ESTIMATING THE OZONE-FORMING POTENTIAL OF URBAN TREES AND SHRUBS

A method is presented for estimating the ozone-forming potential of bi ogenic hydrocarbon emissions from trees and shrubs, using the Californ ia South Coast Air Basin (SoCAB) as a case study. Hourly isoprene and monoterpenes emission rates for 308 tree and shrub species found in th e SoCAB were combined with diurnal temperature and light intensity dat a for a representative summer day in the SoCAB to develop daily emissi on rates. These daily emission rates for each species were then normal ized to a per tree basis using vegetation class biomass factors derive d from reported leaf mass constants and tree canopy volumes. The ozone -forming potential for each of the tree and shrub species was estimate d by combining the daily per tree emission rates with published maximu m incremental reactivities (MIRs) for isoprene and monoterpenes. The r esulting ranking of trees by ozone-forming potential can be used in tr ee species selection for future large-scale tree planting programs, an d provides a more appropriate basis for selection than using only mass emissions of biogenic hydrocarbons. (C) 1997 Published by Elsevier Sc ience Ltd.