کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
7817031 1502245 2018 68 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Dissolved organic matter compositions in 0.6-3.4 km deep fracture waters, Kaapvaal Craton, South Africa
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
Dissolved organic matter compositions in 0.6-3.4 km deep fracture waters, Kaapvaal Craton, South Africa
چکیده انگلیسی
The composition of dissolved organic matter (DOM) in extremely deep groundwaters has rarely been investigated. Focusing on deep fracture waters in billion year old rocks in South Africa, we hypothesized the DOM would be predominantly derived from in situ microbial sources, consistent with H2-driven lithoautotrophic ecosystems previously documented in these fluids. We collected groundwater from 0.6 to 3.4 km depths via boreholes in mines, and characterized the DOM by a variety of analytical methods. Dissolved organic carbon concentrations ranged from 0.25 to 4.9 mg C/L. Low molecular weight organic acids (formate, acetate, lactate, propanoate) and amino acids (after hydrolysis) accounted for varying fractions of the total dissolved organic carbon. UV spectrophotometry, scanning fluorimetry, and nuclear magnetic resonance (NMR) spectra indicated lower concentrations of aromatic compounds than are commonly found in surface waters and shallow groundwaters. Molecular weights of aromatic compounds measured by size-exclusion chromatography were dominantly 500-1000 Da. Scanning fluorimetry revealed humic substances in two shallow (578 and 1300 m) samples; deeper samples showed peaks indicating aromatic amino acids. Intensive study of one sample from a previously sampled borehole in Beatrix mine resulted in large NMR peaks for aliphatics and carboxyls with lesser aromatics peaks; negative electrospray ion Fourier transform ion cyclotron resonance-mass spectrometry detected protein-, lipid-, and lignin-like compounds. These results are consistent with DOM in the form of microbial metabolites, and modified cell components (membrane lipids and proteins). These findings support previous geomicrobiological reports of chemolithoautotrophic microbial ecosystems functioning in isolation from photosynthetic primary production.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Organic Geochemistry - Volume 118, April 2018, Pages 116-131
نویسندگان
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