Nonmethane hydrocarbon, monocarboxylic acid, and low molecular weight aldehyde and ketone emissions from vegetation in central New Mexico

Direct emissions of nonmethane hydrocarbons, monocarboxylic acids, and low molecular weight carbonyl compounds were measured from vegetation typical t o central New Mexico. These species included quaking aspen, cottonwood, Gam bel 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 alpha-pinene. In general, alpha-pinene emissions w ere 100-10 000 ng g(-1) h(-1) and displayed the expected temperature depend ence. Other identified hydrocarbons included isoprene, camphene, beta-pinen e, myrcene, Delta(3)-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 molecul ar weight carbonyl compounds measured. The carbonyl emissions averaged 50-1 660 ng g(-1) h(-1), depending an 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 c arbonyls, poor correlation was found between the acid emissions and the enc losure temperature. The deciduous trees were found to have average (mass-ba sed) emissions of 98% hydrocarbons, 1% carbonyls, and 1% organic acids. The coniferous trees averaged 80%, 8%, and 12%, respectively.