Comparison of different protocols for the leaching of Be-isotope signals from marine sediments

The cosmogenic radionuclide 10Be is a powerful proxy for past variations of the cosmic ray flux into Earth's atmosphere and it enables many applications such as reconstructions of solar activity, geomagnetic field intensity, erosion and denudation rates, as well as dating of different paleoarchives. This requires the analysis of seawater-derived 10Be/9Be in marine sediments, making a precise extraction of the reactive phases of the sediment while avoiding any dissolution of detrital material indispensable. We compared different published leaching protocols aimed to extract reactive Fe-Mn-oxyhydroxides from marine sediments. Specifically, we tested how the strength and duration of a given leaching protocol affects the obtained 10Be/9Be signature. From these experiments we find that a strong, commonly used, extraction solution easily attacks detrital material, while weaker extraction solutions can provide a better compromise between leaching efficiency and dissolution of detrital material. However, the unwanted extraction of detrital material doesn't only depend on the strength of the leaching solution but also on the leaching duration. Furthermore, we find that different leaching methods are unspecific with the respect to the leached mineral phase and that e.g., the effectiveness of leaching solely the carbonate phase depends on the carbonate content of the sample. This can be accounted for by applying a step-wise decarbonization according to the carbonate content of the samples.