A comparative experimental study of gross alpha methods in natural waters

Area of Science:

• Environmental Science
• Radiochemistry
• Analytical Chemistry

Background:

• Accurate measurement of gross alpha activity in natural waters is crucial for environmental monitoring.
• Existing methods like evaporation and co-precipitation have varying precision and potential biases.
• Liquid scintillation counting offers an alternative for total alpha activity determination.

Purpose of the Study:

• To compare the performance of evaporation, co-precipitation, and liquid scintillation counting for gross alpha activity.
• To assess the representativeness of these methods for total alpha activity concentration in natural waters.
• To identify potential significant differences in results based on water characteristics.

Main Methods:

• Analysis of eight natural water samples with diverse radioactive profiles.
• Assay of specific alpha emitters (U, Ra, Po, Th isotopes) using radiochemical separation and alpha spectrometry.
• Determination of gross alpha activity using evaporation, co-precipitation, and total evaporation by liquid scintillation counting.

Main Results:

• Precision was below 28% for evaporation, 18% for co-precipitation, and 10% for liquid scintillation counting (at >0.1 Bq/L).
• Bias was <40% for evaporation, <25% for co-precipitation, and <20% for liquid scintillation counting.
• Methods showed comparable results for most samples, but significant differences arose in high-salinity or very low-activity waters.

Conclusions:

• Liquid scintillation counting provides a precise and reliable method for total alpha activity determination in natural waters.
• Evaporation and co-precipitation methods are generally comparable to total alpha activity, with liquid scintillation counting being more precise.
• Method selection should consider water salinity and activity levels to ensure accurate gross alpha measurements.