1911
Georg von Hevesy conceived the idea of using radioactive tracers. This idea was
later applied to, among other things, medical diagnosis. A radioactive tracer
is a minute amount of a radioactive substance that's used to "tag" a chemical
as it moves through, for instance, a plant. The radioactive substance can be
traced as it moves through the plant, but it doesn't change the plant. Von
Hevesy first applied radioactive tracers to a biological problem in 1923 when
he traced lead absorbed by plants. In 1935, von Hevesy began using artificial
radioisotopes as tracers. He won the Nobel Prize in 1943 for his work with
radioactive tracers.
Radioactive tracers have been used for many purposes. For instance, doctors use
minute amounts of radioactive substances to diagnose the presence of tumors,
ulcers, or non-functioning organs. Biologists use tracers to follow the path of
nutrients through the food chain. Earth scientists use tracers to follow the
path of rainwater as it moves through the groundwater to lakes, rivers, and
reservoirs.
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