Delta carbon

Paradis Y, Bertolo A, Magnan P (2008) What do the empty stomachs of northern pike (Esox lucius) reveal Insights from carbon (delta C-13) and nitrogen (delta N-15) stable isotopes. Environ Biol Fishes 83 441—448... 

A typical 20-MW, a-c furnace is fitted with three 45-in. (114.3-cm) prebaked amorphous carbon electrodes equdateraHy spaced, operating on a three-phase delta connection. The spacing of the electrodes is designed to provide a single reaction zone between the three electrodes. The furnace is rotated to give one revolution in two to four days or it may be oscillated only. Rotation of the furnace relative to the electrodes minimizes silicon carbide buildup in the furnace. 

FIGURE 24.10 The /3-oxidation of saturated fatty acids involves a cycle of fonr enzyme-catalyzed reactions. Each cycle produces single molecnles of FADH, NADH, and acetyl-CoA and yields a fatty acid shortened by two carbons. (The delta [A] symbol connotes a double bond, and its superscript indicates the lower-nnmbered carbon involved.)... 

Water quality issues for the lower Sacramento and San Joaquin rivers and for the Delta include salinity, dissolved organic carbon (DOC), suspended sediment. 

An intermolecular pair distribution function evaluated at the end of Step 2 would consist of delta functions at those distances allowed on the 2nnd lattice. After completion of reverse mapping, which moves the system from the discrete space of the lattice to a continuum, the carbon-carbon intermolecular pair distribution function becomes continuous, as depicted in Fig. 4.7 [144]. 

In arid soils from California, U.S., 73% of the Cd exists in the carbonate fraction and only 13% in the residual fraction (Emmerich et al., 1982). In the delta of the Guadalquiver River of southwestern Spain, more than 50% of Cd is present in the carbonate fraction, and the Cd in the exchangeable fraction increases in polluted soils (Ramos et al., 1994). 

Lead has been found to reside mainly in the carbonate and the residual fractions in arid soils. In Californian soils, most of the Pb is in the carbonate fraction (55%), compared to 20% in the residual fraction (Sposito et al., 1982). In Israeli arid soils, Pb is predominately in the residual and the crystalline Fe oxide bound fractions (Han and Banin, 1999). In the delta of the Guadalquiver River of Southwestern Spain, Pb is primarily present in the Fe-Mn oxide bound fraction, followed by the carbonate fraction, while the organic and the exchangeable fractions are small (Ramos et al., 1994). In uncontaminated arid soils of China, Pb is mainly in the residual fraction, followed by the carbonate and the oxide bound fractions (Jin et al., 1996). 

The most abundant isotope of carbon has a mass of 12 atomic mass units, 12C. A less abundant stable isotope is 13C. And much less abundant is the radioactive isotope t4C, also called radiocarbon. It is convenient to express the abundances of these rare isotopes in terms of ratios of the number of atoms of the rare isotope in a sample to the number of atoms of the abundant isotope. We call this ratio r, generally a very small number. To arrive at numbers of convenient magnitude, it is conventional to express the ratio in terms of the departure of r from the ratio in a standard, which I call. v, and to express this departure in parts per thousand of s. Thus the standard delta notation is... 

For radiocarbon, the standard ratio s is provided by the preindustrial atmosphere, for which 8 = 0. Cosmic rays interacting with atmospheric nitrogen were the main source of preindustrial radiocarbon. In the steady state, this source drsource is just large enough to generate an atmospheric delta value equal to zero. The source appears in equation 9 for atmospheric radiocarbon. Its value, specified in subroutine SPECS, I adjust to yield a steady-state atmospheric delta value of 0. The source balances the decay of radiocarbon in the atmosphere and in all of the oceanic reservoirs. Because radiocarbon has an overall source and sink—unlike the phosphorus, total carbon, 13C, and alkalinity in this simulation—the steady-state values of radiocarbon do not depend on the initial values. 

Fossil fuel source terms appear not only in equation 1 for atmospheric carbon dioxide fuel/matmco2 but also in equations 6 and 9 for carbon isotopes in the atmosphere fuel/matmco2 defuel or drfuel. The 13C delta value for the fossil fuel source is defuel = — 25, and the radiocarbon value is drfuel = —1000, because fossil carbon is devoid of radiocarbon, rfs = 0, and del = — 1 1000. 

The study of isotopes makes it necessary to introduce a further refinement in the general method of solution. I have been using a test of the relative increment to adjust the time step. The relative increment is the change in a dependent variable divided by the value of that variable. This is not a useful test, however, when the value of the variable approaches zero, because the test requires progressively smaller time steps. None of the variables I considered in previous chapters has approached zero, and so there has been no problem with this test. But carbon isotope ratios of seawater have delta values near zero, and a problem may occur when calculating these values. I have modified subroutine CHECKSTEP to permit a flexible response to this situation. 

I have made some changes in GRAFINIT to provide more generally informative real-time plots. The reference value for atmospheric carbon dioxide is set to 1 PAL, so that with a sensitivity of 0.2,1 look at departures from 1. As before, the reference values for alkalinity and dissolved carbon are the starting values. For the isotopes I plot departures of delta from 0, with a sensitivity of 1 for 13C and 100 for 14C. 

Broecker and Peng, p. 59 dlsscon = 7 dissolution constant in DJSS pcpcon = / carbonate precipitation constant disfac -. 01 scaling factor in dissolution rate eole/e 3/y delcorg 10 Fractionation by photosynthetic organises dcse = 2 Delta 13C Isotope ratio for sea eater, per eil... 

The idea for this experiment came from Prof. David Baker of Delta College, University Center, Michigan. http //www.grinnel.edu/courses/bio/qubitmanual/Labs/CQ2/Carbon Dynamics-Part 2.htm (8-25-01)... 

Reference materials that represent the primary deep-sea and coastal depositional environments and biological materials would solve many of the problems that radiochemists face in analysis of sediments from these settings. Radiochemists require reference materials comprising the primary end member sediment and biological types (calcium carbonate, opal, and red clay from the deep-sea and carbonate-rich, silicate-rich, and clay mineral-rich sediments from coastal environments and representative biological materials). Additional sediment reference material from a river delta would be valuable to test the release of radionuclides that occurs as riverine particles contact seawater. 

Isotope ratio mass spectrometry (IR-MS) makes use of these facts to determine the origin or the age of a sample. For convenience, the minor changes in isotopic ratios are expressed using the delta notation stating the deviation of the isotopic ratio from a defined standard in parts per thousand (%c). [8,10] The delta value of carbon, for example, is calculated from... 

There are four allotropic forms of manganese, which means each of its allotropes has a different crystal form and molecular structure. Therefore, each allotrope exhibits different chemical and physical properties (see the forms of carbon—diamond, carbon black, and graphite). The alpha (a) allotrope is stable at room temperature whereas the gamma (y) form is soft, bendable, and easy to cut. The delta A allotrope exists only at temperatures above 1,100°C. As a pure metal, it cannot be worked into different shapes because it is too brittle. Manganese is responsible for the color in amethyst crystals and is used to make amethyst-colored glass. 

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