Radioisotopes as tracers

Uses of radioisotopes as tracers to understand dynamic ecological processes. 

The use of the isotope effect to study rate-determining steps in a sequence of chemical reactions represents an additional advantage of radiotracer methodology. The term isotope effect (to be discussed more fully later) refers to the influence on a reaction rate of the difference in the masses of isotopes. This effect may create significant problems in the use of radioisotopes as tracers but can, nevertheless, be used to advantage in a limited number of cases in order to understand the kinetics of certain chemical reactions. 

Isotope enrichment is a major activity of the nuclear industry. The naturally occurring chemical elements are composed of isotopes with varying nuclear properties. By enriching the chemical element in the nuclide with the desirable nuclear property, the performance of the nuclear processes is enhanced. In addition, the sensitivity of isotopic analysis permits the use of enriched chemical elements in place of radioisotopes as tracers in research, medicine, and industry. 

Independent of budget considerations, the residence time of particles can be estimated by means of radioisotopes as tracers, which become attached to aerosol particles and are removed with them as they are scavenged by precipitation or undergo dry fallout. One of the earliest estimates of this kind was made by Stewart et al. (1956) from the decay of fission products following their dispersal in the northern hemisphere after the nuclear... 

Santschi PH and Honeyman BD (1991) Radioisotopes as tracers for the interactions between trace elements, colloids and particles in natural waters. In Vernet J-P (ed.) Trace Metals in the Environment 1. Heavy Metals in the Environment, pp. 229-246. Amsterdam Elsevier.. 

The profits from the teletherapy business financed an extensive research and development (R D) program that made CPD an international leader in the commercial applications of modern nuclear science by the 1950s. Its physicists and chemists developed many new applications for isotopes, and its engineers and trades people became extremely skilled in designing and building many types of related equipment. Out of this R D came dozens of applications of radioisotopes that benefited industry and medicine. It also led to two significant new businesses for CPD the use of cobalt-60 to sterilize products by irradiation, and the use of other radioisotopes as tracers that could be injected into the human body to help diagnose illnesses. 

There is no reference that summarizes all tracer techniques. Some information is available for inert tracers (34), for chemically reactive tracers (17), for tracers suitable for flow visualization (35) and for radioisotopes as tracers (36-38). In Chapter 2 of Wen and Fan (58) most of the reported tracer studies in chemical reaction engineering are summarized. This includes numerous studies in various reactors using the above described tracers and techniques. 

The increasing availability of radioactive isotopes and of the means of producing them has stimulated a rapid growth both in the number of analytical techniques based upon the use of radioisotopes as tracers and the use of nuclear reactions and accelerators for radioactivation. Radioanalytical methods which, at one time, were considered suitable only for specialized laboratories are now finding widespread routine use. 

Often the mechanism of a chemical reaction or the structure of a species can be inferred from experiments using radioisotopes as tracers. Consider the following experimental proof that the two S atoms in the thiosulfate ion, 8203 , are not equivalent. 

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