Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration

Fuchs, Hendrik; Dorn, H.-P.; Bachner, M.; Bohn, Birger; Brauers, T.; Gomm, Sebastian; Hofzumahaus, A.; Holland, F.; Nehr, Sascha; Rohrer, Franz; Tillmann, Ralf; Wahner, Andreas

doi:10.5194/amt-5-1611-2012

Cited by 85 publications

(76 citation statements)

References 47 publications

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“…Using OH LIF or DOAS measurements made no difference in the OH budget analysis which is consistent with previous experiments in SAPHIR where excellent agreement of the two OH detection techniques was demonstrated under various experimental conditions (Schlosser et al, , 2009Fuchs et al, 2012).…”

Section: Discussionsupporting

confidence: 77%

“…Measurements of trace gas concentrations include volatile organic compounds (proton transfer reaction time of flight mass spectrometry, PTR-TOF-MS), HCHO (Hantzsch reaction), HONO (long path absorption photometry, LOPAP), CO (reduction gas analysis, RGA), CO 2 , CH 4 , H 2 O (cavity ring-down spectroscopy, CRDS), as well as NO, NO 2 and O 3 (chemiluminescence, CL). The reader is referred to previous publications for detailed information on the analytical instrumentation of SAPHIR Fuchs et al, 2010Fuchs et al, , 2012Dorn et al, 2013;Fuchs et al, 2013, and references therein). Table 1 provides an overview of the key instruments for this study and their performances.…”

Section: Analytical Instrumentationmentioning

confidence: 99%

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Atmospheric photochemistry of aromatic hydrocarbons: OH budgets during SAPHIR chamber experiments

et al. 2014

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Abstract. Current photochemical models developed to simulate the atmospheric degradation of aromatic hydrocarbons tend to underestimate OH radical concentrations. In order to analyse OH budgets, we performed experiments with benzene, toluene, p-xylene and 1,3,5-trimethylbenzene in the atmosphere simulation chamber SAPHIR. Experiments were conducted under low-NO conditions (typically 0.1-0.2 ppb) and high-NO conditions (typically 7-8 ppb), and starting concentrations of 6-250 ppb of aromatics, dependent on OH rate constants. For the OH budget analysis a steady-state approach was applied in which OH production and destruction rates (P OH and D OH ) have to be equal. The P OH were determined from measurements of HO 2 , NO, HONO, and O 3 concentrations, considering OH formation by photolysis and recycling from HO 2 . The D OH were calculated from measurements of the OH concentrations and total OH reactivities. The OH budgets were determined from D OH /P OH ratios. The accuracy and reproducibility of the approach were assessed in several experiments using CO as a reference compound where an average ratio D OH /P OH = 1.13 ± 0.19 was obtained. In experiments with aromatics, these ratios ranged within 1.1-1.6 under low-NO conditions and 0.9-1.2 under high-NO conditions. The results indicate that OH budgets during photo-oxidation experiments with aromatics are balanced within experimental accuracies. Inclusion of a further, recently proposed OH production via HO 2 + RO 2 reactions led to improvements under low-NO conditions but the differences were small and insignificant within the experimental errors.

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Section: Discussionsupporting

confidence: 77%

Section: Analytical Instrumentationmentioning

confidence: 99%

Atmospheric photochemistry of aromatic hydrocarbons: OH budgets during SAPHIR chamber experiments

et al. 2014

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“…SAPHIR can be regarded as a large chemical reactor that provides a homogeneous mixture of trace gases in synthetic air, ensuring that instruments sampled the same air mass. It has been shown in several comparison exercises that this assumption is justified for OH (Schlosser et al, 2007(Schlosser et al, , 2009Fuchs et al, 2012). Details of the chamber can be also found in these publications.…”

Section: Experiments In the Simulation Chamber Saphirmentioning

confidence: 97%

“…Details of the instruments that were deployed in previous field and chamber experiments are described in Holland et al (2003); Fuchs et al (2008bFuchs et al ( , 2012; Lu et al (2012). Here, we used the instrument that is permanently installed at the atmosphere simulation chamber SAPHIR .…”

Section: Ro X Detection By Laser-induced Fluorescencementioning

confidence: 99%

Investigation of potential interferences in the detection of atmospheric RO<sub><i>x</i></sub> radicals by laser-induced fluorescence under dark conditions

Fuchs¹,

Tan²,

Hofzumahaus³

et al. 2016

Atmos. Meas. Tech.

