Oxygen and carbon dioxide in soil air

It is self-evident that the oxidation of sulphide minerals entails the consumption of oxygen. The initial source is molecular oxygen from the atmosphere but this must pass into solution in groundwater or soil solutions before any reaction with sulphides is possible. Interstitial air in soils, overburden or porous rocks forms an intermediate reservoir of oxygen between buried sulphides and the free atmosphere. The oxidation may be entirely chemical or may be enhanced by the microbial action of bacteria such as Thiohacillus thiooxidans. The oxidation of sulphides leads to the production of sulphuric acid, which will be neutralised by any available carbonates with the release of gaseous carbon dioxide into the subsurface surroundings and ultimately into the atmosphere. 

The carbon dioxide produced would give a concentration of 0.53% in this same volume of rock or soil. 

The oxidation of sulphides may proceed with extreme rapidity and spontaneous sulphide fires in mines have not been an uncommon occurrence. Bateman (1950) notes that a sulphide vein in a blind and warm stope at the Leonard Mine (Butte, Montana) was oxidised to a depth of 1 m within two years. At the Ely Mine, Nevada, chalcocite ore in a bench in an open pit was oxidised so quickly that, at a depth of 10-15 m, about 15% copper within the ore was removed in solution. 

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Lovell J. S. (2000) Oxygen and carbon dioxide in soil air. In Handbook of Exploration Geochemistry, Geochemical Remote Sensing of the Subsurface (ed. M. Hale). Elsevier, Amsterdam, vol. 7, pp. 451-469. 

Oxygen and carbon dioxide in soil air SAMPLING AND ANALYTICAL METHODS... 

Fig. 14-7. Oxygen and carbon dioxide in soil air over the Filizchai pyrite deposit, Azerbaijan (reproduced with permission from Dadashev et al., 1971).

Fig. 14-2. Oxygen and carbon dioxide content of the soil air at three depths in a sandy-loam and a silty-clay apple orchard.

Most corrosion processes in copper and copper alloys generally start at the surface layer of the metal or alloy. When exposed to the atmosphere at ambient temperature, the surface reacts with oxygen, water, carbon dioxide, and air pollutants in buried objects the surface layer reacts with the components of the soil and with soil pollutants. In either case it gradually acquires a more or less thick patina under which the metallic core of an object may remain substantially unchanged. At particular sites, however, the corrosion processes may penetrate beyond the surface, and buried objects in particular may become severely corroded. At times, only extremely small remains of the original metal or alloy may be left underneath the corrosion layers. Very small amounts of active ions in the soil, such as chloride and nitrate under moist conditions, for example, may result, first in the corrosion of the surface layer and eventually, of the entire object. The process usually starts when surface atoms of the metal react with, say, chloride ions in the groundwater and form compounds of copper and chlorine, mainly cuprous chloride, cupric chloride, and/or hydrated cupric chloride. 

Air (refers to the gaseous portion of soil composed of the same gases found in the atmosphere (oxygen, nitrogen, and carbon dioxide) but in different proportions)... 

Well, where do you get food to eat Bread from wheat, that is, a plant. Meat from, say, cow. Cow eats plants to produce its own body. How do plants produce our food (carbohydrates) From water and carbon dioxide ALL THESE ARE CHEMICALS. Water from soil and carbon dioxide from air. Air Is it a chemical In fact air consists mainly of two chemicals nitrogen and oxygen carbon dioxide is a rather minor component of the atmosphere. 

Aeration is the replacement of this stagnant soil air with fresh air. The movement of water into and out of the soil mainly brings about the process, e.g. rainwater soaks into the soil filling many of the pore spaces and driving out the air. Then, as the surplus water soaks down to the drains or is taken up by plants, fresh air is drawn into the soil to refill the pore spaces. Additionally, oxygen moves into the soil and carbon dioxide moves out by a diffusion process similar to that which happens through the stomata in plant leaves (Chapter 1). The aeration process is also assisted by ... 

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