What does pMC mean, and how is this used in ASTM D6866 and CEN 15747?
The ratio between carbon 14 in a sample and the carbon 14 in a modern reference standard is reported as pMC or percent modern carbon. Through experiments, it is known that materials with 100% present-day carbon have a radiocarbon signature near 107.5 pMC; this value is set to be 100% renewable content. Materials that are from fossil sources, on the other hand, have 0 pMC and 0% renewable content. Materials with both fossil and present-day carbon will have pMC values greater than zero but lesser than 107.5. Biogenic carbon content, as reported in an ASTM D6866 or CEN 15747 results, is the ratio between a sample’s pMC value and 107.5 pMC.
