Kinetic study of the formation and decomposition process of humic substances based on comparison of non-destructive analysis of sediments and experiments simulating chemical processes

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K19958
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 63010:Environmental dynamic analysis-related
• Research Institution: Hokkaido University (2021-2022); Setsunan University (2020)
• Principal Investigator: Nakaya Yuki 北海道大学, 工学研究院, 助教 (60868735)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 腐植物質 / 有機物無機物相互作用 / 紫外可視分光法 / 固体３次元励起蛍光マトリクス分光法 / SPF-EEM分光法 / 蛍光消光

Outline of Final Research Achievements

For understanding the time scale of formation and decomposition of humic substances (HSs), spectroscopic tracing of simulated formation and decomposition of HSs focusing on the interaction with minerals was conducted (laboratory approach). The possibility that iron hydroxide acts like a catalyst to lower the activation energy of decomposition reaction of HSs and to promote the reaction was found. For nondestructive non-extraction analysis of sediment samples (field approach), Solid-Phase Fluorescence Excitation-Emission Matrix (SPF-EEM) spectroscopy was applied to peat samples from cold regions and simulated HSs. It was found that the fluorescence spectral characteristics of HSs might change depending on the solid and liquid. It was also found that fluorescence quenching occurred depending on the blackness of the sample, and an empirical formula for correcting the quenching was partially obtained by experiments with simulated fluorescent substances.

Free Research Field

環境工学

Academic Significance and Societal Importance of the Research Achievements

腐植物質は物質循環や環境汚染などに密接に関連するが，その時間スケールは根本的には腐植物質自身の生成や分解の時間スケールにも関連する．本研究は腐植物質の消長時間スケールが共存鉱物の影響を受けうることを定量的に示し，腐植物質に関わる環境動態の長期的な予測に必要な反応速度論的定数を提供したといえる．また，本研究では堆積物や土壌を対象とした腐植物質の非破壊・非抽出な新規分析法としてSPF-EEM分光法を提案し，定量的・定性的な活用に向けた課題と解決の方向性を見出した．SPF-EEM分光法の発展は，アルカリ抽出の妥当性や腐植物質の実在性に関する近年の議論に影響を与える重要なデータを提供すると期待される．