Biogenic emissions of nonmethane hydrocarbons, monocarboxylic acids, and low molecular weight carbonyl compounds from vegetation in central New Mexico

Direct emissions of nonmethane hydrocarbons, monocarboxylic acids, and low molecular weight carbonyl compounds were measured using a dynamic enclosure technique from vegetation typical to central New Mexico. The tested species included quaking aspen, cottonwood, Gambel oak, Douglas fir, Engelmann spruce, Rocky Mountain juniper, pinyon pine, and ponderosa pine. The hydrocarbon emissions from most the coniferous trees were monoterpenes, with alpha-pinene being the most prevalent. In general, alpha-pinene emissions were 100-1000 ng/g/hr and displayed the expected temperature dependence. Other identified hydrocarbons included isoprene, camphene, beta-pinene, myrcene, d3-carene, and d-limonene. The deciduous trees, as well as the spruce and fir trees, showed isoprene emission rates of 100-10000 ng/g/hr. Formaldehyde and acetaldehyde were the most common low molecular weight carbonyl compounds measured, accounting for 46-96% of the measured vegetative carbonyl emissions. The carbonyl emissions averaged approximately 10 to 200 ng/g/hr, depending on the compound and the trees species. Unlike isoprene and the monoterpenes, the carbonyls displayed little correlation between the emission rate and enclosure temperature. Formic acid emissions averaged about 200 ng/g/hr from the deciduous trees and 34 ng/g/hr from the coniferous trees. Average acetic acid emissions were found to be 350 ng/g/hr and 74 ng/g/hr, from the deciduous and coniferous trees, respectively. As with the carbonyls, poor correlation was found between the acid emissions and enclosure temperature. Total emissions (hydrocarbons, carbonyls, and acids) averaged 8610 ng/g/hr for the deciduous trees and 1649 ng/g/hr for the coniferous trees. The deciduous trees were found to have average emissions (based on mass) composed of 92% hydrocarbons, 3% carbonyls, and 5% organic acids. The coniferous trees averaged 66%, 23%, and 11%, respectively.