Age, of organic matter

According to their acidity, humic substances are hydrophobic and are split into two groups humic and fulvic acids. Humic acids are stable molecules originating from the ageing of organic matter. They are responsible for water coloration and represent 40-60% of natural organic matter in rivers and lakes. Fulvic acids are smaller than the humic acids and are generally less aromatic than humic acids extracted from the same pool of DOM. 

The radiocarbon age of surface sediments averages around 2400 yr in the basins of southern California and around 2900 yr in the Atlantic Ocean (Emery and Bray, 1962 Berger et al, 1966 Benoit et al, 1979). Obviously, the measured age of organic matter in the surface sediment of the California basins is not unique to this environment, nor does it reflect a lack of... 

Radiocarbon dating is a widely used technique to determine the age of organic matter. In a living organism, the ratio of C C is assumed to be a constant because the system is at equilibrium with the atmosphere. However, once the organism has died. 

Raymond, P. A., and J. E. Bauer. 2001. Riverine export of aged terrestrial organic matter to the North Atlantic Ocean. Nature 409 497-500. 

These questions are of prime interest. As we said in the introduction, the study of organic matter in carbonaceous chondrites is interesting because it may give some insight into the origin of our solar system. It is out of the question to discuss here in detail the train of events that is described as the formation of the solar system. Nevertheless, it is important to remember that the age of the solar system is about 4.5 Gyr (4.5 x 109 yr). 

Characterization of Organic Matter in Sulfur-Rich Lacustrine Sediments of Miocene Age (Nordlinger Ries, Southern Germany)... 

Because the bulk of the limestone volume of Bermuda has spent most of its existence in the vadose zone, much of the limestone mass shows the imprint of vadose diagenesis, and progressive depletion in 13C with increasing age. However, limestones older than 125,000 years have spent more time in the phreatic meteoric zone. These limestones are more extensively altered by freshwater and freshwater-seawater mixtures. Their relatively light 813C values, however, imply alteration in a relatively open system in which soil carbon dioxide, depleted in 13C because of oxidation of organic matter, was an important source of carbon for replacement reactions. 

The abundance and ratios of important elements in biological cycles (e.g., C, H, N, O, S, and P) provide the basic foundation of information on organic matter cycling. For example, concentrations of total organic carbon (TOC) provide the most important indicator of organic matter since approximately 50% of most organic matter consists of C. As discussed in chapter 8, TOC in estuaries is derived from a broad spectrum of sources with very different structural properties and decay rates. Consequently, while TOC provides essential information on spatial and temporal dynamics of organic matter it lacks any specificity to source or age of the material. 

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