Plant matter, decaying

Nowadays, the main source of methane is natural gas , which originates in the same way as crude oil, by the anaerobic decomposition of microscopic sea animals under the pressure of layers of silt and mud over a period of millions of years. This can also occur in swamps and marshes, when plant matter decays ( marsh gas ), and in landfill sites in digesters breaking down sewage sludge and by enteric fermentation in livestock e.g. 

The primary component of coal is carbonaceous material resulting from the accumulation and decay of plant matter in marine or freshwater environments and marshes (Hessley et al. 1986). As plant matter accumulates it becomes humified and may eventually be consolidated into coal through a process called coalification. In the organic matrix, C is the major element by weight, with smaller amounts of H, O, N, and S, and many trace elements. The abundance of these trace elements is highly variable, but based on the reported trends in the affinity of elements for the organic fraction of coal (Table 1), elements such as B, Ge, Be, Ti, and V are expected to exist primarily within the organics in coal. 

Hydrocarbons are obtained primarily from coal and petroleum, both formed when plant and animal matter decays in the absence of oxygen. Most of the coal and petroleum that exist today were formed between 280 and 395 million years ago. At that time, Earth was covered with extensive swamps that, because they were close to sea level, periodically became submerged. The organic matter of the swamps was buried beneath layers of marine sediments and was eventually transformed to either coal or petroleum. 

Accumulation by complex formation during decay of plant matter. 

Peat partially carbonized plant matter, formed by slow decay in water. 

Bituminous coal baked in an oven yields a solid carbonaceous material called coke, which is used as a reducing agent in the smelting of iron. Jet is a term applied to high-quality specimens of lignite that have been used to make decorative objects and jewelry. Jet and peat, which is compressed, partially decayed plant matter, will be discussed in Chapter 4 Plants. Cannel coal is another term for hard, compact lignite. This name has been applied to material from Whitby, where most commercial jet comes from, and from Scotland. Objects made of this material date back at least to the Bronze age in Britain (2100-1700 BC). 

Peat is a deposit of partially decayed plant material. It forms in swamps, marshes, and other wetlands. Like coal, the decomposition of dead plant matter is inhibited by the lack of oxygen. Layers of dead plants, trees, fungus, and moss may build up very quickly, depending on the climate and amount of water present. Most modem peat deposits are at or very close to the ground surface, and date from the end of the last great ice age, about 10,000 years ago. 

Other gases are found on the surface of the earth and in the atmosphere. Methane (CH4), formerly known as marsh gas, is produced by bacterial processes, especially in swampy areas. It is a major constituent of natural-gas deposits formed over many millennia by decay of plant matter beneath the surface of the earth. Recovery of methane from municipal landfills for use as a fuel is now a commercially feasible process. Gases also form when liquids evaporate. The most familiar example is water vapor in the air from the evaporation of liquid water it provides the humidity of air. 

Solutes, electrolytes, and nonelectrolytes in the soil solution are the immediate sources of the elements required by plants for growth. This supply can be continuously renewed by the many mechanisms of ion-soil interaction that remove and add ions in the soil solution (1) mineral weathering, (2) organic matter decay, (3) rain, (4) irrigation waters containing salts, (5) fertilization, and (6) release of ions retained by the colloid or clay fraction of soils. 

The rates of soil phosphate reactions also may differ from the rates of phosphate uptake by plants and of phosphate release by organic matter decay. This phosphate turnover would further upset soil phosphate equilibria. If a steady state (concentration is constant with time) existed between the soil and dissolved phosphate ions, it might be described by a reaction such as... 

As early as 1907 Bertram Boltwood had used the discovery of radioactive decay laws by Ernest Rutherford and Frederick Soddy to ascribe an age of over two billion years to a uranium mineral. In 1947 Willard Libby at the University of Chicago used the decay of to measure the age of dead organic matter. The cosmogenic radionuclide, becomes part of all living matter through photosynthesis and the consumption of plant matter. 

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