State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China.
Sci Total Environ. 2021 Mar 25;762:143078. doi: 10.1016/j.scitotenv.2020.143078. Epub 2020 Oct 17.
Rhizosphere, formed via the input of root exudates, is one of the most dynamic biological interfaces on earth. Investigation of carbon dynamics in rhizosphere is thus crucial for the understanding of soil biogeochemical processes. Herein, synchrotron radiation-based Fourier transform infrared (SR-FTIR) combined with two dimensional correlation spectroscopy (2D-COS) was used to probe and identify the changes of chemical constituents and functional groups of organic carbon on the root/soil interface in rhizosphere of two plants [Leptochloa chinensis (L.) Nees and Cyperus rotundus L.]. The SR-FTIR results showed obviously heterogeneous distributions of functional groups in rhizosphere at microscale. Specifically, regardless of plant species, about 20-30 μm regions in rhizosphere can be affected by root activities. The peak area ratios of organic-OH and aliphatic-C to clay-OH on the root/soil interface in rhizosphere were 4.04-8.48 times higher than that in bulk soil, providing direct evidence of the organic carbon storage due to root activities. 2D-COS analysis suggested that the root activities induced the first adsorption or sequestration of newly organics (3350 cm) on the root/soil interface, followed by the destruction of clay-OH (3621 or 860 cm), leading to the release of mineral associated organics and nutrients (e.g., 1510 and 1150 cm) from the soil. These results can enlarge our knowledge on the concentration, distribution, and dynamics of organic carbon in rhizosphere at the microscale level and also the environmental behaviors and fate of other elements and contaminants that associated with organic carbon in rhizosphere. CAPSULE: SR-FTIR combined with 2D-COS can explore the distribution and dynamics of organic carbon on the root/soil interface in rhizosphere.
根际是通过根系分泌物输入而形成的，是地球上最具活力的生物界面之一。因此，研究根际碳动态对于理解土壤生物地球化学过程至关重要。本研究采用同步辐射傅里叶变换红外光谱（SR-FTIR）结合二维相关光谱（2D-COS）技术，探测并识别两种植物[李氏禾（Leptochloa chinensis (L.) Nees）和香附子（Cyperus rotundus L.）]根际中与土壤界面处有机碳的化学组成和官能团的变化。SR-FTIR 结果表明，根际中官能团在微观尺度上呈现明显的不均匀分布。具体而言，无论植物种类如何，根际中约 20-30μm 区域都会受到根系活动的影响。根际中与土壤界面处有机-OH 和脂肪族-C 与粘粒-OH 的峰面积比在根际中是体相土壤中的 4.04-8.48 倍，这为根系活动导致的有机碳存储提供了直接证据。2D-COS 分析表明，根系活动首先诱导新有机物（3350cm）在根/土界面上的首次吸附或螯合，随后破坏粘粒-OH（3621 或 860cm），导致与有机物结合的矿物质和养分（例如 1510 和 1150cm）从土壤中释放。这些结果可以扩大我们对根际中有机碳在微观尺度上的浓度、分布和动态变化的认识，以及与根际中有机碳相关的其他元素和污染物的环境行为和归宿。结论：SR-FTIR 结合 2D-COS 可以探究根际中与土壤界面处有机碳的分布和动态变化。
