Rl. Tanner et B. Zielinska, DETERMINATION OF THE BIOGENIC EMISSION RATES OF SPECIES CONTRIBUTING TO VOC IN THE SAN-JOAQUIN VALLEY OF CALIFORNIA, Atmospheric environment, 28(6), 1994, pp. 1113-1120
As part of an extensive effort to characterize biogenic hydrocarbon em
ission rates in the San Joaquin Valley and surrounding areas during th
e SJVAQS/AUSPEX field experimental period, July-August 1990, measureme
nts were made for the first time of isoprene, terpene, and other VOC e
mission rates from blue oak (Quercus douglasii), foothill pine (Pinus
sabiniana), and a ground cover plant called tarweed (Holocarpha sp.) a
t a rural site near Mariposa, CA. A flow-through plant enclosure metho
d was used to measure the emission flux rates from these species; the
plant limb or whole plant was flushed with clean air just prior to hyd
rocarbon sampling. Samples of the plant emissions were collected on Te
nax GC or Tenax GC-Carbosieve S-II cartridges and analysed by gas chro
matography-Fourier transform infrared-mass spectrometry (GC-FTIR-MS).
Quantifiable biogenic emissions from two blue oak specimens consisted
only of isoprene, with an average emission rate of 8.4 mug g-1 dry bio
mass h-1. Emission rates (above the detection of about 0.05 mug g-1 h-
1) from two foothill pine specimens consisted mostly of alpha-pinene;
an average emission rate of 0.64 mug g-1 h-1 of alpha-pinene was obser
ved. The tarweed species emitted both alpha- and beta-pinenes, along w
ith other terpene and oxygenated species, some of which have been tent
atively identified. The emission rates of biogenic hydrocarbons from f
oothill pine and blue oak species as determined in this study make the
se species potentially significant contributors to summertime VOC leve
ls in the San Joaquin Valley of California, based on vegetation classi
fication data and the predominant summer meteorology.