Journal articles: 'Nitrate radicals'

1

Clarke, Jennifer L., Irida Kastrati, Linda J. Johnston, and Gregory RJ Thatcher. "Photochemical reactions of thiols with organic nitrates Oxygen atom transfer via a thionitrate." Canadian Journal of Chemistry 84, no. 4 (April 1, 2006): 709–19. http://dx.doi.org/10.1139/v06-056.

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Nitroglycerin is an organic nitrate that has been used in the clinical treatment of angina for 130 years, yet important details of its mechanism of action remain unanswered. The biological activity of nitrates suggests that they are bioactivated to NO via a three-electron reduction. The involvement of free or bound protein thiols in this reduction has often been proposed. To examine the involvement of thiyl radicals in such a process, the photochemical generation of benzenethiyl radical from thiol and disulfide precursors was studied in the presence of isopropyl nitrate. Analysis of reaction products and kinetics led to the conclusion that photolysis of the nitrate to NO2 dominated the observed photochemistry. Formation of sulfonothioate and NO as products, and trapping of NO2 by 4-chlorophenol, indicated a mechanism involving oxygen atom transfer from N to S via a thionitrate intermediate. The results of the study did not indicate a rapid reaction between thiyl radical and organic nitrate. Despite weak nitrate absorption of light >300 nm and a relatively high BDE for homolysis to give NO2, the photochemistry under thiyl-generating conditions was driven by nitrate photolysis to NO2. A novel nitrate, containing a phenyl disulfanyl group linked to nitrate groups, did not undergo photolysis to NO2 or generate sulfonothioate, but did yield NO. These observations suggest that reaction between thiyl radicals and nitrates leading to NO release is a viable pathway, but it is subservient to other competing reactions, such as photolysis, in the case of IPN, and reaction with thiolate, in the case of the novel nitrate.Key words: nitrate, photolysis, thiyl radical, nitrogen dioxide, nitric oxide.

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2

Zheng, W., F. M. Flocke, G. S. Tyndall, A. Swanson, J. J. Orlando, J. M. Roberts, L. G. Huey, and D. J. Tanner. "Characterization of a thermal decomposition chemical ionization mass spectrometer for the measurement of peroxy acyl nitrates (PANs) in the atmosphere." Atmospheric Chemistry and Physics 11, no. 13 (July 8, 2011): 6529–47. http://dx.doi.org/10.5194/acp-11-6529-2011.

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Abstract. This paper presents a detailed laboratory characterization of a thermal dissociation chemical ionization mass spectrometer (TD-CIMS) for the atmospheric measurement of Peroxyacetyl nitrate (PAN) and its homologues (PANs). PANs are efficiently dissociated in a heated inlet and the resulting peroxy acyl radicals are reacted with I− ions in a flow tube. The mass spectrometer detects the corresponding carboxylate ions. PAN, peroxypropionyl nitrate (PPN), peroxyisobutyryl nitrate (PiBN), peroxy-n-butyryl nitrate (PnBN), peroxyacryloyl nitrate (APAN), peroxycrotonyl nitrates (CPAN) and peroxymethacryloyl nitrate (MPAN) were cross-calibrated with both a dual channel GC/ECD and a total odd-nitrogen (NOy) instrument for the NCAR TD-CIMS' typical aircraft operation conditions. In addition, the instrument sensitivity to a number of more exotic PANs (peroxyhydroxyacetyl nitrate, methoxyformyl peroxynitrate, and peroxybenzoyl nitrate) was evaluated qualitatively by comparisons with a long-path FTIR instrument. The sensitivity for PPN is slightly higher than that of PAN. Larger aliphatic and olefinic PAN compounds generally showed lower sensitivities. We postulate that these differences are owing to secondary reactions in the thermal decomposition region, which either reduce the yield of peroxy acyl radicals or cause losses of these radicals through intramolecular decomposition. The relative importance of these secondary reactions varies considerably between different PAN species. Results also indicate that the reaction of the larger peroxy acyl radicals with the ion-water cluster, I−(H2O)n proceeds about an order of magnitude faster than with I− alone, as has been observed for peroxy acetyl radicals. Sensitivity variations among the individual PAN species at very low water vapor were observed. The results call for careful evaluation of each PAN species to be measured and for each desired operating condition of a TD-CIMS instrument.

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3

Vrekoussis, M., M. Kanakidou, N. Mihalopoulos, P. J. Crutzen, J. Lelieveld, D. Perner, H. Berresheim, and E. Baboukas. "Role of the NO3 radicals in oxidation processes in the eastern Mediterranean troposphere during the MINOS campaign." Atmospheric Chemistry and Physics 4, no. 1 (February 3, 2004): 169–82. http://dx.doi.org/10.5194/acp-4-169-2004.

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Abstract. During the MINOS campaign (28 July-18 August 2001) the nitrate (NO3) radical was measured at Finokalia station, on the north coast of Crete in South-East Europe using a long path (10.4 km) Differential Optical Absorption Spectroscopy instrument (DOAS). Hydroxyl (OH) radical was also measured by a Chemical Ionization Mass-Spectrometer (Berresheim et al., 2003). These datasets represent the first simultaneous measurements of OH and NO3 radicals in the area. NO3 radical concentrations ranged from less than 3x107 up to 9x108 radicals· cm-3 with an average nighttime value of 1.1x108 radicals· cm-3. The observed NO3 mixing ratios are analyzed on the basis of the corresponding meteorological data and the volatile organic compound (VOC) observations which were measured simultaneously at Finokalia station. The importance of the NO3 radical chemistry relatively to that of OH in the dimethylsulfide (DMS) and nitrate cycles is also investigated. The observed NO3 levels regulate the nighttime variation of DMS. The loss of DMS by NO3 during night is about 75% of that by OH radical during day. NO3 and nitrogen pentoxide (N2O5) reactions account for about 21% of the total nitrate (HNO3(g)+NO-3(g)) production.

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4

Moshage, H., B. Kok, J. R. Huizenga, and P. L. Jansen. "Nitrite and nitrate determinations in plasma: a critical evaluation." Clinical Chemistry 41, no. 6 (June 1, 1995): 892–96. http://dx.doi.org/10.1093/clinchem/41.6.892.

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Abstract Plasma nitrite and nitrate determinations are increasingly being used in clinical chemistry as markers for the activity of nitric oxide synthase and the production of nitric oxide radicals. However, a systematic evaluation of the determination of nitrite and nitrate in plasma has not been performed. In this study the recovery and stability of nitrite and nitrate in whole blood and in plasma, the relation between nitrite and nitrate concentrations in plasma, and possible sources of artifacts were investigated. The main conclusions are: (a) Recovery of nitrite and nitrate from plasma is near-quantitative (87%) and reproducible; (b) nitrite and nitrate are stable in (frozen) plasma for at least 1 year; (c) nitrite in whole blood is very rapidly (> 95% in 1 h) oxidized to nitrate, and therefore plasma nitrite determination alone is meaningless; (d) the ranges of nitrite and nitrate concentrations in plasma samples of 26 healthy persons are 1.3-13 mumol/L (mean 4.2 mumol/L) and 4.0-45.3 mumol/L (mean 19.7 mumol/L), respectively; (e) plasma nitrite and nitrate concentrations were not correlated (nitrite as % of total nitrite + nitrate varied from 3.9% to 88% in plasma samples); and (f) plasma samples should be deproteinized, and background controls for each sample should be included in the assay, to avoid measuring artifactually high nitrite and nitrate concentrations in plasma.

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5

Platt, Ulrich, and Frank Heintz. "Nitrate Radicals in Tropospheric Chemistry." Israel Journal of Chemistry 34, no. 3-4 (1994): 289–300. http://dx.doi.org/10.1002/ijch.199400033.

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6

Rudziński, Krzysztof J., and Rafał Szmigielski. "Aqueous Reactions of Sulfate Radical-Anions with Nitrophenols in Atmospheric Context." Atmosphere 10, no. 12 (December 9, 2019): 795. http://dx.doi.org/10.3390/atmos10120795.

