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| Titel |
Investigation of ambient OH reactivity at a receptor site impacted by industrial, urban and marine emissions: Identification of missing OH reactivity |
| VerfasserIn |
Sébastien Dusanter, Vincent Michoud, Thierry Leonardis, Nadine Locoge, Véronique Riffault, Shouwen Zhang |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106043
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| Publikation (Nr.) |
 EGU/EGU2015-5683.pdf |
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| Zusammenfassung |
| The hydroxyl radical (OH), the main daytime oxidant in the troposphere, plays a key role in
atmospheric chemistry. OH initiates the oxidation of most of the trace gases, including
Volatile Organic Compounds (VOC), leading to the formation of harmful secondary
pollutants such as ozone and secondary organic aerosols. VOCs are directly emitted by a
large number of natural and anthropogenic sources and can be formed photochemically. It is
expected that several thousand VOCs could be present in the troposphere at ppt-ppb levels
(Goldstein and Galbally, ES&T, 2007), making exhaustive measurements of VOCs currently
unfeasible with common analytical techniques. In this context, measuring the total
sink of OH, so called total OH reactivity, can provide insights into the reactivity of
unmeasured trace gases to test the completeness of VOC measurements during field
campaigns.
A Comparative Reactivity Method (CRM) instrument was deployed in Dunkirk (France) to
measure ambient OH reactivity during July 2014. An objective of this field campaign was to
investigate the OH reactivity budget in different types of air masses, characterized by
industrial, urban, and marine emissions, as well as different photochemical ages. Collocated
measurements of non-methane hydrocarbons, oxygenated VOCs, and inorganic gases were
also performed. OH reactivity measurements ranged from the detection limit of 3 s-1 up to
90 s-1, with a campaign average of approximately 14 s-1. Large discrepancies were
observed between OH reactivity measurements and values calculated from measured
trace gases, highlighting the presence of unmeasured reactive compounds. In this
presentation, the measured and missing OH reactivity will be discussed regarding air
mass origins and compositions. We will also present a novel approach that was
implemented on the CRM instrument to identify part of the observed missing OH
reactivity. |
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