Removal of Ozone by Urban and Peri-Urban Forests: Evidence from Laboratory, Field, and Modeling Approaches

A crucial issue in urban environments is the interaction between urban trees and atmospheric pollution, particularly ozone (O-3). Ozone represents one of the most harmful pollutants in urban and peri-urban environments, especially in warm climates. Besides the large interest in reducing anthropogenic and biogenic precursors of O-3 emissions, there is growing scientific activity aimed at understanding O-3 removal by vegetation, particularly trees. The intent of this paper is to provide the state of the art and suggestions to improve future studies of O-3 fluxes and to discuss implications of O-3 flux studies to maximize environmental services through the planning and management of urban forests. To evaluate and quantify the potential of O-3 removal in urban and peri-urban forests, we describe experimental approaches to measure O-3 fluxes, distinguishing laboratory experiments, field measurements, and model estimates, including recent case studies. We discuss the strengths and weaknesses of the different approaches and conclude that the combination of the three levels of investigation is essential for estimating O-3 removal by urban trees. We also comment on the implications of these findings for planning and management of urban forests, suggesting some key issues that should be considered to maximize O-3 removal by urban and peri-urban forests.