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Nitrophenols, hazardous environmental pollutants, react promptly with atmospheric oxidants such as hydroxyl or nitrate radicals. This work aimed to estimate how fast nitrophenols are removed from the atmosphere by the aqueous-phase reactions with sulfate radical-anions. The reversed-rates method was applied to determine the relative rate constants for reactions of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, and 2,4,6-trinitrophenol with sulfate radical-anions generated by the autoxidation of sodium sulfite catalyzed by iron(III) cations at ~298 K. The constants determined were: 9.08 × 108, 1.72 × 109, 6.60 × 108, 2.86 × 108, and 7.10 × 107 M−1 s−1, respectively. These values correlated linearly with the sums of Brown substituent coefficients and with the relative strength of the O–H bond of the respective nitrophenols. Rough estimation showed that the gas-phase reactions of 2-nitrophenol with hydroxyl or nitrate radicals dominated over the aqueous-phase reaction with sulfate radical-anions in deliquescent aerosol and haze water. In clouds, rains, and haze water, the aqueous-phase reaction of 2-nitrophenol with sulfate radical-anions dominated, provided the concentration of the radical-anions was not smaller than that of the hydroxyl or nitrate radicals. The results presented may be also interesting for designers of advanced oxidation processes for the removal of nitrophenol.

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7

Rumagit, Benedicta Irene, Adeanne Caroline Wullur, and Donald Emilio Kalonio. "ANTI-OXIDANT ACTIVITY OF SESEWANUA (Clerodendrum fragrans [Vent.] Willd) LEAF EXTRACT AND FRACTION WITH 1,1-DiPHENYLl-2-PICRYLHYDRAZYL (DPPH) AND NITRATE-OXIDE FREE RADICAL SCAVENGING METHOD." International Research Journal of Pharmacy 11, no. 11 (November 30, 2020): 68–72. http://dx.doi.org/10.7897/2230-8407.111199.

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Free radicals are molecules containing unpaired electrons so that they are not stable and very reactive to other molecules. ROS/RNS radicals have physiological function, but the overproduction of free radicals can initiate oxidative/nitrosative stress that contributes to a high number of diseases. Body has an ability to neutralize the free radicals by forming the endogenous antioxidant. Environmental changes, living style, certain pathological conditions can cause the shift of prooxidant-antioxidant equilibrium. Thus, endogenous antioxidant intake is needed, particularly that originating from natural materials. One of the plants believed to have antioxidant activity is sesewanua (Clerodendrum fragrans [Vent.] Willd.) leaf. This study was aimed to evaluate the antioxidant activity of ethanol extract, hexane fraction, ethyl acetate fraction, and water fraction of the sesewanua leaf using DPPH and nitrate-oxide free radical scavenging method. The study is a laboratory experiment. The sample was sesewanua (Clerodendrum fragrans) obtained from East Malalayang I village, Malalayang district, Manado city, North Sulawesi. The antioxidant activity testing utilized 1,1-Diphenyl-2-Picrylhydrazyl (DPPH) and nitrate-oxide free radical scavenging method. Data included percent inhibition of free radicals and were analyzed using linear regression to determine 50% inhibition concentration (IC50) of DPPH and nitrate-oxide free radicals. As conclusion, the ethanol extract, hexane fraction, ethyl acetate fraction, and water fraction of the sesewanua leaf had antioxidant activity through DPPH free antiradical activity, but not active as antiradical NO.

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8

Zheng, W., F. M. Flocke, G. S. Tyndall, A. Swanson, J. J. Orlando, J. M. Roberts, L. G. Huey, and D. J. Tanner. "Characterization of a thermal decomposition chemical ionization mass spectrometer for the measurement of peroxy acyl nitrates (PANs) in the atmosphere." Atmospheric Chemistry and Physics Discussions 11, no. 3 (March 11, 2011): 8461–513. http://dx.doi.org/10.5194/acpd-11-8461-2011.

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Abstract. This paper presents a detailed laboratory characterization of a thermal dissociation ionization mass spectrometer (TD-CIMS) for the atmospheric measurement of Peroxyacetyl nitrate (PAN) and its homologues. PANs are efficiently dissociated in a heated inlet tube and the resulting peroxy acyl radicals are reacted with I– ions in a flow tube. The CIMS detects the corresponding carboxylate ions to give a specific and quantitative measurement of each PAN species. PAN, peroxypropionyl nitrate (PPN), peroxyisobutyryl nitrate (PiBN), peroxy-n-butyryl nitrate (PnBN), peroxyacryloyl nitrate (APAN), peroxycrotonyl nitrates (CPAN) and peroxymethacryloyl nitrate (MPAN) were cross-calibrated with both a dual channel GC/ECD and a total odd-nitrogen (NOy) instrument for the NCAR TD-CIMS' typical aircraft operation conditions. In addition, the instrument sensitivity to a number of more exotic PAN homologues (peroxyhydroxyacetyl nitrate, methoxyformyl peroxynitrate, and peroxybenzoyl nitrate) was evaluated qualitatively by comparisons with a long-path FTIR instrument. The sensitivity for PPN is slightly higher than that of PAN. Larger aliphatic and olefinic PAN compounds generally showed lower sensitivities. These differences are owing to secondary reactions in the thermal decomposition region, which either reduce the yield of peroxy acyl radicals or cause losses of these radicals through intramolecular decomposition. The relative importance of these secondary reactions varies considerably between different PAN species. Results also indicate that the reaction of the peroxy acyl radicals with the ion-water cluster, I–(H2O)n proceeds about an order of magnitude faster than with I– alone. Variations among the individual PAN species at very low water vapor were observed. The results call for careful evaluation of each PAN species to be measured and for each desired operating condition of a TD-CIMS instrument.

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9

Kalalian, C., E. Roth, and A. Chakir. "Atmospheric reactivity of nitrate radicals: Reaction with peroxy radicals." Atmospheric Environment 190 (October 2018): 308–16. http://dx.doi.org/10.1016/j.atmosenv.2018.07.036.

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10

Croitoru, Mircea Dumitru, Hermina Iulia Petkes, Ibolya Fülöp, Remus Cotârlan, Oana Elena Şerban, Titica Maria Dogaru, Şerban Andrei Gâz Florea, Béla Tőkés, and Cornelia Majdik. "Nitrones: not only extraordinary spin traps, but also good nitric oxide sources in vivo." Acta Pharmaceutica 65, no. 4 (December 1, 2015): 413–26. http://dx.doi.org/10.1515/acph-2015-0032.

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Abstract Free radicals are involved in the development of reperfusion injuries. Using a spin trap, the intensity of such lesions can be reduced. Nitrones (effective in vivo spin traps) were tried in this work as in vivo nitric oxide donors. Nitrite and nitrate concentration values (rabbit blood) were used as biomarkers of nitric oxide production. Most nitrones did not increase plasma concentrations of nitrite and nitrate; on the contrary, reduced plasma concentrations of these indicators were noted. However, glyoxal isopropyldinitrone, in a dose of 50 mg kg-1, was highly effective in increasing nitric oxide production. At the same time, nitrones do not react with hepatic homogenates, proving that the release of nitric oxide takes place in the tissues and is not related to hepatic metabolism. Before using nitrones in vivo, they were tested in vitro for the ability to release nitric oxide following a reaction with the hydroxyl radical.

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11

Teng, A. P., J. D. Crounse, L. Lee, J. M. St. Clair, R. C. Cohen, and P. O. Wennberg. "Hydroxy nitrate production in the OH-initiated oxidation of alkenes." Atmospheric Chemistry and Physics Discussions 14, no. 5 (March 13, 2014): 6721–57. http://dx.doi.org/10.5194/acpd-14-6721-2014.

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Abstract. Alkenes generally react rapidly by addition of OH and subsequently O2 to form beta hydroxy peroxy radicals. These peroxy radicals react with NO to form beta hydroxy nitrates with a branching ratio α. We quantify α for C2–C8 alkenes at 296 K ±3 and 993 hPa. The branching ratio can be expressed as α = (0.042 ± 0.008) × N − (0.11 ± 0.04) where N is the number of heavy atoms (excluding the peroxy moiety), and listed errors are 2σ. These branching ratios are larger than previously reported and are similar to those for peroxy radicals formed from H abstraction from alkanes. We find the isomer distributions of beta hydroxy nitrates formed under NO-dominated peroxy radical chemistry to be similar to the isomer distribution of hydroxy hydroperoxides produced under HO2-dominated peroxy radical chemistry. With the assumption of unity yield for the hydroperoxides, this implies that the branching ratio to form beta hydroxy nitrates from primary, secondary, and tertiary RO2 are similar. Deuterium substitution enhances the branching ratio to form hydroxy nitrates in both propene and isoprene by a factor of ~1.5. These observations provide further evidence for importance of the ROONO lifetime in determining the branching ratio to form alkyl nitrates. We use these measurements to re-evaluate the role of alkene chemistry in the Houston region. We find that small alkenes play a larger role in oxidant formation than previously recognized.

