Night‐time NO<sub>3</sub> and OH radical concentrations in the United Kingdom inferred from hydrocarbon measurements

Khan, M. Anwar H.; Ashfold, Matthew J.; Nickless, G.; Martin, Damien; Watson, Laura; Hamer, P. D.; Wayne, Richard P.; Canosa‐Mas, Carlos E.; Shallcross, Dudley E.

doi:10.1002/asl.175

Cited by 41 publications

(28 citation statements)

References 42 publications

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“…Loss of CO by reaction with the OH radical can be ruled out, as CO loss of 3.3×10 −5 s −1 (mean loss from night-time events) would require a night-time OH radical concentration of 1.6×10 8 molecules cm −3 which is not possible under night-time conditions. Night-time OH radical concentrations in the range of 2±1.5×10 5 molecules cm −3 have been measured and modelled in recent studies (Emmerson and Carslaw, 2009;Geyer et al, 2003) whilst daytime average OH is thought to be 1×10 6 molecules cm −3 (Khan et al, 2008;Prinn et al, 2005). Reaction of CO with the nitrate radical (NO 3 ) is too slow to account for any significant loss (Boyd et al, 1991).…”

Section: Nocturnal Depletions Of H 2 and Comentioning

confidence: 99%

High-frequency urban measurements of molecular hydrogen and carbon monoxide in the United Kingdom

et al. 2010

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Abstract. High-frequency measurements of atmospheric molecular hydrogen (H 2 ) and carbon monoxide (CO) were made at an urban site in the United Kingdom (UK) from mid-December, 2008 until early March, 2009. Very few measurements of H 2 exist in the urban environment, particularly within the UK, but are an essential component in the assessment of anthropogenic emissions of H 2 and to a certain extent CO. These data provide detailed information on urban time-series, diurnal cycles as well as sources and sinks of both H 2 and CO at urban locations. High-frequency data were found to be strongly influenced by local meteorological conditions of wind speed and temperature. Diurnal cycles were found to follow transport frequency very closely due to the sites proximity to major carriageways, consequently a strong correlation was found between H 2 and CO mole fractions. Background subtracted mean and rush hour molar H 2 /CO emission ratios of 0.53±0.08 and 0.57±0.06 respectively, were calculated from linear fitting of data. The scatter plot of all H 2 and CO data displayed an unusual two population pattern, thought to be associated with a large industrial area 85 km to the west of the site. However, the definitive source of this two branch pattern could not be fully elucidated. H 2 emissions from transport in the UK were estimated to be 188±39 Gg H 2 /yr, with 8.1±2.3 Tg/yr of H 2 produced from vehicle emissions globally. H 2 and CO deposition velocities were calculated during stable night-time inversion events when a clear decay of both species was observed. CO was found to have a much higher deposition velocity than H 2 , 1.3±0.8×10 −3 and 2.2±1.5×10 −4 m s −1 (1σ ) respectively, going against the law of molecular diffusivity. The source of this unusual result was investigated, however no conclusive explanation was found for increased loss of CO over H 2 during stable night time inversion events.

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Section: Nocturnal Depletions Of H 2 and Comentioning

confidence: 99%

High-frequency urban measurements of molecular hydrogen and carbon monoxide in the United Kingdom

et al. 2010

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“…Inspection of urban isoprene levels from the UK Air Quality (NETCEN) archive (e.g. Rivett et al, 2003a, b;Khan et al, 2008) show that typical levels in March are around 60 pptv, and not all of this will be of biogenic origin. Using these levels of surface isoprene (higher than those predicted by the emission model) as input into the trajectory model would not generate anywhere near enough formic acid to rectify the model underprediction that is seen up to around 02:30 p.m. Increasing primary morning emissions of formic acid from an anthropogenic source increases formic acid in the early afternoon, but has less effect in the late afternoon, consistent with observations.…”

