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ESTIMATING THE OZONE-FORMING POTENTIAL OF
URBAN TREES AND SHRUBS

MICHAEL T. BENJAMIN and ARTHUR M. WINER
Environmental Science and Engineering Program, School of Public Health, University of California, Los Angeles, CA 90095-1772, USA

Published October 1997 by Elsevier Science Ltd., Great Britain,
Atmospheric Environment, Vol. 32, No. 1, pp.53-68, 1998
http://www.sciencedirect.com/science/journal/13522310

Abstract
A method is presented for estimating the ozone-forming potential of biogenic hydrocarbon emissions from trees and shrubs, using the California South Coast Air Basin (SoCAB) as a case study. Hourly isoprene and monoterpenes emission rates for 308 tree and shrub species found in the SoCAB were combined with diurnal temperature and light intensity data for a representative summer day in the SoCAB to develop daily emission rates. These daily emission rates for each species were then normalized to a per tree basis using vegetation class biomass factors derived from reported leaf mass constants and tree canopy volumes. The ozone-forming potential for each of the tree and shrub species was estimated by combining the daily per tree emission rates with published maximum incremental reactivities (MIRs) for isoprene and monoterpenes. The resulting ranking of trees by ozone-forming potential can be used in tree species selection for future large-scale tree planting programs, and provides a more appropriate basis for selection than using only mass emissions of biogenic hydrocarbons.

[The information provided below is derived from this study]

LOW OZONE-FORMING POTENTIAL TREES AND SHRUBS
The following tree and shrub rankings are based on calculated ozone-forming potential (OFP) values. Low OFP trees and shrubs are preferred over medium and high in order to reduce volatile organic compound (VOC) emissions that react with nitrous oxide (NOx) emissions to produce ozone (the main component of smog). 

To address air quality concerns in landscaping activities, Low OFP trees and shrubs are preferred that are also California native, drought-resistant, and low or non-allergenic. Use the "SelecTree for California" web site database to aid in the determination of other favorable tree traits.

Note: Only the 308 trees and shrubs assigned an ozone-forming potential value by the authors are listed  here. There are many trees and shrubs that have yet to be classified. Also, there are no shrubs listed by the authors assigned a High OFP value.

Additional Resources:

California Air Resources Board web site - Trees and Air Quality
SelecTree for California - Tree Selection Database
A Compilation of Fire Performance Ratings of Residential Landscape Plants
The California Invasive Plant Council - Don't Plant A Pest
Changes in urban landscape can cut smog - here
American Academy of Allergy, Asthma and Immunology - National Allergy Bureau