Environmental tritium (³H) and hydrochemical investigations to evaluate groundwater in Varahi and Markandeya river basins, Karnataka, India

The present study aimed at assessing the activity of natural radionuclides ((3)H) and hydrochemical parameters (viz., pH, EC, F(-), NO(3)(-), Cl(-), Ca(2+), Mg(2+)) in the groundwater used for domestic and irrigation purposes in the Varahi and Markandeya river basins to understand the levels of hydrochemical parameters in terms of the relative age(s) of the groundwater contained within the study area. The recorded environmental (3)H content in Varahi and Markandeya river basins varied from 1.95 ± 0.25T.U. to 11.35 ± 0.44T.U. and 1.49 ± 0.75T.U. to 9.17 ± 1.13T.U. respectively. Majority of the samples in Varahi (93.34%) and Markandeya (93.75%) river basins being pre-modern water with modern recharge, significantly influenced by precipitation and river inflowing/sea water intrusion. The EC-Tritium and Tritium-Fluoride plots confirmed the existence of higher total dissolved solids (SEC > 500 μS/cm) and high fluoride (MAC > 1.5 mg/L) in groundwater of Markandeya river basin, attributed to relatively longer residence time of groundwater interacting with rock formations and vice versa in case of Varahi river basin. The tritium-EC and tritium-chloride plots indicated shallow and deep circulating groundwater types in Markandeya river basin and only shallow circulating groundwater type in Varahi river basin. Increasing Mg relative to Ca with decreasing tritium indicated the influence of incongruent dissolution of a dolomite phase. The samples with high nitrate (MAC > 45 mg/L) are waters that are actually mixtures of fresh water (containing very high nitrate, possibly from agricultural fertilizers) and older 'unpolluted' waters (containing low nitrate levels), strongly influenced by surface source.

Influence of (231)Th in the activity determination of (234)Th by Cerenkov counting

A precise and simple method for the determination of (234)Th activity by Cerenkov counting is described. A calibrated natural uranium solution (having (234m)Pa and (238)U in secular equilibrium) in 0.1M HNO(3) is used to construct the calibration curve. Because (231)Th (a beta-emitting nuclide present in the decay chain of (235)U) contribution to Cerenkov counting is experimentally proved to be negligible only in the case of low enriched uranium samples, simple calculations are needed to accomplish the activity determination.

Radon-222 and related activities in surface waters of the English Lake District

Activities of radon-222 in selected surface waters of the English Lake District have been determined. Very wide variations were observed. The activity present in lakes and streams depends on the nature of the bedrock or sediment, the presence of faulting, the degree of turbulence, and the supply of fresh water from tributaries and ground waters. Radium-226 and uranium-238 activities were found to be comparable but in no case was it found that radon-222 is significantly supported by dissolved radium-226.