Section: Comparison Between Model and Measurementsmentioning

confidence: 99%

Airborne observations of formic acid using a chemical ionization mass spectrometer

et al. 2012

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Abstract. The first airborne measurements of formic acid mixing ratios over the United Kingdom were measured on the FAAM BAe-146 research aircraft on 16 March 2010 with a chemical ionization mass spectrometer using I − reagent ions. The I − ionization scheme was able to measure formic acid mixing ratios at 1 Hz in the boundary layer.In-flight standard addition calibrations from a formic acid source were used to determine the instrument sensitivity of 35 ± 6 ion counts pptv −1 s −1 and a limit of detection of 25 pptv. Routine measurements were made through a scrubbed inlet to determine the instrumental background. Three plumes of formic acid were observed over the UK, originating from London, Humberside and Tyneside. The London plume had the highest formic acid mixing ratio throughout the flight, peaking at 358 pptv. No significant correlations of formic acid with NO x and ozone were found, but a positive correlation was observed between CO and HCOOH within the two plumes where coincident data were recorded.A trajectory model was employed to determine the sources of the plumes and compare modelled mixing ratios with measured values. The model underestimated formic acid concentrations by up to a factor of 2. This is explained by missing sources in the model, which were considered to be both primary emissions of formic acid of mainly anthropogenic origin and a lack of precursor emissions, such as isoprene, from biogenic sources, whose oxidation in situ would lead to formic acid formation.

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“…It is hypothesized that in extremely high OH and HO2 concentrations, all ClO is rapidly converted to HOCl, limiting the formation on significant levels of ClO and subsequently ClONO2. Khan et al (2008) suggest that Cl atoms of around 2x10 4 molecules cm -3 could be present at night via analysis of alkane relative abundance. Although a formation mechanism is not proposed, it provides further evidence that ClO formation at night-time is possible and may represent an unknown reaction pathway, which would agree with the measurements presented in this work.…”

Section: Inorganic Chlorine Abundance and Profilesmentioning

confidence: 96%

Chlorine oxidation of VOCs at a semi-rural site in Beijing: Significant chlorine liberation from ClNO<sub>2</sub> and subsequent gas and particle phase Cl-VOC production

Breton¹,

Hallquist²,

Pathak³

et al. 2018

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Abstract. Nitryl Chloride (ClNO2) accumulation at night-time acts as a significant reservoir for active chlorine 25 and impacts the following day´s photochemistry when the chlorine atom is liberated at sunrise. Here, we report 26 simultaneous measurements of N2O5, a suite of inorganic halogens including ClNO2 and Cl-VOCs in the gas and 34Cl-VOCs were measured in the particle and gas phase for the first time at high time resolution and illustrate how Atmos. Chem. Phys. Discuss., https://doi

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Night‐time NO₃ and OH radical concentrations in the United Kingdom inferred from hydrocarbon measurements

Cited by 41 publications

References 42 publications

High-frequency urban measurements of molecular hydrogen and carbon monoxide in the United Kingdom

High-frequency urban measurements of molecular hydrogen and carbon monoxide in the United Kingdom

Airborne observations of formic acid using a chemical ionization mass spectrometer

Chlorine oxidation of VOCs at a semi-rural site in Beijing: Significant chlorine liberation from ClNO<sub>2</sub> and subsequent gas and particle phase Cl-VOC production

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Night‐time NO3 and OH radical concentrations in the United Kingdom inferred from hydrocarbon measurements

Cited by 41 publications

References 42 publications

High-frequency urban measurements of molecular hydrogen and carbon monoxide in the United Kingdom

High-frequency urban measurements of molecular hydrogen and carbon monoxide in the United Kingdom

Airborne observations of formic acid using a chemical ionization mass spectrometer

Chlorine oxidation of VOCs at a semi-rural site in Beijing: Significant chlorine liberation from ClNO&lt;sub&gt;2&lt;/sub&gt; and subsequent gas and particle phase Cl-VOC production

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Night‐time NO₃ and OH radical concentrations in the United Kingdom inferred from hydrocarbon measurements

Chlorine oxidation of VOCs at a semi-rural site in Beijing: Significant chlorine liberation from ClNO<sub>2</sub> and subsequent gas and particle phase Cl-VOC production