Characterization of Tibouchina granulosa (Desr.) Cong. (Melastomataceae) as a biomonitor of air pollution and quantification of particulate matter adsorbed by leaves

The main anatomical features of Tibouchina granulosa (Desr.) Cong. (Melastomataceae) have been investigated in order to assess the potential of the species as a possible biomonitor of air pollution in the state of São Paulo, Brazil. Various types of trichomes located on the adaxial and abaxial surfaces of the leaves of this ornamental tree were able to adsorb particulate matter (PM) within the size range 2.5–100 μm. Following dry or wet deposition, the particles remained adsorbed to the leaves and did not return to the environment under normal weather conditions. The numbers of particles adsorbed per unit area of leaf differed significantly depending on the location at which the samples were collected. Leaves from a relatively unpolluted site located in a remnant of the Atlantic Forest within the city of São Paulo showed the lowest particle density, while samples collected in the city centers of São Paulo and Cubatão presented the highest numbers of particles with aerodynamic sizes <2.5 and 2.5–10 μm. It is concluded that T. granulosa may be employed as a passive biomonitor, thereby offering a valuable alternative for monitoring air pollution and spatial–temporal evaluation of PM composition. Additionally, landscape cultivation of T. granulosa in inner-city areas may help to improve the quality of air by reducing the concentration of harmful PM2.5 and PM10.