Compound-specific porewater-surface water relationships of taste and odor compounds under contrasting water-level conditions in a reservoir drawdown zone

Elevated odorant concentrations in sediment porewater may not correspond to surface-water occurrence. This study examined four taste-and-odor compounds (odorants), β-cyclocitral (CYC), β-ionone (ION), 2-methylisoborneol (2-MIB), and geosmin (GSM), in paired sediment porewater and surface-water samples from 11 sites in Xiangxi Bay, Three Gorges Reservoir, China. Sampling on 2 July 2025 and 6 January 2026 captured contrasting low- and high-water conditions. CYC and ION showed positive site-level porewater-surface water associations during the July campaign. In January, 2-MIB and GSM generally exhibited higher concentrations in porewater than in surface water, without corresponding site-level associations between compartments. These contrasts show that porewater enrichment and cross-compartment covariation provide different evidence about odorant distribution. Because each condition was sampled once, the differences are interpreted as campaign-specific rather than replicated seasonal or water-level effects. Joint analysis of porewater and surface water may therefore improve the assessment of odorant occurrence in regulated reservoir bays.