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 ozo...
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| Language: | English |
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2009
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| Online Access: | http://hdl.handle.net/2429/4642 |
| Summary: | 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. |
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