Higher Molecular Weight Terpenoids as Indicators of Organic Emissions from Terrestrial Vegetation

Higher molecular weight terpenoids (C₁₅ to C₄₀ carbon units) are naturally occurring compounds that are introduced into the atmosphere from terrestrial vegetation. These compounds are released by a variety of mechanisms such as: (1) direct volatilization due to plant metabolic activities; (2) steam distillation or steam stripping that occurs during large-scale (biomass burning, natural wildfires) and small scale (camp fires, fireplaces) combustion of biofuels; and (3) mechanical processes which include abrasion and disintegration of plant leaf surface waxes and structural materials. Mechanism (2) is illustrated with an example. The C₁₅ to C₄₀ terpenoids encompass a broad range of chemical compositions which makes this class of plant organic matter a diverse category of source material that may be exploited in environmental applications (e.g., the atmosphere). Reviews of the biochemical and phytochemical literature indeed show that many terpenoids in this molecular weight range are specific for major vegetation taxa and in some cases, are exclusive to certain subspecies of vegetation. Consequently, C₁₅ to C₄₀ terpenoid compounds provide a variety of important molecular probes that can be used in biogeochemical studies of atmosphere-biosphere interactions.