A comparative experimental study of gross alpha methods in natural waters
2013
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 (
238
U,
235
U, and
234
U), radium (
226
Ra and
224
Ra),
210
Po, and
232
Th 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
fi
nd out if there was signi
fi
cant variability among the methods. For the
samples with the most common radiochemical characteristics there were no signi
fi
cant differences
among the three studied methods. However differences were detected for samples with a high saline
content or with a very low activity level.
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