Independent physical role of plant morphology in oil retention: Evidence from bionic experiments and numerical...

The independent physical role of plant morphology in initial oil retention remains poorly resolved because it is commonly confounded by the biochemical properties of real vegetation, hindering predictive assessment of vegetation-mediated oil retention in inland spills. To address this gap, bionic experiments were integrated with numerical simulation to isolate morphology-driven retention and parameterize it for river-scale oil-spill modeling. The results identify a multi-stage physical process in which oil retention is governed primarily by interception during initial contact, whereas attachment serves as a secondary but essential stabilizing mechanism. Spatial extensiveness (E_s) captured important structural differences related to interception, whereas the oil-contact wetted-perimeter ratio (λ) was the strongest and most practical predictor of the intrinsic retention coefficient (k). This relationship enabled the establishment of a simplified λ-k-C_R pathway, linking measurable plant morphology and local slick thickness to unit-area retention capacity for model parameterization. The coupled model further revealed a dual-control mechanism: plant morphology determined intrinsic retention capacity once oil-vegetation contact occurred, whereas environmental forcing and vegetation-belt configuration controlled whether and how effectively that capacity was realized. Specifically, wind direction acted as a switch for retention occurrence, wind speed exerted a nonlinear effect, and upstream extension and patchy layouts enhanced retained mass more effectively than simple belt widening by improving the spatiotemporal match between the vegetation interface and the evolving slick trajectory. These findings provide a mechanistic basis for riparian vegetation design and a practical framework for scenario-based assessment of inland oil-spill retention in dynamic riverine environments.