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12

Teng, A. P., J. D. Crounse, L. Lee, J. M. St. Clair, R. C. Cohen, and P. O. Wennberg. "Hydroxy nitrate production in the OH-initiated oxidation of alkenes." Atmospheric Chemistry and Physics 15, no. 8 (April 28, 2015): 4297–316. http://dx.doi.org/10.5194/acp-15-4297-2015.

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Abstract. Alkenes are oxidized rapidly in the atmosphere by addition of OH and subsequently O2 leading to the formation of β-hydroxy peroxy radicals. These peroxy radicals react with NO to form β-hydroxy nitrates with a branching ratio α. We quantify α for C2–C8 alkenes at 295 K ± 3 and 993 hPa. The branching ratio can be expressed as α = (0.045 ± 0.016) × N − (0.11 ± 0.05) where N is the number of heavy atoms (excluding the peroxy moiety), and listed errors are 2σ. These branching ratios are larger than previously reported and are similar to those for peroxy radicals formed from H abstraction from alkanes. We find the isomer distributions of β-hydroxy nitrates formed under NO-dominated peroxy radical chemistry to be different than the isomer distribution of hydroxy hydroperoxides produced under HO2-dominated peroxy radical chemistry. Assuming unity yield for the hydroperoxides implies that the branching ratio to form β-hydroxy nitrates increases with substitution of RO2. Deuterium substitution enhances the branching ratio to form hydroxy nitrates in both propene and isoprene by a factor of ~ 1.5. The role of alkene chemistry in the Houston region is re-evaluated using the RONO2 branching ratios reported here. Small alkenes are found to play a significant role in present-day oxidant formation more than a decade (2013) after the 2000 Texas Air Quality Study identified these compounds as major contributors to photochemical smog in Houston.

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13

Mellouki, A., G. Le Bras, and G. Poulet. "Discharge flow kinetic study of nitrate radical reactions with free radicals: the reaction of nitrate radical with chlorine atom." Journal of Physical Chemistry 91, no. 22 (October 1987): 5760–64. http://dx.doi.org/10.1021/j100306a048.

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14

Vereecken, L., P. T. M. Carlsson, A. Novelli, F. Bernard, S. S. Brown, C. Cho, J. N. Crowley, et al. "Theoretical and experimental study of peroxy and alkoxy radicals in the NO3-initiated oxidation of isoprene." Physical Chemistry Chemical Physics 23, no. 9 (2021): 5496–515. http://dx.doi.org/10.1039/d0cp06267g.

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Under atmospheric conditions, nitrate-RO₂ radicals are equilibrated and react predominantly with HO₂, RO₂ and NO. The nitrate-RO chemistry is affected strongly by ring closure to epoxy radicals, impeding formation of MVK/MACR.

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15

Balint, B., L. E. Donnelly, T. Hanazawa, S. A. Kharitonov, and P. J. Barnes. "Increased nitric oxide metabolites in exhaled breath condensate after exposure to tobacco smoke." Thorax 56, no. 6 (June 1, 2001): 456–61. http://dx.doi.org/10.1136/thx.56.6.456.

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BACKGROUNDCigarette smoking reduces the level of exhaled nitric oxide (NO) in healthy subjects, although the mechanism is unclear. NO is a highly reactive molecule which can be oxidised or complexed with other biomolecules, depending on the microenvironment. The stable oxidation end products of NO metabolism are nitrite and nitrate. This study investigated the effect of smoking on NO metabolites in exhaled breath condensate.METHODSFifteen healthy current smokers were recruited together with 14 healthy non-smokers. Measurement of exhaled NO, lung function, and collection of exhaled breath condensate were performed. Nitrite, nitrite + nitrate, S-nitrosothiols, and nitrotyrosine levels were measured. The effect of inhaling two cigarettes in smokers was also evaluated. The mean level of exhaled NO in smokers was significantly lower than in non-smokers (4.3 (0.3) ppb v 5.5 (0.5) ppb, p<0.05).RESULTSThere was no difference in the levels of nitrite, nitrite + nitrate, S-nitrosothiols, and nitrotyrosine in the exhaled breath condensate at the baseline visit between smokers and non-smokers. After smoking, nitrite + nitrate levels were significantly but transiently increased (from 20.2 (2.8) μM to 29.8 (3.4) μM, p<0.05). There was no significant change in the levels of exhaled NO, nitrite, S-nitrosothiols, or nitrotyrosine 30 and 90 minutes after smoking.CONCLUSIONSThese findings suggest that acute smoking can increase the level of nitrate, but not nitrite, S-nitrosothiols, or nitrotyrosine in breath condensate. The deleterious effect of oxidant radicals induced by smoking may contribute to the epithelial damage of airways seen in smokers.

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16

Stademann, Arne, and Uta Wille. "NO3• Induced Self-Terminating Radical Oxygenations: Diastereoselective Synthesis of Anellated Pyrrolidines." Australian Journal of Chemistry 57, no. 11 (2004): 1055. http://dx.doi.org/10.1071/ch04124.

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Anellated pyrrolidines 19–22 were obtained through a diastereoselective self-terminating, oxidative radical cyclization cascade by treating the cis-cyclopentyl substituted alkynyl amines 14–18 with photochemically generated nitrate radicals, NO3●. A fast and modular access to the starting materials 14–18 was developed, which readily enables variation of the substitution pattern at the pyrrolidine ring formed upon radical cyclization. The diastereoselectivity of this reaction sequence was found to be strongly influenced by the nature of the substituents at the nitrogen atom. This shows that a complex interplay of both steric and stereoelectronic effects orchestrates the stereoselectivity of 5-exo radical cyclizations of highly substituted radicals.

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17

Gutyj, B. V., D. F. Hufriy, V. M. Hunchak, I. I. Khariv, N. D. Levkivska, and V. О. Huberuk. "THE INFLUENCE OF METISEVIT AND METIFEN ON THE INTENSITY OF LIPID PER OXIDATION IN THE BLOOD OF BULLS ON NITRATE LOAD." Scientific Messenger of LNU of Veterinary Medicine and Biotechnology 18, no. 3(70) (September 7, 2016): 67–71. http://dx.doi.org/10.15421/nvlvet7015.

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The level of primary and secondary lipid per oxidation products were investigated: diene conjugates and malondialdehyde in conditions of nitrate loading. It was established that at bulls feeding with sodium nitrite at a dose of 0.2 hNO3ˉ/kg of body weight, the level of diene conjugates and malondialdehyde in their was increased during the entire the experiment. On the 30thday of the experiment the level of diene conjugates in blood of bull, which were conducted with nitrate load was 7.44 ± 0.15 mmol/l, and the level of malondialdehyde – 0.305 ± 0.014 mmol/l.Under conditions of nitrate load , young cattle was used a new integrated drug «Metisevit», which consists of sodium selenite, vitamin E and metifen. It was found the stimulating effect of metifen and metisevit on antioxidant system of the body of young cattle. Depressing effect of metifen and metisevit on the processes and lipid per oxidation in the blood of bulls under conditions of chronic nitrate–nitrite toxicity. Metifen and metisevit interact with radicals of fatty acids and delay the development of a chain reaction of oxidative stress, reduce the oxidation of phospholipids and form a biologically inactive compound with products of per oxidation of fats. Obtained results of the research indicate antioxidant drugs «Metisevit» and «Metifen» in the application of their young cattle.The mentioned changes are occurring through the comprehensive action of the drug components «Medisvit», that leads to the normalization of metabolic processes and free radical in the body of bulls. Obtained results of the research indicate the antioxidant action of the drugs «Metisevit» and «Metifen» in the application of their young cattle and the reasonableness of their administration to improve the antioxidant status of the organism according to nitrate loading.

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18

Rollins, A. W., A. Kiendler-Scharr, J. Fry, T. Brauers, S. S. Brown, H. P. Dorn, W. P. Dubé, et al. "Isoprene oxidation by nitrate radical: alkyl nitrate and secondary organic aerosol yields." Atmospheric Chemistry and Physics Discussions 9, no. 2 (April 3, 2009): 8857–902. http://dx.doi.org/10.5194/acpd-9-8857-2009.

