天然和火成有机质组分与矿物的相互作用机制

Organic matter-mineral complexes are important components in soils, and the organic matter-mineral interaction is critical for the geochemical cycle of soil organic matter. Pyrogenic organic matter (PyOM) fractions are released into the environment during the large-scale application of biochar for soil remediation and carbon sequestration. These PyOM fractions are expected to interact with minerals after biochar deposition. However, in contrast to the natural organic matter (NOM) fractions, very few information is available on the sorption of PyOM fractions by minerals. In this study, fulvic acid (FA), humic acid (HA), and humin (HM) fractions will be isolated from soils and oxidized biochars and characterized using Fourier-transform infrared (FTIR), nuclear magnetic resonance (NMR), X-ray absorption near edge fine structure (NEXAFS), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), thermal analysis, electrospray ionization coupled with Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS), etc. The sorption of PyOM fractions by iron oxyhydroxides (ferrihydrite, goethite, and lepidocrocite) and clay minerals (montmorillonite and kaolinite) will also be examined. We will distinguish differences in composition, structure, conformation, and thermal stability between the NOM and PyOM fractions, examine the fractionation of PyOM fractions induced by adsorption on minerals in comparison with NOM fractions, and determine the effects of pH, ionic strength, and coexisting cation on the sorption of PyOM fractions by minerals. This study helps to understand the characteristics of PyOM fractions and the microscope-mechanism of interactions between PyOM fractions and minerals at the molecular scale. It will provide reliable scientific basis for the evaluation of biogeochemical cycle of PyOM fractions in the environment as well as for the successful application of biochar in soil remediation and carbon sequestration.

有机质-矿物的相互作用对有机质的地球化学循环具有重要影响。目前，这方面的研究主要集中在天然有机质（NOM）组分上，而忽视了对热解产生的火成有机质（PyOM）组分的研究。生物炭的广泛应用会向环境中输入大量的PyOM，与矿物的相互作用会影响PyOM组分的地球化学循环。本研究拟从土壤中提取NOM组分，从生物炭中提取PyOM组分，采用静态吸附法并结合光谱、能谱、热分析和高分辨率质谱等表征技术，研究矿物类型（铁氢氧化物、蒙脱石和高岭土）和环境条件（pH、离子强度和共存离子）对两类有机质组分与矿物相互作用的影响，阐明不同类型矿物对PyOM组分的吸附机制，明确环境条件对有机质-矿物相互作用的影响，探讨NOM组分和PyOM组分与矿物相互作用的差异。该研究从分子水平上解析PyOM组分与矿物相互作用的微观机制，有助于分析PyOM组分的地球化学循环过程，为生物炭在环境修复和固碳领域中的应用提供理论指导。

有机质对污染物和营养元素的地球化学循环具有重要影响。目前，这方面的研究主要集中在天然有机质（NOM）组分上，而忽视了对热解产生的火成有机质（PyOM）组分的研究。生物炭的广泛应用会向环境中输入大量的PyOM，与污染物和营养元素的相互作用会影响它们的地球化学循环。本研究从土壤中提取NOM组分（SDHA、SDOM），从生物炭中提取PyOM组分（BDHA、BDOM），采用静态吸附法并结合光谱、能谱、热分析和高分辨率质谱等表征技术，研究了NOM和PyOM组分的物化特征、对菲的吸附行为、在矿物表面的吸附及其对磷-矿物相互作用的影响，本研究的主要创新成果如下：BDHA的13C NMR 图谱主要由芳香碳和羧基碳组成，芳香度约为96%，是SDHA的两倍左右。SDHA则在脂肪族区域含有丰富的信号。SDHA比BDHA的N2比表面积高1-2个数量级，但两者具有相近的 CO2 比表面积。BDHA 吸附菲的logKoc（Ce = 0.01 Sw）值范围为5.16-5.61 mL/g，显著高于SDHA样品（3.95-5.10 mL/g）。通过“漂白”去除无定型芳香碳后，SDHA对菲的吸附能力增强，且logKoc值与脂肪碳含量大致呈正相关，说明脂肪碳主导着SDHA对菲的吸附。BDHA对菲的logKoc值与芳香碳含量呈正相关，且去除无定型芳香碳后，BDHA 的吸附能力显著降低，这意味着BDHA中的无定型芳香碳对菲的吸附起着重要作用。高岭土吸附SDOM 和BDOM的Kd（Ce = 5 mg-C/L）值分别为1.16和0.041 L/g。高岭土对SDOM的吸附能力更强，这是因为SDOM中脂肪性疏水组分的含量比BDOM高，而高岭土优先选择性吸附脂肪性疏水组分。经粘土矿物吸附后，SDOM和BDOM溶液的SUVA254有所上升，类FA和类HA含量明显减少，说明粘土矿物会优先吸附溶液中的非芳香物质，主要是类FA和类HA组分。与SDOM相比，BDOM中有机质分子小，极性芳香组分含量多，有利于其在铁氧化物表面的吸附，从而显著抑制磷在铁氧化物表面的吸附。该项目研究成果为全面评估生物炭的环境地球化学行为奠定基础，为生物炭在环境修复和固碳领域中的应用提供理论指导。