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Title:What effect does VOC sampling time have on derived OH reactivity?
Authors:Sonderfeld, Hannah (Author)
White, Iain R (Author)
Goodall, Iain C A (Author)
Hopkins, James R (Author)
Lewis, Alistair C (Author)
Koppmann, Ralf (Author)
Monks, Paul S (Author)
Files:This document has no files. This document may have a phisical copy in the library of the organization, check the status via COBISS. Link is opened in a new window
Language:English
Work type:Not categorized (r6)
Tipology:1.01 - Original Scientific Article
Organization:UNG - University of Nova Gorica
Abstract:State-of-the-art techniques allow for rapid measurements of total OH reactivity. Unknown sinks of OH and oxidation processes in the atmosphere have been attributed to what has been termed ĝ€missingĝ€ OH reactivity. Often overlooked are the differences in timescales over which the diverse measurement techniques operate. Volatile organic compounds (VOCs) acting as sinks of OH are often measured by gas chromatography (GC) methods which provide low-frequency measurements on a timescale of hours, while sampling times are generally only a few minutes. Here, the effect of the sampling time and thus the contribution of unmeasured VOC variability on OH reactivity is investigated. Measurements of VOC mixing ratios by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) conducted during two field campaigns (ClearfLo and PARADE) in an urban and a semi-rural environment were used to calculate OH reactivity. VOCs were selected to represent variability for different compound classes. Data were averaged over different time intervals to simulate lower time resolutions and were then compared to the mean hourly OH reactivity. The results show deviations in the range of 1 to 25%. The observed impact of VOC variability is found to be greater for the semi-rural site.The selected compounds were scaled by the contribution of their compound class to the total OH reactivity from VOCs based on concurrent gas chromatography measurements conducted during the ClearfLo campaign. Prior to being scaled, the variable signal of aromatic compounds results in larger deviations in OH reactivity for short sampling intervals compared to oxygenated VOCs (OVOCs). However, once scaled with their lower share during the ClearfLo campaign, this effect was reduced. No seasonal effect on the OH reactivity distribution across different VOCs was observed at the urban site.
Keywords:Hydroxyl radical, Atmospheric chemistry, Box model
Year of publishing:2016
Number of pages:6303-6318
Numbering:16, 10
COBISS_ID:5417723 Link is opened in a new window
URN:URN:SI:UNG:REP:7DNOSKP3
DOI:10.5194/acp-16-6303-2016 Link is opened in a new window
License:CC BY-NC-SA 4.0
This work is available under this license: Creative Commons Attribution Non-Commercial Share Alike 4.0 International
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Record is a part of a journal

Title:Atmospheric Chemistry and Physics
Shortened title:Atmos. Chem. Phys.
Publisher:Copernicus
ISSN:16807316
Year of publishing:2016

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