Atmosphere natural sources

Effect of Nitric Oxide on Ozone Depletion. Nitrous oxide is injected into the atmosphere from natural sources on earth about 10% is converted to nitric oxide (N20 + 0( D) — 2 NO), which in turn can catalyze the destmction of ozone (11,32,75). The two main cycles are 1 and 2. Rate constant data are given in Reference 11. 

Sulfur dioxide occurs in industrial and urban atmospheres at 1 ppb—1 ppm and in remote areas of the earth at 50—120 ppt (27). Plants and animals have a natural tolerance to low levels of sulfur dioxide. Natural sources include volcanoes and volcanic vents, decaying organic matter, and solar action on seawater (28,290,291). Sulfur dioxide is beHeved to be the main sulfur species produced by oxidation of dimethyl sulfide that is emitted from the ocean. 

DMS has been observed in the marine atmosphere since the early 1970s, but it was not until the mid-1980s that there was interest in this gas as being a natural source for sulfate CCN. Sulfate aerosols are, in number terms, the dominant source of CCN. The major role clouds play in the climate system leads to possible climatic implications if changes to DMS production occurred. Furthermore, the dependence of this production on environment conditions means that scope for a feedback process arises this feedback is called the Charlson hypothesis. ... 

The oceans of the world are an important natural source of pollutant material. The ocean is continually emitting aerosols to the atmosphere, in the form of salt particles, which are corrosive to metals and paints. The action of waves on rocks reduces them to sand, which may eventually become airborne. Even the shells washed up on the beach are eroded by wave and tidal action until they are reduced to such a small size that they too may become airborne. 

In a sense this subdivision of the composition of the atmosphere is arbitrary since some of the so-called contaminants are derived partly or wholly from natural sources. However, in that their concentrations vary appreciably within very narrow geographical limits, they may be distinguished from the contents of Table 2.8 (with the possible exception of water vapour). Table 2.6 lists those contaminants which are important from a corrosion standpoint. Excluded are contaminants found only in very specific locations, e.g. in the vicinity of a chemical works. The concentrations given are intended only to indicate general levels in the usual classification of environments and not to define a particular environment. 

Mobile, fixed and natural sources contribute 83,12, and 5% respectively to the 4.9 million metric tons of contaminants yearly emitted into the atmosphere (Table I). 

Concerns over atmospheric methane as a greenhouse gas and the large contribution of biomethanogenesis as a source of this gas make it important to determine the relative significance of various components of this activity. A recent paper (8) summarized estimates (28-30) of source fluxes of atmospheric methane based on several carbon isotopic studies and presented new data on natural sources and biomass burning. These data (Table III) show that of a total flux of 594 million tons (Tg) per year, 83% is produced via biomethanogenesis from a combination of natural (42%) and anthropogenic (41%) sources. 

Tables 7-7-7-11 give a sense of the range of organic molecules present in the atmosphere. Both natural sources and human activity contribute to the variety of organic molecules (Graedel, 1978). The sinks often involve in-situ reactions.

Figure 7.2 Acid rain occurs when water comes into contact with sulfur and nitrogen oxides in the atmosphere, which can come from natural sources or from man-made sources like cars or power plants. These acid rain-damaged coniferous trees live in the Karkonosze National Park in Silesia, Poland.

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