The global beryllium 10 cycle

Abstract

The cosmogenic radionuclide •øBe has generated much interest because of its potential as a tracer in the environment and applications to geology, archaeology, glaciology, and oceanography. Nevertheless, for •øBe to be useful as a tool in the Earth sciences its geochemical cycle as outlined below needs to be understood more fully. Beryllium 10 (t•a = 1.5 x 106 years) is mainly produced in the atmosphere by spallation of oxygen and nitrogen induced by secondary neutrons formed by cosmic ray interactions with the atmosphere, but some is produced in situ on the surface of the Earth. Deposition of •øBe onto the surface of the Earth depends primarily on precipitation. Deposited •øBe is made up of several components, primarily •øBe •r•oduced in the stratosphere and in the troposphere and "Be recycled from dust and soil particles, and secondarily •øBe recycled from the ocean as hygroscopic nuclei and from cosmic dust. Even though paleoprecipitation dominated •øBe deposition at any one location in the past, cosmic ray flux and m•ajor changes in the Earth's magnetic field also influenced •øBe deposition. The •øBe deposited on land will either be fixed in soils or be carried away in overland flow through the fluvial system, or locked in ice. Most of the beryllium is transported in the sediment load and that which stays in solution shows a strong pH dependence and is highly mobile in organic-rich continental waters. Beryllium 10 from sediments and fiver water is quickly deposited in the nearshore sediment along the coastlines along with a small amount of •øBe that is released and dispersed to the deep sea. In the open sea, most of the beryllium is in solution and the rest resides on particulate matter, much of which is of biogenic origin. Beryllium 10 that is added to the sea may be scavenged by such particles, but as they settle out into deeper waters the organic matter may oxidize and calcareous organisms may slowly dissolve, releasing •øBe back into solution, though fecal pellets may carry much of the •øBe to the seafloor. Slow-growing manganese nodules absorb some •øBe directly from the surrounding water, but pelagic and slope sediments act as the ultimate sinks for •øBe as the residence time for •øBe in the sediments approaches that of the mean life of •øBe, 2.18 x 106 years. Nevertheless, a small portion of •øBe is subducted or accreted at the world's trenches, and it has been used as a tracer for the study of island-arc volcanism. Recently, the cosmogenic radionuclide •øBe has generated much interest because of its potential as a tracer in the environment and applications to geology, archaeology, glaciology, and oceanography. For the past several years, •øBe research has been conducted on relatively concentrated •øBe in meteorites, deep-sea sediments, manganese deposits, and soils. Current research on the production of •øBe within terrestrial matter requires added sensitivity from AMS techniques. The potential for Quaternary research may be substantial, but for •øBe to be used as a tool in the Earth sciences its geoch...

The effects of changing solar activity on climate: contributions from palaeoclimatological studies

“…Beryllium-10 is a cosmogenic radionuclide that is produced in the upper atmosphere as a result of the interaction of galactic cosmic rays with nitrogen and oxygen (e.g. McHargue & Damon 1991). During periods of high solar activity (strong ''solar wind'') the intensity of cosmic rays that can reach Earth's upper atmosphere is lower and the amount of 10 Be that is produced is lower.…”

Seasonality of ⁷Be concentrations in Europe and influence of tropopause height

“…The residence time of 7 Be in the stratosphere is typically of the order of a couple of years (e.g. McHargue and Damon, 1991). Once produced,7 Be is rapidly adsorbed onto fine aerosol particles in the stratosphere and further transported to the troposphere.…”

Estimating Solar Forcing of Climate Change during the Maunder Minimum

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