Measurements of water‐column 26Al/27Al ratios above 850 m depth in the Pacific yield values in the range 10−13–10−14, translating into 26Al concentrations of 20–200 atoms kg−1. The atomic ratio of 26Al/10Be in surface ocean is close to 1 × 10−4, at least an order lower than the atmospheric production ratio. Surface‐ocean particulate removal of Al is about 30 times more rapid than that of Be. The results of this first set of data on 26Al in seawater also suggest that the source of 26Al in the sea is dominated by spallation of Ar in the atmosphere (as opposed to eolian and cosmic‐dust inputs) and that the ratio 26Al/10Be in marine sediments can be potentially used to decipher past variations of oceanic particle flux, hence biologic productivity.
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