Green wall plant tolerance to ambient urban air pollution

Abstract

Air pollution exposure can impact plant physiology, morphology and biochemistry, leading to dramatic alterations to plant systems, function and growth. The use of plants for air pollution mitigation is increasing in popularity, particularly in the form of green wall systems, making the identification and classification of pollution sensitive and tolerant species essential. This study aimed to examine the health of common green wall species exposed to ambient air pollution in situ, and thus to identify tolerant species for use in high pollution environments. To do this, 11 plant species were sampled across 15 outdoor green walls, over a 6 month period, and tested for leaf chlorophyll, pH, relative water content and carbon content. Control glasshouse samples were collected simultaneously. Linear mixed models were used to examine patterns in plant health traits across species. Significant differences in plant health between control and in situ samples were observed, however, plant species were not consistent in their responses across health variables. As such, there no clear distinction of the most tolerant species could be made. As most species showed no significant health differences from pollution exposure, it is reasonable to conclude that all test species were able to withstand pollution exposure at the trial sites without any adverse effects.