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Radon is a radioactive gas and a leading cause of lung cancer among non-smokers. An indicator of the level of risk associated with radon inhalation is the Geogenic Radon Potential (GRP) - a function of the soil gas radon concentration and the soil air permeability. Data is scarce on the variation of soil gas radon and GRP across different geological formations in southwest Nigeria. This study was designed to measure and develop a generalized predictive model for soil gas radon concentration and hence GRP on different bedrocks in southwest Nigeria. Soil gas radon was measured with a RAD 7 radon detector in 150 sites randomly selected over 20 major bedrocks. Soil air permeability was derived from soil saturated hydraulic conductivity measured using a constant head permeameter on undisturbed soil samples from the same sites. The GRP was obtained using Neznal relation. A 2 × 8 x 1 Artificial Neural Network (ANN) configuration culminated in the generation of a tested and validated predictive model for soil gas radon in southwest Nigeria. For the 150 sites, the range of values for soil gas radon concentration was 0.28–47.59 kBqm−3 and a mean of 10.39 ± 12.59 kBqm−3; soils on granitic bedrocks had the highest mean soil gas radon concentration (16.89 kBqm−3) and highest mean GRP (13.71). Sediments had the highest mean soil air permeability of 39.84 × 10−12 m2. Using Neznal classification, 75.30% of the sites were of low radon hazard rating. The developed predictive ANN model had a Goodness-of-Prediction (G) of 73.53%, Average Validation Error (AVE) of 0.073, Mean Bias Error (MBE) of 0.42, and Root Mean Square Error (RMSE) of 4.62kBqm−3, respectively. The model, validated using standard procedure had G, MBE, AVE, and RMSE of 86.49%, 0.61, 0.17, and 1.65kBqm−3, respectively which is an indication of good model performance.

Groundwater samples taken from 20 villages of Fazilka district, Punjab, India were analysed for radon concentration using RAD7, which is an electronic radon detector. Radon concentration varies from (1.4±1.0)x10³Bq/m³ to (4.9±3.0)x10³Bq/m³, which is much below the safe limits proposed by US Environmental Protection Agency (US EPA) and UN Scientific Committee on the Effects of Atomic Radiation. The mean annual effective dose calculated for these samples was also found to be within the limits provided by WHO and EU council. These samples were also analysed for concentration of certain heavy elements like As, Pb, Zn, Cu, Hg, Ni and Cd using inductively coupled plasma atomic emission spectrometer. Out of these, concentrations of As and Pb were found to exceed the permissible limits suggested by US EPA. [ABSTRACT FROM AUTHOR]

The results of 222 Rn and 226 Ra activity measurements in drinkable water supplies of the Thu Duc region in Ho Chi Minh City, Vietnam, are presented in this paper. The measurements were performed using a RAD 7 radon detector manufactured by Durridge Company, Inc. Mean concentrations of 222 Rn and 226 Ra were found to be 0.11±0.01 Bq l −1 and 0.11±0.02 Bq l −1 in 14 drinking water samples. They are 0.12±0.01 Bq l −1 and 0.10±0.02 Bq l −1 in 15 tap water samples, respectively. The mean 222 Rn concentration of 1.40±0.03 Bq l −1 in the 20 groundwater samples of this study is also lower than the WHO advised level of 100 Bq l −1 . Fifty percent of groundwater samples analysed have 226 Ra levels in excess of the USEPA recommended maximum contaminant level of 0.185 Bq l −1 . The occurrence of elevated concentrations of 226 Ra in groundwater samples was explained by pH and alkaline conditions. [ABSTRACT FROM AUTHOR]