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Abstract. Alkyl nitrates and secondary organic aerosol (SOA) produced during the oxidation of isoprene by nitrate radicals has been observed in the SAPHIR chamber. We find the yield of nitrates is 70±8% from the isoprene+NO3 reaction, and the yield for secondary dinitrates produced in the reaction of primary isoprene nitrates with NO3 is 40±20%. We find an effective rate constant for reaction of NO3 with the group of first generation oxidation products to be 7×10−14 cm3 s−1. At the low total organic aerosol concentration in the chamber (max ≈0.6 μg m−3) we observed a mass yield (ΔSOA mass/Δisoprene mass) of 2% for the entire 16 h experiment. However a comparison of the timing of the observed SOA production to a box model simulation of first and second generation oxidation products shows that the yield from the first generation products was <0.2% while the further oxidation of the initial products leads to a yield of 10% (defined as ΔSOA/Δisoprene2x where Δisoprene2x is the mass of isoprene which reacted twice with NO3). The SOA yield of 10% is consistent with equilibrium partitioning of highly functionalized C5 products of isoprene oxidation.

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19

Vrekoussis, M., M. Kanakidou, N. Mihalopoulos, P. J. Crutzen, J. Lelieveld, D. Perner, H. Berresheim, and E. Baboukas. "Role of NO3 radical in oxidation processes in the eastern Mediterranean troposphere during the MINOS campaign." Atmospheric Chemistry and Physics Discussions 3, no. 3 (June 19, 2003): 3135–69. http://dx.doi.org/10.5194/acpd-3-3135-2003.

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Abstract. During the MINOS campaign (28 July–18 August 2001) nitrate (NO3) radical was measured at Finokalia, on the north coast of Crete in South-East Europe using a long path (10.4 km) Differential Optical Absorption Spectroscopy instrument (DOAS). Hydroxyl (OH) radical was also measured by a Chemical Ionization Mass-Spectrometer (Berresheim et al., this issue). These datasets represent the first simultaneous measurements of OH and NO3 radicals in the area. NO3 radical concentrations ranged from less than 3·107 up to 9·108 radical·cm-3 with an average value of 1.1·108 radical·cm−3. The observed NO3 mixing ratios are analyzed on the basis of the corresponding meteorological data and the volatile organic compound (VOC) observations simultaneously obtained at Finokalia station. The importance of the NO3 radical relatively to that of OH in the dimethylsulfide (DMS) and nitrate cycles is also investigated. The observed NO3 levels clearly regulate the diurnal variation of DMS. NO3 and N2O5 reactions account for about 21% of the total nitrate (HNO3(g) + NO−3(part)) production.

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20

Bates, Kelvin H., and Daniel J. Jacob. "A new model mechanism for atmospheric oxidation of isoprene: global effects on oxidants, nitrogen oxides, organic products, and secondary organic aerosol." Atmospheric Chemistry and Physics 19, no. 14 (July 31, 2019): 9613–40. http://dx.doi.org/10.5194/acp-19-9613-2019.

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Abstract. Atmospheric oxidation of isoprene, the most abundantly emitted non-methane hydrocarbon, affects the abundances of ozone (O3), the hydroxyl radical (OH), nitrogen oxide radicals (NOx), carbon monoxide (CO), oxygenated and nitrated organic compounds, and secondary organic aerosol (SOA). We analyze these effects in box models and in the global GEOS-Chem chemical transport model using the new reduced Caltech isoprene mechanism (RCIM) condensed from a recently developed explicit isoprene oxidation mechanism. We find many similarities with previous global models of isoprene chemistry along with a number of important differences. Proper accounting of the isomer distribution of peroxy radicals following the addition of OH and O2 to isoprene influences the subsequent distribution of products, decreasing in particular the yield of methacrolein and increasing the capacity of intramolecular hydrogen shifts to promptly regenerate OH. Hydrogen shift reactions throughout the mechanism lead to increased OH recycling, resulting in less depletion of OH under low-NO conditions than in previous mechanisms. Higher organonitrate yields and faster tertiary nitrate hydrolysis lead to more efficient NOx removal by isoprene and conversion to inorganic nitrate. Only 20 % of isoprene-derived organonitrates (excluding peroxyacyl nitrates) are chemically recycled to NOx. The global yield of formaldehyde from isoprene is 22 % per carbon and less sensitive to NO than in previous mechanisms. The global molar yield of glyoxal is 2 %, much lower than in previous mechanisms because of deposition and aerosol uptake of glyoxal precursors. Global production of isoprene SOA is about one-third from each of the following: isoprene epoxydiols (IEPOX), organonitrates, and tetrafunctional compounds. We find a SOA yield from isoprene of 13 % per carbon, much higher than commonly assumed in models and likely offset by SOA chemical loss. We use the results of our simulations to further condense RCIM into a mini Caltech isoprene mechanism (Mini-CIM) for less expensive implementation in atmospheric models, with a total size (108 species, 345 reactions) comparable to currently used mechanisms.

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21

Hsu, Dur-Zong, Ya-Hui Li, Pei-Yi Chu, Srinivasan Periasamy, and Ming-Yie Liu. "Sesame Oil Prevents Acute Kidney Injury Induced by the Synergistic Action of Aminoglycoside and Iodinated Contrast in Rats." Antimicrobial Agents and Chemotherapy 55, no. 6 (March 14, 2011): 2532–36. http://dx.doi.org/10.1128/aac.01597-10.

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ABSTRACTThe aim of the study was to investigate the effect of sesame oil on acute kidney injury induced by the synergistic action of aminoglycoside and iodinated contrast in rats. Acute kidney injury was induced by a 5-day course of daily gentamicin injections (100 mg/kg of body weight, subcutaneously) and then iodinated contrast (4 ml/kg, intravenously) in male specific-pathogen-free Sprague-Dawley rats. Sesame oil (0.5 ml/kg, orally) was given 1 h before iodinated contrast. Renal function and oxidative stress were assessed 6 h after iodinated contrast injection. Renal function was evaluated by measuring serum blood urea nitrogen and creatinine levels. Renal oxidative stress was assessed by determining renal lipid peroxidation, myeloperoxidase, hydroxyl radical, superoxide anion, nitrite/nitrate, and inducible nitric oxide synthase levels. Sesame oil significantly prevented the rise of serum blood urea nitrogen and creatinine levels. Furthermore, there was a parallel inhibition of the rise in levels of expression of renal lipid peroxidation, myeloperoxidase, hydroxyl radicals, superoxide anion, nitrite/nitrate, and inducible nitric oxide synthase in rats with gentamicin-plus-iodinated contrast-induced acute kidney injury. We conclude that sesame oil may attenuate aminoglycoside-plus-iodinated contrast-induced acute kidney injury by inhibiting renal oxidative stress in rats.

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Duan, Lin, Tong Zhang, Weihua Song, Chuanjia Jiang, Yan Hou, Weilu Zhao, Wei Chen, and Pedro J. J. Alvarez. "Photolysis of graphene oxide in the presence of nitrate: implications for graphene oxide integrity in water and wastewater treatment." Environmental Science: Nano 6, no. 1 (2019): 136–45. http://dx.doi.org/10.1039/c8en00637g.

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As the nitrate concentration increases, the dominant pathway of GO transformation changes from direct photolysis to indirect photolysis enhanced by the production of hydroxyl radicals (˙OH) during UV irradiation of nitrate.

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Boyd, C. M., J. Sanchez, L. Xu, A. J. Eugene, T. Nah, W. Y. Tuet, M. I. Guzman, and N. L. Ng. "Secondary organic aerosol formation from the β-pinene+NO3 system: effect of humidity and peroxy radical fate." Atmospheric Chemistry and Physics 15, no. 13 (July 10, 2015): 7497–522. http://dx.doi.org/10.5194/acp-15-7497-2015.

