[Relationships between leaf surface characteristics and dust-capturing capability of urban greening plant species]

Taking 21 representative urban greening species in Xi' an as test objects, their leaf dust-capturing capability was determined by artificial dust-deposition method, and the relationships between the dust-capturing capability and leaf surface features, e.g., trichomes, wettability, surface free energy and its polar and dispersive components on dust-capturing capability were studied. For the tested 21 species, their maximum leaf dust-capturing capability was 0.8-38.6 g x m(-2), and there was a significant difference among them, with the greatest varoiation up to forty times. The amount, distribution, and morphology of trichomes had great influence on the leaf dust-capturing capability, possibly due to the different action patterns between trichomes and particulate matters. There was a significant negative relationship between leaf contact angle and maximum leaf dust-capturing capability (r = -0.523), except for four species whose leaf surface has trichomes. For wettable leaves, their maximum dust-capturing capacity ranged from 2.0 to 8.0 g x m(-2), but for nonwettable leaves, their maximum dust-capturing capacity was below 2.0 g x m(-2). The leaf surface free energy was mainly manifested in the action of dispersive component while contribution of polar free energy was lower than 20%, which could be related to the existence of non-polar or weakly polar substances on leaf surface. The leaf surface free energy and its dispersive component had a significant positive correlation (r = 0.500, 0.572) with the maximum leaf dust-capturing capability, but the positive correlation between polar free energy and maximum dust-capturing capability was not significant (r = 0.244).