Centro de Astrobiología (CSIC-INTA), Madrid, Spain.
Centro de Astrobiología (CSIC-INTA), Madrid, Spain.
Sci Total Environ. 2021 Feb 10;755(Pt 2):142662. doi: 10.1016/j.scitotenv.2020.142662. Epub 2020 Oct 2.
Maritime Antarctica is a climate-sensitive region that has experienced a continuous increase of temperature over the last 50 years. This phenomenon accelerates glacier retreat and promotes the exposure of ice-covered surfaces, triggering physico-chemical alteration of the ground and subsequent soil formation. Here, we studied the biogeochemical composition and evolution extent of soil on three recently exposed peninsulas (Fildes, Barton and Potter) on Southwest (SW) King George Island (KGI). Nine soil samples were analyzed for their lipid biomarkers, stable isotope composition, bulk geochemistry and mineralogy. Their biomarkers profiles were compared to those of local fresh biomass of microbial mats (n = 3) and vegetation (1 moss, 1 grass, and 3 lichens) to assess their contribution to the soil organic matter (SOM). The molecular and isotopic distribution of lipids in the soil samples revealed contributions to the SOM dominated by biogenic sources, mostly vegetal (i.e. odd HMW n-alkanes distributions and generally depleted δC ratios). Microbial sources were also present to a lesser extent (i.e. even LMW n-alkanes and n-alkanoic acids, heptadecane, 1-alkenes, 9-octadecenoic acid, or iso/anteiso 15: 0 and 17:0 alkanoic acids). Additional contribution from petrogenic sources (bedrock erosion-derived hydrocarbons) was also considered although found to be minor. Results from mineralogy (relative abundance of plagioclases and virtual absence of clay minerals) and bulk geochemistry (low chemical weathering indexes) suggested little chemical alteration of the original geology. This together with the low content of total nitrogen and organic carbon, as well as moderate microbial activity in the soils, confirmed little edaphological development on the recently-exposed KGI surfaces. This study provides molecular and isotopic fingerprints of SOM composition in young Antarctic soils, and contributes to the understanding of soil formation and biogeochemistry in this unexplored region which is currently being affected by thermal destabilization.
南极洲海域是一个对气候敏感的地区，在过去的 50 年中，该地区的温度持续上升。这一现象加速了冰川退缩，促进了冰盖表面的暴露，引发了地面的物理化学变化，并随后形成了土壤。在这里，我们研究了西南乔治王岛（KGI）三个最近暴露的半岛（菲尔德斯、巴顿和波特）上土壤的生物地球化学组成和演化程度。分析了 9 个土壤样本的脂质生物标志物、稳定同位素组成、总体地球化学和矿物学。将它们的生物标志物图谱与当地新鲜微生物垫（n=3）和植被（1 种苔藓、1 种草和 3 种地衣）的生物标志物图谱进行了比较，以评估它们对土壤有机质（SOM）的贡献。土壤样本中脂质的分子和同位素分布表明，SOM 的主要来源是生物源，主要是植物源（即奇数高相对分子质量 n-烷烃分布和普遍贫化的 δC 比值）。微生物源的贡献也较小（即偶数低相对分子质量 n-烷烃和 n-烷酸、十七烷、1-烯烃、9-十八烯酸、或 iso/anteiso 15:0 和 17:0 烷酸）。尽管考虑了源自基岩侵蚀的烃类等生源物质的贡献，但这些贡献很小。矿物学（斜长石的相对丰度和虚拟不存在粘土矿物）和总体地球化学（低化学风化指数）的结果表明，原始地质的化学变化很小。这与土壤中总氮和有机碳含量低以及微生物活性适中的情况相结合，证实了 KGI 表面新暴露区域土壤的发育程度较低。本研究提供了南极年轻土壤有机质组成的分子和同位素指纹，有助于理解这一未开发地区的土壤形成和生物地球化学，该地区目前正受到热不稳定性的影响。
