BOOK OF ABSTRACTS 261 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Technologies and Applications P5.4 Fluorescence-Based Prediction of Fractional Carbon Yields during the Preparation of PectinDerived Artificial Humic Substances Jeongseop Oh1, Gyumin Kim1, Hyunsang Shin1† 1 Department of Environmental Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Seoul 01811, South Korea † Corresponding author: Hyunsang Shin (hyuns@seoultech.ac.kr) Citrus peel waste generated during fruit processing amounts to approximately 10 million tons annually, highlighting the need for alternative treatment methods beyond conventional incineration and landfilling [1]. Yang et al. proposed an alkaline hydrothermal process to convert biomass into artificial humic substances (AHS) [2]. Pectin, an acidic polysaccharide abundant in the albedo layer (60–70% of citrus peels), is a promising precursor for such conversion. In this study, we investigated the yield and fluorescence characteristics of pectin-derived artificial humic substances and developed fluorescencebased indices to predict the composition of each fraction without separation. Pectin was subjected to hydrothermal synthesis at 210 °C under a solid–liquid ratio of 1:10, with varying alkaline concentrations (0.05–2.0 M) and reaction times (0.5–8 h). The products were separated into hydrochar (HC) and an alkaline-soluble fraction, which was further fractionated into humic acid (HA), fulvic acid (FA), and non-humic substances (Non) using precipitation and resin separation. The yield of each fraction was quantified by TOC analysis, and fluorescence characteristics were analyzed. Over time, the carbon yields of FA and Non decreased, whereas the yield of HC increased while HA exhibited fluctuating behavior. This suggests that each fraction acts as a precursor in condensation reactions, following a stepwise humification pathway from Non to FA, HA, and ultimately HC. Excitation–emission matrix (EEM) fluorescence analysis of the alkalinesoluble fraction revealed a fluorescence region in which the intensity increased with increasing HA carbon content within the fraction (Excitation: 320–380 nm; Emission: 420–500 nm). The HA carbon content showed a strong correlation with the area-normalized fluorescence intensity in this region (R² = 0.811). In addition, a region where fluorescence intensity increased with increasing carbon content of Non was identified (Excitation: 200–250 nm; Emission: 280–290 nm). The carbon content of Non showed a strong correlation with the area-normalized fluorescence intensity in this region (R² = 0.895).
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