Radon in Himalayan springs: a geohydrological control

This paper presents the results of radon measurements in springs of the Him alayan region by using radon emanometry technique. The radon was measured i n different springs, draining from different geohydrological setups, and fr om stream water in order to find the geohydrological control over radon con centration in groundwater emanating in the form of spring. The radon values were found to vary from 0.4 Bq/l to 887 Bq/l, being observed lowest for a turbulent stream and highest for the spring. The radon values were recorded highest in the springs draining through gneiss, granite, mylonite, etc. Ra don concentrations have been related with four spring types viz. fracture-j oint related spring, fault-lineament related spring, fluvial related spring and colluvial related spring, showing geohydrological characteristics of t he rocks through which they are emanating. The high radon concentration in fracture-joint and fault-lineament spring is related to increased ratio of rock surface area to water volume and uranium mineralisation in the shear z ones present in the close vicinity of fault and thrust. The low concentrati on of radon in fluvial and colluvial springs is possibly because of high tr ansmissivity and turbulent flow within such deposits leading to natural de- emanation of gases.