Chemical processing of biogenic hydrocarbons within and above a temperate deciduous forest

A one-dimensional canopy model was developed to study photochemical process es inside and above a mixed deciduous forest in southern Ontario. The Euler ian model made use of Lagrangian dispersion principles with a correction fa ctor to incorporate the average ensemble time since emission to calculate a tmospheric mixing; traditional diffusion methods were found to provide insu fficient mixing to match the measurements. Neglecting chemical losses while making isoprene emission estimates was found to underestimate emission rat es up to 40%. The ozone oxidation of biogenic and anthropogenic alkenes was found to be a potential source of hydroxyl (OH) and hydroperoxy (HO2) radi cals during the morning and night. Reactions of HO2 with organic peroxy rad icals formed by the OH oxidation of isoprene during the day were shown to b e a significant source of organic peroxide formation above the canopy; The primary pathways of methacrolein and methylvinylketone formation were shown to be ozone oxidation of isoprene and hydroxyl radical oxidation of isopre ne, respectively. Local ozone formation was shown to be limited by low mixi ng ratios of nitrogen oxides, despite high levels of isoprene present at th e site.