ESTIMATING THE OZONE-FORMING POTENTIAL OF

Large-scale urban tree planting programs have beenadvocated as a means of mitigating the heat islandeffect and improving air quality

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.