Heterogeneous reaction of HO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; with airborne TiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; particles and its implication for climate change mitigation strategies

Moon, Daniel R.; Taverna, Giorgio; Anduix‐Canto, Clara; Ingham, T.; Chipperfield, Martyn P.; Seakins, Paul W.; Baeza‐Romero, M. T.; Heard, Dwayne E.

doi:10.5194/acp-18-327-2018

Cited by 15 publications

(14 citation statements)

References 44 publications

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“…when the condensed-phase copper ion concentration is less than 1-2 × 10 −4 M, the heterogeneous uptake of HO 2 is not significant and may mainly be driven by the self-reaction of HO 2 . This threshold is consistent with the results of previous research studies (Mozurkewich et al, 1987;Lakey et al, 2016b). The threshold is also consistent in different heterogeneous media of aerosol and cloud or rain droplets.…”

Section: Model Validationsupporting

confidence: 93%

“…Since there is no direct evidence of the existence of Cu/Fe redox reactions of HO 2 which produce H 2 O rather than H 2 O 2 as proposed by Mao et al (2013), in the scope of this paper, HO 2 uptake produces H 2 O separately by Cuand Fe-free ions as proposed by many research studies (Mozurkewich et al, 1987;Hanson et al, 1992;Thornton and Abbatt, 2005;Thornton et al, 2008;Taketani et al, 2009;Macintyre and Evans, 2011). Fe-free ions can be seen as the equivalent Cu-free ions in the application of the MARK model or the parameterized equation mentioned below.…”

Section: Aerosol Particle Condensed-phase Cu 2+ Molality Calculationmentioning

confidence: 85%

“…Previous studies show that the value of γ HO 2 from the laboratory, field, and modelling studies spans several orders of magnitude, ranging from < 0.002 for dry aerosols (Cooper and Abbatt, 1996;Taketani et al, 2008;George et al, 2013) to 0.2 for liquid deliquesced aerosols. Much higher values of γ HO 2 have been measured and calculated for Cu-doped aerosols (Mozurkewich et al, 1987;Taketani et al, 2008;Thornton et al, 2008;Cooper and Abbatt, 1996;Lakey et al, 2016b;George et al, 2013). For fine particles, the reactions of HO 2 with soluble Cu ions may be fast enough; thus the uptake coefficient is limited by the mass accommodation coefficient α.…”

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confidence: 99%

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Influence of aerosol copper on HO2 uptake: a novel parameterized equation

Song

Chen

et al. 2020

Atmos. Chem. Phys.

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Abstract. Heterogeneous uptake of hydroperoxyl radicals (HO2) onto aerosols has been proposed to be a significant sink of HOx, hence impacting the atmospheric oxidation capacity. Accurate calculation of the HO2 uptake coefficient γHO2 is key to quantifying the potential impact of this atmospheric process. Laboratory studies show that γHO2 can vary by orders of magnitude due to changes in aerosol properties, especially aerosol soluble copper (Cu) concentration and aerosol liquid water content (ALWC). In this study we present a state-of-the-art model called MARK to simulate both gas- and aerosol-phase chemistry for the uptake of HO2 onto Cu-doped aerosols. Moreover, a novel parameterization of HO2 uptake was developed that considers changes in relative humidity (RH) and condensed-phase Cu ion concentrations and which is based on a model optimization using previously published and new laboratory data included in this work. This new parameterization will be applicable to wet aerosols, and it will complement current IUPAC recommendations. The new parameterization is as follows (the explanations for symbols are in the Appendix): 1γHO2=1αHO2+3×υHO24×106×RdHcorrRT×(5.87+3.2×ln⁡(ALWC/[PM]+0.067))×[PM]-0.2×Cu2+eff0.65+υHO2l4RTHorgDorgε. All parameters used in the paper are summarized in Table A1. Using this new equation, field data from a field campaign were used to evaluate the impact of the HO2 uptake onto aerosols on the ROx (= OH + HO2 + RO2) budget. Highly variable values for HO2 uptake were obtained for the North China Plain (median value < 0.1).

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Section: Model Validationsupporting

confidence: 93%

Section: Aerosol Particle Condensed-phase Cu 2+ Molality Calculationmentioning

confidence: 85%

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confidence: 99%

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Influence of aerosol copper on HO2 uptake: a novel parameterized equation

Song

Chen

et al. 2020

Atmos. Chem. Phys.

