The adsorption of soil dissolved organic matter (DOM) by minerals is crucial for long-term carbon storage and has been extensively studied. However, the variations in soil DOM composition resulting from adsorption by different minerals have rarely been investigated from a spectral perspective. This study examined the impact of non‑iron (kaolinite) and iron-bearing (ferrihydrite) minerals on the concentration and characteristics of DOM from dark brown soil during a 60-h-long incubation experiment. Soil dissolved organic carbon was removed more efficiently by ferrihydrite (66.2 %) than by kaolinite (14.8 %). UV–Vis spectroscopic analysis indicated that DOM with high aromaticity and molecular weight exhibited a strong affinity for both ferrihydrite and kaolinite. The fluorescence of soil DOM decreased in the ferrihydrite treatment, with a notable reduction in humic-like fluorescent components identified through fluorescent excitation-emission matrix coupled parallel factor analysis. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy revealed that carboxyl groups were critical in DOM adsorption on ferrihydrite, participating in ligand exchange, hydrogen bonding, and electrostatic attraction. This study highlights the important role of iron-bearing minerals in soil carbon sequestration and demonstrates how different mineral alter soil DOM composition, potentially influencing the cycling of organic carbon in terrestrial systems.

中文翻译：

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矿物质吸附对土壤溶解有机物分子组成的影响：光谱分析的证据


矿物质对土壤溶解有机物（DOM）的吸附对于长期碳储存至关重要，并且已得到广泛研究。然而，由于不同矿物质的吸附而导致的土壤 DOM 组成的变化很少从光谱角度进行研究。本研究在长达 60 小时的培养实验中考察了非铁（高岭石）和含铁（水铁矿）矿物对深棕色土壤中 DOM 浓度和特性的影响。水铁矿（66.2%）比高岭石（14.8%）更有效地去除土壤溶解的有机碳。紫外-可见光谱分析表明，具有高芳香度和分子量的DOM对水铁矿和高岭石均表现出很强的亲和力。水铁矿处理中土壤 DOM 的荧光减弱，通过荧光激发-发射矩阵耦合平行因子分析发现，腐殖质类荧光成分显着减少。傅里叶变换红外光谱和X射线光电子能谱表明，羧基对于DOM在水铁矿上的吸附至关重要，参与配体交换、氢键和静电吸引。这项研究强调了含铁矿物在土壤固碳中的重要作用，并证明了不同矿物如何改变土壤 DOM 组成，从而潜在地影响陆地系统中有机碳的循环。