A New 13C Correction for Radiocarbon Samples from Elevated-CO2 Experiments

Abstract

Radiocarbon can be a valuable tracer of carbon cycling in elevated CO2 experiments. However, the standard method of calculating ∆14C, which corrects sample 14C activity for isotopic fractionation by correcting the sample delta-13C to -25‰, introduces significant errors to the reported 14C values. For elevated-CO2 treatments the error arises because the delta-13C of the sample is not an appropriate measure of isotopic fractionation to use when correcting sample 14C activity for isotopic fractionation. A suggested replacement approach, developed in this paper, is to use the delta-13C of the same type of material (e.g. Leaf, soil organic matter) from the control (ambient-CO2) treatment in place of the sample delta-13C in the correction.