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Dentener, Frank; Williams, J. E.; Metzger, Swen

doi:10.1023/a:1014233910126

Cited by 29 publications

(9 citation statements)

References 24 publications

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“…However, under standard conditions, HNO 4 is rather unstable and decomposes typically within a few seconds. This creates an equilibrium between HNO 4 and HO 2 +NO 2 which is strongly temperature dependent (Dentener et al, 2002). In the simulation, the production and decomposition of HNO 4 occur at the same rate, thus the net effect is zero for the hydroperoxyl radicals.…”

Section: Sources and Sinks Of Ho Xmentioning

confidence: 97%

Observation and modelling of HOx radicals in a boreal forest

Hens¹,

Novelli²,

Martínez³

et al. 2013

Preprint

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Measurements of OH and HO2 radicals were conducted in a pine-dominated forest in southern Finland during the HUMPPA-COPEC-2010 (Hyytiälä United Measurements of Photochemistry and Particles in Air -Comprehensive Organic Precursor Emission and Concentration study) field campaign in summer 2010. Simultaneous side-by-side measurements of hydroxyl radicals were conducted with two instruments using chemical ionization mass spectrometry (CIMS) and laser-induced fluorescence (LIF), indicating small systematic disagreement, OHLIF / OHCIMS = (1.31 ± 0.14). Subsequently, the LIF instrument was moved to the top of a 20 m tower, just above the canopy, to investigate the radical chemistry at the ecosystem-atmosphere interface. Comprehensive measurements including observations of many volatile organic compounds (VOCs) and the total OH reactivity were conducted and analysed using steady-state calculations as well as an observationally constrained box model. Production rates of OH calculated from measured OH precursors are consistent with those derived from the steady-state assumption and measured total OH loss under conditions of moderate OH reactivity. The primary photolytic sources of OH contribute up to one-third to the total OH production. OH recycling, which occurs mainly by HO2 reacting with NO and O3, dominates the total hydroxyl radical production in this boreal forest. Box model simulations agree with measurements for hydroxyl radicals (OHmod. / OHobs. = 1.00 ± 0.16), while HO2 mixing ratios are significantly under-predicted (HO2mod. / HO2obs. = 0.3 ± 0.2), and simulated OH reactivity does not match the observed OH reactivity. The simultaneous under-prediction of HO2 and OH reactivity in periods in which OH concentrations were simulated realistically suggests that the missing OH reactivity is an unaccounted-for source of HO2. Detailed analysis of the HOx production, loss, and recycling pathways suggests that in periods of high total OH reactivity there are additional recycling processes forming OH directly, not via reaction of HO2 with NO or O3, or unaccounted-for primary HOx sources. Under conditions of moderate observed OH reactivity and high actinic flux, an additional RO2 source of approximately 1 x 106 molec cm−3 s−1 would be required to close the radical budget. Nevertheless, a major fraction of the OH recycling occurs via the reaction of HO2 with NO and O3 in this terpene-dominated environment.

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Section: Sources and Sinks Of Ho Xmentioning

confidence: 97%

Observation and modelling of HOx radicals in a boreal forest

Hens¹,

Novelli²,

Martínez³

et al. 2013

Preprint

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show abstract

“…It has been suggested that a reaction between HO 2 × H 2 O and NO 2 could produce HONO at a sufficiently fast rate to be a significant source in the troposphere (Li et al, 2014). It had previously been shown in laboratory studies that this reaction produces negligible HONO yields under dry conditions (Tyndall et al, 1995;Dransfield et al, 2001). However, in the lower troposphere, around 30 % of HO 2 is suggested to be present as an HO 2 × H 2 O complex and hence may show different chemical behaviour.…”

Section: Hono Box Model 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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“…This assumption represents a large source of uncertainty because HSO − 3 is the dominant aqueous S(IV) species under typical cloud water pH (2-7) conditions. NO 2 (Lee and Schwartz, 1983), NO 3 (Feingold et al, 2002), and HNO 4 (Dentener et al, 2002;Warneck, 1999) can also oxidize S(IV) in the aqueous phase. Because of the low solubility of NO 2 , S(IV) + NO 2 is expected to be most important in polluted regions where NO 2 concentrations are high.…”

Section: Oxygen Isotopic Composition Of Sulfatementioning

confidence: 99%

The impact of anthropogenic emissions on atmospheric sulfate production pathways, oxidants, and ice core Δ17O(SO42–)

2011

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Abstract. We use a global three-dimensional chemical transport model to quantify the influence of anthropogenic emissions on atmospheric sulfate production mechanisms and oxidant concentrations constrained by observations of the oxygen isotopic composition ( ). Additional model simulations are conducted to explore the sensitivity of the oxygen isotopic composition of sulfate to uncertainties in the preindustrial emissions of oxidant precursors.

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Untitled

Cited by 29 publications

References 24 publications

Observation and modelling of HO<sub>x</sub> radicals in a boreal forest

Observation and modelling of HO<sub>x</sub> radicals in a boreal forest

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

The impact of anthropogenic emissions on atmospheric sulfate production pathways, oxidants, and ice core Δ<sup>17</sup>O(SO<sub>4</sub><sup>2–</sup>)

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Untitled

Cited by 29 publications

References 24 publications

Observation and modelling of HO&lt;sub&gt;x&lt;/sub&gt; radicals in a boreal forest

Observation and modelling of HO&lt;sub&gt;x&lt;/sub&gt; radicals in a boreal forest

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

The impact of anthropogenic emissions on atmospheric sulfate production pathways, oxidants, and ice core Δ&lt;sup&gt;17&lt;/sup&gt;O(SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2–&lt;/sup&gt;)

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Observation and modelling of HO<sub>x</sub> radicals in a boreal forest

Observation and modelling of HO<sub>x</sub> radicals in a boreal forest

The impact of anthropogenic emissions on atmospheric sulfate production pathways, oxidants, and ice core Δ<sup>17</sup>O(SO<sub>4</sub><sup>2–</sup>)