Origin and fate of dissolved organic matter in the subsoil driven by dynamic exchange and remobilization processes

动态交换和再动员过程驱动的底土中溶解有机物的起源和归宿

• 批准号: 233437591
• 负责人: Professor Dr. Georg Guggenberger
• 金额: --
• 依托单位: Professur für Bodenkunde und Bodenschutz
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/233437591?language=en
• 关键词: Origin; fate; dissolved; organic; matter

Results obtained so far from the subsoil observatories and sequential column experiments indicate a cascade of sorption-desorption processes of dissolved organic matter (DOM) on soil minerals while travelling to the subsoil. Further, results suggest that the sorption capacity of the subsoil is limited, possibly due to high C loading of the reactive minerals in the sandy soil. We assume that the microbial activity might depend on the C loading of the minerals controlling remobilization processes, in addition to the composition of organic matter (OM) on mineral surfaces. Consequently, in the second phase we will address the complex interplay of continuous sorption processes combined with microbial processes and subsequent remobilization depending on source and composition of OM and surface characteristics of the mineral phase. We hypothesize that (i) the composition of DOM entering the mineral soil affects exchange/remobilization processes stronger in the upper part of the soil than deeper subsoil due to an increased microbial processing with increasing soil depth, (ii) the exchange/remobilization of sorbed OM increases with increasing C loading of the minerals, and (iii) microbial transformation of mineral-associated OM is an important source of DOM in larger soil depths. We will approach these hypotheses by a set of experiments starting from complex field conditions to controlled laboratory approaches. The field approaches include a DO13C switch-off pulse in the Grinderwald observatories and a DO13C injection experiment at Grinderwald and two regional sites to study the fate of DOM of different source and composition in the subsoil depending on mineralogical properties and microbial activity. In a comparative way, sorption capacity, C loading, spatial C distribution, C exchange, and OM composition and decomposability (the latter determined by P6) on mineral surfaces will be related to source, composition, C exchange, and microbial stability of DOM. A similar analytical approach will be performed in flow cell experiments, where under defined boundary conditions transport, sorption, and mineralization of the applied DO13C will be assessed. Finally, in a laboratory column experiment with 13C-labeled DOM the effects of microbial activity, manipulated by different incubation temperatures, on the translocation of DOM by sorption and exchange/remobilization processes depending on the mineral surface properties will be studied. With that P5 focuses on the central hypothesis 3 of the frame proposal but also addresses hypotheses 2. P5 will deliver crucial data for the integrative modeling of OC in subsoils such as DOC and DO13C concentration and fluxes, DOM stability against microbial decay, sorption capacity and C loading of the soils and, therefore, for testing the central hypothesis 5.

到目前为止，从底土观测站和连续的柱子实验获得的结果表明，溶解有机质(DOM)在移动到底土时在土壤矿物上存在级联吸附-解吸过程。此外，结果表明，底土的吸附能力是有限的，可能是由于沙土中活性矿物的高C负载量所致。我们推测，微生物的活性可能取决于控制再动员过程的矿物的C含量，以及矿物表面的有机物(OM)的组成。因此，在第二阶段，我们将讨论连续吸附过程与微生物过程相结合的复杂相互作用以及随后的再动员，这取决于OM的来源和组成以及矿物相的表面特征。我们的假设是：(I)进入矿物土壤的DOM的组成对土壤上部的DOM交换/再活化过程的影响比对深层土壤中DOM的影响更大，这是因为随着土壤深度的增加，微生物处理的增加，(Ii)吸附的OM的交换/再活化随着矿物C含量的增加而增加，(Iii)矿物伴生OM的微生物转化是更大土壤深度DOM的重要来源。我们将通过一系列实验来探讨这些假设，从复杂的现场条件到受控的实验室方法。现场方法包括Grinderwald观测站的DO13C关闭脉冲和Grinderwald和两个区域站点的DO13C注入实验，以研究不同来源和组成的DOM在底土中的命运，这取决于矿物学特性和微生物活动。相比之下，矿物表面的吸附容量、C负载量、空间C分布、C交换、OM组成和分解(后者由P6决定)将与DOM的来源、组成、C交换和微生物稳定性有关。类似的分析方法将在流动池实验中进行，在确定的边界条件下，将评估所应用的DO13C的传输、吸附和矿化。最后，在13C标记的DOM的实验室柱实验中，将研究不同培养温度对DOM的吸附和交换/再动员过程的影响，这些影响取决于矿物表面的性质。因此，P5的重点是框架提案的中心假设3，但也涉及假设2。P5将为底土中有机碳的综合模拟提供关键数据，如DOC和DO13C浓度和通量、DOM对微生物腐烂的稳定性、土壤的吸附能力和C负载，因此，用于检验中心假设5。