10Be

Beryllium-10 (¹⁰Be) is a radioactive isotope of beryllium. It is formed mainly by the cosmic ray spallation of oxygen. Beryllium-10 has a half-life of 1.39 × 10⁶ years, · and decays by beta decay to stable boron-10 with a maximum energy of 556.2 keV. It decays through the reaction ¹⁰Be→¹⁰B+e. Light elements in the atmosphere react with high energy galactic cosmic ray particles. The spallation of the reaction products is the source of ¹⁰Be (t, u particles like n or p):

Because beryllium tends to exist in solutions below about pH 5.5 (and rainwater above many industrialized areas can have a pH less than 5), it will dissolve and be transported to the Earth's surface via rainwater. As the precipitation quickly becomes more alkaline, beryllium drops out of solution. Cosmogenic ¹⁰Be thereby accumulates at the soil surface, where its relatively long half-life (1.387 million years) permits a long residence time before decaying to ¹⁰B.

¹⁰Be and its daughter product have been used to examine soil erosion, soil formation from regolith, the development of lateritic soils and the age of ice cores It is also formed in nuclear explosions by a reaction of fast neutrons with ¹³C in the carbon dioxide in air, and is one of the historical indicators of past activity at nuclear test sites.

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