Direct absorption method and liquid scintillation counting for radiocarbon measurements in organic carbon from sediments

Abstract

In this paper, we investigate a procedure for radiocarbon determination in forest soil and slurry from lake sediments. The total carbon in these samples can be both inorganic and organic. Inorganic carbon can be analyzed in a straightforward manner using the direct absorption method by sample acidification and CO2 capture. For organic carbon, we investigate a hybrid method using the wet-oxidation of organic carbon followed by direct absorption. To evaluate the wet-oxidation processes with potassium dichromate (K2Cr2O7) and potassium permanganate (KMnO4), we performed several experiments using different quantities of soil and sediments in order to establish the quantity of CO2 for each type of sample. The 2 methods offer comparable results for 14C-specific activity (about 0.234 ± 0.024 Bq/g C), values that are expected for these kinds of samples. We also investigated the possibility of isotopic fractionation occurring during CO2 production from raw material by measuring δ13C levels from samples and obtained CO2. © 2010 by the Arizona Board of Regents on behalf of the University of Arizona.