Unraveling the Behavior of Stormwater Runoff at Interception Facilities: An Explicit Focus on Dissolved Organic Matter with Analytical Measurement

Interception facilities are essential for managing stormwater runoff before discharge into natural water bodies. This study examines water quality and dissolved organic matter (DOM) characteristics under rain and nonrain conditions using physicochemical analysis and EEM-PARAFAC methods. Kernel PCA revealed that 76.88 and 71.46% of variance during rain and nonrain conditions, respectively, were explained by the first two principal components. Rain-driven variability was influenced by BOD, DO, and EC, while DOM components such as BIX, pH, and C3 were critical during nonrain periods. Two-dimensional correlation spectroscopy (2D-COS) analysis indicated new DOM production (C1) and microbial humic-like substances (C2) dominated rain events, whereas microbial humic-like substances (C1) led during nonrain periods, followed by tryptophan-like and terrestrial humic-like components, obeying the sequence C1 → C2 → C4 → C3 by Noda’s rule. Scanning electron microscopy (SEM) analysis showed suspended solids had the most negative impact on water quality during rain (−0.90), while fresh DOM positively influenced organic matter (FI: 0.94, BIX: 0.78), in contrast to recalcitrant humic substances (C4: −0.96). These findings underscore the role of interception facilities in mitigating pollutant loads, particularly suspended solids and nutrients, and highlight their importance in managing stormwater and regulating DOM dynamics across hydrological conditions.