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“…On dry aerosol surfaces, γ(HO 2 ) is usually low: For example, Bedjanian et al (2005) measured γ(HO 2 ) = 0.075 ± 0.015 on dry soot surfaces which is comparable to the value of γ(HO 2 ) ≤ 0.031 on dust (Matthews et al, 2014) and γ < 0.01 on dry NaCl (Remorov et al, 2002). γ(HO 2 ) increases by more than one order magnitude when RH increases from ∼20% to > 90% (Cooper and Abbatt, 1996;Taketani et al, 2008;Lakey et al, 2015Lakey et al, , 2016Moon et al, 2018). Lakey et al (2015) showed much higher γ(HO 2 ) values on two humic acids (0.0007 ≤ γ(HO 2 ) ≤ 0.06 and 0.043 ≤γ(HO 2 ) ≤ 0.09, respectively) than on pure long-chain carboxylic acids (γ(HO 2 ) < 0.004).…”

Section: Reactive Uptake Coefficient Of the Hydroxy Peroxyl Radical γ(Ho 2 )mentioning

confidence: 78%

The number fraction of iron-containing particles affects OH, HO2 and H2O2 budgets in the atmospheric aqueous phase

Khaled

Zhang

Ervens

2021

Preprint

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Abstract. Reactive oxygen species (ROS), such as OH, HO2, H2O2 affect the oxidation capacity of the atmosphere and cause adverse health effects of particulate matter. The role of transition metal ions (TMIs) in impacting the ROS concentrations and conversions in the atmospheric aqueous phase has been recognized for a long time. Model studies usually assume that the total TMI concentration as measured in bulk aerosol or cloud water samples is distributed equally across all particles or droplets. This assumption is contrary to single-particle measurements that have shown that only a small number fraction of particles contain iron and other TMIs (FN,Fe < 100 %) which implies that also not all cloud droplets contain TMIs. In the current study, we apply a box model with an explicit multiphase chemical mechanism to simulate ROS formation and cycling in (i) aqueous aerosol particles and (ii) cloud droplets. Model simulations are performed for the range of 1 % ≤ FN,Fe ≤ 100 % for constant pH values of 3, 4.5 and 6 and constant total iron concentration (10 or 50 . Model results are compared for two sets of simulations with FN,Fe < 100 % (FeN < 100) and 100 % (FeBulk). We find largest differences between model results in OH and HO2/O2− concentrations at pH = 6. Under these conditions, HO2 is subsaturated in the aqueous phase because of its high effective Henry's law constant and the fast chemical loss reactions of the O2− radical anion. As the main reduction of process of Fe(III) is its reaction with HO2/O2−, we show that the HO2 subsaturation leads to predicted Fe(II)/Fe(total) ratios for FN,Fe < 100 % that are lower by a factor of ≤ 2 as compared to bulk model approaches. This trend is largely independent of the total iron concentration, as both chemical source and sink rates of HO2/O2− scale with the iron concentration. The chemical radical (OH, HO2) loss in particles is usually compensated by its uptake from the gas phase. We compare model-derived reactive uptake parameters γ(OH) and γ(HO2) for the full range of FN,Fe. While γ(OH) is not affected by the iron distribution, the calculated γ(HO2) range from 0.0004 to 0.03 for FN,Fe = 1 % and 100 %, respectively. Implications of these findings are discussed for the application of lab-derived γ(HO2) in models to present reactive HO2 uptake on aerosols. As the oxidant budget in aerosol particles and cloud droplets is related to the oxidative potential, we also conclude that the iron distribution FN,Fe should be taken into account to estimate the ROS concentrations and health impacts of particulate matter that might be overestimated by bulk sampling and model approaches. Our study suggests that the number concentration of iron-containing particles may be more important than the total iron mass concentration in determining ROS budgets and uptake rates in cloud and aerosol water.

