Nitrogen dioxide measurement

Miller, C. C. (1994). Chemiluminescence analysis and nitrogen dioxide measurement. Lancet 343, 1. 

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

Pollutants. The problems posed by ak pollutants are very serious. Within a museum, measures can be taken to remove harmful substances as efficiently as possible by means of the installation of appropriate filter systems in the ventilation equipment. Proposed specification values for museum climate-control systems requke filtering systems having an efficiency for particulate removal in the dioctyl phthalate test of 60—80%. Systems must be able to limit both sulfur dioxide and nitrogen dioxide concentrations <10 /ig/m, and ozone to <2 /ig/m. ... 

Eirst-aid measures for people exposed to nitrogen dioxide are mentioned in Chapter 9. In any event, containment, ventilation and/or appropriate respiratory protection should be considered depending upon scale of operation and level of exposure. 

Here a ehemieal reaetion produees a moleeule with eleetrons in an exeited state. Upon deeay to the ground state the liberated radiation is deteeted. One sueh example is the reaetion between ozone and nitrie oxide to form nitrogen dioxide emitting radiation in the near infra-red in the 0.5-3/x region. The teehnique finds use for measuring nitrie oxide in ambient air or staek emissions. 

The device for nitrogen oxides based on chemiluminescence measures the nitrogen monoxide concentration. The same equipment can be used to measure the concentration of nitrogen dioxide. Nitrogen dioxide is reduced to nitrogen monoxide in a converter by a molybdenum catalyst. In order to... 

Electrochemical cells are sometimes used to measure nitric oxide and nitrogen dioxide. These, together with nitrous tixide (N2O), are measured using the ITIR techniques. 

Nitrogen dioxide concentrations have changed little since 1989, and alterations in measuring techniques make it difficult to accurately assess the trend. Data suggest that NO, concentrations may have increased by 2 percent between 1989 and 1998. 

Potentiometric titration with a sulfide ion-selective electrode as an indicator has been used to measure hydrogen sulfide in the air at ppb levels (Ehman 1976). The method has been shown to have very good accuracy and precision. No interference could be found from nitrogen dioxide, sulfur dioxide, or ozone. 

The kinetics of the gas-phase reaction between nitrogen dioxide (A) and trichloroethene (B) have been investigated by Czamowski (1992) over the range 303-362.2 K. The reaction extent, with the reaction carried out in a constant-volume BR, was determined from measurements of infrared absorption intensities, which were converted into corresponding pressures by calibration. The products of the reaction are nitrosyl chloride, NOC1 (C), and glyoxyloxyl chloride, HC(0)C(0)C1. 

At temperatures in excess of 200 °C nitrogen dioxide decomposes at a measurable rate into nitric oxide and oxygen in accordance with the stoichiometry... 

The gas-phase reactivity of various terpenes has been measured. Stephens and Scott were the first to include two terpenes (pinene and a-phel-landrene) with their study of the relative reactivity of various hydrocar ns. Both monoterpenes showed the high reactivity predicted by their olefinic structure. Conversion of nitric oxide to nitrogen dioxide in e presence of isoprene is at a rate intermediate between those for ethylene and trans-2-butene, and Japar et al, reported rate constants for the a-pinene and terpinolene-ozone reactions. Grimsrud et a/. measured the rate con-... 

London. On the second day, the late afternoon peak exceeded 0.1 ppm. It is apparent that some conversion of nitric oxide to nitrogen dioxide was responsible for the ozone buildups, but it is not as clear a chemical pattern for London as it is for cities in the western United States. The paper did not mention the method of ozone measurement however, qualitative descriptions of the weather patterns suggest that the days of high ozone were characterized by light winds and considerable sunlight. 

FIGURE 4-10 Diurnal variations of air pollutants measured in London from July 12 to July 14, 1972. , Ozone ppb , nitric oxide, ppb , nitrogen dioxide, ppb O, hydrocarbons, ppm. Reprinted permission from Derwent and Steward. ... 

Ozone and ozone precursor concentrations at nonurban locations in the eastern United States were studied extensively. The three parts of the study were field measurements, a quality assurance program, and an airborne monitoring program. The main objective of the study was to establish a data base for nonurban ozone and precursor concentrations. Simultaneous statistical summaries of the concentrations of nitrogen dioxide and nonmethane hydrocarbons were also provided. Another objective was to search for relationships between ozone concentrations and nitrogen dioxide and nonmethane hydrocarbon concentrations. 

Descriptions of field studies of power-plant stack plumes were given by Davis et al. The ozone concentration appears to be lower in regions of high sulfur dioxide content. At 32 km downwind from the stacks, it was claimed that the ozone concentration in the plume (now 11 km wide) is higher than the ambient concentration ( 0.08 ppm) by approximately 0.02 ppm. Simultaneous measurements of nitric oxide and nitrogen dioxide were integrated across the plume. Values of the ratio of nitric... 

The reaction rate is extremely high, so that, even at concentrations smaller than parts per million, the reaction is virtually complete after a few seconds when there is an excess of nitric oxide present. Under these conditions, the amount of ozone added during the titration is equivalent to the amount of nitric oxide consumed and to the amount of nitrogen dioxide formed. The accuracy of this calibration method depends critically on the accurate measurements of the nitric oxide concentration and on the nitric oxide and ozone flow rates. 

Besides ozone, the main indicator of photochemical pollution, other important concomitant products are peroxyacetylnitrate (PAN), hydrogen peroxide, nitrogen dioxide, hydroxyl radicals and various aldehydes that are both products and primary pollutants, particles, sulfates, nitrates, ammonium, chloride, water, and various types of oxygenated organic compounds. The most important precursors of photochemical pollution are nitric oxide and hydrocarbons. The measurement procedures for the hydrocarbons are not as highly developed as those for ozone and the nitrogen oxides. 

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. 

Before 1970, most of the data for nitrogen oxides were obtained by continuous measurements with a colorimetric analyzer that was similar in principle to the colorimetric oxidant analyzer shown in Figure 6-8. The scrubbing agent is a mixture of -(l-naphthyl)ethylenediamine, sulfanilic acid, and acetic acid in aqueous solution. The color is produced when both nitrogen dioxide and nitrites react with this reagent to form an azo dye. The color is not affected by nitric oxide in the air sample. 

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