BOOK OF ABSTRACTS 253 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Environment, Agriculture, and Forestry P4.22 Preparation of Biomass-Derived Artificial Humic Substances: Application for Mulching Film Yejin Seo1, Gyumin Kim1, Hyunsang Shin1† 1 Department of Environmental Engineering, Seoul National University of Science & Technology, 232 Gongneung-ro, Seoul 01811, South Korea † Corresponding author: Hyunsang Shin (hyuns@seoultech.ac.kr) Polyethylene (PE)-based mulching films have improved crop productivity but cause persistent soil contamination due to microplastic residues. This has driven the development of biodegradable alternatives with enhanced functionality. However, optical functionality in such films remains underexplored. Humic substances (HS), possessing diverse functional groups and conjugated structures, exhibit intrinsic light absorption properties, and their molecular characteristics vary depending on precursor materials, enabling wavelength-selective optical control. This study aims to investigate the relationship between the structural characteristics and optical properties of artificial humic substances derived from lignin, cellulose, and pectin, and to apply them to poly(vinyl alcohol)/sodium alginate (PVA/SA)-based biodegradable films. Artificial humic acids and fulvic acids were characterized using FT-IR, UV–Vis spectroscopy, and fluorescence excitation–emission matrix (EEM) analysis. The resulting films, prepared with varying additive contents, were evaluated for UV–Vis–NIR transmittance, photosynthetically active radiation (PAR) transmittance, photothermal conversion, and mechanical properties. The optimal mechanical performance was achieved at a PVA/SA ratio of 8:1 with 4 wt% boric acid and 2 wt% calcium chloride. Optical properties varied significantly depending on the type of humic substances. Lignin-derived humic acids, with higher aromaticity, exhibited enhanced UV absorption and shading performance, whereas cellulose- and pectin-derived humic substances showed higher visible light transmittance and more uniform dispersion. Increasing humic content improved light absorption; however, above 10 wt%, aggregation led to reduced dispersion and mechanical strength. These findings demonstrate that the structural features of artificial humic substances, including aromaticity and functional group composition, govern the optical and photothermal behavior of the films. Moreover, humic acids primarily enhance light shielding and structural stability, while fulvic acids improve dispersion and mobility, enabling tunable functionality. In conclusion, artificial humic substances can serve as structuredependent optical functional materials,
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