Trait-mediated, size-dependent retention of particulate matter by urban roadside vegetation

1 μm) was quantified using a three-stage membrane filtration method, together with measurements of leaf functional traits and surface micromorphology. PM retention capacity differed significantly among species and life forms (p < 0.05). Retention of coarse particles was primarily associated with structural traits that enhance mechanical interception, whereas fine-particle retention was more strongly linked to micro-scale leaf traits, particularly stomatal width, indicating a clear size-dependent shift in trait importance. Although particle-size distributions varied among roadside environments, trait-PM relationships remained broadly consistent across sites. These findings demonstrate that particulate matter retention by urban vegetation is regulated by distinct, size-dependent trait mechanisms rather than by a uniform set of functional traits. By highlighting functional specialization in plant-PM interactions, the present study provides a trait-based framework for optimizing urban roadside vegetation design according to local pollution profiles and mitigation objectives.