| Abstract
| - A novel fossil fuel pollution indicator based on the 13C/12Cisotopic composition of plants has been designed. Thisbioindicator is a promising tool for future mapping of thesequestration of fossil fuel CO2 into urban vegetation.Theoretically, plants growing in fossil-fuel-CO2-contaminatedareas, such as major cities, industrial centers, andhighway borders, should assimilate a mixture of globalatmospheric CO2 of δ13C value of −8.02‰ and of fossil fuelCO2 of average δ13C value of −27.28‰. This isotopicdifference should, thus, be recorded in plant carbon. Indeed,this study reveals that grasses growing near a majorhighway in Paris, France, have strikingly depleted δ13Cvalues, averaging at −35.08‰, versus rural grasses thatshow an average δ13C value of −30.59‰. A simple mixingmodel was used to calculate the contributions of fossil-fuel-derived CO2 to the plant tissue. Calculation based oncontaminated and noncontaminated isotopic end membersshows that urban grasses assimilate up to 29.1% of fossil-fuel-CO2-derived carbon in their tissues. The 13C isotopiccomposition of grasses thus represents a promising new toolfor the study of the impact of fossil fuel CO2 in majorcities.
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