HONO formation as unknown radical source in photochemical smog chamber

Sakamaki, Fumio; Akimoto, Hajime

doi:10.1002/kin.550200204

Cited by 22 publications

(23 citation statements)

References 9 publications

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“…[25][26][27][28][29] This has been observed even when oxides of nitrogen have not been added during the experiment, implying that it must have arisen from contamination from previous experiments. Our studies show that the competition between water and HONO for surface sites leads to desorption of adsorbed HONO from the surface as the RH increases.…”

Section: Atmospheric Implicationsmentioning

confidence: 96%

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HONO decomposition on borosilicate glass surfaces: implications for environmental chamber studies and field experiments

Syomin

Finlayson-Pitts

2003

Phys. Chem. Chem. Phys.

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Nitrous acid (HONO) is the major source of OH in polluted urban atmospheres, so an understanding of its formation and loss processes both in urban atmospheres and in laboratory systems is important. Earlier studies over a limited range of conditions showed that HONO is taken up and undergoes reaction on surfaces. We report here a comprehensive set of studies of the decay of HONO and the formation of gas phase products over a range of initial HONO concentrations (0.1-11 ppm) at 1 atm pressure in N 2 at 296 K and 0, 20 and 50% relative humidity (RH), respectively. The loss of HONO and increase in gas phase products were measured over time using long path FTIR spectroscopy. Studies were carried out in an unconditioned borosilicate glass cell and in the same cell after pretreatment with dry gaseous nitric acid. In the HNO 3 -conditioned cell, the loss of HONO was first order at all values of relative humidity (RH), and NO 2 was the only significant gas phase product. For the unconditioned cell, the reaction order increased from first order at 0% RH to second order at 50% RH. The gas phase products at 0% RH were equal amounts of NO and NO 2 . The yield of NO increased to > 90% at 50% RH while the yield of NO 2 decreased to 10%. For both the unconditioned and the HNO 3 -treated cell, the rate of loss of HONO decreased with increasing RH. These results suggest that there is a competition between water, HONO and HNO 3 for surface sites. Displacement of HONO from the cell walls by water was observed in separate experiments. Possible mechanisms, and the implications for HONO formation in environmental chambers and in air, are discussed.

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Section: Atmospheric Implicationsmentioning

confidence: 96%

“…In environmental chambers used to simulate reactions in air, the production of HONO has been observed from chamber walls, 11,[25][26][27][28][29] even when oxides of nitrogen have not been included in the reaction mixture. Additionally, there have been several studies of the loss of HONO in laboratory systems.…”

Section: Introductionmentioning

confidence: 99%

HONO decomposition on borosilicate glass surfaces: implications for environmental chamber studies and field experiments

Syomin

Finlayson-Pitts

2003

Phys. Chem. Chem. Phys.

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“…This explains the longstanding common observation of a ''wall source'' of HONO and OH during photolysis of mixtures in environmental chambers having different surface composition. [37][38][39][40][41][42] It also indicates that avoiding HONO production from the walls in such chambers is impossible if they have been exposed to nitric acid and water vapor, including that found in air. However, as discussed by Zhou et al, 36 the same chemistry occurs on surfaces in the atmosphere, providing a daytime HONO source as well as a means of ''renoxification'' of nitric acid that has previously been deposited out on the surfaces of particles or boundary layer soils, building materials etc.…”

Section: Modelingmentioning

confidence: 99%

“…In addition, it is critical for interpreting the data from environmental chambers where a substantial flux of HONO has been observed from the chamber walls during photolysis. [37][38][39][40][41][42] In the present study, HONO formation from NO 2 hydrolysis in a borosilicate glass cell has been studied in the presence and absence of UV radiation (320-400 nm). The data are interpreted in the framework of a simplified mechanism similar to that shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

The photochemical production of HONO during the heterogeneous hydrolysis of NO2

Ramazan

Syomin

Finlayson-Pitts

2004

Phys. Chem. Chem. Phys.

