Organic matter, fossilization

The CO2 content of the atmosphere has increased dramatically due to the combustion of fossil fuels and oxidation of soil and organic matter. Fossil fuels are generally depleted in because they were derived from organic material. Consequently, the global d C value of atmospheric CO2 has seen a change from 6.54 in preindustrial times to about 8.04 today. 

At the end of a brief life, the diatom settles to the bottom of the body of water where the organic matter decomposes, leaving the siliceous skeleton. These fossil skeletons, or fmstules, are in the shape of the original diatom plant and have designs as varied and intricate as snowflakes. Examples are shown in Figure 1. 

Our complex modern life style was made possible by the discovery and refining of fossil fuels, fuels that are the result of the decay of organic matter laid down millions of years ago. The natural gas that heats our homes, the gasoline that powers our automobiles, and the coal that provides much of our electrical power are fossil fuels. Vast reserves of petroleum, the source of liquid hydrocarbon fuels such as gasoline and coal, exist in many areas of the world. However, although large, these reserves are limited, and we are using them up at a much faster rate than they can be replaced. 

We have already met carbon dioxide, C02, many times throughout this book. It is formed when organic matter burns in a plentiful supply of air and during animal respiration. It is normally present in the atmosphere but there is widespread and well-founded concern that an increase in atmospheric carbon dioxide due to the combustion of fossil fuels is contributing to global warming (Box 14.2). 

Hare, PE. and von Endt, D. 1990 Variable preservation of organic matter in fossil bone. Annual Report of the Director of the Geophysics Laboratory. Carnegie Institution, Washington. 1989-1990. Washington, D.C., Carnegie Institution ofWashington 115-118. 

These materials are chemically very complex and the composition of fossil organic matter depends on the kind of organism from which the deposit has formed [2],... 

Grimalt, J.O., Simoneit, B.R.T. and Hatcher, P.G. (1989). Chemical affinities between the solvent extractable and bulk organic matter of fossil resin associated with an extinct podocarpaceae. Phytochemistry 28 1167-1171. 

Biomass can provide substitutes for fossil fuels as well as electricity and heat. Its resource base is varied. Arid land, wetlands, forest, and agricultural lands can provide a variety of plants and organic matter for biomass feedstock. 

The crust is the largest carbon reservoir in the crustal-ocean-atmosphere factory (8 x 10 Pg C including the sediments). Most of this carbon is in the form of inorganic minerals, predominantly limestone, with the rest being organic matter, predominantly contained in shale and secondarily in fossil fuel deposits (coal, oil, and natural gas). The oceanic reservoir (4 X lO" Pg C) and the terrestrial reservoir (2 to 3 x 10 Pg C) are both far smaller than the crustal reservoir. The smallest reservoir is found in the atmospheric, primarily as CO2 (preindustrial 6 x 10 Pg C, now 8 x 10 Pg C and rising). The flux estimates in Figure 25.1 have been constrained by an assumption that the preindustrial atmospheric and oceanic reservoirs were in steady state over intermediate time scales (millennia). 

Although the ultimate source of much of particulate organic matter (POM) in the urban aerosol appears to be fossil fuel a specific knowledge of the amounts and classes of organic compounds contributed by various types of sources is lacking. Estimates of source contributions have been based on emission inventories which have been largely directed toward polycyclic aromatic hydrocarbons and/or benzo(a)pyrene. There has been very little work on the development of mathematical and statistical models for POM source identification and allocation (1). In view... 

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