Quantum Yields for Photochemical Production of NO<sub>2</sub> from Organic Nitrates at Tropospherically Relevant Wavelengths

Higgins, Christina; Evans, Louise; Lloyd‐Jones, Guy C.; Shallcross, Dudley E.; Tew, David P.; Orr-Ewing, Andrew J.

doi:10.1021/jp501517t

“…We use the Master Chemical Mechanism version 3.3.1 to determine the products (mapped to GEOS‐Chem species), with rate constants for OH oxidation from the Jet Propulsion Laboratory Data Evaluation v15‐10. Photolysis rates are calculated using the Fast‐JX code (Bian & Prather, ) with cloud treatment following Liu et al () as implemented by Mao et al (), with photolysis cross sections from the MPI‐Mainz UV/VIS Spectral Atlas (http://satellite.mpic.de/spectral_atlas/cross_sections/) and NO 2 quantum yields of unity for all RONO 2 (Higgins et al, ). The full mechanism is given in Table S1 in the supporting information.…”

Section: Model Descriptionmentioning

confidence: 99%

Methyl, Ethyl, and Propyl Nitrates: Global Distribution and Impacts on Reactive Nitrogen in Remote Marine Environments

Fisher

¹

,

Atlas

²

,

Barletta

³

et al. 2018

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Alkyl nitrates (RONO 2 ) are important components of tropospheric reactive nitrogen that serve as reservoirs for nitrogen oxides (NO x ≡ NO + NO 2 ). Here we implement a new simulation of atmospheric methyl, ethyl, and propyl nitrate chemistry in a global chemical transport model (GEOS-Chem). We show that the model can reproduce the spatial and seasonal variability seen in a 20-year ensemble of airborne observations. Methyl nitrate accounts for 17 Gg N globally, with maxima over the tropical Pacific and Southern Ocean. Propyl nitrate is enhanced in continental boundary layers, but its global impact (6 Gg N) is limited by a short lifetime (8 days vs. 26 days for methyl nitrate and 14 days for ethyl nitrate) that inhibits long-range transport. Ethyl nitrate has the smallest impact of the three species (4 Gg N). We find that methyl nitrate is the dominant form of reactive nitrogen (NO y ) in the Southern Ocean marine boundary layer, where its addition to the model corrects a large NO y underestimate in austral winter relative to recent aircraft data. RONO 2 serve as a small net NO x source to the marine troposphere, except in the northern midlatitudes where the continental outflow is enriched in precursors that promote NO x loss via RONO 2 formation. Recent growth in NO x emissions from East Asia has enhanced the role of RONO 2 as a source of NO x to the remote free troposphere. This relationship implies projected future NO x emissions growth across the southern hemisphere may further enhance the importance of RONO 2 as a NO x reservoir.Plain Language Summary Nitrogen in the atmosphere has many impacts on atmospheric chemistry, including affecting how polluted the air is. Many nitrogen-containing gases are released over polluted areas and are quickly broken down-staying far away from remote areas like the ocean. In this paper, we investigate a group of nitrogen gases (called alkyl nitrates) that break down more slowly and so stay in the atmosphere long enough to be transported to the otherwise pollution-free remote Pacific Ocean. These gases are also created naturally in the ocean and then make their way into the atmosphere, changing the atmospheric chemistry over the ocean. We use 20 years of measurements collected from aircraft, combined with a computer model, to determine the abundance and impacts of alkyl nitrates. We find that the smallest alkyl nitrates are particularly important over the Southern Ocean, where there are few other sources of nitrogen. We show that alkyl nitrates are playing an increasingly important role over the remote oceans because of recent growth in East Asian air pollution. This relationship implies that these gases may have a stronger influence on atmospheric chemistry over remote ocean areas in future if anticipated pollution growth in Africa, South America, and Southeast Asia is realised.

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“…n -BuLi (2.6 M in hexane, 12 mL, 31 mmol) was added rapidly. The mixture was left stirring for 5 min, and ethyl nitrate (1.46 g, 16 mmol) was added over the course of 1 h. The reaction was left stirring for 1 h at the same temperature when another portion of n -BuLi (5.8 mL, 15 mmol) was added, followed by ethyl nitrate (0.73 g, 8 mmol). After 30 min, the same addition of n -BuLi and ethyl nitrate was repeated.…”

Section: Methodsmentioning

confidence: 99%

Theoretical and Experimental Study on the Reaction of tert-Butylamine with OH Radicals in the Atmosphere

