Stable isotope tracer , carbon

Mackensen, A. 2001. Oxygen and carbon stable isotope tracers of Weddell Sea water masses new data and some paleoceanographic implications. Deep-Sea Research I, 48, 1401-1422. 

Much use is made of the stable isotopes of carbon as a paleo-water mass isotope fingerprint . The ratio in the tests of foraminifera depends on the relative position of the overlying water mass within the thermohaline circulation system. Flowever, these isotope ratios are modified during the incorporation into organisms, depend on availability of nutrients, and like the isotopes of oxygen, also depend on seawater temperature. (These tracers are dealt with in the relevant articles please refer to the See also section.)... 

Tracers serve as a dye with which to follow the circulation of ocean waters. There are conventional ocean tracers such as temperature, salinity, oxygen, and nutrients. There are stable isotope tracers such as oxygen-18, carbon-13, and there are radioactive tracers both naturally occurring (such as the uranium/thorium series, and radium), and those produced both naturally and by the bomb tests (such as tritium and carbon-14). The bomb contributions from the latter two are called transient tracers, as are the CFCs, because they have been in the atmosphere for a short time. This implies an anthropogenic source and a nonsteady input function. 

Using isotopes In this method, evidence of bioremediation at the field scale can be collected by using stable isotopes of carbon and hydrogen via a fractionation approach or as tracer (Scow and Hicks, 2005)... 

Stable isotopes serve as naturally occurring tracers that can provide much information about how chemical reactions proceed in nature, such as which reactants are consumed and at what temperature reactions occur. The stable isotopes of several of the lighter elements are sufficiently abundant and fractionate strongly enough to be of special usefulness. Foremost in importance are hydrogen, carbon, oxygen, and sulfur. 

One of the most sensitive tracers recording the composition of ancient sea water is the isotopic composition of chemical sediments precipitated from sea water. The following discussion concentrates on the stable isotope composition of oxygen, carbon, and sulfur, but in recent years other isotope systems have been included such as Ca (De La Rocha and De Paolo 2000 Schmitt et al. 2003 Fantle and de Paolo 2005 Farkas et al. 2007) and B (Lemarchand et al. 2000, 2002 Joachimski et al. 2005) and Li (Hoefs and Sywall 1997). One of the fundamental questions in all these approaches is which kind of sample provides the necessary information, in the sense that it represents the ocean water composition at its time of formation and has not been modified subsequently by diagenetic reactions. 

Wolfe has presented an excellent description of the systematic application of stable and radioactive isotope tracers in determining the kinetics of substrate oxidation, carbon dioxide formation (including C02 breath tests), glucose oxidation, and fat oxidation in normal and diseased states. Quantification of the rate and extent of substrate oxidation can be achieved by using a specific or C-substrate which upon oxidation releases radioactive carbon dioxide. 

Naturally occurring stable isotopes of C, N, and S have been used extensively for over a decade as direct tracers of element cycling in marine and terrestrial food webs (34-39). Carbon and sulfur isotopes fractionate very little between food and consumer thus their measurement indicates which primary producers or detrital pools are sources of C and S for consumers. For example, a study of plants and animals in Texas sand dunes showed that insect species had 813C values either like those of C3 plants or like those of C4 plants (-27 and -13%o, respectively). Rodent species had intermediate values near -20%o that indicated mixed diets of both C3 and C4 plants (40). The 13C measurements, used in simple linear mixing models, proved to be quick and reliable indicators of which plant sources provided the carbon assimilated by higher trophic levels. 

Rodelli, M.R., Gearing, 3.N., Gearing, P.3., Marshall, N. and Sasekumar, A., 1984. Stable isotope ratio as a tracer of mangrove carbon in Malaysian ecosystems. Oecologia, 61 326-333. 

Isotopic Tools Tracers. Carbon has three stable or long-lived isotopes 98.9% of earth s C is 12C, -1.1% is 13C (a stable isotope), and about one in a trillion (1 in 1012) carbon atoms is 14C. By enriching or depleting the ratios of the rare isotopes in plants, plant litter, or other organic material put in soil, it is possible to follow the pulse of altered isotopic ratios (and the carbon compounds they were associated with) as they move through the system. 

The use of the stable isotope as a tracer in biological research has become increasingly common as evidenced by recent bibliographies (1,2), The effective use of this isotope has been established in the field of nutrition, where it has been applied in human clinical studies (3,4), in food science research and in ecological studies of animal food habits (6,7) Many nutrition studies are carried out at natural abundance levels of C Because these levels are low and because differences in the content of natural materials are small, stable carbon isotope ratios (13q/1 ) expressed in relative terms as 6 values A value represents the per mil (parts per thousand) deviation of the content of the sample from the international PDB limestone standard, the value of which has been set arbitrarily to 0 /oo Thus, a value of -27 0 %o would mean that the sample contained 27 parts per thousand less than the PDB standard Although the PDB standard no... 

Stable isotopes studies. Numerous researchers have taken advantage of the difference in carbon isotope fractionation during photosynthesis of plants with C3 and C4 photosynthetic pathways as a natural tracer to study soil carbon dynamics (Balesdent et al., 1987). If a C3 forest is converted to a C4 pasture or C4 agricultural field, the whole soil carbon turnover time (t) can be calculated as... 

Recent advances in analytical instrumentation and methodology promise to add many more geochemical proxies to the palaeoceanographer s toolbox. MC-ICP-MS has opened up a number of isotopic systems previously considered intractable, such as zinc (which shows potential as a tracer of nutrient utilization Vance et al. 2006) and germanium, whose isotopic composition has recently been measured in biogenic opal (Rouxel et al. 2006). Meanwhile improvements in gas source mass spectrometry techniques now permit precise measurement of the abundance of C- 0 bonds in biogenic carbonate. C- 0 abundance shows promise as a palaeothermometer which, unlike 8 0, is independent of the stable isotope composition of seawater (Ghosh et al. 2006). 

There are four stable isotopes of strontium that are found naturally. In addition there are about twenty radioactive isotopes, including strontium-90, a deadly by-product of nuclear-bomb detonations. The natural forms of strontium are relatively nontoxic. Similar to calcium both physically and chemically, elemental strontium is a soft, shiny metal. Like calcium and other alkaline earth metals, it is easily oxidized and thus not found naturally in its free elemental state. Instead, it almost always is found in the + 2 oxidation state, forming such compounds as strontium oxide (SrO), strontium sulfate (SrS04, from the mineral celestite), strontium carbonate (SrCOj, from the mineral strontianite), and strontium chloride (SrC. Strontium nitrate, Sr(N03)2, is used to produce the brilliant red color seen in some fireworks and signal flares and is also used in making tracer bullets that can be seen when fired at night. Other strontium compounds are sometimes used in the manufacture of special glasses. Yet overall, strontium is not a very important element industrially or commercially, see ALSO Davy, Humphry... 

The chemical type of stable carbon is specific to each ecosystem. I herefore, isotopic tracers are more appropriate to understand turnover and stability of SOM. 

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