Geo-spatial analysis of radon in spring and well water using kriging interpolation method

Radon activity concentration was measured in 101 springs and well water samples collected from Muzaffarabad city and its outskirts. Sixty springs and 41 well water samples were analyzed, using RAD7, an electronic radon detector manufactured by Durridge Company Inc., for the estimation of radon borne activities and their relevant effects. Results obtained show that for spring water, the water borne radon activity varied from 0.246 +/- 0.348 to 34.36 +/- 5.54 Bq L-1 with an average value of 10.16 +/- 2.42 Bq L-1. For well water, the water borne radon activity varied from 0.86 +/- 0.10 to 16.12 +/- 0.22 Bq L-1 with an average value of 4.21 +/- 0.13 Bq L-1. Concentration of radon borne activities were subsequently used for determination of inhalation and ingestion doses. The inhalation and ingestion doses for spring water samples varied from 0.0062 +/- 0.0087 to 0.865 +/- 0.14 mSv y(-1) and 0.052 +/- 0.073 to 7.22 +/- 1.16 mSv y(-1), respectively. The inhalation and ingestion doses for well water varied from 0.022 +/- 0.0025 to 0.41 +/- 0.0054 mSv y(-1) and 0.18 +/- 0.021 to 3.38 +/- 0.045 mSv y(-1), respectively. 33.33% of spring and 7.32% of well water samples were found with values above the recommendation levels of the United States Environmental Protection Agency (similar to 11.1 Bq L-1). As a single measurement cannot serve as a best estimate of the unsampled areas in the region, Kriging interpolation method, a geo-statistical method, was used to get an estimate of spatial distribution of water borne radon in the area of study. Kriging mapping shows that higher radon concentrations are found in areas with lithology consisting of sandstones, siltstones, shales and claystones.