Nitrogen emissions

An example of a set of emission limits based on the rollback approach is the limits adopted by the United States for carbon monoxide, hydrocarbons, and oxides of nitrogen emissions from new automobiles (Table 25-2). 

Reduction in nitrogen excretion is often set equal to a reduction in nitrogen emission. This is only true in those cases where the excess nitrogen in the commercial fertiliser can be caught and retained in the agricultural nutrient cycle. If the nutrients are, however, discharged from the cycle and emitted... 

Sulfur dioxide emissions in both Canada and the USA peaked in the early 1970s and have declined ever since with year-to-year variability. Actions to reduce acid deposition have been focused mainly on S02 emissions because they play generally a much higher role in rainfall acidification than nitrogen oxides. However, this is not the case in some areas of North America, like California, where nitrogen emissions are predominant and consequently contribute the major part in acidity as well. 

Because of decreased SO2 emissions, the importance of nitrogen for freshwater acidification becomes more and more determinant. Therefore, uncertainties in the evolution of nitrogen emissions make it difficult to predict future trends in freshwater recovery. On the other hand, climate warming may increase the number of alkaline rain episodes (containing Saharan dust) and enhance weathering reactions, which buffer better acid precipitation, increasing alkalinity and pH. 

Turns, S. R., F. H. Myhr, R. V. Bamdaru, and E. R. Maund. 1993. Oxide of nitrogen emission from turbulent jet flames Part 11 — Fuel dilution and partial premixing effects. Combustion Flame 93 255-69. 

TT states that the advantages of FTO technology include the lack of an open flame, the high destruction and removal efficiencies that can be achieved, low nitrogen emissions, and the range of process flow rates that are acceptable for treatment. 

The detrimental effects of acid rain are a major reason why legislation such as the Clean Air Act places strict limitations on sulfur and nitrogen emissions. It is also a reason why low sulfur coal is preferred over high sulfur coal. To reduce sulfur dioxide emissions, industry also uses a technique call scrubbing. Industrial scrubbers employ a variety of physical and chemical processes to remove sulfur dioxide from emissions. Another technique used to combat acidification of lakes is to treat these systems with lime. The lime acts to neutralize the acid, but such techniques are usually costly and are only a temporary remedy for combating the problem. 

The principal cause of acid rain is the combustion of fossil fuels that produce sulfur and nitrogen emissions. The primary sources are electrical power plants, automobiles, and smelters. Power plants produce most of the sulfur emissions and automobiles most of the nitrogen emissions. Other sources of acid rain include nitrogen fertilizers, jet aircraft, and industrial emissions. Just as in our discussion of ozone, numerous reactions are involved in the formation of acid rain. The process can be understood by considering the transformation of sulfur and nitrogen oxides into their respective acidic forms sulfuric acid and nitric acid. Sulfur, present up to a few percent in fuels such as coal, is converted to sulfur dioxide when the fuel is burned. The sulfur dioxide reacts with water to produce sulfurous acid, H,SO ,, that is then oxidized to sulfuric... 

In short, the concentrations of tropospheric ozone, which is also a greenhouse gas, have also increased over the past century, an increase attributed to increased oxides of nitrogen emissions associated with fossil fuel combustion (e.g., see Volz and Kley, 1988 and Janach, 1989). 

Emission studies show that lead is only a small part of the automotive pollution problem. Prior to control, hydrocarbon emissions were more than 40 times and the oxides of nitrogen emissions more than 15 times the emission of the lead compounds. Obviously, however, legislation will result in the eventual elimination of lead from gasoline. The removal of lead, besides eliminating a possible toxic pollutant, simplifies the problem of handling other automotive exhaust pollutants in that catalytic exhaust chambers perform much better in the absence of lead contaminant. All emission standards become particularly severe in 1975 and 1980. The particulate standards are equivalent to 1 gram Pb/gal in 1975 and 0.3 gram Pb/gal in 1980. Since the particulates include all solid materials, tolerable lead levels will be less than indicated above. 

When biodiesel is blended with diesel fuel, the emissions results change somewhat. A significant decrease in hydrocarbon and carbon monoxide emissions is typical, no change or a small increase in oxides of nitrogen emissions, and significant reduction in particulate emissions. Emissions of toxins would also decrease according to the percentage substitution of diesel fuel. 

Grant R, Blicher-Mathiesen G (2004) Danish policy measures to reduce diffuse nitrogen emissions from agriculture to the aquatic environment. Water Sci Technol 49 91-99... 

Figure 2. Estimates of oxides of nitrogen emissions in the California South...

Yang W. X. and Meixner F. X. (1997) Laboratory studies on the release of nitric oxide from sub-tropical grassland soils the effect of soil temperature and moisture. In Gaseous Nitrogen Emissions from Grasslands (eds. S. C. Jarvis and B. F. Pain). CAB International, Wallingford, UK, pp. 67-71. 

Moomaw W. R. (2002) Energy, industry and nitrogen strategies for reducing reactive nitrogen emissions. Amfiio 31,184-189. 

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