A study from the University of Gothenburg, Sweden, reveals that trees and their leaves are great air filters for urban environments.

The potential of trees to purify the air is already known, but the team of researchers wanted to understand what their real importance is in the air in urban areas.

According to the Green Severs portal, the project analyzed seven areas of the city of Gothenburg in the summer of 2018, measuring pollutants present in the air and leaves in trees of the Quercus palustris species, specifically Polycyclic Aromatic Hydrocarbons (PAHs) and nitrogen dioxide (NO2). The results show a concentration of pollutants in the leaves that was increased over time, which demonstrates their ability to clean the air.

"The study establishes that leaves collect air pollutants during the summer, thus reducing human exposure to harmful substances in the air," explains Håkan Pleijel, professor of environmental sciences at the University. "These kinds of extensive measurements of pollutants in vegetation and air are unusual, and the study confirms that trees play a role in improving air quality in cities."

In a second phase, the scientists also analyzed the needles of the black pine tree (Pinus nigra) for the same pollutants. The data showed that the three-year-old needles carried more pollutants than the one-year-old ones, which suggests that this species, too, contributes to air quality in the city.

"One advantage of conifers is that the needles remain on the trees even in winter, when pollution levels in cities are usually highest," adds Jenny Klingberg, a researcher at the Gothenburg Botanical Garden.