Environmental NMR Centre and Department of Chemistry, University of Toronto, Toronto, Ontario, Canada.
Environ Sci Technol. 2012 Apr 3;46(7):3753-61. doi: 10.1021/es203942y. Epub 2012 Mar 15.
Glaciers and ice sheets are the second largest freshwater reservoir in the global hydrologic cycle, and the onset of global climate warming has necessitated an assessment of their contributions to sea-level rise and the potential release of nutrients to nearby aquatic environments. In particular, the release of dissolved organic matter (DOM) from glacier melt could stimulate microbial activity in both glacial ecosystems and adjacent watersheds, but this would largely depend on the composition of the material released. Using fluorescence and (1)H NMR spectroscopy, we characterize DOM at its natural abundance in unaltered samples from a number of glaciers that differ in geographic location, thermal regime, and sample depth. Parallel factor analysis (PARAFAC) modeling of DOM fluorophores identifies components in the ice that are predominantly proteinaceous in character, while (1)H NMR spectroscopy reveals a mixture of small molecules that likely originate from native microbes. Spectrofluorescence also reveals a terrestrial contribution that was below the detection limits of NMR; however, (1)H nuclei from levoglucosan was identified in Arctic glacier ice samples. This study suggests that the bulk of the DOM from these glaciers is a mixture of biologically labile molecules derived from microbes.
冰川和冰原是全球水文循环中第二大淡水储库，随着全球气候变暖的出现，有必要评估它们对海平面上升的贡献以及向附近水生环境释放营养物质的潜力。特别是，冰川融化释放的溶解有机物质（DOM）可能会刺激冰川生态系统和邻近流域的微生物活动，但这在很大程度上取决于释放物质的组成。本研究使用荧光和（1）H NMR 光谱法，以天然丰度对来自地理位置、热状况和样本深度不同的多个冰川的未经改变的样本中的 DOM 进行了表征。DOM 荧光团的平行因子分析（PARAFAC）模型确定了冰中以蛋白质为主要特征的成分，而（1）H NMR 光谱揭示了可能源自原生微生物的小分子混合物。光谱荧光还揭示了一种在 NMR 检测限以下的陆源贡献；然而，在北极冰川冰样本中鉴定出了左旋葡聚糖的（1）H 核。本研究表明，这些冰川的 DOM 主要是由微生物衍生的生物可利用分子的混合物组成。
