Aluminum-26 and Beryllium-10 in Greenland Ice

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Science  29 Dec 1967:
Vol. 158, Issue 3809, pp. 1690-1692
DOI: 10.1126/science.158.3809.1690


Activities of beryllium-10 and aluminum-26 dissolved in 200-year-old Greenland ice were found to be 18.4 (+ 8.4, - 4.8) x 10-6 and 3.2 ± 0.9 x 10-7 disintegration per minute per liter, respectively. From these values and the precipitation rate (30 milliliters of water per square centimeter per year), the production rates of these isotopes are calculated to be 3.6 (+ 1.6, - 0.9) x 10-2 and 1.7 ± 0.5 x 10-4 atom per second * square centimeter. These rates agree with the rates calculated for the production of these isotopes by cosmic rays in the atmosphere. Probably all the Al26 in the ice is accounted for by such atmospheric production; however, an upper limit for the influx of cosmic dust bearing aluminum-26 is calculated at 3.2 x 105 tons per year for Earth. Only upper limits could be found for Al26 and Be10 in the undissolved particulate matter in the ice; their addition to the activities in the dissolved material leaves our conclusions unchanged.