Evidence for a geochemical origin of the mysterious circles in the Pro-Namib desert

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• 作者：Y. Naudé ; ^a ; ^{yvette.naude@up.ac.za} ; M.W. van Rooyen^b ; ^{gretel.vanrooyen@up.ac.za} ; E.R. Rohwer^a ; ^{egmont.rohwer@up.ac.za}
• 关键词：Fairy circle ; Hydrocarbon microseepage ; Mima mound (heuweltjies) ; Polydimethylsiloxane sorptive extraction ; Termites ; Vegetation stress
• 刊名：Journal of Arid Environments
• 出版年：2011
• 出版时间：May 2011
• 年：2011
• 卷：75
• 期：5
• 页码：446-456
• 全文大小：1069 K

文摘

The origin of the so-called “fairy circles” has not yet been established. Carbon monoxide (as an indicator of a natural gas microseep) was monitored inside and outside of the selected fairy circles in the Namib, Namibia, Southern Africa. Hydrocarbons were extracted from the soil by a novel method for trapping analytes onto silicone rubber designed for thermal desorption into a gas chromatograph–mass spectrometer (GC–MS). Unresolved complex mixtures with resolvable alkanes were detected in soil collected from two newly formed circles. Alkenes, the microbial degradation product of alkanes (microbial food source), were more abundant in the circles compared to the levels of alkenes detected in the matrix between circles. Results show a microseepage of gases and hydrocarbons which is expressed at the surface as a geobotanical anomaly of barren circles and circles of altered vegetation. In addition, this finding may suggest a new approach to the origin of the mima mounds (heuweltjies) of the Western Cape in South Africa.