OH reactivity of the urban air in Helsinki, Finland, during winter

Praplan, Arnaud P.; Pfannerstill, Eva Y.; Williams, Jonathan; Hellén, Heidi

doi:10.1016/j.atmosenv.2017.09.013

Cited by 24 publications

(39 citation statements)

References 35 publications

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“…These values are comparable to urban observations in the lower range, such as in in Helsinki, Finland (Praplan et al, 2017), or Mainz, Germany (Sinha et al, 2008). The OH reactivity over the Red Sea, Gulf of Aden and Gulf of Oman can largely be attributed to the influence of maritime transport in these busy, relatively constricted seaways.…”

Section: Seaways Influenced By Maritime Traffic: Red Sea Gulf Of Adesupporting

confidence: 83%

Shipborne measurements of total OH reactivity around the Arabian Peninsula and its role in ozone chemistry

Pfannerstill¹,

Wang²,

Edtbauer³

et al. 2019

Preprint

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The Arabian Peninsula is characterized by high and increasing levels of photochemical air pollution. Strong solar irradiation, high temperatures and large anthropogenic emissions of reactive trace gases result in intense photochemical activity, especially during the summer months. However, air chemistry measurements in the region are scarce. In order to assess regional pollution sources and oxidation rates, the first ship-based direct measurements of total OH reactivity were 15 performed in summer 2017 from a vessel travelling around the peninsula during the AQABA (Air Quality and Climate Change in the Arabian Basin) campaign. Total OH reactivity is the total loss frequency of OH radicals due to all reactive compounds present in air and defines the local lifetime of OH, the most important oxidant in the troposphere. During the AQABA campaign, the total OH reactivity ranged from below the detection limit (5.4 s -1 ) over the north-western Indian Ocean (Arabian Sea) to a maximum of 32.8 ± 9.6 s -1 over the Arabian Gulf (also known as Persian Gulf) when air originated 20 from large petroleum extraction/processing facilities in Iraq and Kuwait. In the polluted marine regions, OH reactivity was broadly comparable to highly populated urban centers in intensity and composition. The permanent influence of heavy maritime traffic over the seaways of the Red Sea, Gulf of Aden and Gulf of Oman resulted in median OH sinks of 7.9−8.5 s -1 . Due to the rapid oxidation of direct volatile organic compound (VOC) emissions, oxygenated volatile organic compounds (OVOCs) were observed to be the main contributor to OH reactivity around the Arabian Peninsula (9−35 % by 25 region). Over the Arabian Gulf, alkanes and alkenes from the petroleum extraction and processing industry were an important OH sink with ~9 % of total OH reactivity each, whereas NO x and aromatic hydrocarbons (~10 % each) played a larger role in the Suez Canal, which is influenced more by ship traffic and urban emissions. We investigated the number and identity of chemical species necessary to explain the total OH sink. Taking into account ~100 individually measured chemical species, the observed total OH reactivity can typically be accounted for within the measurement uncertainty, with 30 10 dominant trace gases accounting for 20−39 % of regional total OH reactivity. The chemical regimes causing the intense ozone pollution around the Arabian Peninsula were investigated using total OH reactivity measurements. Ozone vs. OH reactivity relationships were found to be a useful tool for differentiating between ozone titration in fresh emissions and https://doi.photochemically aged air masses. Our results show that the ratio of NO x -and VOC-attributed OH reactivity was favorable for ozone formation almost all around the Arabian Peninsula, which is due to NO x and VOCs from ship exhausts and, often, oil/gas production. Therewith, total OH reactivity measurements help to elucidate the chemical processes underlying the extreme tropospheric ozone concentrations observed in sum...

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Section: Seaways Influenced By Maritime Traffic: Red Sea Gulf Of Adesupporting

confidence: 83%

Shipborne measurements of total OH reactivity around the Arabian Peninsula and its role in ozone chemistry

Pfannerstill¹,

Wang²,

Edtbauer³

et al. 2019

Preprint

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“…The CRM method is more commonly used than the direct OH measurement techniques because of the commercial availability of PTR-MS instruments. It is applied by the Max Planck Institute Mainz (MPI) (Sinha et al, 2008), IMT Lille Douai, formally called Mines Douai (MDOUAI) Michoud et al, 2015), Laboratoire des Sciences du Climat et de l'Environnement (LSCE) (Zannoni et al, 2015), Indian Institute of Science Education and Research Mohali (Kumar et al, 2014), the Finnish Meteorological Institute (Praplan et al, 2017), Peking University (Yang et al, 2017), the University of Leicester and University of California, Irvine (Kim et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR

Fuchs¹,

Novelli²,

Rolletter³

et al. 2017

Atmos. Meas. Tech.

