Hydropyrolysis as a new tool for radiocarbon pre-treatment and the quantification of black carbon

Abstract

The first results concerning the potential of hydrogen pyrolysis (hypy) as a new tool for the quantification and isolation of Black Carbon (BC) for radiocarbon analysis are reported. BC is a highly stable form of carbon, produced during pyrolysis of biomass to materials such as charcoal. Isolation and quantification of this component is therefore of great interest in radiocarbon measurement, particularly for more ancient samples, where contamination issues become more critical. Hypy has been demonstrated to reliably separate labile and refractory carbonaceous sample components for engineering and geological applications, but its potential in 14C geochronological investigation has previously been unexplored. Here, we test the hypy technique using a selection of soil standard samples and ancient charcoals from deposits of geological and archaeological significance. The results show that hypy can effectively and reproducibly isolate different carbon fractions within a variety of sample types and thus has the potential to provide a rapid and robust pre-treatment technique for radiocarbon analysis. Hypy has the additional advantage that the non-BC fraction removed from a sample can be quantitatively collected for subsequent further analysis. The technique represents a promising new approach not only for ensuring reliable decontamination of pyrogenic carbon samples prior to radiocarbon dating, but also for BC quantification in a variety of environmental matrices.