Analysis of monoterpene hydrocarbons in rural atmospheres

Abstract

Gas chromatographic/mass spectrometric analysis of monoterpenes from a rural forested site in the northwestern United States is described. Use of a glass capillary column provided excellent resolution of the hydrocarbons. Increased sensitivity and specificity of the mass spectrometer detector over the flame ionization detector were demonstrated for trace (parts per trillion) atmospheric hydrocarbons. As little as 10 ppt of compound was detectable in 100-cc air samples. Two analytical methods (cryogenic and solid adsorbent-Tenax-GC) were used in the collection of ambient air. Analytical results from the two techniques compared very well. Rural concentrations of the monoterpenes varied considerably depending upon location within the forest canopy. The concentration of individual species never exceeded I ppb of compound during a 10-month sampling period. The monoterpene total for all samples fell in the range of 0.5-to 16-ppb compound for C•o terpene.

A review and synthesis of monoterpene speciation from forests in the United States

“…The west coast, interior west, and the southern pine regions Table 3 Comparison of daytime ambient measurements of monoterpene composition (percentage with standard deviation in parentheses) with estimated monoterpene emission composition for the corresponding location proposed for BEIS3. References are Eastern GA , Northern CO (Roberts et al, 1983(Roberts et al, ,1985, Northern Idaho (Holdren et al, 1979), Western Alabama , North Central Florida (Kim et al, 1995), eastern Tennessee (Holdren et al, 1979), and eastern California Sierra Nevada Mountains (Helmig and Arey , 1992). Trace amounts (t) represent less than 0.5% of total monoterpenes.…”

“…The sites are located in eastern Georgia , eastern California (Helmig and Arey, 1992) (Sierra Nevada Mountains), northern Colorado (Roberts et al, 1985(Roberts et al, ,1983, northern Idaho (Holdren et al, 1979), western Alabama , north central Florida (Kim et al, 1995), and eastern Tennessee . The BEIS3 estimates were determined by applying the MC derived from the enclosure data (Table 1) for each tree species to the foliage quantities estimated for those corresponding species within approximately 50 km of the measurement site.…”

Essential Oils and Waxes

“…Containers made of stainless steel or glass have also been used for the collection of monoterpenes in the field (Holdren et al 1979). Samples are usually gathered with an evacuated container by opening a valve or, filled to a positive pressure with a pump.…”

“…Since they are chemically reactive, the concern about their role in atmospheric chemistry has prompted several investigations to determine their ambient air concentrations (Rasmussen and Went 1965;Holdren et al 1979;Yokouchi et al1981bYokouchi et al , 1983Roberts et a1.1983bRoberts et a1. Monoterpenes are mainly emitted from coniferous trees, and are often responsible for the aroma of forest air, while isoprene is dominantly emitted from deciduous trees.…”

Factors Affecting the Emission of Monoterpenes from Red Pine (Pinus densiflora)

“…they potentially serve as photochemical oxidant precursors, their global emission rate (9,14), their atmospheric reactivity (2,4), and their ambient concentration (5,13) have been studied in an attempt to determine their contribution to air pollution. To estimate the contribution of monoterpenes to air pollution, it is necessary to establish a clear relationship between monoterpene emission rates and environmental conditions.…”