Nitrogen dioxide nitric oxide and ozone

B. Nitric Oxide, Nitrogen Dioxide, and Ozone Cycles... 

FIGURE 2-1 Diurnal variation of nitric oxide, nitrogen dioxide, and ozone concentrations in Los Angeles, July 19, 1965. Reprinted from Air Quality Criteria for Photochemical Oxidants. ... 

Rehme, K. A., B. E. Martin, and J. A. Hodgeson. Tentative Method for the Calibration of Nitric Oxide, Nitrogen Dioxide, and Ozone Analyzers hy Gas Phase lltration. EPA-R2-73-246. Research Triangje Park, N.C. U.S. Environmental Protection Agency, 1974. 16 pp. 

Ritter, J. A., D. H. Stedman, and T. J. Kelly, Ground-Level Measurements of Nitric Oxide, Nitrogen Dioxide and Ozone in Rural Air, in Nitrogenous Air Pollutants Chemical and Biological Implications, pp. 325-343, Ann Arbor Science Publishers, Ann Arbor, MI., (1979). 

FIGURE 3-13 Relations between conversion of nitric oxide to nitrogen dioxide and ozone, atomic oxygen, and hydroxyl-radical reaction rate constants. Reprinted with permission from Grosjean. ... 

The technol( for the routine measurement of the nitrogen oxides (nitrogen dioxide and nitric oxide) is fairly well advanced. The epa is on the verge of officially proposing that chemiluminescence produced by the reaction of nitric oxide with ozone be the reference method for nitrogen dioxide.This method is even more suitable for nitric oxide. Because no national air quality standard has been promulgated for nitric oxide, no reference method will be specified. However, its measurement in the atmosphere is crucial for establishing the relation of its emission to the formation of atmospheric ozone and other photochemical oxidants. 

Kagawa and Toyama in Tokyo followed 20 normal 11-yr-old school children once a week from June to December 1972 with a battery of pulmonary-function tests. Environmental factors studied included oxidant, ozone, hydrocarbon, nitric oxide, nitrogen dioxide, sulfur dioxide, particles, temperature, and relative humidity. Temperature was found to be the most important environmental factor affecting respiratory tests. The observers noted that pulmonary-function tests of the upper airway were more susceptible to increased temperature than those of the lower airway. Although the effect of temperature was the most marked, ozone concentration was significantly associated with airway resistance and specific airway conductance. Increased ozone concentrations usually occur at the same time as increased temperature, so their relative contributions could not be determined. 

So-called Kyodai nitration - a novel methodology of nitration with nitrogen dioxide and ozone - has been applied to several benzimidazoles with formation of 1-nitrobenzimidazoles and following conversion to 1-nitrobenzotriazoles [275], The nitration of benzotriazole /V-oxide with dilute nitric acid gives the 7-nitro derivatives, whereas nitration with a mixture of nitric and acetic acids leads to 5-nitro- and 7-nitro isomers in a ratio of 1 9 [276],... 

The temperature and density structure of the troposphere, along with the concentrations of major constituents, are well documented and altitude profiles have been measured over a wide range of seasons and latitudes for the minor species water, carbon dioxide, and ozone. A few profiles are available for carbon monoxide, nitrous oxide, methane, and molecular hydrogen, while only surface or low-altitude measurements have been made for nitric oxide, nitrogen dioxide, ammonia, sulfur dioxide, hydrogen sulfide, and nonmethane hydrocarbons. No direct measurements of nitric acid and formaldehyde are available, though indirect information does exist. The concentrations of a number of other important species, such as peroxides and oxy and peroxy radicals, have never been determined. Therefore, while considerable information concerning trace constituent concentrations is available, the picture is far from complete. 

Nitrogen pentoxide, NjO-, the anhydride of nitric acid, can be made, as white crystals, by carefully dehydrating nitric acid with phosphorus pentoxide or by oxidizing nitrogen dioxide with ozone. It is unstable, decomposing spontaneously at room temperature into nitrogen dioxide and oxygen. 

The problem of identifying and measuring ozone in the complex gaseous-aerosol mixture which is smog is formidable. There are such gases present as nitric oxide, nitrogen dioxide, sulfur dioxide, hydrocarbon vapors from methane up to probably xylene, plus such partial oxidation products as aldehydes, ketones, and acids. The search for a method of high specificity has been an intensive one. 

Air pollutants can affect plants both directly and indirectly. The principal phytotoxic air pollutants are ozone, nitric oxide, nitrogen dioxide, sulfur dioxide, fluorides, and peroxyacyl nitrate (PAN). Their toxic effects have been demonstrated convincingly through field measure-... 

The calibration of a chemiluminescent analyzer using these standards is verified when both the nitrogen dioxide and nitric oxide channels respond similarly to charges from the (ylinder of diluted nitric oxide. Agreement with the response of the nitric oxide channel should also be obtained when the standard nitric oxide mixture is titrated with a previously established source of ozone. Chemiluminescent instruments have simplified monitoring of nitrogen oxides, but accurate calibration requires well-trained personnel. 

Equation 2-4, [Oj] = kJNOjJ/JlTj [NO], should be tested in the real atmosphere, as well as in laboratory experiments. Simultaneous measurements of the concentrations of ozone, nitric oxide, and nitrogen dioxide and of the intensity of sunlight for a variety of conditions will provide a much-needed check on this dynamic equilibrium. 

The oldest chemiluminescent detector was the thermal energy analyzer (TEA), which was specific for N-nitroso compounds. N-nitroso compounds such as nitrosamines are catalytically pyrolyzed and produce nitric oxide which reacts with ozone to produce nitrogen dioxide in the excited ] state, which decays to the ground state with the emission of a photon. A photomultiplier in the reaction chamber measures the emission. Nitrosodi-methylamines have been detected to about 30-40 pg [108]. 

More recently, chemiluminescence detectors based on redox reactions have made possible the detection of many classes of compounds not detected by flame ionization. In the redox chemiluminescence detector (RCD), the effluent from the column is mixed with nitrogen dioxide and passed across a catalyst containing elemental gold at 200-400°C. Responsive compounds reduce the nitrogen dioxide to nitric oxide. The nitric oxide is reacted with ozone to give the chemiluminescent emission. The RCD yields a response from compounds capable of undergoing dehydrogenation or oxidation and produces sensitive emissions from alcohols, aldehydes, ketones, acids, amines, olifins, aromatic compounds, sulfides, and thiols. 

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