ECOScience du 18 décembre 2025

Abstract: Geochemists have observed the occurrence of free and bound organics compounds in complex samples, yet their significance has been limited due to the lack of criteria to clearly distinguish free and bound homologues. Here I show that free and bound n-alkanes in soils can be isotopically distinguished in a 23-years experiment of 13C-labelling by maize cultivation. 13C-dating allows to calculate the relative age of five temporal pools of the C31 n-alkane in the same soil sample. These molecular clocks are the basis of a new discipline, single sample molecular chronology, that could be developed in all disciplines of physical, biological, and environmental sciences manipulating complex media, to study the history of individual compounds.