engleski

Correlation between radon in water, radon in soil gas and indoor radon based on the extensive measurements in Croatia

Radon is known as the main source of radiation for the general public. Radon is a part of the uranium (238U) decay chain and is formed by radioactive decay of its parent radium nucleus (226Ra) inside various geological structures (both rock and soil minerals) in which radium is naturally present in various concentrations. Radon enters water most often by dissolving in groundwater that surrounds geological structures. And to a much lesser extent, radon can enter water by dissolving from the air. Clean and safe tap water for human consumption is one of the important goals of the EU according to the Horizon Europe – the next EU research and innovation programme 2021 – 2027. Results of extensive measurements of radon in water samples collected from private wells, natural springs and public water supply in Croatia are presented and annual effective doses are estimated. Since 2011 water samples were gathered during targeted indoor radon surveys (schools, kindergartens and homes) in 10 counties (out of 21) in Croatia. Radon activity concentrations in water were determined by two different methods: by using the emanometry method (AlphaGUARD instrument with additional AquaKIT module) and the liquid scintillation method (LSC TriCarb). A total of almost 1000 water samples gathered in the field gave the arithmetic mean of 5 Bq/l (with the measured minimum value below detection limit - around 1 Bq/l ; on the other hand, maximum measured value was 154 Bq/l). These concentrations result in average ingestion doses around 30 μSv for adults and 50 μSv for children. Correlation between radon concentration in water samples, indoor radon concentrations (measured by SSNTDs in a yearlong measurements) and calculated geogenic radon potential (based on the radon in soil gas measured by radon detector RM-2 and soil permeability measured by Radon-JOK instrument) in selected counties are examined. All of these measurements were performed in the investigated dwellings or in its immediate vicinity. The results of these correlations can serve as a starting point for more detailed investigations in defining radon priority areas in Croatia, in the future. By doing a statistical analysis of the data gathered in each county the Spearman correlation coefficients (nonparametric version of the Pearson correlation coefficient) are calculated in order to measure the degree of association between two variables based on their ranks. We wanted to analyse correlations between these measured variables: indoor radon, radon in soil gas, geogenic radon potential (GRP) and radon in water. In all of the cases a positive correlation is found with strong (rs = 0.6 - 0.8) or moderate (rs = 0.4 - 0.6) relationship between measured variables.

radon concentration in water ; indoor radon concentartions ; geogenic radon potential ; Spearman correlation coefficient

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