Tan

¹

,

Zhu

²

,

Mikoviny

³

et al. 2018

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The OH-initiated atmospheric degradation of tert-butylamine (tBA), (CH)CNH, was investigated in a detailed quantum chemistry study and in laboratory experiments at the European Photoreactor (EUPHORE) in Spain. The reaction was found to mainly proceed via hydrogen abstraction from the amino group, which in the presence of nitrogen oxides (NO ), generates tert-butylnitramine, (CH)CNHNO, and acetone as the main reaction products. Acetone is formed via the reaction of tert-butylnitrosamine, (CH)CNHNO, and/or its isomer tert-butylhydroxydiazene, (CH)CN═NOH, with OH radicals, which yield nitrous oxide (NO) and the (CH)Ċ radical. The latter is converted to acetone and formaldehyde. Minor predicted and observed reaction products include formaldehyde, 2-methylpropene, acetamide and propan-2-imine. The reaction in the EUPHORE chamber was accompanied by strong particle formation which was induced by an acid-base reaction between photochemically formed nitric acid and the reagent amine. The tert-butylaminium nitrate salt was found to be of low volatility, with a vapor pressure of 5.1 × 10 Pa at 298 K. The rate of reaction between tert-butylamine and OH radicals was measured to be 8.4 (±1.7) × 10 cm molecule s at 305 ± 2 K and 1015 ± 1 hPa.

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“…We use the Master Chemical Mechanism version 3.3.1 to determine the products (mapped to GEOS-Chem species), with rate constants for OH oxidation from the Jet Propulsion Laboratory Data Evaluation v15-10. Photolysis rates are calculated using the Fast-JX code (Bian & Prather, 2002) with cloud treatment following Liu et al (2006) as implemented by Mao et al (2010), with photolysis cross sections from the MPI-Mainz UV/VIS Spectral Atlas (http://satellite.mpic.de/spectral_atlas/cross_sections/) and NO 2 quantum yields of unity for all RONO 2 (Higgins et al, 2014). The full mechanism is given in Table S1 in the supporting information.…”

Section: Chemistry Chemical Production Of Rono 2 Occurs Via Reaction mentioning

confidence: 99%

Methyl, ethyl, and propyl nitrates: global distribution and impacts on reactive nitrogen in remote marine environments

Fisher¹,

Atlas²,

Barletta³

et al. 2018

Preprint

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Alkyl nitrates (RONO2) are important components of tropospheric reactive nitrogen that serve as reservoirs for nitrogen oxides (NOx ≡ NO + NO2). Here we implement a new simulation of atmospheric methyl, ethyl, and propyl nitrate chemistry in a global chemical transport model (GEOS‐Chem). We show that the model can reproduce the spatial and seasonal variability seen in a 20‐year ensemble of airborne observations. Methyl nitrate accounts for 17 Gg N globally, with maxima over the tropical Pacific and Southern Ocean. Propyl nitrate is enhanced in continental boundary layers, but its global impact (6 Gg N) is limited by a short lifetime (8 days, versus 26 days for methyl nitrate and 14 days for ethyl nitrate) that inhibits long‐range transport. Ethyl nitrate has the smallest impact of the three species (4 Gg N). We find that methyl nitrate is the dominant form of reactive nitrogen (NOy) in the Southern Ocean marine boundary layer, where its addition to the model corrects a large NOy underestimate in austral winter relative to recent aircraft data. RONO2 serve as a small net NOx source to the marine troposphere, except in the northern mid‐latitudes where the continental outflow is enriched in precursors that promote NOx loss via RONO2 formation. Recent growth in NOx emissions from East Asia has enhanced the role of RONO2 as a source of NOx to the remote free troposphere. This relationship implies projected future NOx emissions growth across the southern hemisphere may further enhance the importance of RONO2 as a NOx reservoir.

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Quantum Yields for Photochemical Production of NO₂ from Organic Nitrates at Tropospherically Relevant Wavelengths

Cited by 8 publications

References 43 publications

Methyl, Ethyl, and Propyl Nitrates: Global Distribution and Impacts on Reactive Nitrogen in Remote Marine Environments

Methyl, Ethyl, and Propyl Nitrates: Global Distribution and Impacts on Reactive Nitrogen in Remote Marine Environments

Theoretical and Experimental Study on the Reaction of tert-Butylamine with OH Radicals in the Atmosphere

Methyl, ethyl, and propyl nitrates: global distribution and impacts on reactive nitrogen in remote marine environments

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Quantum Yields for Photochemical Production of NO2 from Organic Nitrates at Tropospherically Relevant Wavelengths

Cited by 8 publications

References 43 publications

Methyl, Ethyl, and Propyl Nitrates: Global Distribution and Impacts on Reactive Nitrogen in Remote Marine Environments

Methyl, Ethyl, and Propyl Nitrates: Global Distribution and Impacts on Reactive Nitrogen in Remote Marine Environments

Theoretical and Experimental Study on the Reaction of tert-Butylamine with OH Radicals in the Atmosphere

Methyl, ethyl, and propyl nitrates: global distribution and impacts on reactive nitrogen in remote marine environments

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Product

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Quantum Yields for Photochemical Production of NO₂ from Organic Nitrates at Tropospherically Relevant Wavelengths