生分解による草本および木本植物由来の溶存有機物の塩素反応性の変化

Litter-derived dissolved organic matter (DOM) is a major source of disinfection byproduct (DBP) precursors in vegetated catchments. However, the composition difference and DBP formation potential (DBP-FP) between DOM derived from herbaceous (HCP-DOM) and woody (WDP-DOM) plant litter, especially after biodegradation, remain poorly understood. Here, DOM was extracted from ten types of plant litter, categorized into HCP- and WDP-DOM, and subjected to controlled biodegradation. Both pristine and biodegraded DOM were characterized using UV-vis and fluorescence spectroscopies, Fourier transform ion cyclotron resonance mass spectrometry, and DBP-FP assays. HCP-DOM featured a greater abundance of protein- and amino sugar-like compounds, whereas WDP-DOM contained more lignin- and condensed aromatic-like components. Biodegradation led to a decrease in protein-like compounds, along with increases in terrestrial and microbial humic-like components in both DOM types. These compositional shifts drove 57-82% reductions in the formation of trihalomethanes, haloacetic acids, and chloral hydrate, yet triggered up to 147% increase in haloacetonitrile (HAN) production. Notably, biodegraded WDP-DOM generated over 50% more HAN than biodegraded HCP-DOM, highlighting its elevated nitrogenous DBP formation risk. Correlation analysis and random forest modeling further identified nitrogen-associated transformations and dynamic shifts in protein-, amino sugar-, and lignin-like components as key drivers of DBP formation. Overall, both vegetation type and microbial processing critically shape the chlorine reactivity of litter-derived DOM. Our findings underscore the need to prioritize monitoring and managing HAN precursors in source waters influenced by woody vegetation.