Beryllium

Cosmogenic ¹⁰Be and ⁷Be isotopes are produced in the atmosphere, largely by cosmic-ray spallation of nitrogen and oxygen. Because of its relatively short half-life (⁷Be, half-life t_1/2=53 d, compared to that of ¹⁰Be, half-life t_1/2=1.39×10⁶ a, where the unit symbol “d” stands for day and “a” stands for year), measurements of cosmogenic ⁷Be, and especially the isotope-amount ratio n(⁷Be)/n(¹⁰Be), have been used to study rates of atmospheric circulation, mixing, formation of aerosols (fine solids or liquids suspended in a gas; e.g. smoke and mist are aerosols), and particle deposition [44]. Cosmogenic atmospheric beryllium isotopes (⁷Be and ¹⁰Be) are deposited on the Earth’s surface, where they accumulate in soils, sediments, and snow while decaying away. Measurements of cosmogenic beryllium isotopes in such deposits are used to explore rates of soil formation, erosion, sedimentation, and snow accumulation on time scales ranging from months (⁷Be) to millions of years (¹⁰Be) [45], [46]. The minerals in rocks at the Earth’s surface interact with cosmic rays and form substantial quantities of ¹⁰Be and ⁷Be, thus providing a tool to determine the ages of geologic processes. In some situations, it is possible to estimate “exposure ages” for rocks in eroding terrains [47], [48], [49]. By comparing measured ¹⁰Be concentrations with estimated rates of in situ cosmogenic ¹⁰Be production, the rate of rock erosion and formation of canyons and other geologic features can be determined (Fig. IUPAC.4.1). Anthropogenic ¹⁰Be was produced by nuclear bomb explosions largely through the reaction of fast neutrons (neutrons produced by nuclear fission having high kinetic energy) with ¹³C via the ¹³C (n, alpha) ¹⁰Be reaction in atmospheric CO₂. Although the quantity of ¹⁰Be produced in this way is small, its presence above natural background concentrations in some environmental samples can potentially provide information about bomb-related processes and contamination [50].