Abstract：
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.
摘要：
来自作物残留物分解的有机物（OM）作为镉（Cd）固定的吸附剂起着关键作用。很少有研究探索有矿物质存在的秸秆分解过程，以及新生成的有机矿物配合物对重金属吸附的影响。在这项研究中,我们研究了在有或没有矿物质（针铁矿和高岭石）的稻草分解过程中结构和组成的变化，以及秸秆分解影响Cd固定化的吸附行为和机理。使用激发-发射基质（EEM）荧光和紫外可见光谱（UV-vis）评估了提取的秸秆有机物的腐殖化程度，同时采用FTIR光谱和XPS表征吸附机理。光谱分析揭示了高度芳香和疏水成分的富集，表明在孵化过程中，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的腐化。吸附实验表明，秸秆腐殖化提高了对Cd的吸附能力。值得注意的是,与不含矿物质（RS）和高岭石（SK）的有机物相比，SG表现出明显更高的吸附性能。使用FT-IR光谱和XPS的进一步分析证实，Cd固定的主要机制是与-OH和-COOH的肤色有关，以及Cd-π在固体OMs表面与芳香C=C结合的形成。这些发现将有助于了解稻草与土壤矿物分解的相互作用及其对Cd污染农田的修复效果。
