The Influence of Light and Temperature on Isoprene Emission Rates from Live Oak |
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Authors: | DAVID T TINGEY MARYBETH MANNING LOUIS C GROTHAUS WALTER F BURNS |
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Institution: | U.S. Environmental Protection Agency and Northrop Services, Inc., 200 S.W. 35th Street, Corvallis, Oregon 97330 |
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Abstract: | There is a growing awareness of the role of vegetation as a source of reactive hydrocarbons that may serve as photochemical oxidant precursors. A study was designed to assess independently the influence of variable light and temperature on isoprene emissions from live oak (Quercus virginiana Mill.). Plants were conditioned in a growth chamber and then transferred to an environmentally controlled gas-exchange chamber. Samples of the chamber atmosphere were collected; isoprene was concentrated cryogenically and measured by gas chromatography. A logistic function was used to model isoprene emission rates. Under regimes of low temperature (20°C) or darkness, isoprene emissions were lowest. With increasing temperature or light intensity, the rate of isoprene emission increased, reaching maxima at 800 μE m-2 s-1 and 40–44°C, respectively. Higher temperatures caused a large decrease in emissions. Since the emissions of isoprene were light-saturated at moderate intensities, temperature appeared to be the main factor controlling emissions during most of the day. Carbon lost through isoprene emissions accounted for 0.1 to 2% of the carbon fixed during photosynthesis depending on light intensity and temperature. |
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Keywords: | Quercus virginiana isoprene hydrocarbon emission |
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