14C of grasses as an indicator of fossil fuel CO2 pollution

Measuring the amount of fossil fuel carbon stored in the vegetation is now crucial to understand the mechanisms ruling climate changes. In this respect, highly polluted areas such as major towns represent "natural" laboratories because fossil fuel CO2 (C-14-free) is isotopically distinct from mean atmospheric CO2 (C-14-labeled). Here, a C-14 study of urban grasses near a major highway in Paris, France, shows that plants store up to 13% of fossil fuel carbon. The C-14 composition of urban grasses is thus a novel parameter to assess the fossil fuel CO2 pollution.