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Abstract. Hydroxyl (OH) radical reactivity (k OH ) has been measured for 18 years with different measurement techniques. In order to compare the performances of instruments deployed in the field, two campaigns were conducted performing experiments in the atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich in October 2015 and April 2016. Chemical conditions were chosen either to be representative of the atmosphere or to test potential limitations of instruments. All types of instruments that are currently used for atmospheric measurements were used in one of the two campaigns. The results of these campaigns demonstrate that OH reactivity can be accurately measured for a wide range of atmospherically relevant chemical conditions (e.g. water vapour, nitrogen oxides, various organic compounds) by all instruments. The precision of the measurements (limit of detection < 1 s −1 at a time resolution of 30 s to a few minutes) is higher for instruments directly detecting hydroxyl radicals, whereas the indirect comparative reactivPublished by Copernicus Publications on behalf of the European Geosciences Union. H. Fuchs et al.: OH reactivity comparison in SAPHIRity method (CRM) has a higher limit of detection of 2 s −1 at a time resolution of 10 to 15 min. The performances of the instruments were systematically tested by stepwise increasing, for example, the concentrations of carbon monoxide (CO), water vapour or nitric oxide (NO). In further experiments, mixtures of organic reactants were injected into the chamber to simulate urban and forested environments. Overall, the results show that the instruments are capable of measuring OH reactivity in the presence of CO, alkanes, alkenes and aromatic compounds. The transmission efficiency in Teflon inlet lines could have introduced systematic errors in measurements for low-volatile organic compounds in some instruments. CRM instruments exhibited a larger scatter in the data compared to the other instruments. The largest differences to reference measurements or to calculated reactivity were observed by CRM instruments in the presence of terpenes and oxygenated organic compounds (mixing ratio of OH reactants were up to 10 ppbv). In some of these experiments, only a small fraction of the reactivity is detected. The accuracy of CRM measurements is most likely limited by the corrections that need to be applied to account for known effects of, for example, deviations from pseudo first-order conditions, nitrogen oxides or water vapour on the measurement. Methods used to derive these corrections vary among the different CRM instruments. Measurements taken with a flowtube instrument combined with the direct detection of OH by chemical ionisation mass spectrometry (CIMS) show limitations in cases of high reactivity and high NO concentrations but were accurate for low reactivity (< 15 s −1 ) and low NO (< 5 ppbv) conditions.

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“…The experimental total OH reactivity, R exp , can be measured with the Comparative Reactivity Method (CRM, Sinha et al,115 2008; Michoud et al, 2015). The specific instrument used for this study is described in Praplan et al (2017Praplan et al ( , 2019 and the measurement principle briefly explained in the following section together with the application of the method to measure the OH Reactivity of Emissions (OHRE).…”

Section: Oh Reactivitymentioning

confidence: 99%

“…However, corrections due to the presence of ozone (O 3 ) and nitrogen oxides (NO x ) described elsewhere (e.g. Michoud et al, 2015;Fuchs et al, 2017;Praplan et al, 2017Praplan et al, , 2019 are not required in the present study due to the use of zero air through the dynamic branch enclosure. Only the correction due to the difference in relative humidity (RH) in the reactor between C 2 and C 3 levels and the correction due to the deviation 155 from pseudo-first-order kinetics need to be taken into account.…”

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confidence: 99%

OH reactivity from different tree species: Investigating the missing reactivity in a boreal forest

Praplan

Tykkä

Schallhart

et al. 2020

Preprint

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In forested area, a large fraction of total hydroxyl radical (OH) reactivity remain unaccounted for. Very few studies have been looking at total OH reactivity from biogenic emissions and its variations. In the present study, we investigate the total OH reactivity from three common boreal tree species (Scots pine, Norway spruce, and Downy birch), by comparing it with the calculated reactivity from the chemically identified emissions. Total OH reactivity was measured using the Comparative 5 Reactivity Method (CRM), and the chemical composition of the emissions was quantified with two gas chromatographs coupled to mass spectrometers (GC-MSs). Dynamic branch enclosures were used and emissions from one branch of a tree at the time were measured by rotating between them periodically.Results show that birch had the highest values of total OH reactivity of the emissions (TOHRE), while pine had the lowest.The main drivers for the known reactivity of pine and spruce were monoterpenes and sesquiterpenes. For birch, emissions were 10 dominated by sesquiterpenes, even though monoterpenes and GLVs could be found too. However, calculated reactivity values remained low leading to the highest missing fraction of reactivity (>96 %), while pine and spruce had similar missing reactivity fractions between 56 % and 82 % (higher in the spring and decreasing as the summer proceeded). The high average values were driven by low reactivity periods and the fraction of missing reactivity got smaller for pine and spruce when the TOHRE values increased. Important exceptions were identified for periods when the emission profiles changed from terpenes to Green Leaf 15 Volatiles (GLVs), a family of compounds containing a 6 carbon atoms backbone with various functionalities (e.g. alcohols, aldehydes, esters) that indicate that the plant is suffering from stress. Then, very high TOHRE values were measured and the missing fraction remained high.This study found a different trend in the missing OHRE fraction of Norway spruce from spring to autumn compared to one previous study (Nölscher et al., 2013), which indicates that additional studies are required to fully understand the complexity 20 of biogenic reactive emissions. Future studies of boreal trees in situ should be conducted to confirm the findings presented.

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OH reactivity of the urban air in Helsinki, Finland, during winter

Cited by 24 publications

References 35 publications

Shipborne measurements of total OH reactivity around the Arabian Peninsula and its role in ozone chemistry

Shipborne measurements of total OH reactivity around the Arabian Peninsula and its role in ozone chemistry

Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR

OH reactivity from different tree species: Investigating the missing reactivity in a boreal forest

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