Tracking fossil fuel CO₂ with corn

The distribution of fossil-fuel-produced CO₂ in the lower atmosphere may be reflected in the tissues of annual plants—corn in particular—a new study suggests. Fossil fuels contain no ¹⁴C, a trait that renders the CO₂ produced when we burn coal, oil, and gas distinguishable from other atmospheric CO₂ sources. Annual plants take in this CO₂ during their growth cycle. In areas with higher fossil-fuel-derived CO₂, carbon in the plant tissue contains relatively lower percentages of ¹⁴C. This allows scientists to monitor atmospheric composition over an entire season. With this in mind, James T. Randerson, of the University of California, Irvine, and colleagues measured levels of ¹⁴C in corn plants in dozens of farmers' fields throughout North America and found a clear pattern: The Rocky Mountains, where ¹⁴C levels were highest, act as a barrier to fossil fuel CO₂ migration across the U.S. Fossil fuel CO₂ levels were higher in California and on the East Coast, particularly in states such as Pennsylvania and West Virginia (Geophys. Res. Lett. 2007, 34, L02816).