Methane tracer

The oxidation of 2 mol butyric acid to 4 mol acetic acid is coupled with the reduction of 1 mol of carbon dioxide to methane. Tracer experiments showed that 98% of the methane is derived from carbon dioxide. In these examples of methane fermentation involving carbon dioxide reduction, no carbon dioxide is formed in the oxidation of the substrate. The fermentation of propionic acid by M. propionicum is more complicated because it involves both carbon dioxide formation and consumption (Stadtman and Barker, 1951) ... 

Tracer experiments with C-labeled carbon dioxide or propionic acid indicate that approximately 1 mol of carbon dioxide is formed per mole of propionic acid consumed and that carbon dioxide is the precursor of most of the methane. Tracer experiments were also conducted with propionic acid using enrichment... 

If incompletely devolatilized char enters the reduction zone, tar may evolve there and will remain largely unconverted in the gas. The second reason for undesired tar in the product gas may be incomplete conversion of tar in the oxydation zone. To study this problem, three types of experiments have been carried out a) methane tracer injection in the gasifier b) cold flow model tests c) tar production measurement at different geometries. 

Figure 4. Methane tracer injection con-version of additionally injected methane in Point (1) 0.36 (2) 0.24 (3) 0.35 (4)...

To improve the evaluation of a water and gas pilot, tracers were injected in the gas phase at the beginning of the first two-gas injection periods. Per-fluoromethylcyclopentane and perfluoromethylcyclohexane were used. In laboratory studies, these compounds were shown to have a higher partitioning to the oil phase than did tritiated methane. This caused a minor retention of the tracer [518,1119],... 

Fig. 3.1.10 Molecular lifetimes xintra and. aii in H-ZSM-5 crystallites obtained using the NMR tracer desorption technique and calculated via Eq. (3.3.15), respectively. Tracing by probe molecules (methane, measurement at 296 K) after an H-ZSM-5 catalyst has been kept for different coking times in a stream of n-hexane (filled symbols) and mesitylene (open symbols) at elevated temperature. The inserts present the evidence provided by a comparison of xintra and r]1,]]], with respect to the distribu-...

Methane emission from ruminants can be estimated by using the ERUCT technique (Emissions from Ruminants Using a Calibrated Tracer). The tracer can either be isotopic or nonisotopic. Isotopic tracer techniques generally require simple experimental designs and relatively straightforward calculations [31]. Isotopic methods involve the use of (3H-)CH4 or (14C-)CH4 and ruminally cannulated animals. 

Warren Spring describes calibration with methane as a tracer gas. The same holds for cleaning the device. In France it is proposed to clean with superheated steam, followed by a test if every trace of odour is eliminated. 

The physical properties of a tracer gas must also be considered since control and measuring devices usually respond to mass flow rates or thermal conductivity. Thus, the response to pure C02 or methane would differ substantially from air, although correction factors can often be calculated. 

Calibration can be done with a tracer gas, e.g. methane. Once a year, a standard experiment should be carried out with a large panel and H2S as well as n-butanol as odorants. 

Taylor JA, Brasseur GP, Zimmermann PR, Cicerone RJ. 1991. A study of the sources and sinks of methane and methyl chloroform using a global three-dimensional Lagrangian tropospheric tracer transport model. Journal of Geophysical Research 96D 3013-3044. 

Johnson, K., M. Huyler, H. Westberg, B. Lamb, and P. Zimmerman, Measurement of Methane Emissions from Ruminant Livestock Using a SF() Tracer Technique, Environ. Sci. Technol., 28, 359-362 (1994). 

Martens, C.S., and Chanton, J.P. (1989) Radon as a tracer of biogenic gas equilibration and transport from methane-saturated sediments. J. Geophys. Res. 94, 3451-3459. 

Helium or nitrogen were used as carrier gas and methane was the tracer gas. A pulse of tracer gas was injected through a six-way valve into the carrier gas flow. The concentration of the tracer in the effluent was continuously measured by means of a thermal conductivity detector and recorded. 

It has been found possible to concentrate the heavy isotope in most of the lighter elements by diffusion at low pressures using many mercury diffusion pumps in series.8 Very recently9 the heavy isotope of carbon has been enriched seven fold by circulating twenty-five liters of methane gas for twelve hours at eight millimeters pressure through a battery of thirty-five mercury vapor diffusion pumps, but the yield in the experiment reported was only 1.6 cc. at atmospheric pressure. For tracer experiments in kinetics one needs large quantities with which to work. 

The Oxford results have recently been used by Solomon and Garcia to examine the distribution of long-lived tracers and chlorine species in the middle atmosphere. This important paper has crystallized many of the issues relating to the hydroxyl and chlorine species, particularly the relationship between the variability in methane concentration and the variability in CIO. Figure 10 summarizes the correlation between the two-dimensional model of Solomon and Garcia [18] and the Oxford CH4 maps. These results are then used to define the expected variability in local CIO concentrations reported by in situ observations. 

Hydrogen, helium, nitrogen and argon were used as carrier gases (C). The same gases plus methane (99.9 % purity) were used as tracers (T). 

Figure 6 Plot of methane concentration versus turnover time for samples collected in the Eel River Basin seep area. Turnover time is the CH4 concentration divided by the oxidation rate determined with C3H4 tracer experiments. The maximum turnover time of 40 years is the lower detection limit for these studies, but it is consistent with similar estimates by Scranton and Brewer (1978) and Rehder et al. (1999) (source Valentine et al, 2001).

Johnson K. A., Huyler M. T., Westberg H. H., Lamb B. K., and Zimmerman P. (1994) Measurement of methane emissions from ruminant livestock using a SFs tracer technique. Environ. Sci. Technol. 28, 359-362. 

Kessler J., Reeburgh W., Southon J., and Tyler S. (2(X)3) Natural radiocarbon in Black Sea water column methane a tracer of hydrate-derived methane EGS/AGU/EUG abstracts, 5, 12216, Apr. 6-11, Nice, Erance. 

Marik T. and Levin I. (1996) A new tracer experiment to estimate methane emissions from a dairy cow shed using sulfur hexafluoride (SFg). Global Biogeochem. Cycles 10, 413-418. 

Happen J. D., Chanton J. P., Whiting G. J., and Showers W. J. (1993) Stable isotopes as tracers of methane dynamics in Everglades marshes with and without active populations of methane oxidizing bacteria. J. Geophys. Res. 98, 14771-14782. 

VIII. Tracer Experiments on Fatty Acid Oxidation by Methane Bacteria, /. Bacteriol, (1951) 61, 67-80. 

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