Radioactive tracers in hydrologic studies

Abstract

The use of radioactive tracers to study phenomena in hydrology that have not previously been easily amenable to investigation is proceeding at a rapid pace. A group of experiments was carried out in lakes and reservoirs in Massachusetts to determine eddy diffusion coefficients. The average eddy diffusion coefficient divided by the radius of the eddy was found to be 0.09 ft/sec. A group of experiments to determine the average velocity of streams and the dilution in streams by use of radioactive tracers was then performed. The diffusion coefficients found in the test of the streams were compared with the theoretical diffusion coefficients of G. I. Taylor for straight pipes and found to be larger due to the increased dispersion caused by bends and obstructions in the stream. A mathematical formulation for general use in determining dilution and dispersion in rivers and streams by radioactive tracers was established. A correction is made for the absorption and decay of the isotope depending upon its chemical and nuclear properties. Work is under way at Harvard University to delineate further the absorption coefficients of important isotopes under various conditions leading to a better determination of the eddy diffusion coefficient.

Uptake and transport of radionuclides by stream sediments

“…Very few experiments directly applicable to turbulent diffusion of material from sources in alluvial open channels are available. Those of Taylor (1954), Orlob (1958), Parker (1958), and Harleman and others (1959) seem the most applicable. There are, however, some excellent papers in the literature on the use of radioisotopes for beach-and harbor-drift studies.…”

“…However, the situation of a channel containing both sediment and biota is the most common one in nature. Parker (1958) is one of the few to attempt an analytical expression for concentration including sediment and biota. He multiplied the expression for the concentration distribution derived from so-called Fickian theory for a simple geometry by e~Nt where e is the base of Naperian logarithms, N is a "river-uptake coefficient" and t is the time.…”

“…AllParker (1958) reported on several field experiments on pipelines, reservoirs and open channels. These experiments do not adequately elucidate turbulent diffusion in open channels.…”

Stream dispersion at selected sites

“…Also the dispersion pattern with respect to x is normally distributed with a mean of x=Vt, and a standard deviation of ax = ^/2Kt. Note that the solution predicts the pattern of dispersion for a given value of K. K must be evaluated independently from theory or by experiments that yield a normal dispersion pattern: The theoretical evaluation of K has been attempted by Taylor (1954) for pipe flow and by Elder (1959), Parker (1958), and I. E. Thomas (written commun., 1958) for open-channel flow.…”

Physical hydrology

“…Although a few earlier papers exist (e.g. Hours, 1955;Moser et al, 1957;Bolin, 1958;Parker, 1958;Smith and Eakins, 1958) the advances in both nuclear physics and hydrological interpretation and application that have made these developments possible essentially date from the early 1960s. For example, one can highlight the Tokyo Symposium referred to above and the appearance of the first publication of the International Atomic Energy Agency (IAEA) in this field in 1962 (IAEA, 1962).…”