In situ measurements of radon levels in water and soil and exhalation rate in areas of Malwa belt of Punjab (India)

RADON CONCENTRATION IN SOIL AND GROUNDWATER OF WEST COASTAL AREA, BANGLADESH

On-site radon concentration has been measured in soil gas and ground water using AlphaGUARD PQ2000 PRO (Saphymo, Germany) radon monitor at the west coastal area of Bangladesh. The measured radon concentration in ground water samples is in the range of 1.41 ± 0.29 to 3.2 ± 0.59 Bq/l with the mean value of 2.33 ± 0.50 Bq/l, which lies within the safe limit recommended by UNSCEAR (2008). The total annual effective dose estimated due to radon concentration in ground water ranges from 3.85 to 8.74 μSv/y with the mean value of 6.37 μSv/y, which is lower than the safe limit set by WHO (2004) and EU (1998). In soil samples, radon concentration has been measured at three different depths (0, 20 and 40 cm) in each location. The highest and the lowest concentrations are 4790 ± 51 and 10 ± 04 Bq/m3 at 40 and 0 cm (surface) depth, respectively, which lie within the natural background levels.

Distribution and correlation of radon and uranium and associated hydrogeochemical processes in alluvial aquifers of northwest India

The spatial and vertical distributions of radon and uranium are evaluated in relation to the hydrogeology, geomorphology, and hydrochemistry of southwest Punjab. Radon activity of the groundwater ranges from 580 to 3633 Bq/m³ (shallow groundwater 580 to 2438 Bq/m³ and deep groundwater 964 to 3633 Bq/m³), and uranium concentration varies from 24.4 to 253 μg/L (shallow groundwater 24.4 to 253 μg/L and deep groundwater 27.6 to 76.3 μg/L). Shallow groundwater shows higher U concentration compared with deeper ones, which can be attributed to the presence of dissolved oxygen (DO) and NO₃^- as oxidants and HCO₃^- as stabilizing agent in shallow zone. Unlike uranium, the radon activities were found to be similar in both shallow and deep groundwater. Rn_excess over secular equilibrium was used to confirm the possibility of additional sources of radon, such as secondary minerals present in the subsurface. Surface manifestations show significant influence on radon and uranium distributions in the shallow zone but not in deep zone due to limited hydraulic connectivity. Depth profiles and correlations of radon and uranium with trace elements and hydrochemical parameters indicate that groundwater exhibits different redox characteristics in shallow (younger and oxidizing) and deep zones (older and reducing). The present study provides critical information that can be helpful for planning sustainable groundwater development in this region and other similar regions without contaminating the relatively safer deep aquifers.