Nitrogen oxides emission sources

National nitrogen oxide emissions by source category, 1997. Electric utilities and "on-road vehicles" account for more than half of the NO emissions. Total NO emissions for 1997 were 21.4 million metric tons. 

While natural emissions of sulphur and nitrogen exist, over 95% of the sulphur emissions in eastern North America are of man-made origin. Natural sources of nitrogen are less well estabUshed but are estimated to be small when compared to the man-made emissions 21). The distribution of North American sources of sulphur dioxide and nitrogen oxides are shown in Figure 2. In 1980, which has served as the base period for the assessment of emissions,it was estimated that sulphur dioxide emissions were Canada - 4.8 million tonnes (metric) and the United States - 24 million tonnes nitrogen oxides emissions were Canada - 1.8 million tonnes and the United States - 20 million tonnes. The more recent trends for sulphur dioxide emissions in Canada and the emission control limits are shown in Figure 3 14). 

The pH of precipitation that has absorbed S02 or sulfates will depend on the other ions present, which can include N03" formed from nitrogen oxide emissions and base cations from various dust sources, as well as HC03 from atmospheric C02 and organic acids from natural sources. Precipitation with pH values below 5.6 (the value for equilibrium with atmospheric C02) is popularly referred to as "acid rain."... 

In general, the greatest resolution can be obtained in estimates of current or recent historical (within the last 10 to 15 years) emissions. This is because reliable data on fuel use (both quality and quantity) and other activity levels are available, and good estimates of emission coefficients and control efficiencies are available. As one goes further back in time, the data needed for detailed emission estimates are either not available or are less reliable. Recently, SOp and nitrogen oxide emissions were estimated for EPA for the period 1900 to 1980 at the state level by fuel and source sector (4J1). It was particularly difficult to obtain reliable estimates of pre-1940 fuel use and quality, control efficiency, and emission coefficients. Obviously, the less data that are available, the simpler the methodology that must be used. A discussion of a data set required for detailed analysis of emissions and deposition is beyond the scope of this paper, but is available elsewhere (6). 

Control Techniques for Nitrogen Oxide Emissions from Stationary Sources, ... 

Discharges of nitrogen oxides in the U.S.A. in 1981 totaled 19.5 million metric tonnes, only slightly less than the total discharges of sulfur dioxide for the same year. Stationary combustion sources, however, were still the most significant contributor to nitrogen oxides emission with a total of 10.2 million... 

Postformation nitrogen oxide emission control measures include selective catalytic and noncatalytic reduction with ammonia, which between them are used by some 900 power station installations worldwide [51]. The catalytic removal methods are 70-90% efficient at NOx removal, but are more expensive to operate than the noncatalytic methods which are 30-80% efficient. Ammonia or methane noncatalytic reduction of NOx to elemental nitrogen is also an effective method which is cost-effective for high concentration sources such as nitric acid plants (Chap. 11). NOx capture in packed beds is less expensive, but this method is not particularly effective [23]. It is also not a very practical method either for utilities or for transportation sources. Two-stage scrubbing has also been proposed as an effective end-of-pipe NOx control measure. The first stage uses water alone and the second uses aqueous urea. 

An order of magnitude of the relative importance of traffic in the total emissions of carbon monoxide, hydrocarbons, nitrogen oxides, sulfur oxides and dust is shown in Fig. 2. From these data, it is apparent that road traffic is one of the major sources of carbon monoxide, hydrocarbons and nitrogen oxides emissions [1]. 

Olcese, L.E., Palancar, G.G. and Toselli, B.M. (2001) An inexpensive method to estimate carbon monoxide and nitrogen oxide emissions from mobile sources. Atmos Environ, 35 (35), 6213-6218. 

Determination of nitrogen oxide emissions from stationary sources... 

Determination of nitrogen oxide emissions from stationary sources—ion chromatographic method Determination of nitrogen oxide emissions from stationary sources (ultraviolet spectrophotometry)... 

Figure 3.4. Relationships between sulfur dioxide and nitrogen oxide emissions for the source area of the Hubbard Brook Experimental Forest (see Figure 3.2) and annual volume-weighted concentrations of sulfate and nitrate in bulk deposition...

The emissions data which are presented in this section are values for the entire United States. It is assiimed that the trends for these emissions data are representative of the sources contributing to the precipitation quality sites in the northeastern United States. A study of the geographical distribution of the 1972 emissions data has shown that the EPA air quality regions I-IV (basically the eastern United States) contributed 80% of the total nitrogen oxide emissions.The same study showed that six states, New York, Pennsylvania, Ohio, Michigan, Indiana, and Illinois, contributed 45% of the total. For sulfur oxides the study indicated that the northeast sector of the United States accounted for about half of the total sulfur oxide emissions. 

US EPA (1994) Method 7A Determination of Nitrogen Oxide Emissions from Stationary Sources - Ion Chromatographic Method, US Environmental Protection Agency, Washington DC, p. 626. 

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