Behaviour of radium discharged with waste waters into the surface settling pond

摘要

As a result of a discharge of radium-bearing waters from coal mines into settlement ponds and later into rivers a significant increase of radium concentration in bottom sediments can be observed. Sometimes there is also a contamination of river banks, soils and vegetation. Mine waters contain mainly two radium isotopes i.e. ~(226)Ra from uranium series and 228Ra from thorium series in chloride rich solution. Due to the chemical properties of such discharged brines, these waters contain usually no uranium, no thorium but occasionally elevated concentration of other radio-isotopes as ~(210)Pb and ~(210)Po. It is only after fixing by deposition or adsorption of radium isotopes that the built-up of the activity of their progeny begins. Therefore concentrations of radium isotopes are higher than the decay products. The paper describes results of investigation of waters and sediments with enhanced natural radioactivity, that occur in settling pond, where mine waters have been dumped. The results of measurements show that these deposits contain mainly ~(226)Ra and ~(228)Ra (in the form of sulphates) and radium progeny. The influence of bottom sediments with enhanced radium concentration on the natural environment in the vicinity of settlement ponds was also studied. The results show clearly enhanced radioactivity of pond bottom sediments and water in the settling ponds and in the river, into which the water drains, but no evident enhancement was found in the adjacent land. The investigated coal mine is located in the drainage area of the Vistula river, and river sediments with enhanced radium concentrations were found in the Vistula several kilometres downstream from the discharge point.