<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gordon, M.</style></author><author><style face="normal" font="default" size="100%">Vlasenko, A.</style></author><author><style face="normal" font="default" size="100%">Staebler, R. M.</style></author><author><style face="normal" font="default" size="100%">Stroud, C.</style></author><author><style face="normal" font="default" size="100%">Makar, P. A.</style></author><author><style face="normal" font="default" size="100%">Liggio, J.</style></author><author><style face="normal" font="default" size="100%">Li, S. -M.</style></author><author><style face="normal" font="default" size="100%">Brown, S.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Uptake and emission of VOCs near ground level below a mixed forest at Borden, Ontario</style></title><secondary-title><style face="normal" font="default" size="100%">ATMOSPHERIC CHEMISTRY AND PHYSICS</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2014</style></year></dates><number><style face="normal" font="default" size="100%">17</style></number><volume><style face="normal" font="default" size="100%">14</style></volume><pages><style face="normal" font="default" size="100%">9087-9097</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Understanding of the atmosphere/forest canopy exchange of volatile organic compounds (VOCs) requires insight into the deposition, emission, and chemical reactions of VOCs below the canopy. Between 18 July and 9 August 2009, VOCs were measured with proton-transfer-reaction mass spectrometry (PTR-MS) at six heights between 1 and 6 m beneath a 23 m high mixed-forest canopy. Measured VOCs included methanol, isoprene, acetone, methacrolein and methyl vinyl ketone (MACR + MVK), monoterpenes, and sesquiterpenes. There are pronounced differences in the behaviour of isoprene and its by-products and that of the terpenes. Non-terpene mixing ratios increase with height, suggesting predominantly downward fluxes. In contrast, the terpene mixing ratios decrease with height, suggesting upward fluxes. A 1-D canopy model was used to compare results to measurements with and without surface deposition of isoprene and MACR + MVK and emissions of monoterpenes and sesquiterpenes. Results suggest deposition velocities of 2.7 mm s(-1) for isoprene and 1.2 mm s(-1) for MACR + MVK and daytime surface emission rates of 63 mu g m(-2) h(-1) for monoterpenes. The modelled isoprene surface deposition is approximately 2% of the canopy-top isoprene emissions and the modelled emissions of monoterpenes comprise approximately 15 to 27% of the canopy-top monoterpene emissions to the atmosphere. These results suggest that surface monoterpene emissions are significant for forest canopy/atmosphere exchange for this mixed-forest location and surface uptake is relatively small for all the species measured in this study.</style></abstract></record></records></xml>