Lightning, nitrogen oxides

Nitrogen oxides are generated by both human and nonhuman action, but the major sources of NO, are high-temperature combustion processes such as those occurring in power plants and automobile engines. Natural sources of NO., include lightning, chemical processes that occur in soil, and the metabolic activities of plants. 

A Lightning is a major source of fixed nitrogen. It provides the energy needed to convert N2 to nitrogen oxides. 

Volcanic outgassing is probably the major source of N2, and formation of nitrogen oxides (NO ) by lightning may be a sink for N2 on Venus. The timescales for both of these processes are uncertain, but are plausibly very long. 

Not all atmospheric acidity is due to atmospheric pollution, as Earth also has natural sources of sulfur and nitrogen. Natural sources of sulfur dioxide include volcanoes and forest fires. Air is a natural source of nitrogen oxides, as is lightning, according to the following reactions ... 

In the troposphere, the production of ozone results from the day-time oxidation of methane, nonmethane hydrocarbons, and carbon monoxide in the presence of nitrogen oxides. Under natural conditions, methane, produced in oxygen-deficient environments, is released primarily by wetlands, lakes, and rivers. Nonmethane hydrocarbons, such as isoprene and terpenes, are emitted by various types of trees. Nitric oxide is released by soils as a result of microbial activity and is produced in the atmosphere by lightning in thunderstorm systems. 

Nitric oxide is formed in the combustion of fossil fuels and is present in automobile and power plant exhausts it can also be formed from the action of lightning on atmospheric N2 and O2. In the atmosphere, NO is oxidized to NO2. These gases, often collectively des-—E 2 HNO3 -E NO ignated NO., contribute to acid rain, primarily because NO2 reacts with atmospheric water to form nitric acid. Nitrogen oxides are also believed to be instrumental in the destruction of the Earth s ozone layer (Section 8.8.1). 

Schumann, U. and H. Huntrieser (2007) The global lightning-induced nitrogen oxides source. 

Normally the atmospheric concentration of NOg is a few parts per hillion (ppb) or less most of the nitrogen oxides formed during lightning storms are washed out by rain. This is one of the ways nitrogen is made available to plants. Looking at all the sources of oxides of nitrogen (Table 4.2), it is apparent that combustion processes are their primary sources. In the United States, most oxides of nitrogen from sources other than nature are produced from fossil fuel combustion in vehicles, industry, and power plants. 

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