Determination of air-loop volume and radon partition coefficient for measuring radon in water sample.
Bottom Line:
In order to verify this approach, we measured the radon partition coefficient in deionized water in the temperature range of 10-30 °C and compared the values to those calculated from the well-known Weigel equation.The results were within 5 % variance throughout the temperature range.The results have shown good agreement between this method and the standard methods.
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PubMed Central - PubMed
Affiliation: Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources, 124 Gwahang-no, Yuseong-gu, Daejeon, 305-350 Korea.
ABSTRACT
A simple method for the direct determination of the air-loop volume in a RAD7 system as well as the radon partition coefficient was developed allowing for an accurate measurement of the radon activity in any type of water. The air-loop volume may be measured directly using an external radon source and an empty bottle with a precisely measured volume. The partition coefficient and activity of radon in the water sample may then be determined via the RAD7 using the determined air-loop volume. Activity ratios instead of absolute activities were used to measure the air-loop volume and the radon partition coefficient. In order to verify this approach, we measured the radon partition coefficient in deionized water in the temperature range of 10-30Â Â°C and compared the values to those calculated from the well-known Weigel equation. The results were within 5Â % variance throughout the temperature range. We also applied the approach for measurement of the radon partition coefficient in synthetic saline water (0-75Â ppt salinity) as well as tap water. The radon activity of the tap water sample was determined by this method as well as the standard RAD-H2O and BigBottle RAD-H2O. The results have shown good agreement between this method and the standard methods. No MeSH data available. |
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Mentions: The volume of the air loops (V1 and V2) and the radon activity in each air loop (C1 and C2) were obtained as described in the experimental section. Using these data, the radon k can be estimated by the following:3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{C}}_{1} ({\text{V}}_{1} - {\text{V}}_{\text{t}} ) = {\text{C}}_{\text{we}} {\text{V}}_{\text{w}} + {\text{C}}_{2} {\text{V}}_{\text{g}} $$\end{document}C1(V1âˆ’Vt)=CweVw+C2Vg4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{k}} = \frac{{{\text{C}}_{1} ({\text{V}}_{1} - {\text{V}}_{\text{t}} )}}{{{\text{C}}_{2} {\text{V}}_{\text{w}} }} - \frac{{{\text{V}}_{\text{g}} }}{{{\text{V}}_{\text{w}} }} $$\end{document}k=C1(V1âˆ’Vt)C2Vwâˆ’VgVwwhere C1 and C2 are the same as in Eq. (2), Cwe is the radon activity in water (originally radon free) at equilibrium, and Vg (V1Â +Â V2Â âˆ’Â VtÂ âˆ’Â Vw) and Vw are the total air and water volumes of the AÂ +Â B-loop, respectively. Using this approach, the radon k of deionized water, 3 saline water samples and a laboratory tap water was measured and the deionized water and tap water sample results were compared with Weigelâ€™s value (Fig.Â 4). The radon k in radon free deionized water showed good comparison to the values calculated by Weigel equation in the temperature range of 9â€“30Â Â°C. It was found that the radon k observed here was within the experimental uncertainty of those calculated from the Weigel equation. The radon k for pure water and in the 3 saline water samples were determined to be 0.258 (18.9Â Â°C), 0.237, 0.221 and 0.185 for 0.0, 19.5, 38.5 and 75.6Â â€°, respectively (Fig.Â 5). The radon k values obtained from this work were within the estimated uncertainty of those obtained from Schubert et al.â€™s experiment [12]. The radon k in the tap water was determined to be 0.238, about 6.7Â % different, but within the statistical error than predicted by the Weigel equation. The radon activity of the tap water (Cws) can be calculated by mass balance and the experimental data shown above as follows:5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{C}}_{\text{ws}} {\text{V}}_{\text{w}} = {\text{C}}_{\text{we}} {\text{V}}_{\text{w}} + {\text{C}}_{\text{g}} {\text{V}}_{\text{g}} = {\text{kC}}_{\text{g}} {\text{V}}_{\text{w}} + {\text{C}}_{\text{g}} {\text{V}}_{\text{g}} $$\end{document}CwsVw=CweVw+CgVg=kCgVw+CgVg6\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{C}}_{\text{ws}} = {\text{C}}_{\text{g}} \left( {{\text{k}} + \frac{{{\text{V}}_{\text{g}} }}{{{\text{V}}_{\text{w}} }}} \right) $$\end{document}Cws=Cg(k+VgVw)where, Cws and Cwe are the original and equilibration radon activity of the tap water, Cg is the radon activity in the air loops, Vw and Vg are the volumes of the water samples and the total air volumes of the AÂ +Â B-loop, respectively. The determination of the radon activity in the tap water by the RAD-H2O, BigBottle RAD-H2O and our method are shown in TableÂ 1. Our result is within 5Â % uncertainty with the others. As can be seen in the table, the radon k from the standard Weigel equation is 0.255 (19.8Â Â°C) while the radon k determined here is 0.238. Hence, the results from two conventional methods, applying the Weigel k value, could overestimate (6.7Â %) the true result because of the higher k. It may be that the tap water has some impurities that may have affected the partition coefficient.Fig.Â 4 |
View Article: PubMed Central - PubMed
Affiliation: Geologic Environment Division, Korea Institute of Geoscience and Mineral Resources, 124 Gwahang-no, Yuseong-gu, Daejeon, 305-350 Korea.
A simple method for the direct determination of the air-loop volume in a RAD7 system as well as the radon partition coefficient was developed allowing for an accurate measurement of the radon activity in any type of water. The air-loop volume may be measured directly using an external radon source and an empty bottle with a precisely measured volume. The partition coefficient and activity of radon in the water sample may then be determined via the RAD7 using the determined air-loop volume. Activity ratios instead of absolute activities were used to measure the air-loop volume and the radon partition coefficient. In order to verify this approach, we measured the radon partition coefficient in deionized water in the temperature range of 10-30Â Â°C and compared the values to those calculated from the well-known Weigel equation. The results were within 5Â % variance throughout the temperature range. We also applied the approach for measurement of the radon partition coefficient in synthetic saline water (0-75Â ppt salinity) as well as tap water. The radon activity of the tap water sample was determined by this method as well as the standard RAD-H2O and BigBottle RAD-H2O. The results have shown good agreement between this method and the standard methods.
No MeSH data available.