Urban measurements of atmospheric nitrous acid: A caveat on the interpretation of the HONO photostationary state

Lee, Ben H.; Wood, Ezra C.; Herndon, S. C.; Lefer, B. L.; Luke, Winston T.; Brune, William H.; Nelson, David D.; Zahniser, M. S.; Munger, J. William

doi:10.1002/2013jd020341

Cited by 42 publications

(51 citation statements)

References 40 publications

(35 reference statements)

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“…This equilibrium can only explain a minor portion of gas phase HONO observed at remote and rural sites (Kleffmann, 2007;Su et al, 2008b;Sörgel et al, 2011a;Wong et al, 2012) but may play an important role in measurement results obtained in urban areas (Lee et al, 2013). The budget calculations of Sörgel et al (2011a) and Li et al (2012) showed that including heterogeneous reactions of NO 2 (R4) only slightly improves the discrepancy between [HONO] PSS and measured HONO mixing ratios.…”

Section: R Oswald Et Al: Comparison Of Hono Budgets For Two Measurementioning

confidence: 96%

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A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland

et al. 2015

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Abstract. Atmospheric concentrations of nitrous acid (HONO), one of the major precursors of the hydroxyl radical (OH) in the troposphere, significantly exceed the values predicted by the assumption of a photostationary state (PSS) during daytime. Therefore, additional sources of HONO were intensively investigated in the last decades. This study presents budget calculations of HONO based on simultaneous measurements of all relevant species, including HONO and OH at two different measurement heights, i.e. 1 m above the ground and about 2 to 3 m above the canopy (24 m above the ground), conducted in a boreal forest environment. We observed mean HONO concentrations of about 6.5 × 10 8 molecules cm −3 (26 ppt) during daytime, more than 20 times higher than expected from the PSS of 0.2 × 10 8 molecules cm −3 (1 ppt). To close the budgets at both heights, a strong additional source term during daytime is required. This unidentified source is at its maximum at noon (up to 1.1 × 10 6 molecules cm −3 s −1 , 160 ppt h −1 ) and in general up to 2.3 times stronger above the canopy than close to the ground. The insignificance of known gas phase reactions and other processes like dry deposition or advection compared to the photolytic decomposition of HONO at this measurement site was an ideal prerequisite to study possible correlations of this unknown term to proposed HONO sources. But neither the proposed emissions from soils nor the proposed photolysis of adsorbed HNO 3 contributed substantially to the unknown source. However, the unknown source was found to be perfectly correlated to the unbalanced photolytic loss of HONO.

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Section: R Oswald Et Al: Comparison Of Hono Budgets For Two Measurementioning

confidence: 96%

“…Horizontal transport (T h ) can strongly influence budget calculations in urban regions (Lee et al, 2013). However, Hyytiälä is surrounded by a uniform boreal forest with up to 95 % of the area within a 5 km radius being forested, with mostly Scots pine and spruce creating a homogenous fetch.…”

Section: Hono Budget Calculationsmentioning

confidence: 99%

A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland

et al. 2015

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“…In this approach, the sources and sinks of the species in question are assumed to balance each other and is thus only suitable for species with a short lifetime, such as free radicals. However, it has been widely used to study the daytime HONO budget, despite its lifetime being in the range of 10-20 min during the day Wong et al, 2012), resulting in significant uncertainties, especially for measurements close to emission sources (Lee et al, 2013). However, the measurement site in this study is described as an urban background site and thus is relatively free from the influence of major roads or point sources.…”

Section: Hono Photostationary State Approachmentioning

confidence: 99%

Detailed budget analysis of HONO in central London reveals a missing daytime source

et al. 2016

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Abstract. Measurements of HONO were carried out at an urban background site near central London as part of the Clean air for London (ClearfLo) project in summer 2012. Data were collected from 22 July to 18 August 2014, with peak values of up to 1.8 ppbV at night and non-zero values of between 0.2 and 0.6 ppbV seen during the day. A wide range of other gas phase, aerosol, radiation, and meteorological measurements were made concurrently at the same site, allowing a detailed analysis of the chemistry to be carried out. The peak HONO / NO x ratio of 0.04 is seen at ∼ 02:00 UTC, with the presence of a second, daytime, peak in HONO / NO x of similar magnitude to the night-time peak, suggesting a significant secondary daytime HONO source. A photostationary state calculation of HONO involving formation from the reaction of OH and NO and loss from photolysis, reaction with OH, and dry deposition shows a significant underestimation during the day, with calculated values being close to 0, compared to the measurement average of 0.4 ppbV at midday. The addition of further HONO sources from the literature, including dark conversion of NO 2 on surfaces, direct emission, photolysis of ortho-substituted nitrophenols, the postulated formation from the reaction of HO 2 × H 2 O with NO 2 , photolysis of adsorbed HNO 3 on ground and aerosols, and HONO produced by photosensitized conversion of NO 2 on the surface increases the daytime modelled HONO to 0.1 ppbV, still leaving a significant missing daytime source. The missing HONO is plotted against a series of parameters including NO 2 and OH reactivity (used as a proxy for organic material), with little correlation seen. Much better correlation is observed with the product of these species with j (NO 2 ), in particular NO 2 and the product of NO 2 with OH reactivity. This suggests the missing HONO source is in some way related to NO 2 and also requires sunlight. Increasing the photosensitized surface conversion rate of NO 2 by a factor of 10 to a mean daytime first-order loss of ∼ 6 ×10 −5 s −1 (but which varies as a function of j (NO 2 )) closes the daytime HONO budget at all times (apart from the late afternoon), suggesting that urban surfaces may enhance this photosensitized source. The effect of the missing HONO to OH radical production is also investigated and it is shown that the model needs to be constrained to measured HONO in order to accurately reproduce the OH radical measurements.

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“…However, concentrations are not only controlled by the local ground surfaces source processes but also depend on the convective mixing in the atmosphere, leading to a potential misinterpretation of the correlation results. In addition, the assumed PSS conditions may also not be fulfilled when HONO and its precursors were measured close to their sources (Lee et al, 2013;Crilley et al, 2016).…”

Section: S Laufs Et Al: Diurnal Fluxes Of Hono Above a Crop Rotationmentioning

confidence: 99%

Diurnal fluxes of HONO above a crop rotation

Laufs¹,

Cazaunau²,

Stella³

et al. 2017

Atmos. Chem. Phys.

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Abstract. Nitrous acid (HONO) fluxes were measured above an agricultural field site near Paris during different seasons. Above bare soil, different crops were measured using the aerodynamic gradient (AG) method. Two LOPAPs (LOng Path Absorption Photometer) were used to determine the HONO gradients between two heights. During daytime mainly positive HONO fluxes were observed, which showed strong correlation with the product of the NO 2 concentration and the long wavelength UV light intensity, expressed by the photolysis frequency J (NO 2 ). These results are consistent with HONO formation by photosensitized heterogeneous conversion of NO 2 on soil surfaces as observed in recent laboratory studies. An additional influence of the soil temperature on the HONO flux can be explained by the temperature-dependent HONO adsorption on the soil surface. A parameterization of the HONO flux at this location with NO 2 concentration, J (NO 2 ), soil temperature and humidity fits reasonably well all flux observations at this location.

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Urban measurements of atmospheric nitrous acid: A caveat on the interpretation of the HONO photostationary state

Cited by 42 publications

References 40 publications

A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland

A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland

Detailed budget analysis of HONO in central London reveals a missing daytime source

Diurnal fluxes of HONO above a crop rotation

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