Extractions

Soil organic matter (SOM) has attracted a great deal of interest and has been the focus of many recent studies because of the potential for soils to store organic matter and mitigate human derived CO₂ emissions. Although recent studies have addressed different aspects of SOM behavior in soils, transport properties of different soil organic matter compounds, which may be directly and/or indirectly related to their stability, are poorly understood, and insufficiently documented. The objectives of the study was to develop a workflow that enables us to 1) Investigate the advective and diffusive mass transport and desorption behavior of the soil organic matter compounds (compare mass transport of different compounds); 2) Measure the extent and rates of the desorption reactions using experimental data from stop-and continuous-flow experiments; 3) Conduct high-resolution imaging inspections and pre-and post-experimental extractions to provide additional insights on soil microporosity control on SOM compound-specific mobility. A series of stop- and continuous-flow column experiments were performed with small diameter intact cores (which allowed for high-resolution imaging) of two representative soil samples collected in a cultivated and an undisturbed/uncultivated area. X-ray computed tomography (XCT) imaging was used to characterize soil porosity and pore network connectivity in the intact cores and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) based analyses were carried out for SOM characterization.土壤有机质（Soil Organic Matter, SOM）因其具备储存有机质、缓解人为源二氧化碳排放的潜力，近年来受到广泛关注，成为诸多研究的核心议题。尽管已有研究围绕土壤中SOM的多种行为特征展开探讨，但不同土壤有机质组分的运移特性——这一特性或直接/间接与其稳定性相关——目前仍未得到充分理解与系统记录。本研究的目标是构建一套标准化工作流程，以实现以下三项任务：1）探究土壤有机质组分的平流、扩散质量运移与解吸行为（对比不同组分的质量运移特征）；2）利用间歇流与连续流实验的实测数据，定量解吸反应的程度与速率；3）开展高分辨率成像检测及实验前后的萃取处理，以深入解析土壤微孔隙结构对SOM组分特异性迁移行为的调控机制。本研究针对分别采自耕作区与未扰动/未耕作区的两份典型土壤样品，采用小直径原状土柱（可支持高分辨率成像）开展了一系列间歇流与连续流柱实验。通过X射线计算机断层扫描（X-ray Computed Tomography, XCT）成像技术表征原状土柱的孔隙特征与孔隙网络连通性，并基于傅里叶变换离子回旋共振质谱（Fourier-transform Ion Cyclotron Resonance Mass Spectrometry, FT-ICR-MS）开展分析以实现SOM的组分表征。