Caption title. At head of title: Project summary. "June 1982." "EPA/600-S3-82-010."

"A new method for quantifying biogenic hydrocarbon emission rates without disturbing the vegetation is presented. An energy balance/Bowen ratio approach was used to estimate fluxes of alpha-pinene from measurements of net radiation and vertical gradients of alpha-pinene, temperature, and water vapor above a loblolly pine forest canopy. The mean flux for 20 determinations ranging from 19 to 84 /micro-g/m2/min was 41 /micro-g/mVmin. This method was compared to an enclosure method, in which foliage is enclosed with a Teflon bag for emission rate determinations. For this comparison, the energy balance/Bowen ratio flux values were converted to emission rate units of micro-g alpha-pinene/g dry needle mass/hr using site-specific biomass factors. Seventeen enclosure method determinations from mature loblolly pine trees yielded a median value of 4.7 /micro-g/g/hr over a range of 1.2 to 32 micro-g/g/hr. While both methods displayed relatively high variances, the variance of the enclosure method was considerably higher than that of the energy balance/Bowen ratio method. There was no statistically significant difference between the results of the two methods."--P. [1].