Reactive Trace Gases within and above a Grassland Canopy: Challenges for Flux and Transport Process Determination
type: CreativeWork
description: Nitrogen oxide (NO), nitrogen dioxide (NO2) and ozone (O3) constitute a reactive trace gas triad, which is highly important for the oxidizing capacity of the atmosphere, the functioning of ecosystems and climate change. Terrestrial ecosystems, such as grasslands, represent considerable sources and sinks for the NO-NO2-O3 triad and, thus, are crucial for atmospheric budgets of these species. The experimental quantification of surface-atmosphere exchange of the NO-NO2-O3 triad is difficult, and permanent flux monitoring networks are still at their infancy. Due to their fast reactivity, vertical gradients and fluxes of these species differ significantly from the respective theoretical descriptions for non-reactive trace gases. This effect is referred to as “chemical flux divergence”. Compared to the layer above, plant canopies exhibit an increased aerodynamic resistance, resulting in prolonged transport times of air within the canopy. This may provide sufficient time for in-canopy flux divergence and for interactions of trace gases such as the NO-NO2-O3 triad with plants. A prominent example is the fate of soilemitted NO that undergoes chemical reaction with O3 within the canopy and is subsequently recaptured by the surrounding vegetation in the form of NO2. This process is referred to as “NOx canopy reduction” (NOx = NO+NO2). NOx canopy reduction is commonly applied in global atmospheric chemistry and transport models, but was never investigated for grassland canopies, which cover vast terrestrial areas. This thesis focusses on the following topics investigated for a natural grassland canopy: (i) the quantification of in-canopy transport characteristics such as aerodynamic resistances and transport times, (ii) validation of the dynamic chamber technique for routine O3 flux measurements at low canopy ecosystems and (iii) the analysis of chemical flux divergence and NOx canopy reduction. The quantification of in-canopy transport characteristics is of a major importance …
abstract: Nitrogen oxide (NO), nitrogen dioxide (NO2) and ozone (O3) constitute a reactive trace gas triad, which is highly important for the oxidizing capacity of the atmosphere, the functioning of ecosystems and climate change. Terrestrial ecosystems, such as grasslands, represent considerable sources and sinks for the NO-NO2-O3 triad and, thus, are crucial for atmospheric budgets of these species. The experimental quantification of surface-atmosphere exchange of the NO-NO2-O3 triad is difficult, and permanent flux monitoring networks are still at their infancy. Due to their fast reactivity, vertical gradients and fluxes of these species differ significantly from the respective theoretical descriptions for non-reactive trace gases. This effect is referred to as “chemical flux divergence”. Compared to the layer above, plant canopies exhibit an increased aerodynamic resistance, resulting in prolonged transport times of air within the canopy. This may provide sufficient time for in-canopy flux divergence and for interactions of trace gases such as the NO-NO2-O3 triad with plants. A prominent example is the fate of soilemitted NO that undergoes chemical reaction with O3 within the canopy and is subsequently recaptured by the surrounding vegetation in the form of NO2. This process is referred to as “NOx canopy reduction” (NOx = NO+NO2). NOx canopy reduction is commonly applied in global atmospheric chemistry and transport models, but was never investigated for grassland canopies, which cover vast terrestrial areas. This thesis focusses on the following topics investigated for a natural grassland canopy: (i) the quantification of in-canopy transport characteristics such as aerodynamic resistances and transport times, (ii) validation of the dynamic chamber technique for routine O3 flux measurements at low canopy ecosystems and (iii) the analysis of chemical flux divergence and NOx canopy reduction. The quantification of in-canopy transport characteristics is of a major importance …
author: Plake, Daniel
date published: 2014-04-15
date modified: 2026-07-27T18:49:36Z
provider: Universität Bayreuth
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Universität Bayreuth