Identification of nonmethane organic compound emissions from grassland vegetation

Emissions of nonmethane organic compounds (NMOCs) from grassland vegetation were collected in Summa(R) passivated stainless-steel canisters with a sta tic enclosure technique and were analyzed by high-resolution gas chromatogr aphy with dame ionization and ion trap mass spectrometric detectors. Approx imately 40 NMOCs with 6-10 carbon atoms were observed in samples analyzed b y high-resolution gas chromatography with the flame ionization detector. Ni neteen NMOCs in this molecular weight range (6 aliphatic oxygenates; I arom atic hydrocarbon: and 4 acyclic, 5 monocyclic, and 3 bicyclic monoterpenoid s) were identified by ion trap mass spectrometry. Mass spectrometry was par ticularly useful for identifying myrcene and cis-3-hexenylacetate, which co eluted on a fused-silica capillary column coated with a 1-mu m-thick film o f polydimethylsiloxane. An evaluation of the reactivity of the grassland em issions revealed that the aliphatic oxygenates have lifetimes of a few hour s with respect to oxidation by OH and O-3 in the atmosphere. This value is similar to the lifetimes of the bicyclic monoterpenoids. The expected lifet imes of the monoterpenoids with respect to oxidation by NO3 are only severa l minutes. (C) 2000 Elsevier Science Ltd. All rights reserved.