Book/Dissertation / PhD Thesis

FZJ-2018-05911

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Chamber study of biogenic volatile organic compounds: plant emission, oxidation products and their OH reactivity

Yu, Z. (Corresponding author)FZJ*

2018
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-356-3

Please use a persistent id in citations: http://hdl.handle.net/2128/20336  urn:nbn:de:0001-2018120623

Abstract: Volatile organic compounds (VOC)(Fuchs et al., 2017) are ubiquitous in the atmosphere with an estimated atmospheric VOC species of 10$^{4}$-10$^{5}$. Natural and anthropogenic activities emit VOCs into the atmosphere, with about 90% of the global VOC emissions originating from land vegetation. VOCs play a vital role in the global carbon budget and in the regional formation of ozone in the troposphere. They can also serve as a source of secondary organic aerosol (SOA). Atmospheric lifetime of VOCs varies from minutes to years and is predominantly determined by the reactions with hydroxyl radical (OH), nitrate radical (NO$_{3}$), or ozone (O$_{3}$). By atmospheric VOCs oxidation intermediate products are formed. The detailed chemical mechanisms involved are insufficiently known to date and need to be understood for air quality management and climate change predictions. OH radical as the primary oxidant in the troposphere, initiates the degradation of nearly all types of VOCs. The total OH reactivity is the first-order loss rate of OH in reaction with compounds present in ambient air, which provides an insight of the total loading of reactive compounds in the atmosphere. Previous studies comparing directly measured OH reactivity with that calculated from VOC measurements often reported a "missing OH reactivity" in the calculated one, suggesting the existence of unquantified OH sink terms. This work presents the emission of Biogenic VOCs (BVOCs) from 7 sets of trees and the oxidation of VOCs in a chamber system. The focus of this work is to investigate the atmospheric degradation of VOCs and to improve the knowledge of the sum of reactive trace gases involved in atmospheric processes by using the OH reactivity parameter. A Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (PTR-TOF-MS) was used for real-time measurements of VOCs. Monoterpene and sesquiterpene speciations from an offline gas-chromatograph (GC) measurements were adopted forOHreactivity calculation due to the reaction rate coefficient difference among different monoterpenes and sesquiterpenes. The intercomparison between PTR and online GC during the selected campaigns exhibited that the measured concentrations of the main reactants used in this study (isoprene, monoterpenes and benzene-D$_{6}$) were linearly correlated and differed within 15%. The newly built plant chamber SAPHIR-PLUS was characterized with the average BVOCs transfer efficiency of 0.85 from inlet to outlet, and 0.8 from PLUS to the atmosphere simulation chamber SAPHIR. The BVOCs emission pattern from $\textit{Quercus ilex}$ trees has been determined by the use of SAPHIR-PLUS. The detected BVOCs emissions were dominated by monoterpenes, with minor emissions of isoprene and methanol, consistent with the overall emission pattern typical for $\textit{Quercus ilex}$ trees in the growing season. Monoterpenes and isoprene emissions showed to be triggered by light rather than temperature, because these two compounds have no storage pools in $\textit{Quercus ilex}$, their release are thus directly connected with the photosynthesis processes in the plant. Additionally, their emissions showed clear exponential temperature dependence under constant light condition, with a slope of 0.11 $\pm$ 0.02 $^{\circ}$C$^{-1}$ for monoterpenes emission. As a tracer for leaf growth, methanol emission exhibited an abrupt increase at the beginning of illumination. This was explained as instantaneous release from stomata of leaves, that stored produced methanol during the night and opened upon light exposure. Emission of methanol increased linearly with temperature.

Note: Universität Wuppertal, Diss., 2018

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Contributing Institute(s):

1. Troposphäre (IEK-8)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

Appears in the scientific report 2018

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Database coverage:
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