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Abstract. Direct detection of highly reactive, atmospheric hydroxyl radicals (OH) is widely accomplished by laserinduced fluorescence (LIF) instruments. The technique is also suitable for the indirect measurement of HO 2 and RO 2 peroxy radicals by chemical conversion to OH. It requires sampling of ambient air into a low-pressure cell, where OH fluorescence is detected after excitation by 308 nm laser radiation. Although the residence time of air inside the fluorescence cell is typically only on the order of milliseconds, there is potential that additional OH is internally produced, which would artificially increase the measured OH concentration. Here, we present experimental studies investigating potential interferences in the detection of OH and peroxy radicals for the LIF instruments of Forschungszentrum Jülich for nighttime conditions. For laboratory experiments, the inlet of the instrument was over flowed by excess synthetic air containing one or more reactants. In order to distinguish between OH produced by reactions upstream of the inlet and artificial signals produced inside the instrument, a chemical titration for OH was applied. Additional experiments were performed in the simulation chamber SAPHIR where simultaneous measurements by an open-path differential optical absorption spectrometer (DOAS) served as reference for OH to quantify potential artifacts in the LIF instrument. Experiments included the investigation of potential interferences related to the nitrate radical (NO 3 , N 2 O 5 ), related to the ozonolysis of alkenes (ethene, propene, 1-butene, 2,3-dimethyl-2-butene, α-pinene, limonene, isoprene), and the laser photolysis of acetone. Experiments studying the laser photolysis of acetone yield OH signals in the fluorescence cell, which are equivalent to 0.05 × 10 6 cm −3 OH for a mixing ratio of 5 ppbv acetone. Under most atmospheric conditions, this interference is negligible. No significant interferences were found for atmospheric concentrations of reactants during ozonolysis experiments. Only for propene, α-pinene, limonene, and isoprene at reactant concentrations, which are orders of magnitude higher than in the atmosphere, could artificial OH be detected. The value of the interference depends on the turnover rate of the ozonolysis reaction. For example, an apparent OH concentration of approximately 1×10 6 cm −3 is observed when 5.8 ppbv limonene reacts with 600 ppbv ozone. Experiments with the nitrate radical NO 3 reveal a small interference signal in the OH, HO 2 , and RO 2 detection. Dependencies on experimental parameters point to artificial OH formation by surface reactions at the chamber walls or in molecular clusters in the gas expansion. The signal scales with the presence of NO 3 giving equivalent radical concentrations of 1.1×10 5 cm −3 OH, 1×10 7 cm −3 HO 2 , and 1.7 × 10 7 cm −3 RO 2 per 10 pptv NO 3 .

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“…The uncertainty of the OH measurement, determined by the accuracy of the calibration of the LIF instrument, is 10 % (1σ ). The LIF instrument is described in detail by Fuchs et al (2012). The OH radicals in these experiments are predominantly formed from the ozonolysis of the VOCs, and to a minor extent by HONO and ozone photolysis .…”

Section: Analytical Instrumentationmentioning

confidence: 99%

Evolution of the complex refractive index in the UV spectral region in ageing secondary organic aerosol

Zhao²,

et al. 2014

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Abstract. The chemical and physical properties of secondary organic aerosol (SOA) formed by the photochemical degradation of biogenic and anthropogenic volatile organic compounds (VOC) are as yet still poorly constrained. The evolution of the complex refractive index (RI) of SOA, formed from purely biogenic VOC and mixtures of biogenic and anthropogenic VOC, was studied over a diurnal cycle in the SAPHIR photochemical outdoor chamber in Jülich, Germany. The correlation of RI with SOA chemical and physical properties such as oxidation level and volatility was examined. The RI was retrieved by a newly developed broadband cavity-enhanced spectrometer for aerosol optical extinction measurements in the UV spectral region (360 to 420 nm). Chemical composition and volatility of the particles were monitored by a high-resolution time-of-flight aerosol mass spectrometer, and a volatility tandem differential mobility analyzer. SOA was formed by ozonolysis of either (i) a mixture of biogenic VOC (α-pinene and limonene), (ii) biogenic VOC mixture with subsequent addition of an anthropogenic VOC (p-xylene-d 10 ), or (iii) a mixture of biogenic and anthropogenic VOC. The SOA aged by ozone/OH reactions up to 29.5 h was found to be non-absorbing in all cases. The SOA with p-xylene-d 10 showed an increase of the scattering component of the RI correlated with an increase of the O / C ratio and with an increase in the SOA density. There was a greater increase in the scattering component of the RI when the SOA was produced from the mixture of biogenic VOCs and anthropogenic VOC than from the sequential addition of the VOCs after approximately the same ageing time. The increase of the scattering component was inversely correlated with the SOA volatility. Two RI retrievals determined for the pure biogenic SOA showed a constant RI for up to 5 h of ageing. Mass spectral characterization shows the three types of the SOA formed in this study have a significant amount of semivolatile components. The influence of anthropogenic VOCs on the oxygenated organic aerosol as well as the atmospheric implications are discussed.

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Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration

Cited by 85 publications

References 47 publications

Atmospheric photochemistry of aromatic hydrocarbons: OH budgets during SAPHIR chamber experiments

Atmospheric photochemistry of aromatic hydrocarbons: OH budgets during SAPHIR chamber experiments

Investigation of potential interferences in the detection of atmospheric RO<sub><i>x</i></sub> radicals by laser-induced fluorescence under dark conditions

Evolution of the complex refractive index in the UV spectral region in ageing secondary organic aerosol

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Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration

Cited by 85 publications

References 47 publications

Atmospheric photochemistry of aromatic hydrocarbons: OH budgets during SAPHIR chamber experiments

Atmospheric photochemistry of aromatic hydrocarbons: OH budgets during SAPHIR chamber experiments

Investigation of potential interferences in the detection of atmospheric RO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; radicals by laser-induced fluorescence under dark conditions

Evolution of the complex refractive index in the UV spectral region in ageing secondary organic aerosol

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Investigation of potential interferences in the detection of atmospheric RO<sub><i>x</i></sub> radicals by laser-induced fluorescence under dark conditions