A comparative experimental study of gross alpha methods in natural waters

• Published in: Journal of environmental radioactivity 2013-04, Vol.118, p.1-8
• Main Authors: Montaña, M., Fons, J., Corbacho, J.A., Camacho, A., Zapata-García, D., Guillén, J., Serrano, I., Tent, J., Baeza, A., Llauradó, M., Vallés, I.
• Format: Article
• Language: English
• Subjects: Analysis methods; analysis of variance; Applied sciences; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Enginyeria química; evaporation; Evaporation and co-precipitation methods; Exact sciences and technology; Gross alpha activity; Indústria dels processos químics; isotopes; Lasers; Natural water pollution; Pollution; Pollution, environment geology; Productes químics; Química física; Radium; Radium - analysis; Scintillation Counting; spectroscopy; Spectrum Analysis; Total evaporation and measurement by liquid scintillation counting; uranium; Uranium - analysis; Water Pollutants, Radioactive - analysis; Water treatment and pollution; Àrees temàtiques de la UPC
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2012.10.009

The aim of the present work was to compare the results obtained with gross alpha methods such as evaporation, co-precipitation and total evaporation by liquid scintillation counting and to check whether these results are representative of the real total alpha activity concentration on the sample. The study was carried out on eight natural waters with very different radioactive characteristics. For all the samples uranium (238U, 235U, and 234U), radium (226Ra and 224Ra), 210Po, and 232Th isotopes were also assayed by using radiochemical separation and alpha spectrometry in order to determine the sum of the activities of these alpha emitters. Precision (expressed as relative standard deviation) was below 28% for evaporation and below 18% for co-precipitation. In the case of total by liquid scintillation counting it was below 10% for samples with Total Alpha activity above 0.1 Bq/L (this value is about three times the MDA). Furthermore, for most of the studied waters, the Total Alpha activity and the gross alpha activity determined by the three methods were comparable. The obtained bias by the evaporation, co-precipitation, and total evaporation by liquid scintillation counting methods was lower than 40%, 25% and 20%, respectively. The ANOVA test was applied to find out if there was significant variability among the methods. For the samples with the most common radiochemical characteristics there were no significant differences among the three studied methods. However differences were detected for samples with a high saline content or with a very low activity level. ► Three methods analyzing gross alpha activity in natural waters are compared. ► Gross alpha activities do not differ from Total Alpha measured by α spectrometry. ► The elapsed time between sample preparation and measurement was studied.