Environmental chemistry of nitrogen

Discnss the environmental chemistry of nitrogen in small forest catchments. Define the process of nitrogen saturation in Forest ecosystems and give characteristic examples. 

Stoddard J. L. (1994) Long-term changes in watershed retention of nitrogen its causes and aquatic consequences. In Environmental Chemistry of Lakes and Reservoirs, ACS Advances in Chemistry No. 237 (ed. L. A. Baker). American Chemical Society, Washington, pp. 223 -284. 

The redox chemistry of nitrogen monoxide has attracted further attention partly in an environmental context. It is reduced by Fe(II) to give HNO and hence N2O. Further reduction to N2 does not occur below pH The first stage is the formation of the Fe(II) nitrosyl complex,... 

One of the most important ways of relating the environmental chemistry of the five environmental spheres is through biogeochemical cycles. These are commonly expressed in terms of key elements, including essential nutrient elements. Often, as is the case with the nitrogen cycle, they contain an atmospheric component, though in some cases, such as the phosphorous cycle, the atmospheric component is not significant. Before the appearance of humans on Earth, the anthrospheric... 

Reactions. The chemistry of the /V-nitrosamines is extensive and will be only summarized here (8,35,42). Most of the reactions of the nitrosamines, with respect to thek biological or environmental behavior, involve one of two main reactive centers, either the nitroso group itself or the C—H bonds adjacent (a) to the amine nitrogen. The nitroso group can be removed readily by a reaction which is essentially the reverse of the nitrosation reaction, or by oxidation or reduction (68,69). 

In this chapter we discuss the detailed chemistry of selected high-temperature processes where gas-phase reactions are important. Most research on gas-phase reactions has been motivated by environmental issues in atmospheric chemistry or in combustion. Significant advances in the detailed understanding of fuel-oxidation chemistry, as well as nitrogen, sulphur, and chlorine chemistry, have allowed development of modeling tools that can be used for design purposes for a number of combustion and industrial processes. 

Emissions of nitrogen oxides and sulfur oxides from combustion systems constitute important environmental concerns. Sulfur oxides (SO ), formed from fuel-bound sulfur during oxidation, are largely unaffected by combustion reaction conditions, and need to be controlled by secondary measures. In contrast, nitrogen oxides (NO ) may be controlled by modification of the combustion process, and this fact has been an important incentive to study nitrogen chemistry. Below we briefly discuss the important mechanisms for NO formation and destruction. A more thorough treatment of nitrogen chemistry can be found in the literature (e.g., Refs. [39,138,149,274]). 

Reasons for interest in the catalyzed reactions of NO, CO, and COz are many and varied. Nitric oxide, for example, is an odd electron, hetero-nuclear diatomic which is the parent member of the environmentally hazardous oxides of nitrogen. Its decomposition and reduction reactions, which occur only in the presence of catalysts, provide a stimulus to research in nitrosyl chemistry. From a different perspective, the catalyzed reactions of CO and COz have attracted attention because of the need to develop hydrocarbon sources that are alternatives to petroleum. Carbon dioxide is one of the most abundant sources of carbon available, but its utilization will require a cheap and plentiful source of hydrogen for reduction, and the development of catalysts that will permit reduction to take place under mild conditions. The use of carbon monoxide in the development of alternative hydrocarbon sources is better defined at this time, being directly linked to coal utilization. The conversion of coal to substitute natural gas (SNG), hydrocarbons, and organic chemicals is based on the hydrogen reduction of CO via methanation and the Fischer-Tropsch synthesis. Notable successes using heterogeneous catalysts have been achieved in this area, but most mechanistic proposals remain unproven, and overall efficiencies can still be improved. 

Dolan, E. Zhang, Y. Klarup, D. The Distribution Coefficient of Atrazine with Illinois Soils ALaboratory Exercise in Environmental Chemistry, /. Chem. Educ. 1998, 75, 1609-1610. Driscoll, J. A. Acid Rain Demonstration The Formation of Nitrogen Oxides as By-Products of High Temperature Flame in Connection with Internal Combustion Engines, /. Chem. Educ. 1997, 74, 1424-1425. 

The investigation of environmental performance of the plant has focussed, among other things, on the nitrogen chemistry during gasification and combustion. Results from this investigation are presented below. 

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