Lung Dose Estimates from Rn-222 in Arizona Groundwater Based on Liquid Scintillation Measurements
J. Matthew Barnett, Keith E. Holbert, Barry D. Stewart, Wayne K. Hood
Since August 1989, Rn-222 groundwater samples from across the state of Arizona have been collected and analyzed using liquid scintillation. Of the 253 specimens acquired, 65% have Rn-222 concentrations above 11 Bq/L (300 pCi/L), while 16% have Rn-222 activities over 37 Bq/L (1,000 pCi/L). The geometric mean Rn-222 concentration for all the wells tested is 13 Bq/L ×/÷ 4; the arithmetic mean is 37 ± 122 Bq/L. Using the geometric mean, it is estimated that an additional tracheobronchial lung dose equivalent of 0.19 mSv/yr ×/÷ 13.9 is delivered to Arizona residents from the well water to home pathway.
Health Physics, Vol. 68, No. 5, pp. 699-703, 1995.
Measurement of Radioactivity in Arizona Groundwater Using Improved Analytical Techniques for Samples with High Dissolved Solids
K. E. Holbert, B. D. Stewart, P. Eshraghi
Radiochemical analyses of 667 samples collected over the five-year period 1989 to 1993 indicate that approximately 2% of Arizona drinking water supplies from groundwater sources violate current regulatory standards. About 1% of the population is affected. The 1996 change in regulatory requirements will bring some Arizona water systems into compliance through Ra-226 limit relaxation, while others will become noncompliant due to new limits on uranium levels. Maximum concentrations in Arizona of adjusted gross alpha, gross beta, and Ra-226 activities are higher than levels found in a U.S. Environmental Protection Agency's national survey. Sampling results show a correlation between radionuclide concentration and localized geology. Improved radiochemical methods are described that result in greater accuracy and sensitivity for samples high in dissolved solids, as are typical in Arizona.
Health Physics, Vol. 68, No. 2, pp. 185-194, 1995.
Rn-222 in Arizona Groundwater: Lung Dose Estimates Based on Liquid Scintillation Characterization
J. M. Barnett, K. E. Holbert, B. D. Stewart, W. K. Hood
Since August 1989, Rn-222 groundwater samples from across the state of Arizona have been collected and analyzed using liquid scintillation. The goals of our research were to measure <3.7 Bq/L using liquid scintillation techniques, to assess Rn-222 in Arizona groundwater, and to estimate the additional dose to the tracheobronchial lung region due to Rn-222 liberated in homes vie the water pathway. Herein we detail the water collection method, analysis method, dose model, and results. Of the 367 specimens acquired, 65% have Rn-222 concentrations above 11 Bq/L (300 pCi/L), while 12% have Rn-222 activities over 37 Bq/L (1,000 pCi/L). The geometric mean Rn-222 concentration for all the wells tested is 18 Bq/L ×/÷ 2.55; the arithmetic mean is 31 ± 102 Bq/L. Using the geometric mean, it is estimated that an additional tracheobronchial lung dose equivalent of 0.26 mSv/yr ×/÷ 12.1 is delivered to Arizona residents from the well water to home pathway.
Proceedings from Advances in Liquid Scintillation Spectrometry, Glasgow, Scotland, August 1994.
Better Estimation of the Detection Efficiency for Total Radium in Drinking Water Samples
Keith E. Holbert, Barry D. Stewart
Radium measurements in drinking water are complicated by the buildup of daughter radionuclides. The EPA method of calculating the ingrowth factor (R) of radium daughter products does not account for the difference in self-absorption between the radium alpha emissions and the higher energy alpha emissions from the daughters. A relatively simple procedure is developed which compensates for the difference in detection efficiency. Rather than multiply the exponential buildup of daughters by a factor of three (3), a new fitted parameter H is introduced. Results have shown values of H that range from 3 to 5 for increasing precipitate masses from 7 to 100 mg, respectively. Utilization of this fitted parameter typically yields improvements of 5%, but can easily provide corrections of 20% or more, depending on the amount of ingrowth prior to the start of the count. The theoretical basis and procedure for determining H are presented.
Radioactivity & Radiochemistry, Vol. 4, No. 3, pp. 42-49, 1993.