138

139

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The heterogeneous hydrolysis of NO 2 in thin water films, a major source of HONO and hence OH radicals in polluted urban atmospheres, has been previously reported to be photoenhanced (H. Akimoto, H. Takagi and F. Sakamaki, Int. J. Chem. Kinet., 1987, 19, 539, ref. 1) which has important implications for OH production both in environmental chambers and in the lower atmosphere. We report here studies of the impact of 320-400 nm radiation on HONO formation during the heterogeneous NO 2 hydrolysis at 296 K. The experiments were carried out in a borosilicate glass cell using long path Fourier transform infrared (FTIR) spectroscopy with three initial NO 2 concentrations (20, 46, and 54 ppm) at relative humidities of 33, 39, and 57%, respectively. Nitrous acid was first allowed to accumulate from NO 2 hydrolysis in the dark, and then the mixture of reactants and products was irradiated. The measured concentration-time profiles of the gases were compared to the predictions of a kinetics model developed for this system. The initial loss of HONO upon irradiation was consistent with its photolysis and known secondary gas phase chemistry without any photoenhancement. While the fundamental NO 2 heterogeneous hydrolysis is not itself photoenhanced, there is clear evidence in these experiments for the generation of gas phase HONO by photolysis of adsorbed HNO 3 formed during the heterogeneous hydrolysis. The mechanisms and atmospheric implications of HONO as well as NO 2 formation by the photolysis of surfaceadsorbed HNO 3 are discussed.

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“…In previous chamber studies a significant OH production was found which could not be attributed to known precursors. To explain this OH production the photolysis of heterogeneously formed HONO was assumed to be responsible, at least in part, for this so called background reactivity in the chambers (Akimoto et al, 1987;Carter et al, 1982;Glasson and Dunker, 1989;Killus and Whitten, 1990;Sakamaki and Akimoto, 1988). It was postulated that HONO is formed by two processes, a) the heterogeneous dark Reaction (R2) of NO 2 and water (e.g.…”

Section: Introductionmentioning

confidence: 99%

Characterisation of the photolytic HONO-source in the atmosphere simulation chamber SAPHIR

Rohrer¹,

Bohn²,

Brauers³

et al. 2005

Atmos. Chem. Phys.

268

270

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Abstract. HONO formation has been proposed as an important OH radical source in simulation chambers for more than two decades. Besides the heterogeneous HONO formation by the dark reaction of NO 2 and adsorbed water, a photolytic source has been proposed to explain the elevated reactivity in simulation chamber experiments. However, the mechanism of the photolytic process is not well understood so far. As expected, production of HONO and NO x was also observed inside the new atmospheric simulation chamber SAPHIR under solar irradiation. This photolytic HONO and NO x formation was studied with a sensitive HONO instrument under reproducible controlled conditions at atmospheric concentrations of other trace gases. It is shown that the photolytic HONO source in the SAPHIR chamber is not caused by NO 2 reactions and that it is the only direct NO y source under illuminated conditions. In addition, the photolysis of nitrate which was recently postulated for the observed photolytic HONO formation on snow, ground, and glass surfaces, can be excluded in the chamber. A photolytic HONO source at the surface of the chamber is proposed which is strongly dependent on humidity, on light intensity, and on temperature. An empirical function describes these dependencies and reproduces the observed HONO formation rates to within 10 %. It is shown that the photolysis of HONO represents the dominant radical source in the SAPHIR chamber for typical tropospheric O 3 /H 2 O concentrations. For these conditions, the HONO concentrations inside SAPHIR are similar to recent observations in ambient air.

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HONO formation as unknown radical source in photochemical smog chamber

Cited by 22 publications

References 9 publications

HONO decomposition on borosilicate glass surfaces: implications for environmental chamber studies and field experiments

HONO decomposition on borosilicate glass surfaces: implications for environmental chamber studies and field experiments

The photochemical production of HONO during the heterogeneous hydrolysis of NO2

Characterisation of the photolytic HONO-source in the atmosphere simulation chamber SAPHIR

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