Distribution of aliphatic ketones in Chinese soils: Potential environmental implications

Lipid extracts from 28 modern soils collected across different climate zones in China and Mongolia have been analyzed systematically using gas chromatography–mass spectrometry (GC–MS). These extracts contain C16–C22 n-alkan-2-ones with a predominance of even carbon number homologues and n-alkan-3-ones with exclusively odd carbon numbers. The predominance of n-alkan-2-ones is attributed to microbial reworking of soil organic matter in warm and wet southeast and southwest China. Lower molecular weight (LMW) n-alkan-3-ones (C15–C21), maximizing at C17 or C19, dominate in southeast and southwest China, while the higher molecular weight (HMW) n-alkan-3-ones (C23–C33) with a mode at C27 or C29 dominate in cold, arid northwest China and Mongolia. The n-alkan-2-ones and n-alkan-3-ones exhibit strong regional variations, in agreement with the spatial distribution of climate and vegetation. Their C15–21/C22–33 ratios and the carbon preference indices of the HMW (C23–C35) n-alkan-2-ones (CPI(H) KET) sensitively reflect the variation in soil ecosystem response.