Probing changes in humus chemical characteristics in response to biochar addition and varying bulking agents during composting: A holistic multi-evidence-based approach. (15th December 2021)

• Record Type: Journal Article
• Authors: Liu, Hong-tao; Guo, Hao-nan; Guo, Xiao-xia; Wu, Shubiao
• Is Part Of: Journal of environmental management. Volume 300(2021)
• Publication Date: 2021-12-15
• Subjects: Composting -- Humus -- Biochar -- Bulking agent -- Near-edge X-ray absorption fine structure; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2021.113736
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: 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 ( 13 C-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, 13 C-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, 13 C-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. Graphical abstract: Image 1 Highlights: 3D-EEM, FTIR, 13 C-NMR, NEXAFS were used to detect humus chemical characteristics. HA was verified as a core functional substance with rich aromatic rings and carboxyl groups. Aromaticity and unsaturation degree of HA gradually increased during composting. Biochar and higher bulking agent ratio promoted HA aromatization and carboxylation. Biochar addition favored the diversification of C, N, O species in HA.