Ozone and urban forests in Italy.

Ozone levels along urban-to-rural gradients in three Italian cities (Milan, Florence, Bari)showed that average AOT40 values at rural and suburban sites were 2.6 times higher than those determined at urban sites. However, O3 also exceeded the European criteria to protect forest health at urban sites, even when the standards for human health protection were met. For protecting street trees in Mediterranean cities, the objectives of measurement at urban sites should extend from the protection of human health to the protection of vegetation as well. A review of forest effects on O3 pollution and of O3 pollution on forest conditions in Italian cities showed that it was not possible to distinguish the effect of O3 in the complex mixture of urban pollutants and stressors. A preliminary list of tree species for urban planning in the Mediterranean area shows the average tree capacity of O3 removal and VOC emission.