Carbon decay rate

Thus, three species from the gas phase, O2, CO, and CO2, take part in the reaction, and the generalized volatiles component, L, is extracted. The following formulae for the volatiles extraction and carbon decay rates from the fth model... 

During the 1950s, Professor W. F. Libby (1908-1980) of the University of Chicago and others worked out a method for determining the age of organic material It is based on the decay rate of carbon-14. The method can be applied to objects from a few hundred up to 50,000 years old. It has been used to determine the authenticity of canvases of Renaissance painters and to check the ages of relics left by prehistoric cave dwellers. 

Ar (42), in both cases within a factor of four of the theoretical prediction. Also, a similar decay rate was obtained in sc CH4 (6.2 + 0.6 x 106s 1), and in heptane (8.1 + 0.7 x 107s 1) (42). The observed decay rate constant in sc Ar doped with H2, 3.3( + 0.1) x 106s 1, mentioned above, is also close to these values. Finally, in sc Ar doped with carbon monoxide, the rate of decay is 5.3 x 106 s-1 (42). All of these values are in reasonable agreement with the computed rate constant k31 considering the many uncertainties involved in predicting the latter, associated with errors in the computed energy of MECP noL and in the NA-TST itself. 

Based on this modified activated sludge concept, it was possible to produce acceptable model simulation results for the water-phase processes of the heterotrophic carbon transformations in sewers. However, problems were identified for the description of the heterotrophic biomass decay. A major problem was the magnitude of the 1-order decay rate constant with respect to the biomass concentration. Henze et al. (1987) and Kappeler and Gujer (1992)... 

The Rothamsted Carbon Model (RothC) uses a five pool structure, decomposable plant material (DPM), resistant plant materials (RPM), microbial biomass, humified organic matter, and inert organic matter to assess carbon turnover (Coleman and Jenkinson 1996 Guo et al. 2007). The first four pools decompose by first-order kinetics. The decay rate constants are modified by temperature, soil moisture, and indirectly by clay content. RothC does not include a plant growth sub-module, and therefore NHC inputs must be known, estimated, or calculated by inverse modeling. Skjemstad et al. (2004) tested an approach for populating the different pools based on measured values. 

The fluorescence and phosphorescence of luminescent materials are modulated by the characteristics of the environment to which these materials are exposed. Consequently, luminescent materials can be used as sensors (referred also as transducers or probes) to measure and monitor parameters of importance in medicine, industry and the environment. Temperature, oxygen, carbon dioxide, pH, voltage, and ions are examples of parameters that affect the luminescence of many materials. These transducers need to be excited by light. The manner in which the excited sensor returns to the ground state establishes the transducing characteristics of the luminescent material. It is determined by the concentration or value of the external parameter. A practical and unified approach to characterize the luminescence of all sensors is presented in this chapter. This approach introduces two general mechanisms referred as the radiative and the nonradiative paths. The radiative path, in the general approach, is determined by the molecular nature of the sensor. The nonradiative path is determined by the sensor environment, e.g., value or concentration of the external parameter. The nonradiative decay rate, associated with the nonradiative path, increases... 

Radioactive decay rates are statistical averages of large numbers of decaying atoms. Because of the relatively short half-life of carbon-14, only trace amounts would be left after 50,000 years—too little to be statistically accurate. 

By adding carbonate to ozonated water, the half-life of ozone can be increased. Even some few pmoles decrease the decay rate of ozone by about a factor of ten or more (Hoigne and Bader, 1977). Increasing the concentration of bicarbonate/carbonate up to a concentration of 1.5 mM increases the stability of ozone. Thereafter no further stabilization occurs (Forni et al., 1982). 

A systematic dependence of reaction order on temperature and pH is not visible, n varies between one and two. Different experimental conditions and/or missing details about these conditions as well as different analytical methods make a comparison of these results impossible. Staehelin and Hoigne (1985) proposed a possible explanation for the second order reaction (n = 2). Since in clean water ozone not only reacts with the hydroxide ions but also with the intermittently produced hydroxyl radicals (see Chapter A 2), it behaves like a promoter and the decay rate increases with the square of the liquid ozone concentration. This is supported by the results obtained by Gottschalk (1997). She found a second order decay rate in deionized water, compared to a first order decay rate in Berlin tap water, which contains about 4 mg L DOC and 4 mmol LT1 total inorganic carbon. Staehelin and Hoigne (1982) also found first order in complex systems. 

Fig. 8.2. Apparatus used by Mills for studies of the positronium negative ion Gi is a pile-up-reducing grid, G2 is the Ps -forming carbon film and G3 is the acceleration grid. See the text for further details. Reprinted from Physical Review Letters 50, Mills, Measurement of the decay rate of the positronium negative ion, 671-674, copyright 1983 by the American Physical Society.

H.T. Schmidt, P. Forck, M. Grieser, D. Habs, J. Kenntner, G. Miersch, et al., High-precision measurement of the magnetic-dipole decay rate of metastable heliumlike carbon ions in a storage ring, Phys. Rev. Lett. 72 (1994) 1616. 

Figure 7.23 Applications of the NMR-MOUSE to elastomer materials (a) T2 values for a curing series of carbon-black filled NR. Comparison of values obtained at high homogeneous field (DMX 300) and with the NMR-MOUSE, (b) cross-link series of unfilled SBR with different sulfur content, (c) T2 versus glass-transition temperature Tg of unfilled SBR by the CPMG and the steady-state CPMG methods, (d) normalized Hahn-echo decay curves for poly(butadiene) latex samples. Different decay rates are obtained for small medium and large cross-link densities...

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. 

Fig. 2. Temperature dependence of carbon radical decay rate constants a-polyvinylacetate, b-polystyrene, c-polymethylmetacrylate...

Pseudo-first-order rate constants, fci (normalized to unit substrate concentration IS]), were determined from current-collection-efficiency data (02 decay rates) with a glassy-carbon-glassy-carbon ring-disk electrode that was rotated at 900 rpm. (O2 was produced at the disk electrode from dissolved O2, which reacted with 2 mM substrate, and the unreacted O2 was determined by its oxidation at the ring electrode.)... 

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