Spatial distribution of methane in the Lake Biwa sediments and its carbon isotopic compositions.

Abstract

The spatial variation of methane contents and its stable carbon isotopic composition of sediments from a mesotrophic lake (Lake Biwa) were determined. Methane concentrations in the sediments (0-10 cm), ranging from 0.04 to 2.41 µmol ml -1 , were weakly correlated with the amounts of organic carbon in the surface sediments (0-2 cm), but were poorly correlated with the nitrogen isotopic composition of the bulk sediments used as an indicator of the origin of the organic matter (autochthonous vs. allochthonous). The carbon isotopic composition of methane ranged from -61 to -80‰ and exhibited positive correlation with methane concentration and the carbon isotopic composition of total carbonate (∑CO 2 ). The apparent fractionation factor (αcCH 4 -CO 2 ) between methane and ∑CO 2 was in the range between 1.07 and 1.085, which were rather high compared to previously reported values in freshwater sediments. The results suggested that major parts of methane were produced via CO 2 -H 2 in the Lake Biwa sediments.

An inter-regional assessment of concentrations and δ13C values of methane and dissolved inorganic carbon in small European lakes

“…However, d 13 C values remarkably more negative than -65 % have recently been reported for lacustrine CH 4 , leading to the conclusion that hydrogenotrophic methanogenesis might also be a significant pathway in lake ecosystems (e.g. Murase and Sugimoto 2001;Kankaala et al 2007;Mandic-Mulec et al 2012). In all our 32 lakes, the d 13 C value of CH 4 measured in the sediments is more negative than -61 % and in 30 lakes more negative than -65 % (Fig.…”

“…5a). Hydrogenotrophic methanogenesis may An inter-regional assessment of concentrations and d 13 C values of methane and dissolved… be a more relevant pathway for CH 4 production in freshwater sediments if the availability of organic substrates for methanogenesis is low (Hornibrook et al 1997(Hornibrook et al , 2000Murase and Sugimoto 2001), which may be the case in our Fennoscandian lakes with a larger proportion of SOM of terrestrial origin. Hydrogenotrophic methanogenesis would be expected to lead to larger offsets between d 13 C values of SOM and of CH 4 in these sites than in sites with a higher relevance of acetotrophic methanogenesis.…”

Detection Methanogens in Newly Settled Sediments from Xuanwu Lake in Nanjing, China

“…The concentration of CH 4 was lower in surface sediments (0-6 cm) than that in deeper sediment (Table 2). In fact, the major part of methane production was in the subsurface layer, deeper than 6 cm depth from the surface of the sediment, where the OM content is much lower than the surface [19]. In addition, CH 4 can react with many oxidants like sulfate in surface sediments [19][20][21] or be degraded by the high rates of anaerobic methanotrophy in sediments [18,22].…”

“…Among the five sites, the lowest CH 4 fluxes were detected at site E. These might be ascribed to the released oxygen by aquatic plants at site E, since the O 2 can regulate the CH 4 concentration and the diffusive CH 4 fluxes in the sediment [17]. Methane production is mediated by a complex microbial community and influenced by several factors like the oxygen, oxidizers, and available OMs [18,19]. PCA is a multivariate statistical technique that can simplify large data sets and allow reducing the number of variables to a smaller set of orthogonal factors of easier interpretation by displaying the correlations existing among the original variable.…”

Unsanitary Landfill Fires as a Source of a PCDD/Fs Contamination

“…Having in mind that typical organic matter contains approximately 50 % of carbon, these results are comparable with those reported for different lakes of a similar trophy level. [33][34][35] Mineral composition of the investigated sediments was uniform. The prevailing mineral phase was calcite, followed by quartz, micas, and pyrite.…”