土壤微界面热区有机质转化的固-液耦合过程研究

Preservation of Soil organic matter (SOM) is the result of mutual coupling of physical, chemical and biological transformation processes. However, based on the traditional method of bulk soil analysis, such as chemical extraction and separation, the process-oriented study on soil microscale processes is still scarce, thus effects of mineral-organic-microbe interactions on transformation of soil organic matter on soil micro-interface hotspot areas are still poorly understood. In this project, soil samples with gradient iron content in typical subtropical regions are taken as materials and SoilChip technology developed by ourselves is used to simulate the formation process of soil micro-interface. To dynamically reveal the inherent coupling characteristics of organic matter transformation between the solution microenvironment and solid soil micro-interfaces, X-ray photoelectron spectroscopy and ion etching, microelectrode and biochemical analysis are comprehensively used. Meanwhile, microbial metabolism characteristics in different micro-environments are monitored using the micro-calorimetry. Our study on the organic matter transformation processes at the solid-liquid micro-interfacial hotspot will help to promote a process-oriented understanding on organic matter cycle, and provide a theoretical basis for the improvement of soil fertility and the reduction of greenhouse gas emissions.

土壤有机质转化和固持是多尺度的物理、化学和生物过程相互耦合作用的结果。然而，基于传统的整体土壤提取和分离等分析方法限制了以过程为导向的土壤微观过程观测，土壤微界面热区上矿物-有机质-微生物相互作用过程及其对有机质转化的影响机制尚不清楚。本项目以亚热带典型区域铁含量梯度水稻土壤为研究对象，拟采用土壤芯片技术，模拟土壤微界面形成过程；结合X-射线光电子能谱和离子刻蚀技术、微电极、酶学和光谱学等表征技术，动态揭示固相微界面物质组成与溶液微环境参数之间的同步耦合特征；同时，结合微量热仪技术监测土壤微环境中微生物能量代谢特征。上述固-液界面过程研究将有助于揭示土壤微界面热区矿物-有机质-微生物多元互作过程特征和热力学规律，促进以过程为导向的有机质转化和固持理论的形成，为实现土壤地力提升和温室气体减排措施提供理论依据。

基于传统的整体土壤提取和分离等分析方法限制了以过程为导向的土壤微观过程观测，土壤微界面热区上矿物-有机质-微生物相互作用过程及其对有机质转化的影响机制尚存在争议。本项目以亚热带典型区域水稻土壤和东北地区的黑土为研究对象，采用土壤芯片技术，模拟土壤微界面形成过程；结合X-射线光电子能谱系统监测了红壤表面的 有机无机互作动态过程；通过有机质元素组成和结构的解析，定量揭示了有机质在红壤微界面的转化和积累过程；动态比较发现氮肥添加能显著的增加微生物的多糖合成过程，进而显著增加有机质的覆盖度。基于土壤芯片技术，结合X-射线光电子能谱和离子刻蚀技术、酶学和光谱学等表征技术，动态揭示黑土固相微界面物质组成与溶液微环境参数之间的同步耦合特征；首次证实了固-液界面过程能够促进能够形成纳米厚度的有机层；特别是通过氩离子团簇逐层刻蚀分析技术发现在Z轴方向上厚的微生物量碳（MBC，>130nm）和有机无机复合物（20nm-130nm）仍在逐渐增加。同时，结合微量热仪技术监测土壤微环境中微生物能量代谢特征，发现有机质的层状累积，限制了有机质的可利用性，对微生物活性有限制作用。上述固-液界面过程研究有利于有机质转化和固持理论的形成，为实现土壤地力提升和温室气体减排措施提供理论依据。