Interaction of OH Radicals with Arizona Test Dust: Uptake and Products

Bedjanian, Yuri; Romanías, Manolis N.; Zein, Atallah El

doi:10.1021/jp311235h

Cited by 28 publications

(35 citation statements)

References 31 publications

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“…However, in our opinion, the transformation of H 2 O 2 on the ATD surface is not the main reason for the absence of H 2 O 2 in gaseous products of the HO 2 + ATD reaction. Thus in a recent study from our group H 2 O 2 was distinctly observed as a gaseous product of the interaction of the OH radical with the same ATD surface, although with a relatively low yield of 10 % (Bedjanian et al, 2013). The present results seem to indicate that HO 2 uptake by atmospheric aerosols does not necessarily produce H 2 O 2gas .…”

Section: Discussionsupporting

confidence: 53%

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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Section: Discussionsupporting

confidence: 53%

Uptake of HO2 radicals on Arizona Test Dust

2013

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“…Please note that uptake coefficients reported by Bedjanian et al (2013b) are based on the geometrical area of the rod coated with ATD particles and thus should be considered as the upper limit.…”

Section: Oh Radicalsmentioning

confidence: 99%

“…5, with the most evident one being the effect of RH. Park et al (2008) found that γ (OH) increased significantly with RH for both SiO 2 and Al 2 O 3 , while Bedjanian et al (2013b) suggested that γ (OH) showed a negative dependence on RH. It is not clear yet whether different minerals used by these two studies can fully account for the different RH dependence observed.…”

Section: Oh Radicalsmentioning

confidence: 99%

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Heterogeneous reactions of mineral dust aerosol: implications for tropospheric oxidation capacity

et al. 2017

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Abstract. Heterogeneous reactions of mineral dust aerosol with trace gases in the atmosphere could directly and indirectly affect tropospheric oxidation capacity, in addition to aerosol composition and physicochemical properties. In this article we provide a comprehensive and critical review of laboratory studies of heterogeneous uptake of OH, NO 3 , O 3 , and their directly related species as well (including HO 2 , H 2 O 2 , HCHO, HONO, and N 2 O 5 ) by mineral dust particles. The atmospheric importance of heterogeneous uptake as sinks for these species is assessed (i) by comparing their lifetimes with respect to heterogeneous reactions with mineral dust to lifetimes with respect to other major loss processes and (ii) by discussing relevant field and modeling studies. We have also outlined major open questions and challenges in laboratory studies of heterogeneous uptake by mineral dust and discussed research strategies to address them in order to better understand the effects of heterogeneous reactions with mineral dust on tropospheric oxidation capacity.

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“…Black contour lines show ClO x mixing ratios from the Mt Pinatubo simulation (S2) in ppbv. (Romanias et al, 2012) and OH radicals (Bedjanian et al, 2013) -and found that the measured uptake coefficients varied only by a factor of 2-3 or less across a wide temperature range. However, it is unclear whether temperature would have a significant effect on γ (ClONO 2 ) for TiO 2 particles, and therefore our simulated impact of heterogeneous reaction of ClONO 2 with TiO 2 on stratospheric chemistry may have large uncertainties.…”

Section: Implication For Stratospheric Particle Injectionmentioning

confidence: 97%

Heterogeneous reaction of ClONO2 with TiO2 and SiO2 aerosol particles: implications for stratospheric particle injection for climate engineering

et al. 2016

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Abstract. Deliberate injection of aerosol particles into the stratosphere is a potential climate engineering scheme. Particles injected into the stratosphere would scatter solar radiation back to space, thereby reducing the temperature at the Earth's surface and hence the impacts of global warming. Minerals such as TiO 2 or SiO 2 are among the potentially suitable aerosol materials for stratospheric particle injection due to their greater light-scattering ability than stratospheric sulfuric acid particles. However, the heterogeneous reactivity of mineral particles towards trace gases important for stratospheric chemistry largely remains unknown, precluding reliable assessment of their impacts on stratospheric ozone, which is of key environmental significance. In this work we have investigated for the first time the heterogeneous hydrolysis of ClONO 2 on TiO 2 and SiO 2 aerosol particles at room temperature and at different relative humidities (RHs), using an aerosol flow tube. The uptake coefficient, γ (ClONO 2 ), on TiO 2 was ∼ 1.2 × 10 −3 at 7 % RH and remained unchanged at 33 % RH, and increased for SiO 2 from ∼ 2 × 10 −4 at 7 % RH to ∼ 5 × 10 −4 at 35 % RH, reaching a value of ∼ 6 × 10 −4 at 59 % RH. We have also examined the impacts of a hypothetical TiO 2 injection on stratospheric chemistry using the UKCA (United Kingdom Chemistry and Aerosol) chemistry-climate model, in which heterogeneous hydrolysis of N 2 O 5 and ClONO 2 on TiO 2 particles is considered. A TiO 2 injection scenario with a solar-radiation scattering effect very similar to the eruption of Mt Pinatubo was constructed. It is found that, compared to the eruption of Mt Pinatubo, TiO 2 injection causes less ClO x activation and less ozone destruction in the lowermost stratosphere, while reduced depletion of N 2 O 5 and NO x in the middle stratosphere results in decreased ozone levels. Overall, no significant difference in the vertically integrated ozone abundances is found between TiO 2 injection and the eruption of Mt Pinatubo. Future work required to further assess the impacts of TiO 2 injection on stratospheric chemistry is also discussed.

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Interaction of OH Radicals with Arizona Test Dust: Uptake and Products

Cited by 28 publications

References 31 publications

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

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

Heterogeneous reactions of mineral dust aerosol: implications for tropospheric oxidation capacity

Heterogeneous reaction of ClONO<sub>2</sub> with TiO<sub>2</sub> and SiO<sub>2</sub> aerosol particles: implications for stratospheric particle injection for climate engineering

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Interaction of OH Radicals with Arizona Test Dust: Uptake and Products

Cited by 28 publications

References 31 publications

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

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

Heterogeneous reactions of mineral dust aerosol: implications for tropospheric oxidation capacity

Heterogeneous reaction of ClONO&lt;sub&gt;2&lt;/sub&gt; with TiO&lt;sub&gt;2&lt;/sub&gt; and SiO&lt;sub&gt;2&lt;/sub&gt; aerosol particles: implications for stratospheric particle injection for climate engineering

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

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

Heterogeneous reaction of ClONO<sub>2</sub> with TiO<sub>2</sub> and SiO<sub>2</sub> aerosol particles: implications for stratospheric particle injection for climate engineering