. The inner copper cylindrical chamber was filled with 67 grams of the same y-alumina used in the isosteric heat of adsorption experiments for the establishment of the distribution function. The y-alumina was, however, free of any paramagnetic material to permit ortho-para separation factor measurements. 

With chemical relaxation methods, the equilibrium of a reaction mixture is rapidly perturbed by some external factor such as pressure, temperature, or electric-field strength. Rate information can then be obtained by following the approach to a new equilibrium by measuring the relaxation time. The perturbation is small and thus the final equilibrium state is close to the initial equilibrium state. Because of this, all rate expressions are reduced to first-order equations regardless of reaction order or molecularity. Therefore, the rate equations are linearized, simplifying determination of complex reaction mechanisms (Bernasconi, 1986 Sparks, 1989),... 

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