Nitric from lightning

Nitric acid occurs naturally, in traces, in the atmosphere in rain w from the electrical discharge of lightning and from nuclear expins. Indeed, the natural nitrates of the world have probably been formed by the action of naturally occurring nitric acid to the extent of 4-6 lbs of combined nitrogen per acre (Ref 30)... 

This is an extremely important reaction to which we wiU refer throughout this book. It is responsible for all NO, formation in the atmosphere (the brown color of the air over large cities) as well as nitric acid and acid rain. This reaction only occurs in high-temperature combustion processes and in lightning bolts, and it occurs in automobile engines by free-radical chain reaction steps, which will be the subject of Chapter 10. It is removed from the automobile exhaust in the automotive catalytic converter, which wiU be considered in Chapter 7. 

The highly endothermic nitric oxide can be synthesized from the elements dinitrogen and dioxygen in an electric arc (AEf = 180.6kJmol ). This also takes place in the natural nitrogen fixation by lightning. 

Nitric oxide is formed in the combustion of fossil fuels and is present in the exhausts of automobiles and power plants 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 designated NO, contribute to the problem of acid rain, primarily because NO2 reacts with atmospheric water to form nitric acid ... 

Other natural soil acidifying agents are found in the atmosphere. Carbon dioxide has a concentration of only 350 parts per million (by volume) in the open atmosphere, so that rainwater in equilibrium with this air is a very dilute solution of carbonic acid (10 M). This source of H2CO3 is of much less consequence than the carbonic acid generated from biological activity within soils. Lightning can oxidize atmospheric nitrogen, N2, to produce NO which further oxidizes to nitric acid ... 

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 in the troposphere (ti/2 about 1 day) stems from bacteria, lightning and for the main part from emissions of combustion engines. 

Acid precipitation. Rainfall probably always contained small amounts of nitric and sulfuric acids from oxidation of nitrogen and sulfur compounds in photochemical and lightning induced processes, but increased levels are well... 

As for the primary trace chemical species in the remote natural atmosphere where there is no influence of anthropogenic activities, methane (CH4) emitted from lakes and marshes, biogenic volatile organic compounds (BVOCs), nitric oxide (NO) from natural soils and lightning, dimethyl sulfide (DMS) from marine organisms, O3 descended from the stratosphere can be conceived. Among them, the most important chemical species that is subjected to photolysis by the actinic flux (see Sect. 3.5) in the troposphere is O3 and NO2 (see Sects. 4.2.1 and 4.2.2). 

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