Measurement of biogenic hydrocarbon emissions from vegetation in the Lower Fraser Valley, British Columbia

Biogenic volatile organic compounds (VOCs) are a diverse class of hydrocarbon released during the normal physiological processes of some species of vegetation. These substances can participate in many chemical reactions and in some cases have potential to promote the formation of ground level ozone. The Fraser Valley located in southwestern British Columbia occasionally experiences these air pollution episodes during the summer. In order to effectively reduce the frequency and magnitude of these episodes, it is important that we understand the relative role of biogenic hydrocarbons from the abundant vegetated surfaces in the region. The thesis presents the results of measurements conducted on four common tree species in the lower Fraser Valley using a branch enclosure apparatus. Hydrocarbon emission rates from Cottonwoods trees were approximately one hundred times greater than those from coniferous trees and were dominated by the compound isoprene. Monoterpenoid emissions from four tree species were highly variable in magnitude and demonstrated no statistically significant relationship with temperature. Comparison of the observed results with a simple model from the literature shows relatively close agreement in the case of isoprene but poor agreement with monoterpene emissions. Results of these branch enclosure studies were extrapolated to larger scales to yield an areal emission rate assuming reasonable biomass densities. Isoprene measurements in this study reveal an areal emission rate approximately twenty times that of the assumed value in current emissions inventories. This discrepancy could be quite significant considering its magnitude and the possible sensitivity of the chemical reactions that produce ground level ozone to changes in isoprene concentration.Arts, Faculty ofGeography, Department ofGraduat