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-C22n-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.