Particulate matter and polycyclic aromatic hydrocarbon uptake in relation to leaf surface functional traits in Mediterranean evergreens: Potentials for air phytoremediation

Abstract

We explored relationships between particulate matter (PM) and polycyclic aromatic hydrocarbon (PAHs) leaf concentrations, uptake rates and leaf surface functional traits in four Mediterranean evergreen trees (Chamaerops humilis, Citrus × aurantium, Magnolia grandiflora, and Quercus ilex) during a dry month. Pollutant leaf concentration at different dates and uptake rate were correlated. We quantified PM by gravimetric analysis, PAHs were extracted from intact and dewaxed leaves and analyzed by GC-MS, and cuticle thickness, number and surface of stomata (N_s and S_S) and trichomes (N_t and S_t) were determined by optical microscopy. Infrared spectroscopy was used to investigate the leaves surfaces composition and assess esterification index (E). Studied species were characterized by unique combinations of functional traits and pollutant uptake capacities. PM₁₀ uptake scaled positively with S_S, S_t and upper cuticle thickness (T_c,u) across species. PM_2.5 uptake scaled positively with T_c,u, and thicker cuticles were also associated with greater shares of uptake of hydrophobic PM fractions. Uptakes of different fractions of PAH were generally weakly related to different leaf functional traits, except for some correlations with E and S_S. We conclude that both plant surface morphological and chemical leaf traits influence PM and PAH retention, unveiling their potential role in air phytoremediation.

Keywords: Air phytoremediation; Air pollution; Particulate matter; Plant functional traits; Polycyclic aromatic hydrocarbons.