Project at a Glance
Title: Hydrocarbon emissions from vegetation found in California's central valley.
Principal Investigator / Author(s): Winer, Arthur M
Contractor: Statewide Air Pollution Research Center, UC Riverside
Contract Number: A732-155
Research Program Area: Atmospheric Processes
An essential database for modeling photochemical air pollution in California's Central Valley is a reliable gridded emission inventory for reactive organic gases (ROG). To date, however, there has been a lack of quantitative information concerning the amounts of organic gases emitted from natural sources, particularly vegetation, in the Sacramento Valley and San Joaquin Valley Air Basins. To address this need, we have measured the rates of emission of speciated hydrocarbons from more than thirty of the most important (based on acreage) agricultural and natural plant types relevant to California's Central Valley. These measurements employed flow-through Teflon chambers, solid adsorbent/thermal desorption sample collection, and the close coupling of gas chromatography (CC) and U-mass spectrometry (CC/MS) for compound identification and quantitation. Emission rate protocols were conducted in the summers of 1988 and 1989 on plant specimens grown at UC Riverside according to standard agricultural practices. Some four dozen individual compounds were identified as emissions from the agricultural and natural plant species studied. In addition to isoprene and the monoterpenes, sesquiterpenes, alcohols, acetates, aldehydes, ketones, ethers, esters, alkanes , alkenes and aromatics were all observed. Data obtained in this study demonstrated again that there can be large variations in emission rates from a single specimen of a given plant species, as well as from multiple specimens of a cultivar. Mean emission rates for total monoterpenes ranged from none detected in the case of beans, grapes, rice and wheat, to as high as ~12-30 µg hr -1 pm-1 for pistachio and tomato (normalized to dry leaf and total biomass, respectively). Other agricultural species exhibiting substantial rates of emission of monoterpenes included carrot, cotton, lemon, orange and walnut. All of the agricultural crops and natural plant species for which full sampling protocols were conducted showed total assigned plant emission (TAPE) rates above the detection limits in this study, with a range between 0.1 and 70 µg hr -1 gm-1. Reliable measurements of biomass are required before the importance of these emission rates to the ROG inventory for California's Central Valley can be determined.
For questions regarding research reports, contact: Heather Choi at (916) 322-3893
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