Daytime HO2 concentrations at Oki Island, Japan, in summer 1998: Comparison between measurement and theory

Kanaya, Yugo; Sadanaga, Yasuhiro; Matsumoto, Jun; Sharma, U. K.; Hirokawa, Jun; Kajii, Yoshizumi; Akimoto, Hajime

doi:10.1029/2000jd900308

Cited by 71 publications

(104 citation statements)

References 71 publications

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“…The agreement between modelled and measured [HO 2 ] is variable. Some studies show a reasonable agreement with the measurements (within 25%), but generally the models tend to overestimate [HO 2 ] by a factor of 2 or more (Carslaw et al, , 2002Kanaya et al, 2000Kanaya et al, , 2001. In PEM Tropics B Tan et al (2001) reported a modelled to observed ratio of 1.12 for HO 2 near the surface.…”

Section: Introductionsupporting

confidence: 52%

“…Table 5. The agreement between the models and the measurements is roughly within a factor of 2 around midday, which is better than was found in previous modelling results for HO 2 (Carslaw et al, , 2001George et al, 1999;Kanaya et al, 2000;Stevens et al, 1997).…”

Section: Oh Measured To Modelled Comparisonscontrasting

confidence: 42%

“…There is substantial uncertainty about the effect of aerosol uptake on OH and HO 2 concentrations, mainly due to a lack of ancillary aerosol data recorded during many of the recent MBL campaigns Kanaya et al, 2000Kanaya et al, , 2001.…”

Section: Treatment Of Aerosol Loss In the Modelmentioning

confidence: 99%

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OH and HO2 chemistry in clean marine air during SOAPEX-2

et al. 2004

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Abstract. Model-measurement comparisons of HO x in extremely clean air ([NO]<3 ppt) are reported. Measurements were made during the second Southern Ocean Photochemistry Experiment (SOAPEX-2), held in austral summer 1999 at the Cape Grim Baseline Air Pollution Station in northwestern Tasmania, Australia.The free-radical chemistry was studied using a zerodimensional box-model based upon the Master Chemical Mechanism (MCM). Two versions of the model were used, with different levels of chemical complexity, to explore the role of hydrocarbons upon free-radical budgets under very clean conditions. The "detailed" model was constrained to measurements of CO, CH 4 and 17 NMHCs, while the "simple" model contained only the CO and CH 4 oxidation mechanisms, together with inorganic chemistry. The OH and HO 2 (HO x ) concentrations predicted by the two models agreed to within 5-10%.The model results were compared with the HO x concentrations measured by the FAGE (Fluorescence Assay by Gas Expansion) technique during four days of clean Southern Ocean marine boundary layer (MBL) air. The models overestimated OH concentrations by about 10% on two days and about 20% on the other two days. HO 2 concentrations were measured during two of these days and the models overestimated the measured concentrations by about 40%. Better agreement with measured HO 2 was observed by using data from several MBL aerosol measurements to estimate the aerosol surface area and by increasing the HO 2 uptake coefficient to unity. This reduced the modelled HO 2 overestimate by ∼40%, with little effect on OH, because of the poor HO 2 to OH conversion at the low ambient NO x concentrations.Local sensitivity analysis and Morris One-At-A-Time analysis were performed on the "simple" model, and showed

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Section: Introductionsupporting

confidence: 52%

Section: Oh Measured To Modelled Comparisonscontrasting

confidence: 42%

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OH and HO2 chemistry in clean marine air during SOAPEX-2

et al. 2004

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“…Heterogeneous HO 2 loss constitutes 5-10% of the homogeneous gas-phase chemical loss for low to moderate aerosolloading conditions and becomes comparable to gas-phase chemical loss for high aerosol loading (17,18). These estimates assume that HO 2 is irreversibly destroyed after being accommodated by the aerosol surface, and this assumption remains the principle uncertainty in the process.…”

Section: Discussion and Implications For The Interactions Of Ho 2 Andmentioning

confidence: 99%

On the interactions between atmospheric radicals and cloud droplets: A molecular picture of the interface

