caa a22 4500 477061362 CHVBK 20180405111401.0 cr unu---uuuuu 170330e19960901xx s 000 0 eng 10.1007/BF00053286 doi (NATIONALLICENCE)springer-10.1007/BF00053286 Ambient biogenic hydrocarbons and isoprene emissions from a mixed deciduous forest [Elektronische Daten] [J. Fuentes, D. Wang, H. Neumann, T. Gillespie, G. Den Hartog, T. Dann] Experiments were conducted during the growing season of 1993 at a mixed deciduous forest in southern Ontario, Canada to investigate the atmospheric abundance of hydrocarbons from phytogenic origins, and to measure emission rates from foliage of deciduous trees. The most abundant phytogenic chemical species found in the ambient air were isoprene and the monoterpenes α-pinene and β-pinene. Prior to leaf-bud break during spring, ambient hydrocarbon mixing ratios above the forest remained barely above instrument detection limit (∼20 parts per trillion), but they became abundant during the latter part of the growing season. Peak isoprene mixing ratios reached nearly 10 parts per billion (ppbv) during mid-growing season while maximum monoterpene mixing ratios were close to 2 ppbv. Both isoprene and monoterpene mixing ratios exhibited marked diurnal variations. Typical isoprene mixing ratios were highest during mid-afternoon and were lowest during nighttime. Peak isoprene mixing ratios coincided with maximum canopy temperature. The diurnal pattern of ambient isoprene mixing ratio was closely linked to the local emissions from foliage. Isoprene emission rates from foliage were measured by enclosing branches of trees inside environment-controlled cuvette systems and measuring the gas mixing ratio difference between cuvette inlet and outlet airstream. Isoprene emissions depended on tree species, foliage ontogeny, and environmental factors such as foliage temperature and intercepted photosynthetically active radiation (PAR). For instance, young (<1 month old) aspen leaves released approximately 80 times less isoprene than mature (>3 months old) leaves. During the latter part of the growing season the amount of carbon released back to the atmosphere as isoprene by big-tooth and trembling aspen leaves accounted for approximately 2% of the photosynthetically fixed carbon. Significant isoprene mixing ratio gradients existed between the forest crown and at twice canopy height above the ground. The gradient diffusion approach coupled with similarity theory was used to estimate canopy isoprene flux densities. These canopy fluxes compared favorably with values obtained from a multilayered canopy model that utilized locally measured plant microclimate, biomass distribution and leaf isoprene emission rate data. Modeled isoprene fluxes were approximately 30% higher compared to measured fluxes. Further comparisons between measured and modeled canopy biogenic hydrocarbon flux densities are required to assess uncertainties in modeling systems that provide inventories of biogenic hydrocarbons. Kluwer Academic Publishers, 1996 biogenic hydrocarbons nationallicence isoprene nationallicence terpenes nationallicence biogenic emissions nationallicence emission inventories nationallicence fluxes nationallicence Fuentes J. Department of Environmental Sciences, University of Virginia, 22903, Charlottesville, VA, U.S.A. aut Wang D. Environment Protection Service, Environment Canada, 3439 River Road South, K1A OH3, Ottawa, Ontario, Canada aut Neumann H. Atmospheric Environment Service, Environment Canada, 4905 Dufferin Street, Downsview, M3H 5T4, Ontario, Canada aut Gillespie T. Department of Land Resource Science, University of Guelph, N1 2W1, Ontario, Canada aut Den Hartog G. Atmospheric Environment Service, Environment Canada, 4905 Dufferin Street, Downsview, M3H 5T4, Ontario, Canada aut Dann T. Environment Protection Service, Environment Canada, 3439 River Road South, K1A OH3, Ottawa, Ontario, Canada aut Journal of Atmospheric Chemistry Kluwer Academic Publishers; http://gopger://gopher.wkap.nl 25/1(1996-09-01), 67-95 0167-7764 25:1<67 1996 25 10874 https://doi.org/10.1007/BF00053286 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00053286 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Fuentes J. Department of Environmental Sciences, University of Virginia, 22903, Charlottesville, VA, U.S.A aut NATIONALLICENCE 700 1- Wang D. Environment Protection Service, Environment Canada, 3439 River Road South, K1A OH3, Ottawa, Ontario, Canada aut NATIONALLICENCE 700 1- Neumann H. Atmospheric Environment Service, Environment Canada, 4905 Dufferin Street, Downsview, M3H 5T4, Ontario, Canada aut NATIONALLICENCE 700 1- Gillespie T. Department of Land Resource Science, University of Guelph, N1 2W1, Ontario, Canada aut NATIONALLICENCE 700 1- Den Hartog G. Atmospheric Environment Service, Environment Canada, 4905 Dufferin Street, Downsview, M3H 5T4, Ontario, Canada aut NATIONALLICENCE 700 1- Dann T. Environment Protection Service, Environment Canada, 3439 River Road South, K1A OH3, Ottawa, Ontario, Canada aut NATIONALLICENCE 773 0- Journal of Atmospheric Chemistry Kluwer Academic Publishers; http://gopger://gopher.wkap.nl/ 25/1(1996-09-01), 67-95 0167-7764 25:1<67 1996 25 10874 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer