13C values of grasses as a novel indicator of pollution by fossil-fuel-derived greenhouse gas CO2 in urban areas
Résumé
A novel fossil-fuel pollution indicator based on the 13C/12C isotopic composition of plants has been designed. This bioindicator is a promising tool for future mapping of the sequestration of fossil-fuel CO2 into urban vegetation. Theoretically, plants growing in fossil-fuel CO2 contaminated areas such as major cities, industrial centers, and highway borders, should assimilate a mixture of global atmospheric CO2 of δ13C value of - 8.02‰ and of fossil-fuel CO2 of average δ13C value of 27.28‰. This isotopic difference should thus be recorded in plant carbon. Indeed, this study reveals that grasses growing near a major highway in Paris, France, have a strikingly depleted δ13C values averaging at -35.08‰, versus rural grasses that show an average δ13C value of 30.59‰. A simple mixing model was used to calculate the contributions of fossil-fuel derived CO2 to the plant tissue. Calculation based on contaminated and non-contaminated isotopic end-members shows that urban grasses assimilate up to 29.1% of fossil-fuel CO2 derived carbon in their tissues. The 13C isotopic composition of grasses thus represents a promising new tool for the study of the impact of fossil fuel CO2 in major cities.
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