Despite the various benefits of humus, the changes in its chemical characteristics during composting in response to biochar addition and varying bulking agents remain to be further explored. In this study, three treatments were conducted, in which swine manure, bulking agent, and biochar were mixed at ratios of 4:1:0, 8:1:0, and 8:1:1. Fourier transform infrared spectroscopy (FTIR), carbon nuclear magnetic resonance spectroscopy (¹³C-NMR), three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM), and near-edge X-ray absorption fine structure (NEXAFS) were employed to characterize the chemical and structural properties of humus from multiple perspectives. The 3D-EEM spectra in this study showed a larger increase in humic acids (HAs) content (56%) and HAs to fulvic acids ratio (128%) during composting, indicating stronger humification in biochar-amended treatment. FTIR, ¹³C-NMR, and NEXAFS all confirmed the essential properties of HA as the core agronomic functional substance with rich aromatic and carboxyl groups, and that its aromaticity increased gradually during composting. In addition, ¹³C-NMR demonstrated that biochar addition and a relatively higher bulking agent ratio aided an increase in the carboxyl C proportion in HA after composting. In particular, NEXAFS revealed that biochar addition promoted the diversification of C, N, and O species in HA, with the emergence of quinone C and O-alkyl C as the main representatives. This work suggests that biochar addition and a relatively high bulking agent ratio could enhance humification and improve the agronomic function of humus.

尽管腐殖质有各种好处，但在堆肥过程中其化学特性因生物炭添加和不同填充剂而发生的变化仍有待进一步探索。在本研究中，进行了三种处理，其中猪粪、填充剂和生物炭以 4:1:0、8:1:0 和 8:1:1 的比例混合。傅里叶变换红外光谱 (FTIR)、碳核磁共振光谱 ( ¹³C-NMR）、三维激发发射矩阵荧光光谱（3D-EEM）和近边X射线吸收精细结构（NEXAFS）从多个角度表征腐殖质的化学和结构特性。本研究中的 3D-EEM 光谱显示，堆肥过程中腐殖酸 (HAs) 含量 (56%) 和 HAs 与富里酸的比率 (128%) 有更大的增加，表明在生物炭改良处理中腐殖化作用更强。FTIR、¹³ C-NMR和NEXAFS均证实了HA作为具有丰富芳香和羧基的核心农艺功能物质的基本性质，并且在堆肥过程中其芳香性逐渐增强。此外，¹³C-NMR 表明，生物炭的添加和相对较高的填充剂比例有助于堆肥后 HA 中羧基 C 比例的增加。特别是NEXAFS揭示了生物炭的添加促进了HA中C、N和O物种的多样化，其中以醌C和O-烷基C为主要代表。这项工作表明，生物炭的添加和相对较高的填充剂比例可以增强腐殖质并改善腐殖质的农艺功能。