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Abstract. The formation of secondary organic aerosol (SOA) from the oxidation of β-pinene via nitrate radicals is investigated in the Georgia Tech Environmental Chamber (GTEC) facility. Aerosol yields are determined for experiments performed under both dry (relative humidity (RH) < 2 %) and humid (RH = 50 % and RH = 70 %) conditions. To probe the effects of peroxy radical (RO2) fate on aerosol formation, "RO2 + NO3 dominant" and "RO2 + HO2 dominant" experiments are performed. Gas-phase organic nitrate species (with molecular weights of 215, 229, 231, and 245 amu, which likely correspond to molecular formulas of C10H17NO4, C10H15NO5, C10H17NO5, and C10H15NO6, respectively) are detected by chemical ionization mass spectrometry (CIMS) and their formation mechanisms are proposed. The NO+ (at m/z 30) and NO2+ (at m/z 46) ions contribute about 11 % to the combined organics and nitrate signals in the typical aerosol mass spectrum, with the NO+ : NO2+ ratio ranging from 4.8 to 10.2 in all experiments conducted. The SOA yields in the "RO2 + NO3 dominant" and "RO2 + HO2 dominant" experiments are comparable. For a wide range of organic mass loadings (5.1–216.1 μg m−3), the aerosol mass yield is calculated to be 27.0–104.1 %. Although humidity does not appear to affect SOA yields, there is evidence of particle-phase hydrolysis of organic nitrates, which are estimated to compose 45–74 % of the organic aerosol. The extent of organic nitrate hydrolysis is significantly lower than that observed in previous studies on photooxidation of volatile organic compounds in the presence of NOx. It is estimated that about 90 and 10 % of the organic nitrates formed from the β-pinene+NO3 reaction are primary organic nitrates and tertiary organic nitrates, respectively. While the primary organic nitrates do not appear to hydrolyze, the tertiary organic nitrates undergo hydrolysis with a lifetime of 3–4.5 h. Results from this laboratory chamber study provide the fundamental data to evaluate the contributions of monoterpene + NO3 reaction to ambient organic aerosol measured in the southeastern United States, including the Southern Oxidant and Aerosol Study (SOAS) and the Southeastern Center for Air Pollution and Epidemiology (SCAPE) study.

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Hering, T., T. Slanina, A. Hancock, U. Wille, and B. König. "Visible light photooxidation of nitrate: the dawn of a nocturnal radical." Chemical Communications 51, no. 30 (2015): 6568–71. http://dx.doi.org/10.1039/c5cc01580d.

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Highly oxidizing nitrate radicals (NO₃˙) are easily accessed from readily available nitrate salts by visible light photoredox catalysis using a purely organic dye as the catalyst and oxygen as the terminal oxidant.

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25

Boyd, C. M., J. Sanchez, L. Xu, A. J. Eugene, T. Nah, W. Y. Tuet, M. I. Guzman, and N. L. Ng. "Secondary Organic Aerosol (SOA) formation from the β-pinene + NO3 system: effect of humidity and peroxy radical fate." Atmospheric Chemistry and Physics Discussions 15, no. 2 (January 28, 2015): 2679–744. http://dx.doi.org/10.5194/acpd-15-2679-2015.

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Abstract. The formation of secondary organic aerosol (SOA) from the oxidation of β-pinene via nitrate radicals is investigated in the Georgia Tech Environmental Chamber facility (GTEC). Aerosol yields are determined for experiments performed under both dry (RH < 2%) and humid (RH = 50% and RH = 70%) conditions. To probe the effects of peroxy radical (RO2) fate on aerosol formation, "RO2 + NO3 dominant" and "RO2 + HO2 dominant" experiments are performed. Gas-phase organic nitrate species (with molecular weights of 215, 229, 231 and 245 amu) are detected by chemical ionization mass spectrometry and their formation mechanisms are proposed. The ions at m/z 30 (NO+) and m/z 46 (NO2+) contribute about 11% to the total organics signal in the typical aerosol mass spectrum, with NO+ : NO2+ ratio ranging from 6 to 9 in all experiments conducted. The SOA yields in the "RO2 + NO3 dominant" and "RO2 + HO2 dominant" experiments are comparable. For a wide range of organic mass loadings (5.1–216.1 μg m−3), the aerosol mass yield is calculated to be 27.0–104.1%. Although humidity does not appear to affect SOA yields, there is evidence of particle-phase hydrolysis of organic nitrates, which are estimated to compose 45–74% of the organic aerosol. The extent of organic nitrate hydrolysis is significantly lower than that observed in previous studies on photooxidation of volatile organic compounds in the presence of NOx. It is estimated that about 90 and 10% of the organic nitrates formed from the β-pinene + NO3 reaction are primary organic nitrates and tertiary organic nitrates, respectively. While the primary organic nitrates do not appear to hydrolyze, the tertiary organic nitrates undergo hydrolysis with a lifetime of 3–4.5 h. Results from this laboratory chamber study provide the fundamental data to evaluate the contributions of monoterpene + NO3 reaction to ambient organic aerosol measured in the southeastern United States, including the Southern Oxidant and Aerosol Study (SOAS) and the Southeastern Center for Air Pollution and Epidemiology (SCAPE) study.

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26

Vinge, Sydney L., Samuel W. Shaheen, Charles M. Sharpless, and Karl G. Linden. "Nitrate with benefits: optimizing radical production during UV water treatment." Environmental Science: Water Research & Technology 6, no. 4 (2020): 1163–75. http://dx.doi.org/10.1039/c9ew01138b.

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27

Vrekoussis, M., N. Mihalopoulos, E. Gerasopoulos, M. Kanakidou, P. Crutzen, and J. Lelieveld. "Two-years of NO3 radical observations in the boundary layer over the Eastern Mediterranean." Atmospheric Chemistry and Physics Discussions 6, no. 5 (September 28, 2006): 9517–44. http://dx.doi.org/10.5194/acpd-6-9517-2006.

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Abstract. This is the first study that investigates the seasonal variability of nitrate (NO3) radicals in the marine boundary layer over the East Mediterranean Sea. An extensive data set of NO3 radical observations on the north coast of Crete for more than two years (June 2001–September 2003) is presented here. NO3 radicals follow a distinct seasonal dependency with maximum mixing ratios in summer (5.6±1.2 pptv) and minimum in winter (1.2±1.2 pptv). Episodes with high NO3 mixing ratios have been encountered mainly in polluted air masses originating from mainland Greece, Central and East Europe, and Turkey. Ancillary measurements of ozone, nitrogen dioxide (NO2 and meteorological parameters have been conducted and used to explain the observed NO3 variability. The acquired NO2 nighttime observations provide the up-to-date most complete overview of NO2 temporal variability in the area. The data show that the NO3 nighttime mixing ratios are primarily dependent on NO2 (positive correlation) and relative humidity (negative correlation) and to a lesser extend on temperature (positive correlation). As inferred from these observations, on average the major sink of NO3 radicals in the area is the heterogeneous reaction of dinitrogen pentoxide (N2O5) on aqueous particles whereas the homogeneous gas phase reactions of NO3 are most important during spring and summer. NO 3 chemistry in the area significantly contributes to VOC oxidation and to the nighttime formation of peroxy radicals, nitric acid and particulate nitrate.

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Bianco, A., M. Passananti, H. Perroux, G. Voyard, C. Mouchel-Vallon, N. Chaumerliac, G. Mailhot, L. Deguillaume, and M. Brigante. "A better understanding of hydroxyl radical photochemical sources in cloud waters collected at the puy de Dôme station: experimental vs. modeled formation rates." Atmospheric Chemistry and Physics Discussions 15, no. 10 (May 18, 2015): 13923–55. http://dx.doi.org/10.5194/acpd-15-13923-2015.

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Abstract. The oxidative capacity of the cloud aqueous phase is investigated during three field campaigns from 2013 to 2014 at the top of the puy de Dôme station (PUY) in France. Forty-one cloud samples are collected, and the corresponding air masses are classified as highly marine, marine and continental. Hydroxyl radical (HO·) formation rates (RHO·f) are determined using a photochemical setup (Xenon lamp that can reproduce the solar spectrum) and a chemical probe coupled with spectroscopic analysis that can trap all of the generated radicals for each sample. Using this method, the obtained values correspond to the total formation of HO· without its chemical sinks. These formation rates are correlated with the concentrations of the naturally occurring sources of HO·, including hydrogen peroxide, nitrite, nitrate and iron. The total hydroxyl radical formation rates are measured as ranging from approximately 2 × 10−11 to 4 × 10−10 M s−1, and the hydroxyl radical quantum yield formation (ΦHO·) is estimated between 10−4 and 10−2. Experimental values are compared with modeled formation rates calculated by the model of multiphase cloud chemistry (M2C2), considering only the chemical sources of the hydroxyl radicals. The comparison between the experimental and the modeled results suggests that the photoreactivity of the iron species as a source of HO· is overestimated by the model, and H2O2 photolysis represents the most important source of this radical (between 70 and 99%) for the cloud water sampled at the PUY station (primarily marine and continental).

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Mihelcic, D., D. Klemp, P. M�sgen, H. W. P�tz, and A. Volz-Thomas. "Simultaneous measurements of peroxy and nitrate radicals at Schauinsland." Journal of Atmospheric Chemistry 16, no. 4 (May 1993): 313–35. http://dx.doi.org/10.1007/bf01032628.

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30

Pak, V. Kh, and V. A. Nevostruev. "The formation and decay of radicals in potassium nitrate." High Energy Chemistry 34, no. 4 (July 2000): 246–50. http://dx.doi.org/10.1007/bf02770892.

