Radioactive isotopes of any element behave in the same way as non-radioactive isotopes as far as their chemical and biochemical behaviour are concerned. Radioactive isotopes can take part in any of the chemical and biochemical reactions just as ordinary isotopes of an element do.
However, the property of radio-isotopes to emit characteristic radiations labels them and makes them conspicuous wherever they are in the system. Radiations emitted by radio-isotopes can be detected by suitable instruments (such as a photographic plate or Geiger-Muller counter) which enable us not only to identify them but measure their concentration as well.
In general radioactive tracer techniques are used more commonly in biological research where movement of an element has to be traced through a series of biochemical reactions. The movement of carbon through photosynthetic pathway was elucidated by using radioactive tracer techniques only. In environmental studies radioactive tracer technique is used to study the movement and fate of various contaminants through different components of the environment.
It is very helpful in the study of the phenomenon of bioaccumulation and biomagnifications of pesticides and other toxic trace elements in an ecosystem. Pesticides labelled with radioactive carbon when introduced into a system can be traced and measured wherever they migrate in the environment. It is by using this technique only that pesticides sprayed in Florida were detected in Siberia and Arctic region.