New aspects on the impact of vegetation in urban environment.

The impact of vegetation in urban air quality is receiving increasing attention for large-scale tree planting programs. Besides the uptake of atmospheric carbon, many trees can emit gases known as volatile organic compounds (VOCs) that can contribute to the production of ozone and particles, especially in polluted urban airsheds. The present study investigated the effectiveness in carbon sequestration and the VOC emission capacity of 11 widespread ornamental broad-leaf species by using a dynamic leaf enclosure system. Light-saturated CO2 assimilation (Amax) ranged between 7.2 µmol m-2 s-1 and 22.6 µmol m-2 s-1. Monoterpene emission rates of the plant species varied from negligible (Fraxinus ornus) up to 12.4 µg gDW-1 h-1 (Liquidambar styraciflua). In order to provide useful information for the suitability of these trees to improve air quality in urban environment, the species were classified as low- or moderate-emitters.