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31

Sommar, J., M. Hallquist, and E. Ljungström. "On the reaction of nitrate radicals with dimethyl mercury." Journal of Aerosol Science 28, no. 6 (September 1997): 1115–16. http://dx.doi.org/10.1016/s0021-8502(97)88137-2.

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32

Cook, Andrew R., Nada Dimitrijevic, Benjamin W. Dreyfus, Dan Meisel, Larry A. Curtiss, and Donald M. Camaioni. "Reducing Radicals in Nitrate Solutions. The NO32-System Revisited." Journal of Physical Chemistry A 105, no. 14 (April 2001): 3658–66. http://dx.doi.org/10.1021/jp0038052.

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33

Easton, Christopher J., Andrew J. Ivory, and Craig A. Smith. "Nitrate esters in the generation of amino acid radicals." Journal of the Chemical Society, Perkin Transactions 2, no. 3 (1997): 503–8. http://dx.doi.org/10.1039/a606362d.

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34

Rollins, A. W., A. Kiendler-Scharr, J. L. Fry, T. Brauers, S. S. Brown, H. P. Dorn, W. P. Dubé, et al. "Isoprene oxidation by nitrate radical: alkyl nitrate and secondary organic aerosol yields." Atmospheric Chemistry and Physics 9, no. 18 (September 15, 2009): 6685–703. http://dx.doi.org/10.5194/acp-9-6685-2009.

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Abstract. Alkyl nitrates and secondary organic aerosol (SOA) produced during the oxidation of isoprene by nitrate radicals has been observed in the SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) chamber. A 16 h dark experiment was conducted with temperatures at 289–301 K, and maximum concentrations of 11 ppb isoprene, 62.4 ppb O3 and 31.1 ppb NOx. We find the yield of nitrates is 70±8% from the isoprene + NO3 reaction, and the yield for secondary dinitrates produced in the reaction of primary isoprene nitrates with NO3 is 40±20%. We find an effective rate constant for reaction of NO3 with the group of first generation oxidation products to be 7×10−14 molecule−1 cm3 s−1. At the low total organic aerosol concentration in the chamber (max=0.52 μg m−3) we observed a mass yield (ΔSOA mass/Δisoprene mass) of 2% for the entire 16 h experiment. However a comparison of the timing of the observed SOA production to a box model simulation of first and second generation oxidation products shows that the yield from the first generation products was <0.7% while the further oxidation of the initial products leads to a yield of 14% (defined as ΔSOA/Δisoprene2x where Δisoprene2x is the mass of isoprene which reacted twice with NO3). The SOA yield of 14% is consistent with equilibrium partitioning of highly functionalized C5 products of isoprene oxidation.

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Ng, Nga Lee, Steven S. Brown, Alexander T. Archibald, Elliot Atlas, Ronald C. Cohen, John N. Crowley, Douglas A. Day, et al. "Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic aerosol." Atmospheric Chemistry and Physics 17, no. 3 (February 13, 2017): 2103–62. http://dx.doi.org/10.5194/acp-17-2103-2017.

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Abstract. Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 decades, during which time a large body of research has emerged from laboratory, field, and modeling studies. NO3-BVOC reactions influence air quality, climate and visibility through regional and global budgets for reactive nitrogen (particularly organic nitrates), ozone, and organic aerosol. Despite its long history of research and the significance of this topic in atmospheric chemistry, a number of important uncertainties remain. These include an incomplete understanding of the rates, mechanisms, and organic aerosol yields for NO3-BVOC reactions, lack of constraints on the role of heterogeneous oxidative processes associated with the NO3 radical, the difficulty of characterizing the spatial distributions of BVOC and NO3 within the poorly mixed nocturnal atmosphere, and the challenge of constructing appropriate boundary layer schemes and non-photochemical mechanisms for use in state-of-the-art chemical transport and chemistry–climate models. This review is the result of a workshop of the same title held at the Georgia Institute of Technology in June 2015. The first half of the review summarizes the current literature on NO3-BVOC chemistry, with a particular focus on recent advances in instrumentation and models, and in organic nitrate and secondary organic aerosol (SOA) formation chemistry. Building on this current understanding, the second half of the review outlines impacts of NO3-BVOC chemistry on air quality and climate, and suggests critical research needs to better constrain this interaction to improve the predictive capabilities of atmospheric models.

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36

Reeves, Claire E., Graham P. Mills, Lisa K. Whalley, W. Joe F. Acton, William J. Bloss, Leigh R. Crilley, Sue Grimmond, et al. "Observations of speciated isoprene nitrates in Beijing: implications for isoprene chemistry." Atmospheric Chemistry and Physics 21, no. 8 (April 27, 2021): 6315–30. http://dx.doi.org/10.5194/acp-21-6315-2021.

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Abstract. Isoprene is the most important biogenic volatile organic compound in the atmosphere. Its calculated impact on ozone (O3) is critically dependent on the model isoprene oxidation chemical scheme, in particular the way the isoprene-derived organic nitrates (IN) are treated. By combining gas chromatography with mass spectrometry, we have developed a system capable of separating and unambiguously measuring individual IN isomers. In this paper we use measurements from its first field deployment, which took place in Beijing as part of the Atmospheric Pollution and Human Health in a Chinese Megacity programme, to test understanding of the isoprene chemistry as simulated in the Master Chemical Mechanism (MCM) (v.3.3.1). Seven individual isoprene nitrates were identified and quantified during the campaign: two β-hydroxy nitrates (IHN), four δ-carbonyl nitrates (ICN), and propanone nitrate. Our measurements show that in the summertime conditions experienced in Beijing the ratio of (1-OH, 2-ONO2)-IHN to (4-OH, 3-ONO2)-IHN (the numbers indicate the carbon atom in the isoprene chain to which the radical is added) increases at NO mixing ratios below 2 ppb. This provides observational field evidence of the redistribution of the peroxy radicals derived from OH oxidation of isoprene away from the kinetic ratio towards a new thermodynamic equilibrium consistent with box model calculations. The observed amounts of δ-ICN demonstrate the importance of daytime addition of NO3 to isoprene in Beijing but suggest that the predominant source of the δ-ICN in the model (reaction of NO with δ-nitrooxy peroxy radicals) may be too large. Our speciated measurements of the four δ-ICN exhibit a mean C1 : C4 isomer ratio of 1.4 and a mean trans : cis isomer ratio of 7 and provide insight into the isomeric distribution of the δ-nitrooxy peroxy radicals. Together our measurements and model results indicate that propanone nitrate was formed from the OH oxidation of δ-ICN both during the day and night, as well as from NO3 addition to propene at night. This study demonstrates the value of speciated IN measurements in testing understanding of the isoprene degradation chemistry and shows how more extensive measurements would provide greater constraints. It highlights areas of the isoprene chemistry that warrant further study, in particular the impact of NO on the formation of the IHN and the NO3-initiated isoprene degradation chemistry, as well as the need for further laboratory studies on the formation and the losses of IN, in particular via photolysis of δ-ICN and hydrolysis.

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Wei, Wenjuan, Corinne Mandin, and Olivier Ramalho. "Reactivity of Semivolatile Organic Compounds with Hydroxyl Radicals, Nitrate Radicals, and Ozone in Indoor Air." International Journal of Chemical Kinetics 49, no. 7 (April 11, 2017): 506–21. http://dx.doi.org/10.1002/kin.21093.

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38

Bianco, A., M. Passananti, H. Perroux, G. Voyard, C. Mouchel-Vallon, N. Chaumerliac, G. Mailhot, L. Deguillaume, and M. Brigante. "A better understanding of hydroxyl radical photochemical sources in cloud waters collected at the puy de Dôme station – experimental versus modelled formation rates." Atmospheric Chemistry and Physics 15, no. 16 (August 19, 2015): 9191–202. http://dx.doi.org/10.5194/acp-15-9191-2015.

