Automatic apparatus for sampling and preparing gases for mass spectral analysis in studies of carbon isotope fractionation during methane metabolism

Abstract

may require from 50 to 150 seconds for processing. A spectrum containing 200 lines will usually require about 3 to 7 minutes for processing.The program HIRES2 usually requires 10 to 60 seconds for identifying the standard masses and computing the masses of all the lines.The computing time required by HIRES3 depends on the number of atoms to be considered and on the size of the constants which define the maximum number of each atom permitted in a given formula. About 40 to 60 seconds is typical for computing all possible combinations of C, C13, , O, and N for a spectrum containing 200 lines when one C13 and 2 to 4 O and N atoms are permitted in each ion. ACKNOWLEDGMENTThe authors acknowledge the valuable advice of A. C. Jones and J. H. Schachtschneider in some of the mathematical aspects of these programs.

Carbon and hydrogen isotope fractionation resulting from anaerobic methane oxidation

“…Methane oxidation by aerobic bacteria has been studied extensively in the laboratory, but the significance of its role in the global methane cycle is uncertain. Isotope fractionation factors, ranging from 1.005 to 1.031 for carbon and 1.103 to 1.325 for hydrogen, have been measured by cuk turing aerobic methylotrophs in a closed system, and monitoring changes in stable isotope ratios in either methane or the products of oxidation, CO• and H•O [Silverman and Oyama, 1968;Barker and Fritz, 1981;Coleman et al, 1981]. Since fractionation factors may be a function of physiological as well as environmental variables, kinetic isotope effects calculated from laboratory experiments may not be directly applicable to environmental data.…”

Big Soda Lake (Nevada). 3. Pelagic methanogenesis and anaerobic methane oxidation1

“…To our knowledge, Lidstrom (1983) was the first to report biological consumption of unlabeled methane in anoxic water samples. In addition, because aerobic, methane-oxidizing bacteria are capable of sizable isotope fractionation (Silverman and Oyama 1968;Barker and Fritz 198 1;Coleman et al 198 I), reports of 13C-enriched methane (Bernard 1978;Oremland and Des Marais 198 3) and "C-deplctcd carbon dioxide (Claypool and Kaplan 1974) within the sulfate-reduction zone of anoxic sediments provide circumstantial evidence for an anaerobic counterpart to aerobic bacterial oxidation.…”

Origin of 13C-enriched methane in the crater lake Towada, Japan.

“…It is difficult to believe that the value reflect actual source 613C composition of the hot spring water in the lake. Such an 13C enriched isotopic composition could be due to the work of methane oxidizing bacteria in the lake water column, since the bacteria prefer 12C and thus leave unoxidized CH4 enriched in 13C (Silverman and Oyama, 1968;Barker and Fritz, 1981;Coleman et al, 1981;Whiticar and Faber, 1986). For samples that were incubated for two weeks, the measured initial and residual methane con centration and carbon isotopic composition at each depth are given in Table 1.…”