Beryllium-10 (
10Be) is a
radioactive isotope of
beryllium. It is formed in the Earth's atmosphere mainly by
cosmic ray spallation of nitrogen and oxygen.
Beryllium-10 has a
half-life of 1.39 × 10
6 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
Spallation is a process in which fragments of material (spall) are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection of material from a target during impact by a projectile. In planetary p ...
of the reaction products is the source of
10Be (t, u particles like n or p):
:
14N(t,5u)
10Be; Example:
14N(n,p α)
10Be
:
16O(t,7u)
10Be
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
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a base (chemistry), basic, ionic compound, ionic salt (chemistry), salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as ...
, 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
10 B.
10Be and its daughter product have been used to examine
soil erosion
Soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, and ...
,
soil formation from
regolith, the development of
lateritic soils
Laterite is both a soil and a rock type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by ...
and the age of
ice core
An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ic ...
s.
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.
10Be decay is a significant isotope used as a
proxy data measure for
cosmogenic nuclides to characterize solar and extra-solar attributes of the past from terrestrial samples.
See also
*
Surface exposure dating
References
{{Authority control
Isotopes of beryllium
Radionuclides used in radiometric dating