Chemical Properties and Geochemical Significance of Humic Acids and Kerogens in the Sediments from the Gannan Marsh
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摘要: 本文应用元素分析和红外光谱分析，研究了甘南沼泽沉积物２ｍ深度内胡敏酸和干酪根的化学性质及其地球化学信息。结果表明，胡敏酸显示了高碳低氢低氮和贫脂肪族物质，反映了陆地沼泽沉积环境的特征。随着剖面深度增加，元素组成和红外光谱特征均反映了胡敏酸的缩合度和芳构化度增高。根据胡敏酸和干酪根化学性质之间的关系，提出了干酪根是由胡敏酸转化而成的认识，这种转化经历了缩合和芳构化作用。Abstract: Studied samples were collected from the Gannan marsh,southern Gansu Provice,where the climate is cold and moist,and organism consists mainly of herbs,for example,kobresia Humilis and Festuca sp. Peat distribution is wide and the mean peat thickness is about 4 m in this region. Sedimentary medium is acidic with a pH value of 5-5. 4. We here have studied chemical properties and geochemical significance of humic acids and kerogens by analyses of element and infrared spectra. Results show as follows:(1)The humic acids in the Gannan marsh sediment contain higher carbon content and lower hydro-gen and nitrogen contents as compared with those isolated from marine sediments. In-frayed spectra of humic acids in the studied samples show aromatic一rich and aliphatic一poor characteristics relative to those isolated from marine sediments. Those above indicate the features of land一marsh sedimentary enviroment. (2) With increasing depth,H/C,N/C and O/C atomic ratios and the carbohydrate content of infrared spectra for humic acids decrease,and the aromatic content of infrared spectra for humic acids increases,which shows an increase of condensation and aromaticity of humic acids with burial depth.(3) In the plot of O/C vs H/C atomic ratios,hmic acids and kerogens fall on the very im-mature region of maturation pathway of Type Ⅲ kerogen,while kerogens fall toward higher maturation than the corresponding humic acids. Infrared spectra show that kero-gens have a lower carbohydrate content and higher aromatic content relative to humic acids. Those above indicate the transformation of humic acids to kerogens,which under-ges condensation and aromaticity reactions.
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Key words:
- marsh peat /
- humic acid /
- kerogen /
- elementary composition /
- infrared spec-trum
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