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Abstract. The oxidative capacity of the cloud aqueous phase is investigated during three field campaigns from 2013 to 2014 at the top of the puy de Dôme station (PUY) in France. A total of 41 cloud samples are collected and the corresponding air masses are classified as highly marine, marine and continental. Hydroxyl radical (HO•) formation rates (RHO•f) are determined using a photochemical setup (xenon lamp that can reproduce the solar spectrum) and a chemical probe coupled with spectroscopic analysis that can trap all of the generated radicals for each sample. Using this method, the obtained values correspond to the total formation of HO• without its chemical sinks. These formation rates are correlated with the concentrations of the naturally occurring sources of HO•, including hydrogen peroxide, nitrite, nitrate and iron. The total hydroxyl radical formation rates are measured as ranging from approximately 2 × 10−11 to 4 × 10−10 M s−1, and the hydroxyl radical quantum yield formation (ΦHO•) is estimated between 10−4 and 10−2. Experimental values are compared with modelled formation rates calculated by the model of multiphase cloud chemistry (M2C2), considering only the chemical sources of the hydroxyl radicals. The comparison between the experimental and the modelled results suggests that the photoreactivity of the iron species as a source of HO• is overestimated by the model, and H2O2 photolysis represents the most important source of this radical (between 70 and 99 %) for the cloud water sampled at the PUY station (primarily marine and continental).

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Fry, Juliane L., Steven S. Brown, Ann M. Middlebrook, Peter M. Edwards, Pedro Campuzano-Jost, Douglas A. Day, José L. Jimenez, et al. "Secondary organic aerosol (SOA) yields from NO3 radical + isoprene based on nighttime aircraft power plant plume transects." Atmospheric Chemistry and Physics 18, no. 16 (August 16, 2018): 11663–82. http://dx.doi.org/10.5194/acp-18-11663-2018.

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Abstract. Nighttime reaction of nitrate radicals (NO3) with biogenic volatile organic compounds (BVOC) has been proposed as a potentially important but also highly uncertain source of secondary organic aerosol (SOA). The southeastern United States has both high BVOC and nitrogen oxide (NOx) emissions, resulting in a large model-predicted NO3-BVOC source of SOA. Coal-fired power plants in this region constitute substantial NOx emissions point sources into a nighttime atmosphere characterized by high regionally widespread concentrations of isoprene. In this paper, we exploit nighttime aircraft observations of these power plant plumes, in which NO3 radicals rapidly remove isoprene, to obtain field-based estimates of the secondary organic aerosol yield from NO3 + isoprene. Observed in-plume increases in nitrate aerosol are consistent with organic nitrate aerosol production from NO3 + isoprene, and these are used to determine molar SOA yields, for which the average over nine plumes is 9 % (±5 %). Corresponding mass yields depend on the assumed molecular formula for isoprene-NO3-SOA, but the average over nine plumes is 27 % (±14 %), on average larger than those previously measured in chamber studies (12 %–14 % mass yield as ΔOA ∕ ΔVOC after oxidation of both double bonds). Yields are larger for longer plume ages. This suggests that ambient aging processes lead more effectively to condensable material than typical chamber conditions allow. We discuss potential mechanistic explanations for this difference, including longer ambient peroxy radical lifetimes and heterogeneous reactions of NO3-isoprene gas phase products. More in-depth studies are needed to better understand the aerosol yield and oxidation mechanism of NO3 radical + isoprene, a coupled anthropogenic–biogenic source of SOA that may be regionally significant.

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Pryor, W. A., and G. L. Squadrito. "The chemistry of peroxynitrite: a product from the reaction of nitric oxide with superoxide." American Journal of Physiology-Lung Cellular and Molecular Physiology 268, no. 5 (May 1, 1995): L699—L722. http://dx.doi.org/10.1152/ajplung.1995.268.5.l699.

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Nitric oxide and superoxide, which are produced by several cell types, rapidly combine to form peroxynitrite. This reaction can result in nitric oxide scavenging, and thus mitigation of the biological effects of superoxide. Also, superoxide can trap and hence modulate the effects of nitric oxide; superoxide dismutase, by controlling superoxide levels, therefore can influence the reaction pathways open to nitric oxide. The production of peroxynitrite, however, causes its own sequelae of events: Although neither .NO nor superoxide is a strong oxidant, peroxynitrite is a potent and versatile oxidant that can attack a wide range of biological targets. The peroxynitrite anion is relatively stable, but its acid, peroxynitrous acid (HOONO), rearranges to form nitrate with a half-life of approximately 1 s at pH 7, 37 degrees C. HOONO exists as a Boltzmann distribution of rotamers; at 5-37 degrees C HOONO has an apparent acidity constant, pKa,app, of 6.8. Oxidation reactions of HOONO can involve two-electron processes (such as an SN2 displacement) or a one-electron transfer (ET) reaction in which the substrate is oxidized by one electron and peroxynitrite is reduced. These oxidation reactions could involve one of two mechanisms. The first mechanism is homolysis of HOONO to give HO. and .NO2, which initially are held together in a solvent cage. This caged pair of radicals (the "geminate" pair) can either diffuse apart, giving free radicals that can perform oxidations, or react together either to form nitrate or to reform HOONO (a process called cage return). A large amount of cage return can explain the small entropy of activation (Arrhenius A-factor) observed for the decomposition of HOONO. A cage mechanism also can explain the residual yield of nitrate that appears to be formed even in the presence of high concentrations of all of the scavengers studied to date, since scavengers capture only free HO. and .NO2 and not caged radicals. If the cage mechanism is correct, the rate of disappearance of peroxynitrite be slower in solvents of higher viscosity, and we do not find this to be the case. The second mechanism is that an activated isomer of peroxynitrous acid, HOONO*, can be formed in a steady state. The HOONO* mechanism can explain the inability of hydroxyl radical scavengers to completely block either nitrate formation or the oxidation of substrates such as methionine, since HOONO* would be less reactive, and therefore more selective, than the hydroxyl radical itself.(ABSTRACT TRUNCATED AT 400 WORDS)

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Matveichuk, Yulya V. "NITRATE-SELECTIVE ELECTRODE AND ITS USE FOR ANALYSIS OF VEGETABLES AND MINERAL WATERS." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 62, no. 9 (August 30, 2019): 20–26. http://dx.doi.org/10.6060/ivkkt.20196209.6004.

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The effect of the length of the radicals at the exchange center of the quaternary ammonium salts on the selectivity and the detection limit of the nitrate-selective electrode is investigated. The observed effects of improving the analytical characteristics while reducing the steric availability of the exchange center for quaternary ammonium salts are explained on the basis of the theory of ion association. The composition of the polyvinyl chloride (33 wt.%) electrode membrane for the quaternary ammonium salt (3,4,5-tris bromide (dodecyloxy)benzyltricethylammonium bromide, 5 wt.%) and the plasticizer (o-nitrophendecyl ether, 62 wt.%) was optimized. The developed electrode has a low detection limit (2.0∙10−7 mol/l) and a close to theoretical slope of the electrode function (56.8 mV/pNO3), and the potential of the nitrate-selective electrode is not affected by fluoride, nitrite, bicarbonate-, dihydrophosphate-, sulfate ions. The interfering action of chloride, bromide, and iodide ions can be eliminated by introducing 1·10–3 mol/l of a background solution of silver sulfate. Thiocyanate and perchlorate ions interfere with the operation of the electrode, but they are practically not found in real objects. The developed electrode was used to determine the nitrate ions in vegetables (white cabbage, cucumber, lettuce, tomato, onion, carrots, and potatoes), greens (dill, parsley) and mineral water. It was established that the maximum permissible concentration of nitrates is exceeded more than 4.5 times for cabbage (MAC = 500 mg/kg), almost 2 times for salad (maximum permissible concentration 1500 mg/kg), 1.5 times for potatoes (maximum permissible concentration 250 mg/kg) and 3 times for dill (maximum permissible concentration 1500 mg/kg).

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Becerra, Rosa, and Christian Pfrang. "Kinetic Studies of Nitrate Radicals: Flash Photolysis at 193 nm." International Journal of Chemical Kinetics 48, no. 12 (September 26, 2016): 806–11. http://dx.doi.org/10.1002/kin.21035.

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43

de Sémainville, Ph G., B. D Anna, and Ch George. "Aqueous Phase Reactivity of Nitrate Radicals (NO3) Toward Dicarboxylic Acids." Zeitschrift für Physikalische Chemie 224, no. 7-8 (August 2010): 1247–60. http://dx.doi.org/10.1524/zpch.2010.6150.

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Mattei, Coraline, Henri Wortham, and Etienne Quivet. "Heterogeneous atmospheric degradation of current-use pesticides by nitrate radicals." Atmospheric Environment 211 (August 2019): 170–80. http://dx.doi.org/10.1016/j.atmosenv.2019.05.016.

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Parker, Kimberly M., and William A. Mitch. "Halogen radicals contribute to photooxidation in coastal and estuarine waters." Proceedings of the National Academy of Sciences 113, no. 21 (May 9, 2016): 5868–73. http://dx.doi.org/10.1073/pnas.1602595113.

