Leaf surface functional traits influence particulate matter and polycyclic aromatic hydrocarbons air pollution mitigation: Insights from Mediterranean urban forests

Abstract

In this work the leaf surface functional traits, potentially useful for air phytoremediation of particulate matter (PM) and polycyclic aromatic hydrocarbons (PAH), of 28 woody species have been characterized, and the role of these stomata, trichomes and cuticle traits in phytoremediation have been assessed looking at existing correlations with species-specific ability to sequester and retain airborne pollutants. Leaves were sampled in urban area in August and September and functional traits were measured using Scanning Electron Microscopy and Fourier-transform infrared spectroscopy. Pollutants were extracted by leaves and their concentrations and daily uptake rates were measured using gas chromatography. Significant differences were found between species in the arrangement of functional traits, concentrations and daily uptake of pollutants. Correlations between variables were studied by means of principal component analysis. The trichomes-related traits scaled positively with PM concentration daily uptake, whereas for PAH air phytoremediation, the cuticle physical and chemical features are relevant. Trichomes increase the leaf area several fold providing extra surfaces for PM retention, while cuticle thickness and esterification regulate the PAH retention and translocation in subcuticular tissues. Results provide novelty on the relationships between leaf surface functional traits and plant species phytoremediation potential, outlining an innovative way of measuring leaf surface functional traits. In addition to broadening the economic spectrum of functional traits, it is emphasized how important leaf surface functional traits are in the nature-based solutions definition and planning.