Ozone and urban forests in Italy

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Urban Ecology

Background:

• Ozone (O3) poses a threat to vegetation, including urban trees.
• European criteria exist to protect forest health from O3 pollution.
• Urban environments present complex mixtures of pollutants and stressors.

Purpose of the Study:

• To assess ozone levels across urban-to-rural gradients in Italian cities.
• To evaluate O3 impact on vegetation in urban settings.
• To inform urban planning regarding tree species selection for O3 mitigation.

Main Methods:

• Ozone levels (AOT40) were measured along urban-to-rural gradients in Milan, Florence, and Bari.
• A review of existing literature on forest effects and O3 pollution was conducted.
• A preliminary list of tree species was compiled based on O3 removal and VOC emission capacities.

Main Results:

• Average AOT40 values were 2.6 times higher at rural and suburban sites compared to urban sites.
• Ozone exceeded forest health criteria even when human health standards were met in urban areas.
• It was challenging to isolate O3's specific impact within the complex urban pollutant mixture.

Conclusions:

• Urban monitoring for ozone should prioritize both human and vegetation health.
• Street trees in Mediterranean cities require protection from ozone pollution.
• Understanding tree O3 removal and VOC emission is crucial for sustainable urban planning.