水稻土溶解性有机质与Cu2+结合过程及机制研究

农田土壤中Cu²⁺的迁移转化对生物体健康产生重要影响，然而，水稻土中的溶解性有机质（DOM）与Cu²⁺的结合过程和机制尚不清楚。本研究通过动态光散射、三维荧光、同步荧光以及X射线光电子能谱（XPS）等方法，探究水稻土中DOM的粒径、光谱和结构特征及其与Cu²⁺的结合过程及机制。结果表明，土壤DOM的SUVA₂₅₄值为（3.25±0.07）L·（mg·m）^-1，低于4 L·（mg·m）^-1，其亲水性较高同时芳香性偏低，并且其芳香结构中含有较多的含氧官能团。水稻土DOM的构成以类富里酸和类腐植酸为主，Cu²⁺与类腐植酸络合稳定常数（lgK_M=5.07）高于类富里酸（lgK_M=4.81）。表明稻田土壤DOM中的类腐植酸组分与Cu²⁺优先结合，尤其以短波类腐植酸中的酚基、羟基和酚羟基等含氧基团对Cu²⁺的添加表现得更为敏感。另外，DOM表面疏松的介孔结构、负电荷和羟基、酚羟基以及氨基等官能团对Cu²⁺吸附起到关键作用。

Process and mechanism of complexation of dissolved organic matter(DOM) and Cu2+ in paddy soil

The migration and transformation of Cu²⁺ in farmland soils have an important impact on biological health; however, the process and mechanism of binding Cu²⁺ to dissolved organic matter(DOM) in paddy soils are unclear. In this study, paddy soil DOM''s particle size and spectral and structural characteristics, together with the process and mechanism of its binding with Cu²⁺, were investigated by dynamic light scattering, three-dimensional fluorescence, synchronized fluorescence, and X-ray photoelectron spectroscopy(XPS). The results showed that the SUVA₂₅₄ of soil DOM was(3.25±0.07) L·(mg·m) ^-1, which is less than 4 L·(mg·m) ^-1. It had high hydrophilicity and low aromaticity, and the aromatic structure contained more oxygen-containing functional groups. DOM was mainly composed of fulvic acid-and humic acid-like components. The stability constaned of Cu²⁺ and humic acid-like components(lgK_M=5.07) was higher than that of fulvic acid-like components(lgK_M=4.81). The humic acid fractions in the DOM of the paddy field preferentially interacted with Cu²⁺. Particularly the phenolic, carboxyl, and phenolic hydroxyl groups of short-wave humic acid were more sensitive to the addition of Cu²⁺. In addition, the loose mesoporous structure, negative charge, and functional groups, such as hydroxyl, phenolic hydroxyl, and amino groups on the DOM surface, played a key role in the adsorption of Cu²⁺.