Andosol genesis: Transition from silandic to aluandic properties and the related changes for organic carbon storage.

安多索成因：从硅质到阿卢安质的转变以及有机碳储存的相关变化。

• 批准号: 414785220
• 负责人: Dr. Klaus Kaiser
• 金额: --
• 依托单位: Professur für Bodenkunde und Bodenschutz
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/414785220?language=en
• 关键词: Andosol; genesis; Transition; silandic; aluandic

Andosols are subdivided in silandic and aluandic Andosols, which are often seen as endmembers of the Andosols genesis. Silandic Andosols mainly consist of organic‒mineral associations formed by OM and imogolite-type phases, including allophanes, imogolites, and protoimogolites. Aluandic Andosols consist mainly of aluminium‒OM complexes (Al‒OM complexes). In both subgroups the result is an intimate association of OM and the soil mineral matrix. The current theory is that silandic and aluandic properties are direct results of primary weathering, i.e., result from two different lines of pedogenesis.Our own previous investigations, however, suggest that horizons with silandic properties may transform to horizons with aluandic properties over time. We think that this is caused by acidic dissolved organic matter (DOM) entering the subsoil with the percolating water, causing dissolution of the imogolite-type phases and releasing aluminium. The released aluminium and DOM instantly form into Al‒OM complexes.Thus, the proposed work aims at testing this hypothesis and determining the factors influencing that process. We will study a one-layered Ecuadorian Andosol, with pre-dominating aluandic properties in the topsoil and pre-dominating silandic properties in the subsoil. First, we are going to determine if the sub- and topsoils are saturated with OM by performing sorption batch experiments. Then, the in situ transformation from silandic to aluandic properties will be monitored in a percolation experiment, using an acidic DOM solution (pH at which imogolite-type phases dissolve).We will track changes of the mineral phase with a combination of different techniques. Imogolite-type phases as well as Al‒OM complexes are challenging to characterize and quantify in soil samples due to their short range-ordered and nano- or micro-crystalline nature. Also, they are often closely associated with each other. In order to characterize and quantify them, we will apply a combination of density fractionation, chemical extractions and microscopy (transmission electron microscopy in combination with element detection) as well as modern spectroscopic techniques (Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, synchrotron-based Al K-edge X-ray absorption spectroscopy).We expect to gain new insights into the genesis of Andosols, as well as on the formation and transformation of short range-ordered mineral phases. These mineral phases play a key role for accumulating and storing organic matter in Andosols and other soils.

灰成土又分为硅质灰成土和硅质灰成土，它们通常被视为灰成土成因的端员。硅质灰壤主要由有机质和伊毛戈兰型相组成的有机矿物组合组成，包括脲基芳、伊毛戈兰和原伊毛戈兰。石灰岩型的安多土主要由铝-有机质复合物（Al-有机质复合物）组成。在这两个亚组中，结果是OM和土壤矿物基质的密切关联。目前的理论是，硅氧和铝氧性质是原生风化的直接结果，即，然而，我们以前的研究表明，具有硅质性质的层位可能随着时间的推移而转变为具有铝质性质的层位。我们认为，这是由于酸性溶解有机质（DOM）进入底土与软化水，造成溶解的伊毛戈兰型相和释放铝。释放的铝和DOM立即形成铝-DOM复合物。因此，拟议的工作旨在验证这一假设，并确定影响这一过程的因素。我们将研究一个一层的厄瓜多尔安多土壤，在表土中占主导地位的aluandic属性和占主导地位的silandic属性在底土。首先，我们将通过进行吸附批次实验来确定下层土和表层土是否被OM饱和。然后，在渗滤实验中，使用酸性DOM溶液（伊毛戈兰型相溶解的pH值）监测从硅质到铝质的原位转化。我们将结合不同的技术跟踪矿物相的变化。由于其短程有序和纳米或微晶性质，伊毛沸石型相以及Al Al 2 O3 OM复合物在土壤样品中的表征和定量具有挑战性。而且，它们往往彼此密切相关。为了表征和量化它们，我们将应用密度分级、化学提取和显微镜的组合（透射电子显微镜与元素检测相结合）以及现代光谱技术（傅里叶变换红外光谱，X射线光电子能谱，同步辐射Al K边X射线吸收光谱）。我们期望获得新的见解的成因，以及短程有序矿物相的形成和转变。这些矿物相在灰壤和其他土壤中积累和储存有机质方面起着关键作用。