An investigation of two methods for source identification of ambient isoprene in the Lower Fraser Valley, British Columbia

This thesis is an investigation of two methods for identifying sources of ambient isoprene in the Lower Fraser Valley of British Columbia. The first portion of this study investigated the potential use of the 13C/12C ratio to separate biogenic from anthropogenic sources of ambient isoprene. Results showed a dependence of delta 13C in isoprene emitted by Velvet Bean on temperature, light and leaf age, with typical values of -28.06 +/- 1.94 per mil. The variation could be explained by competition between discrimination against 13 CO2 by photosynthesis and the isoprene production mechanism itself. The fractionation values for biogenic isoprene overlap with those from anthropogenic sources, ruling out the use of this technique as a direct source tracer for ambient isoprene. The second portion of this study investigated the use of more traditional source apportionment techniques for identifying sources of ambient isoprene in and around Vancouver, B.C. The results showed a significant anthropogenic combustion source of isoprene on a year round basis in the Lower Fraser Valley, as well as a significant biogenic contribution whose strength was dependent on location, meteorology and season.