Nonmethane Hydrocarbon, Monocarboxylic Acid, and Low Molecular Weight Aldehyde and Ketone Emissions from Vegetation in Central New Mexico

Abstract

Direct emissions of nonmethane hydrocarbons, monocarboxylic acids, and low molecular weight carbonyl compounds were measured from vegetation typical to central New Mexico. These species included quaking aspen, cottonwood, Gambel oak, Douglas fir, Engelmann spruce, Rocky Mountain juniper, pinyon pine, and ponderosa pine. The hydrocarbon emissions from most of the coniferous trees were dominated by α-pinene. In general, α-pinene emissions were 100−10 000 ng g-1 h-1 and displayed the expected temperature dependence. Other identified hydrocarbons included isoprene, camphene, β-pinene, myrcene, Δ3-carene, and d-limonene. The deciduous trees as well as the spruce and fir trees showed isoprene emission rates of 100−100 000 ng g-1 h-1. Formaldehyde and acetaldehyde were the most common low molecular weight carbonyl compounds measured. The carbonyl emissions averaged 50−1660 ng g-1 h-1, depending on the compound and the trees species. Unlike the hydrocarbons, the carbonyl emissions displayed little correlation with enclosure temperature. Formic acid emissions averaged 15−920 ng g-1 h-1, and acetic acid emissions averaged 50−1300 ng g-1 h-1. As with the carbonyls, poor correlation was found between the acid emissions and the enclosure temperature. The deciduous trees were found to have average (mass-based) emissions of 98% hydrocarbons, 1% carbonyls, and 1% organic acids. The coniferous trees averaged 80%, 8%, and 12%, respectively.