Associations of allophanic constituents and organic matter: Formation, properties and stabilization of organic matter

火山灰的风化作用通常会形成灰成土，其矿物土壤可能含有水铝英石和/或伊毛戈兰。在所有陆地土壤中，硅铝石含有最多的有机质。水铝英石组分是粘土组分中的短程有序矿物，具有可变的Al：Si比，也形成于灰壤和形成土中。它们的形成受到土壤水分状况，土壤溶液中Si的活性和pH值的影响。脲基化合物组分和土壤有机质之间的相互作用被认为是一个重要的稳定过程。然而，土壤有机质可能会阻碍或促进脲基化合物的形成。因此，拟议的项目旨在澄清在土壤有机质存在下脲基化合物的形成和相关有机质的命运。我们将检查有机质对脲基化合物的结晶度，从表土和底土溶解有机质的吸附程度和有机质的分馏吸附的影响。为此目的，合成的脲基化合物成分的存在下，天然溶解的有机物质（获得在表层土壤中的蒸渗仪，在底土中的吸盘，或通过提取）在可变的Al：Si的比例和pH值的吸附和共沉淀的变种将在一系列的实验室实验中进行。反应产物将通过Si-、Al和C-NMR光谱和红外光谱表征。此外，我们将澄清在孵育实验中使用以前产生的矿物有机协会是否土壤微生物利用有机物相关的共沉淀，以及是否添加一个容易获得的有机基质可能会刺激相关的有机物的共代谢裂解。本项目的研究成果将加深对脲基化合物及其伴生有机质的形成、性质和动力学的认识。我们将有助于更详细地了解土壤中有机质的储存和归宿过程，以及土壤的形成和性质。

Weathering of volcanic ashes typically results in the formation of Andosols, the mineral soil of which may contain allophane and/or imogolite. Allophanes contain the largest amounts of organic matter among all terrestrial soils. Allophanic constituents are short-range ordered minerals in the clay fraction with variable Al:Si ratios, which also form in Podzols and Cambisols. Their formation is affected by the soil-moisture regime, the activity of Si in the soil solution, and pH. The interaction between allophanic constituents and soil organic matter is considered an important stabilization process. However, soil organic matter may impede or promote the formation of allophanic constituents. Therefore, the proposed project aims at clarifying the formation of allophanic constituents in the presence of soil organic matter and the fate of associated organic matter. We will check effects of organic matter on the crystallinity of allophanic constituents, the extent of sorption from topsoil and subsoil dissolved organic matter and fractionation of organic matter upon sorption. For that purpose, syntheses of allophanic constituents in the presence of natural dissolved organic matter (obtained in topsoil by a lysimeter, in subsoil by suction cups, or by extraction) at variable Al:Si ratios and pH in adsorption and co-precipitation variants will be performed in a series of laboratory experiments. The reaction products will be characterized by Si-, Al and C-NMR spectroscopy and infrared spectroscopy. In addition, we will clarify in incubation experiments using previously produced mineral-organic associations whether soil microorganisms make use of organic matter associated by co-precipitation, and whether the addition of an easily available organic substrate might stimulate the co-metabolic cleavage of the associated organic matter. The findings of this project will deepen the understanding on the formation, the properties and the dynamics of allophanic constituents and associated organic matter. We will contribute to a more detailed comprehension of the processes of storage and fate of organic matter in soils and the formation and properties of Andosols.