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Although halogen radicals are recognized to form as products of hydroxyl radical (•OH) scavenging by halides, their contribution to the phototransformation of marine organic compounds has received little attention. We demonstrate that, relative to freshwater conditions, seawater halides can increase photodegradation rates of domoic acid, a marine algal toxin, and dimethyl sulfide, a volatile precursor to cloud condensation nuclei, up to fivefold. Using synthetic seawater solutions, we show that the increased photodegradation is specific to dissolved organic matter (DOM) and halides, rather than other seawater salt constituents (e.g., carbonates) or photoactive species (e.g., iron and nitrate). Experiments in synthetic and natural coastal and estuarine water samples demonstrate that the halide-specific increase in photodegradation could be attributed to photochemically generated halogen radicals rather than other photoproduced reactive intermediates [e.g., excited-state triplet DOM (3DOM*), reactive oxygen species]. Computational kinetic modeling indicates that seawater halogen radical concentrations are two to three orders of magnitude greater than freshwater •OH concentrations and sufficient to account for the observed halide-specific increase in photodegradation. Dark •OH generation by gamma radiolysis demonstrates that halogen radical production via •OH scavenging by halides is insufficient to explain the observed effect. Using sensitizer models for DOM chromophores, we show that halogen radicals are formed predominantly by direct oxidation of Cl− and Br− by 3DOM*, an •OH-independent pathway. Our results indicate that halogen radicals significantly contribute to the phototransformation of algal products in coastal or estuarine surface waters.

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Musat, R., J. L. Marignier, C. Le Naour, S. Denisov, L. Venault, Ph Moisy, and M. Mostafavi. "Pulse radiolysis study on the reactivity of NO3˙ radical toward uranous(iv), hydrazinium nitrate and hydroxyl ammonium nitrate at room temperature and at 45 °C." Physical Chemistry Chemical Physics 22, no. 9 (2020): 5188–97. http://dx.doi.org/10.1039/c9cp07034f.

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47

Perring, A. E., A. Wisthaler, M. Graus, P. J. Wooldridge, A. L. Lockwood, L. H. Mielke, P. B. Shepson, A. Hansel, and R. C. Cohen. "A product study of the isoprene+NO3 reaction." Atmospheric Chemistry and Physics 9, no. 14 (July 24, 2009): 4945–56. http://dx.doi.org/10.5194/acp-9-4945-2009.

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Abstract. Oxidation of isoprene through reaction with NO3 radicals is a significant sink for isoprene that persists after dark. The main products of the reaction are multifunctional nitrates. These nitrates constitute a significant NOx sink in the nocturnal boundary layer and they likely play an important role in formation of secondary organic aerosol. Products of the isoprene+NO3 reaction will, in many locations, be abundant enough to affect nighttime radical chemistry and to persist into daytime where they may represent a source of NOx. Product formation in the isoprene + NO3 reaction was studied in a smog chamber at Purdue University. Isoprene nitrates and other hydrocarbon products were observed using Proton Transfer Reaction-Mass Spectrometry (PTR-MS) and reactive nitrogen products were observed using Thermal Dissociation–Laser Induced Fluorescence (TD-LIF). The organic nitrate yield is found to be 65±12% of which the majority was nitrooxy carbonyls and the combined yield of methacrolein and methyl vinyl ketone (MACR+MVK) is found to be ∼10%. PTR-MS measurements of nitrooxy carbonyls and TD-LIF measurements of total organic nitrates agreed well. The PTR-MS also observed a series of minor oxidation products which were tentatively identified and their yields quantified These other oxidation products are used as additional constraints on the reaction mechanism.

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Laversin, H., J. Cousin, L. Joly, E. Roth, G. Durry, and A. Chakir. "Kinetic study of the reaction of nitrate radicals with ethylperoxy radicals between 277 and 358 K." Chemical Physics Letters 644 (January 2016): 14–19. http://dx.doi.org/10.1016/j.cplett.2015.11.045.

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Ling, Zhenhao, Hai Guo, Isobel Jane Simpson, Sandra Maria Saunders, Sean Ho Man Lam, Xiaopu Lyu, and Donald Ray Blake. "New insight into the spatiotemporal variability and source apportionments of C1–C4 alkyl nitrates in Hong Kong." Atmospheric Chemistry and Physics 16, no. 13 (July 6, 2016): 8141–56. http://dx.doi.org/10.5194/acp-16-8141-2016.

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Abstract. C1–C4 alkyl nitrates (RONO2) were measured concurrently at a mountain site, Tai Mo Shan (TMS), and an urban site, Tsuen Wan (TW), at the base of the same mountain in Hong Kong from September to November 2010. Although the levels of parent hydrocarbons were much lower at TMS (p < 0.05), similar alkyl nitrate levels were found at both sites regardless of the elevation difference, suggesting various source contributions of alkyl nitrates at the two sites. Prior to using a positive matrix factorization (PMF) model, the data at TW were divided into "meso" and "non-meso" scenarios for the investigation of source apportionments with the influence of mesoscale circulation and regional transport, respectively. Secondary formation was the prominent contributor of alkyl nitrates in the meso scenario (60 ± 2 %, 60.2 ± 1.2 pptv), followed by biomass burning and oceanic emissions, while biomass burning and secondary formation made comparable contributions to alkyl nitrates in the non-meso scenario, highlighting the strong emissions of biomass burning in the inland Pearl River delta (PRD) region. In contrast to TW, the alkyl nitrate levels measured at TMS mainly resulted from the photooxidation of the parent hydrocarbons at TW during mesoscale circulation, i.e., valley breezes, corresponding to 52–86 % of the alkyl nitrate levels at TMS. Furthermore, regional transport from the inland PRD region made significant contributions to the levels of alkyl nitrates (∼ 58–82 %) at TMS in the non-meso scenario, resulting in similar levels of alkyl nitrates observed at the two sites. The simulation of secondary formation pathways using a photochemical box model found that the reaction of alkyl peroxy radicals (RO2) with nitric oxide (NO) dominated the formation of RONO2 at both sites, and the formation of alkyl nitrates contributed negatively to O3 production, with average reduction rates of 4.1 and 4.7 pptv pptv−1 at TMS and TW, respectively.

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Nelson, David M., Urumu Tsunogai, Dong Ding, Takuya Ohyama, Daisuke D. Komatsu, Fumiko Nakagawa, Izumi Noguchi, and Takashi Yamaguchi. "Triple oxygen isotopes indicate urbanization affects sources of nitrate in wet and dry atmospheric deposition." Atmospheric Chemistry and Physics 18, no. 9 (May 4, 2018): 6381–92. http://dx.doi.org/10.5194/acp-18-6381-2018.

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Abstract. Atmospheric nitrate deposition resulting from anthropogenic activities negatively affects human and environmental health. Identifying deposited nitrate that is produced locally vs. that originating from long-distance transport would help inform efforts to mitigate such impacts. However, distinguishing the relative transport distances of atmospheric nitrate in urban areas remains a major challenge since it may be produced locally and/or be transported from upwind regions. To address this uncertainty we assessed spatiotemporal variation in monthly weighted-average Δ17O and δ15N values of wet and dry nitrate deposition during one year at urban and rural sites along the western coast of the northern Japanese island of Hokkaido, downwind of the East Asian continent. Δ17O values of nitrate in wet deposition at the urban site mirrored those of wet and dry deposition at the rural site, ranging between ∼ +23 and +31 ‰ with higher values during winter and lower values in summer, which suggests the greater relative importance of oxidation of NO2 by O3 during winter and OH during summer. In contrast, Δ17O values of nitrate in dry deposition at the urban site were lower (+19 – +25 ‰) and displayed less distinct seasonal variation. Furthermore, the difference between δ15N values of nitrate in wet and dry nitrate deposition was, on average, 3 ‰ greater at the urban than rural site, and Δ17O and δ15N values were correlated for both forms of deposition at both sites with the exception of dry deposition at the urban site. These results suggest that, relative to nitrate in wet and dry deposition in rural environments and wet deposition in urban environments, nitrate in dry deposition in urban environments forms from relatively greater oxidation of NO by peroxy radicals and/or oxidation of NO2 by OH. Given greater concentrations of peroxy radicals and OH in cities, these results imply that dry nitrate deposition results from local NOx emissions more so than wet deposition, which is transported longer distances. These results illustrate the value of stable isotope data for distinguishing the transport distances and reaction pathways of atmospheric nitrate pollution.

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Journal articles on the topic 'Nitrate radicals'

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