The movement of radioactive sodium and ruthenium through a simulated aquifer

Abstract

The interaction of water solutions with the particulate matter composing a natural aquifer is of steadily increasing interest with the new emphasis on pollution of our natural resources. As a means of studying the contribution made by water to the transport of ionic materials through soils, radioactive solutions were injected into a model aquifer containing 725 kilograms of sand with dimensions of 1 × 2 × 0.25 meters. As the radioactivity passed through the sand, its progress was followed by a collimated Geiger‐Müller tube situated on the exterior of the bed. The appearance of the radioactivity in the effluent, which marked the arrival of the sodium front, was found to be correlated with an increase in suspended particulate matter, potassium and calcium concentrations, and over‐all conductivity. Of particular significance was that portion of the radioactivity shown to be related directly to the filterable mass of particles in the effluent, despite the high solubility of the ion used. The results with the sodium were compared with those of similar tests on the movement of trivalent ruthenium, which is not soluble at the pH of the solutions used. Both the sodium and ruthenium studies indicated that a significant amount of radioactivity was transported through the test bed on particulate matter which was large enough to be trapped on 0.45 micron membrane filters.