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“…However, the majority of aerosols, >90 %, had diameters in the range that could be directly detected. Previously, we had determined by imaging the aerosols using a scanning electron microscope (SEM) that the particles were spherical (Moon et al, 2018…”

Section: Aerosol Generation and Detectionmentioning

confidence: 99%

Production of HONO from heterogeneous uptake of NO2 on illuminated TiO2 aerosols measured by Photo-Fragmentation Laser Induced Fluorescence

Dyson¹,

Boustead²,

Fleming³

et al. 2020

Preprint

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Abstract. The rate of production of HONO from illuminated TiO2 aerosols in the presence of NO2 was measured using an aerosol flow tube coupled to a photo-fragmentation laser induced fluorescence detection apparatus. The reactive uptake coefficient of NO2 to form HONO, γNO2→HONO, was determined for NO2 mixing ratios in the range 34–400 ppb, with γNO2→HONO spanning the range (9.97 ± 3.52) × 10−6 to (1.26 ± 0.17) × 10−4 at a relative humidity of 15 ± 1 % and for a lamp photon flux of (1.63 ± 0.09) × 1016 photons cm−2 s −1 (integrated between 290 and 400 nm), which is similar to values of ambient actinic flux at midday. γNO2→HONO increased as a function of NO2 mixing ratio at low NO2 before peaking at (1.26 ± 0.17) × 10−4 at 51 ppb NO2 and then sharply decreasing at higher NO2 mixing ratios, rather than levelling off which would be indicative of surface saturation. The dependence of HONO production on relative humidity was also investigated, with a peak in production of HONO from TiO2 aerosol surfaces found at ~25 % RH. Possible mechanisms consistent with the observed trends in both the HONO production and reactive uptake coefficient were investigated using a zero-dimensional kinetic box model. The modelling studies supported a mechanism for HONO production on the aerosol surface involving two molecules of NO2, as well as a surface HONO loss mechanism which is dependent upon NO2. In a separate experiment, significant production of HONO was observed from illumination of mixed nitrate/TiO2 aerosols in the absence of NO2. However, no statistically significant production of HONO was seen from the illumination of pure nitrate aerosols. The rate of production of HONO observed from mixed nitrate/TiO2 aerosols was scaled to ambient conditions found at the Cape Verde Atmospheric Observatory (CVAO) in the remote tropical marine boundary layer. The rate of HONO production from aerosol particulate nitrate photolysis containing a photocatalyst was found to be similar to the missing HONO production rate necessary to reproduce observed concentrations of HONO at CVAO. These results provide evidence that particulate nitrate photolysis may have a significant impact on the production of HONO and hence NOx in the marine boundary layer where mixed aerosols containing nitrate and a photocatalytic species such as TiO2, as found in dust, are present.

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Heterogeneous reaction of HO<sub>2</sub> with airborne TiO<sub>2</sub> particles and its implication for climate change mitigation strategies

Cited by 15 publications

References 44 publications

Influence of aerosol copper on HO<sub>2</sub> uptake: a novel parameterized equation

Influence of aerosol copper on HO<sub>2</sub> uptake: a novel parameterized equation

The number fraction of iron-containing particles affects OH, HO<sub>2</sub> and H<sub>2</sub>O<sub>2</sub> budgets in the atmospheric aqueous phase

Production of HONO from heterogeneous uptake of NO<sub>2</sub> on illuminated TiO<sub>2</sub> aerosols measured by Photo-Fragmentation Laser Induced Fluorescence

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Heterogeneous reaction of HO&lt;sub&gt;2&lt;/sub&gt; with airborne TiO&lt;sub&gt;2&lt;/sub&gt; particles and its implication for climate change mitigation strategies

Cited by 15 publications

References 44 publications

Influence of aerosol copper on HO&lt;sub&gt;2&lt;/sub&gt; uptake: a novel parameterized equation

Influence of aerosol copper on HO&lt;sub&gt;2&lt;/sub&gt; uptake: a novel parameterized equation

The number fraction of iron-containing particles affects OH, HO&lt;sub&gt;2&lt;/sub&gt; and H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; budgets in the atmospheric aqueous phase

Production of HONO from heterogeneous uptake of NO&lt;sub&gt;2&lt;/sub&gt; on illuminated TiO&lt;sub&gt;2&lt;/sub&gt; aerosols measured by Photo-Fragmentation Laser Induced Fluorescence

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Heterogeneous reaction of HO<sub>2</sub> with airborne TiO<sub>2</sub> particles and its implication for climate change mitigation strategies

Influence of aerosol copper on HO<sub>2</sub> uptake: a novel parameterized equation

Influence of aerosol copper on HO<sub>2</sub> uptake: a novel parameterized equation

The number fraction of iron-containing particles affects OH, HO<sub>2</sub> and H<sub>2</sub>O<sub>2</sub> budgets in the atmospheric aqueous phase

Production of HONO from heterogeneous uptake of NO<sub>2</sub> on illuminated TiO<sub>2</sub> aerosols measured by Photo-Fragmentation Laser Induced Fluorescence