The influence of coal mining on radon potential

Pit waters from hard-coal and brown-coal mining, as well as sediments and soils along sewers and rivers in the vicinity of collieries, are investigated in the scope of radiation protection. The greatest amount of Ra is discharged by hard-coal collieries in the order of several tons of Bq l(-1) in presence of high mineralised brines. In contact with sulphate bearing surface water, Ra co-precipitates with Ba and is deposited as radiobarite. The contamination with Ra lead to high activity concentrations (up to 32 000 Bq kg(-1)) and increased gamma dose rates (6 000 nSv h(-1)). The special situation of diadochic incorporation of Ra into the dense crystal lattice prevents Rn from emanation. However in sediments influenced by brown-coal mining Ra is adsorbed at the surfaces of ferric hydroxides and therefore, Rn can emanate easily.