Shi

Belair

Francisco

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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How gas-phase materials become incorporated with cloud droplets has been an intriguing subject for decades, and considerable work has been done to understand the interactions between closed-shell molecules and liquid water. The interactions between open-shell radical species and liquid-phase cloud droplets, however, are not well understood. To probe these interactions we used quantum chemistry calculations to predict the energetics of the hydroperoxy radical (HO2) in the presence of an (H2O)20 spherical water cage. Our calculations show that it is energetically favorable for the radical to bind to the outside of the cage. This configuration has the hydrogen and the terminal oxygen of the radical as its primary bonding sites. Free-energy calculations suggest that, at atmospheric conditions, there will be a partitioning between HO2 radicals that are surface-bound and HO2 radicals that dissolve into the bulk. This may have important ramifications for our understanding of radical chemistry and may lend insight into the role that clouds and aerosols play in atmospheric chemical processes.R adical species play an important role in controlling the chemistry of the atmosphere. The uptake of radicals by both aqueous atmospheric aerosols and cloud droplets can impact gas-phase chemistry by removing reactant radicals from the gas phase. For example, the uptake of HO 2 radicals by cloud droplets slows down the gas-phase loss of ozone (O 3 ) because HO 2 can react with O 3 as follows (1):Lack of HO 2 concentration can also suppress the formation of O 3 by the reaction sequenceHowever, the mechanism by which HO 2 is taken up by an aqueous medium and what happens to the HO 2 after uptake both are unclear. Knowing whether a particular radical species is adsorbed (surface-bound) or absorbed (dissolved into the bulk) is critical to an understanding of its kinetics and reaction dynamics.The current model for how a gas-phase molecule is taken up by a water droplet (2) is depicted in Fig. 1. The first step involves gas-phase diffusion to the surface of the droplet. The second step involves accommodation of the gas-phase molecule at the surface. This is the crucial step, and little is known about how a radical interacts with the surface. Studies by Gertner and Hynes (3) have looked at how closed-shell molecules interact with water surfaces, but no studies to date have explained how open-shell species might be accommodated. Once a molecule is accommodated, the third step involves diffusion within the water droplet. Reaction within the bulk, diffusion of the reaction products back to the surface, and desorption from the droplet make up the remainder of the sequence. An understanding of each of these steps is essential to comprehend reactive uptake by water droplets, which is important for atmospheric models and the interpretation of heterogeneous processes occurring in the atmosphere.Field observations have offered evidence for the uptake of HO 2 by atmospheric aerosols (4, 5), which act as nucleating sites for cloud droplets. Furtherm...

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“…Numerous previous studies have consistently reported a discrepancy between modelled and observed concentrations of HO 2 in different regions. The overestimation of HO 2 concentrations by the models has been attributed to heterogeneous loss of these radicals on aerosol surface as a missing HO 2 sink, not properly accounted for in the models (Cantrell et al, 1996a, b;Jaeglé et al, 2000;Kanaya et al, 2000;Sommariva et al, 2004Sommariva et al, , 2006de Reus et al, 2005;Mao et al, 2010). The laboratory database for uptake coefficients of HO 2 on different surface types is rather scarce, especially for solid surfaces.…”

Section: Introductionmentioning

confidence: 99%

Uptake of HO2 radicals on Arizona Test Dust

2013

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Abstract. The interaction of HO2 radicals with solid films of Arizona Test Dust (ATD) was studied using a low-pressure flow reactor (1–9 Torr) combined with a modulated molecular beam mass spectrometer for monitoring of the gaseous species involved. The reactive uptake coefficient of HO2 was measured from the kinetics of HO2 consumption on Pyrex rods coated with ATD as a function of HO2 concentration ((0.35–3.30) × 1012 molecule cm−3), relative humidity (RH = 0.02–94%), temperature (T = 275–320 K) and UV irradiance intensity (JNO2 = 0–0.012 s−1). The initial uptake coefficient was found to be independent of concentration of HO2, temperature and irradiation conditions, and to decrease with increasing relative humidity: γ0 = 1.2/(18.7 + RH1.1) (with 30% estimated conservative uncertainty). The uptake coefficient was calculated using geometric surface area and should be considered as an upper limit of γ0. An upper limit of 5% was found for the gaseous H2O2-forming pathway of the HO2 reaction with ATD surface. The results of the measurements indicate that HO2 loss on dust aerosol may be a non-negligible sink for HOx species in the troposphere with the effect depending on specific local conditions.

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Daytime HO₂ concentrations at Oki Island, Japan, in summer 1998: Comparison between measurement and theory

Cited by 71 publications

References 71 publications

OH and HO<sub>2</sub> chemistry in clean marine air during SOAPEX-2

OH and HO<sub>2</sub> chemistry in clean marine air during SOAPEX-2

On the interactions between atmospheric radicals and cloud droplets: A molecular picture of the interface

Uptake of HO<sub>2</sub> radicals on Arizona Test Dust

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Daytime HO2 concentrations at Oki Island, Japan, in summer 1998: Comparison between measurement and theory

Cited by 71 publications

References 71 publications

OH and HO&lt;sub&gt;2&lt;/sub&gt; chemistry in clean marine air during SOAPEX-2

OH and HO&lt;sub&gt;2&lt;/sub&gt; chemistry in clean marine air during SOAPEX-2

On the interactions between atmospheric radicals and cloud droplets: A molecular picture of the interface

Uptake of HO&lt;sub&gt;2&lt;/sub&gt; radicals on Arizona Test Dust

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Daytime HO₂ concentrations at Oki Island, Japan, in summer 1998: Comparison between measurement and theory

OH and HO<sub>2</sub> chemistry in clean marine air during SOAPEX-2

OH and HO<sub>2</sub> chemistry in clean marine air during SOAPEX-2

Uptake of HO<sub>2</sub> radicals on Arizona Test Dust