Comparison of terpene oil composition and volatile emissions from Ponderosa and Austrian pine

Non-methane biogenic volatile organic compounds (BVOCs) account for about 90% of VOC global emissions. Terpenes (C₁₀H₁₆) are VOCs naturally emitted into the atmosphere from vegetation, especially flowering plants and conifers. VOCs play a role in atmospheric chemistry, participating in the formation of air pollutants, such as ozone and carbon monoxide, through a series of photochemical reactions. Several factors affect terpene emissions from vegetation: they are species specific and are strongly dependent on temperature. However, there have not been detailed studies that correlate emissions with terpene pools found in the foliage of plants or describe the variability of terpene composition within individual plants and between plants. This project attempted to close that gap by surveying the variation in both the concentration and composition of terpenes in Pinus ponderosa and Pinus nigra needles to determine (1) whether variation occurs between needle position (e.g., north-, east-, west-, south-facing) and age within individual trees (e.g., new, 1 and 2 year old needles); (2) whether variation occurs between different trees, and (3) whether terpene composition is correlated with emissions. Preliminary results show that samples taken from different positions did not differ in composition or concentrations, but they do differ with age groups.  Additionally, myrcene was found in emission samples in the presence of light, but not in terpene pools of pine needles, suggesting that myrcene is produced and emitted immediately, and not stored. A numerical model will be developed relating terpene emissions to temperature for emissions from stored terpenes and also for light dependent emission.