Monoterpenes (C₁₀H₁₆) are volatile organic compounds (VOCs) naturally emitted into the atmosphere from vegetation, especially flowering plants and conifers. VOCs play a role in controlling atmospheric chemistry and they participate in the formation of air pollutants, such as ozone. Monoterpene em... Show moreMonoterpenes (C₁₀H₁₆) are volatile organic compounds (VOCs) naturally emitted into the atmosphere from vegetation, especially flowering plants and conifers. VOCs play a role in controlling atmospheric chemistry and they participate in the formation of air pollutants, such as ozone. Monoterpene emissions from vegetation are species-specific and strongly dependent on temperature. There have been no detailed studies that correlate monoterpene emissions into the atmosphere with monoterpenes found in storage reservoirs in plant foliage nor are there detailed studies that describe the variability of monoterpene composition within individual plants and between plants of the same species. Using a gas chromatograph equipped with a mass spectrometer and flame ionization detector, this study surveyed the variation in concentration and composition of monoterpenes in Pinus ponderosa and Pinus nigra needles to determine (1) whether variation occurs between needle orientation (e.g., north-, east-, west-, south-facing) or needle age within individual trees (new, one-, and two-year-old needles); (2) whether variation of oil composition exists among different trees of the same species, and (3) whether differences occur between monoterpene composition stored within needles and emissions. Results show that compositions and concentrations did not differ in samples taken from different positions within a tree, but they do differ between age groups in ponderosa pine. Additionally, sabinene and myrcene were found in emission samples in the presence of light, but not in monoterpene pools of Austrian pine needles, suggesting that they are produced and emitted immediately and not stored. Future study will develop a numerical model for emissions incorporating temperature and concentrations. Show less
