Plot showing variations in solar activity, including variation in 10Be concentration which varies inversely with solar activity. (Note that the beryllium scale is inverted, so increases on this scale indicate lower beryllium-10 levels).
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.
^G. Korschinek; A. Bergmaier; T. Faestermann; U. C. Gerstmann (2010). "A new value for the half-life of 10Be by Heavy-Ion Elastic Recoil Detection and liquid scintillation counting". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 268 (2): 187-191. Bibcode:2010NIMPB.268..187K. doi:10.1016/j.nimb.2009.09.020.