MOVEMENT OF MATERIALS IN THE HYPOLIMNION OF A LAKE AS STUDIED BY THE ADDITION OF RADIOACTIVE PHOSPHORUS

Abstract

Approximately 100 millicuries of radioactive phosphorus in the form of potassium dihydrogen phosphate were introduced into the hypolimnion of a small acid-bog lake by causing a bottle containing a solution of the material to burst about 3 meters below the thermocline and about 1 meter above the bottom. The depth of water at the point of introduction of the bottle was 6 meters. After bursting the bottle the distribution of the radioactive phosphate through the waters of the lake was followed by withdrawing and analyzing samples of water from different localities and from different depths. Samples of ooze from the bottom of the lake were also taken for measurement of their content of radioactive phosphorus. It was found that the radioactive phosphate moved through the hypolimnion in a lateral direction at a rate of some 3 meters per day. Although it moved laterally to the end of the lake (42 meters), the extent of its movement vertically appeared to be not greater than 2 or 3 meters, i.e., it scarcely penetrated the thermocline to a measurable extent. The radioactive phosphorus appeared early in the mud of the lake bottom, and its concentration there increased to such values as to suggest that a large part was removed by the mud, probably by a process of exchange of phosphate between mud and water.