The Basics: 14C and Fossil Fuels
Tracer for Emissions
Carbon-14 (or 14C) is also known as radiocarbon, because it is the only carbon isotope that is radioactive. It is perhaps most famous for its use in radiocarbon dating of archeological artifacts ranging from mummies to cave drawings, and it plays a crucial role in studying fossil fuel carbon dioxide emissions as well.
Fossil fuels are, well, fossils, and are millions of years old. Because of this, all of the radiocarbon initially present has decayed away, leaving no 14C in this ancient organic matter. All other atmospheric carbon dioxide comes from young sources–namely land-use changes (for example, cutting down a forest in order to create a farm) and exchange with the ocean and terrestrial biosphere. This makes 14C an ideal tracer of carbon dioxide coming from the combustion of fossil fuels. Scientists can use 14C measurements to determine how much 14CO2 has been diluted with 14C-free CO2 in air samples, and from this can calculate what proportion of the carbon dioxide in the sample comes from fossil fuels.
To learn more about 14C radioactivity and its half-life, visit Radioactive Decay.