Journal Article

PreJuSER-22396

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration

Fuchs, H.FZJ* ; Dorn, H.-P.FZJ* ; Bachner, M.FZJ* ; Bohn, B.FZJ* ; Brauers, T.FZJ* ; Gomm, S.FZJ* ; Hofzumahaus, H.FZJ* ; Holland, F.FZJ* ; Nehr, S.FZJ* ; Rohrer, F.FZJ* ; Tillmann, R.FZJ* ; Wahner, A.FZJ*

2012
Copernicus Katlenburg-Lindau

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Please use a persistent id in citations: http://hdl.handle.net/2128/7542  doi:10.5194/amt-5-1611-2012

Abstract: During recent field campaigns, hydroxyl radical (OH) concentrations that were measured by laser-induced fluorescence (LIF) were up to a factor of ten larger than predicted by current chemical models for conditions of high OH reactivity and low NO concentration. These discrepancies, which were observed in forests and urban-influenced rural environments, are so far not entirely understood. In summer 2011, a series of experiments was carried out in the atmosphere simulation chamber SAPHIR in Julich, Germany, in order to investigate the photochemical degradation of isoprene, methyl-vinyl ketone (MVK), methacrolein (MACR) and aromatic compounds by OH. Conditions were similar to those experienced during the PRIDE-PRD2006 campaign in the Pearl River Delta (PRD), China, in 2006, where a large difference between OH measurements and model predictions was found. During experiments in SAPHIR, OH was simultaneously detected by two independent instruments: LIF and differential optical absorption spectroscopy (DOAS). Because DOAS is an inherently calibration-free technique, DOAS measurements are regarded as a reference standard. The comparison of the two techniques was used to investigate potential artifacts in the LIF measurements for PRD-like conditions of OH reactivities of 10 to 30 s(-1) and NO mixing ratios of 0.1 to 0.3 ppbv. The analysis of twenty experiment days shows good agreement. The linear regression of the combined data set (averaged to the DOAS time resolution, 2495 data points) yields a slope of 1.02 +/- 0.01 with an intercept of (0.10 +/- 0.03) x 10(6) cm(-3) and a linear correlation coefficient of R-2 = 0.86. This indicates that the sensitivity of the LIF instrument is well-defined by its calibration procedure. No hints for artifacts are observed for isoprene, MACR, and different aromatic compounds. LIF measurements were approximately 30-40% (median) larger than those by DOAS after MVK (20 ppbv) and toluene (90 ppbv) had been added. However, this discrepancy has a large uncertainty and requires further laboratory investigation. Observed differences between LIF and DOAS measurements are far too small to explain the unexpected high OH concentrations during the PRIDE-PRD2006 campaign.

Keyword(s): J

Note: This work was supported by the EU FP-7 program EUROCHAMP-2 (grant agreement no. 228335) and by the EU FP-7 program PEGASOS (grant agreement no. 265307). S. Nehr and B. Bohn thank the Deutsche Forschungsgemeinschaft for funding under grant BO 1580/3-1. We thank M. Kaminski, R. Wegener, K. D. Lu, X. Li, A. Buchholz, P. Schlag, H.-C. Wu, S. Dixneuf, P. Musgen and R. Haseler for additional measurements during this campaign and technical support.

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Contributing Institute(s):

1. Troposphäre (IEK-8)

Research Program(s):

1. Atmosphäre und Klima (P23)
2. EUROCHAMP-2 - Integration of European Simulation Chambers for Investigating Atmospheric Processes - Part 2 (228335) (228335)
3. BROWSE - Bystanders, Residents, Operators and WorkerS Exposure models for plant protection products (265307) (265307)

Appears in the scientific report 2012

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Database coverage:
; ; ; Current Contents - Social and Behavioral Sciences ; JCR ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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