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.