title: To what extent do molecular collisions arising from water vapour efflux impede stomatal O3 influx?
abstract: Pre-requisite for reliable O(3) risk assessment for plants is determination of stomatal O(3) uptake. One unaddressed uncertainty in this context relates to transpiration-induced molecular collisions impeding stomatal O(3) influx. This study quantifies, through physical modelling, the error made when estimating stomatal O(3) flux without accounting for molecular collisions arising from transpiratory mass flow of gas out of the leaf. The analysis demonstrates that the error increases with increasing leaf-to-air water vapour mole fraction difference (Δw), being zero in water vapour saturated air and 4.2% overestimation at Δw of 0.05. Overestimation is approximately twice as large in empirical studies quantifying stomatal O(3) flux from measured leaf or canopy water flux, if neglecting both water vapour-dry air collisions (causing overestimation of leaf conductance) and collisions involving O(3). Correction for transpiration-induced molecular collisions is thus relevant for both empirical research and for large-scale modelling of stomatal O(3) flux across strong spatial Δw gradients.
authors: Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden. johan.uddling@dpes.gu.se
authors: Johan
authors: J
authors: Uddling
authors: Rainer
authors: R
authors: Matyssek
authors: Jan B C
authors: JB
authors: Pettersson
authors: Gerhard
authors: G
authors: Wieser
mesh_terms: D008958:Models, Molecular; D010126:Ozone / Q000737:chemistry* / Q000378:metabolism; D054046:Plant Stomata / Q000378:metabolism*; D018526:Plant Transpiration; D013227:Steam; D014867:Water / Q000737:chemistry* / Q000378:metabolism
chemical_list: D013227:Steam; D014867:Water; D010126:Ozone