Macrocyclic alkanes in modern soils of China

Macrocyclic alkanes and their methylated analogues have been detected for the first time in modern soils of China deposited under conditions of continuous climate change from tropical to arid temperate. Homologous series (ranging from C18 to C22) and their methylated derivatives (from C19 to C23) were detected using single ion monitoring (SIM) GC–MS after pre-treatment [Soxhlet extraction, silica gel and alumina (4:1) chromatographic separation]. The series of macrocyclic alkanes exhibits an even carbon number predominance, while the methylated analogues show an odd carbon number predominance. We calculated the proportions of the C18/C20/C22 components for the macrocyclic alkanes and those of the C19/C21/C23 components for the methylated macrocyclic alkanes. Based on the distribution characteristics of these biomarkers, we suggest that they record information related to climate change.