College of Environment and Ecology, Hunan Agricultural University, Changsha 410128, China.
School of Environment, South China Normal University, Guangzhou 510006, China.
J Environ Sci (China). 2025 Feb;148:553-566. doi: 10.1016/j.jes.2024.01.052. Epub 2024 Feb 10.
Organic matter (OM) derived from the decomposition of crop residues plays a key role as a sorbent for cadmium (Cd) immobilization. Few studies have explored the straw decomposition processes with the presence of minerals, and the effect of newly generated organo-mineral complexes on heavy metal adsorption. In this study, we investigated the variations in structure and composition during the rice straw decomposition with or without minerals (goethite and kaolinite), as well as the adsorption behavior and mechanisms by which straw decomposition affects Cd immobilization. The degree of humification of extracted straw organic matter was assessed using excitation-emission matrix (EEM) fluorescence and Ultraviolet-visible spectroscopy (UV-vis), while employing FTIR spectroscopy and XPS to characterize the adsorption mechanisms. The spectra analysis revealed the enrichment of highly aromatic and hydrophobic components, indicating that the degree of straw decomposition and humification were further intensified during incubation. Additionally, the existence of goethite (SG) accelerated the humification of OM. Sorption experiments revealed that the straw humification increased Cd adsorption capacity. Notably, SG exhibited significantly higher adsorption performance compared to the organic matter without minerals (RS) and the existence of kaolinite (SK). Further analysis using FT-IR spectroscopy and XPS verified that the primary mechanisms involved in Cd immobilization were complexion with -OH and -COOH, as well as the formation of Cd-π binds with aromatic C=C on the surface of solid OMs. These findings will facilitate understanding the interactions of the rice straw decomposing with soil minerals and its remediation effect on Cd-contaminated farmland.
有机物质（OM）来源于作物残体的分解，在镉（Cd）固定化方面起着关键的吸附剂作用。很少有研究探讨在矿物质存在的情况下，秸秆分解的过程以及新生成的有机-矿物络合物对重金属吸附的影响。在这项研究中，我们研究了有或没有矿物质（针铁矿和高岭石）存在时水稻秸秆分解过程中的结构和组成变化，以及秸秆分解对 Cd 固定化的吸附行为和机制。采用激发-发射矩阵（EEM）荧光和紫外可见光谱（UV-vis）评估提取的秸秆有机质的腐殖化程度，同时采用傅里叶变换红外光谱（FTIR）和 X 射线光电子能谱（XPS）来表征吸附机制。光谱分析表明，高度芳香化和疏水性成分的富集，表明在孵育过程中，秸秆分解和腐殖化的程度进一步加剧。此外，针铁矿（SG）的存在加速了 OM 的腐殖化。吸附实验表明，秸秆腐殖化增加了 Cd 的吸附容量。值得注意的是，SG 的吸附性能明显高于无矿物质的有机质（RS）和存在高岭石（SK）的情况。进一步使用 FT-IR 光谱和 XPS 分析验证了 Cd 固定化的主要机制涉及-OH 和-COOH 的络合以及 Cd-π 与固体 OMs 表面芳香 C=C 的形成。这些发现将有助于理解水稻秸秆与土壤矿物质的相互作用及其对 Cd 污染农田的修复效果。
