Introduction. Chapter 1 [The Environmental Behaviour of Polonium]

For many years, the IAEA has supported efforts to develop publications on the environmental behaviour and use of radionuclides in response to the needs of its Member States. Since ²¹⁰Po is the main contributor to internal doses due to ingestion of radionuclides from the uranium and thorium decay series, it was determined that a resource publication for polonium would be beneficial. Polonium-210 is an alpha emitting radionuclide with no radioactive progeny and produces only very-low-intensity gamma rays at very low abundance; thus, the dose largely arises from internal exposure. The main reasons for its radiological importance are its relatively high activity concentrations in certain foods and its relatively high ingestion dose coefficient. relatively high ingestion dose coefficient. There are seven polonium isotopes naturally present in the environment: 210Po, 214Po and 218Po of the uranium decay series; ²¹²Po and ²¹⁶Po of the thorium decay series; and ²¹¹Po and ²¹⁵Po of the actinium decay series. Polonium-210 has a half-life of approximately 138 days, which is long enough to play a significant role in many environmental processes. All of the other naturally occurring isotopes have half-lives of only 3 minutes or less. The isotopes ²¹⁴Po and ²¹⁸Po are short lived progeny of ²²²Rn, and are important in dose assessment. However, they are best examined in relation to the environmental behaviour of radon and other short lived radon progeny. Hence, the primary focus of this publication is the environmental behaviour of ²¹⁰Po.