Methane release from carbonate rock formations in the Siberian permafrost area during and after the 2020 heat wave

Anthropogenic global warming may be accelerated by a positive feedback from the mobilization of methane from thawing Arctic permafrost. There are large uncertainties about the size of carbon stocks and the magnitude of possible methane emissions. Methane cannot only be produced from the microbial decay of organic matter within the thawing permafrost soils (microbial methane) but can also come from natural gas (thermogenic methane) trapped under or within the permafrost layer and released when it thaws. In the Taymyr Peninsula and surroundings in North Siberia, the area of the worldwide largest positive surface temperature anomaly for 2020, atmospheric methane concentrations have increased considerably during and after the 2020 heat wave. Two elongated areas of increased atmospheric methane concentration that appeared during summer coincide with two stripes of Paleozoic carbonates exposed at the southern and northern borders of the Yenisey-Khatanga Basin, a hydrocarbon-bearing sedimentary basin between the Siberian Craton to the south and the Taymyr Fold Belt to the north. Over the carbonates, soils are thin to nonexistent and wetlands are scarce. The maxima are thus unlikely to be caused by microbial methane from soils or wetlands. We suggest that gas hydrates in fractures and pockets of the carbonate rocks in the permafrost zone became unstable due to warming from the surface. This process may add unknown quantities of methane to the atmosphere in the near future.

Mineralogical, chemical and stable C and O isotope characteristics of surficial carbonate structures from the Mediterranean offshore Israel indicate microbial and thermogenic methane origin

The Eastern Mediterranean continental slope offshore Israel became a focus of exploration for, and production of, natural gas in recent years. The 2010–2011 Nautilus ROV expedition performed detailed video recordings and sampling in two areas offshore Israel: the Palmachim disturbance, southwest of Tel Aviv, and an area offshore Acre, north of Haifa. An analytical programme regarding the carbonate structures was carried out, examining the overall mineralogy, stable C and O isotopes, and Ca, Mg, and Mn concentrations. This provided information on their composition and as a result, an indication of the carbon sources and temperature of formation. The major authigenic minerals identified comprised magnesian calcite, dolomite, aragonite, and kutnohorite. The detrital minerals included quartz, clays, feldspars, and rare augite and enstatite, likely transported from the Nile estuary. The carbon isotope composition of aliquots taken from nineteen samples from these areas have an overall δ13C range from −62.0 to −0.1‰PDB, indicating a range of microbial/biogenic and thermogenic methane contributions. The range of δ18O from 2.7 to 7.0‰PDB reflects the range of temperatures of formation. The δ18O characteristics differ among areas. In general, high values; δ18O >5‰PDB are recorded from area N2 of the Palmachim disturbance, indicating low temperature of formation. Low values of δ18O (<5‰PDB) were measured from areas W2 and W3 of the Palmachim disturbance, together with samples from area N2 of the Palmachim disturbance, and samples from areas A1 and A2 offshore Acre indicate high temperature origin. Samples from an inactive chimney from area N2 range from pure dolomite to pure magnesian calcite. This trend is linked to δ13C increase from −39.9 to −0.1‰(PDB), and δ18O decrease from 6.2 to 4.7‰(PDB). These values indicate a decrease in the methane-derived carbon contribution and an increase in temperature. Kutnohorite, Ca(Mn2+, Mg, Fe 2+)(CO3)2 is a major component in samples from Acre, and less so in the Palmachim disturbance. An exploratory investigation of the relationship between Mn/Ca, δ18O and δ13C revealed that samples having Mn/Ca < 0.1(wt./wt.) have δ13C<−50‰PDB indicating a microbial methane source, while samples with Mn/Ca > 0.1 have δ13C between −35 and −22‰PDB suggesting a thermogenic origin. These results suggest that the mineralogical, isotopic δ13, δ18O, and chemical (Mn/Ca indicative of kutnohorite) characteristics of surficial carbonate structures can indicate and distinguish between deep and shallow methane sources in the Eastern Mediterranean.

Geochemistry of oil-and-gas seepage in Lake Baikal: towards understanding fluid migration system

&lt;p&gt;Baikal is a Cenozoic syn-rift sedimentary basin with many surficial manifestations of distinct hydrocarbon system. Focused gas seeps, gas-hydrate accumulations, and various mud volcanoes are abundant all over the lake bottom and were recently studied in order to characterize an upward fluid migration from deeper strata. Highly concentrated oil seeps which can provide detailed information on basin fluid migration pathway configurations are mostly developed at the east coast and rift flank of Lake Baikal.&lt;/p&gt;&lt;p&gt;Herewith, we report results of detailed geochemical studies (gases, organic matter, bitumen, pore waters, and sediments) completed on samples collected from an area of active oil and gas seepage, asphalt/tar edifices and subbottom gas-hydrates occurrences located 18 km offshore the Gorevoy Utes cape (the eastern coast of the lake) at the depth of 850-950 m.&lt;/p&gt;&lt;p&gt;As a part of the Class@Baikal-2018 expedition, two high-resolution seismic profiles (total length of about 10 km) crossing the fluid discharge zone in transverse directions were acquired to locate 22 bottom sampling stations and to retrieve samples. Four more seismic lines and 12 sampling cores were collected during the follow up Class@Baikal-2019 cruise.&lt;/p&gt;&lt;p&gt;The highest concentrations of all gases and a fresh crude oil in sediments are characteristic for a spot of only about 500 m in diametre, marking a probable centre of the most intense deep fluid migration to the surface. The elemental composition characteristic of sampled oil was determined as follow: C=83.84%, H=10.67%, N=0.37%, and S&lt;0.08% by wt. And its molecular compounds are 15% asphaltenes, 20% resins, 35% aromatic hydrocarbons, and 30% saturates.&lt;/p&gt;&lt;p&gt;High concentration of methane was also detected in samples at the distance from this central spot all around the studied field. According to isotopic analyses, this indicates lateral redistribution of thermogenic methane ongoing together with enhanced bacterial methane generation in surrounding sediments. &amp;#948;13&amp;#1057; of methane from the peripheries varies from -70.98 &amp;#8240; to -88.46 &amp;#8240;, whereas the &amp;#948;13&amp;#1057; of methane from the central spot is heavier (up to -41.00 &amp;#8240;). The high content of methane homologues (ethane and propane) and carbon dioxide is characteristic and indicative for all samples taken from the central spot. A few samples collected outside of the central zone demonstrated the high thermogenic methane concentration, carbon dioxide content and presence of some methane homologues as well. Most likely this points out at existence of locally permeable segments aside of main conduit, probably some fractures accompanying the central pathway. Interestingly, no fresh oil was found in those samples.&lt;/p&gt;&lt;p&gt;Rock-Eval pyrolysis, isotopic analyses and biomarker studies revealed that the source rocks for both hydrocarbon gases and oil are terrigeneous and contain predominant humic organic matter components (kerogen type III). These strata belong to different maturation stages, ranging from low-mature to peak-mature, which is well explained by the complex structure of the rift sedimentary infill and documented presence of local thermal anomalies in the region.&lt;/p&gt;&lt;p&gt;Results of geochemical studies are incorporated into an integrated model of source-to-surface fluid migration to explain the observed peculiarities of the Gorevoy Utes seepage area.&lt;/p&gt;

Physiology and Distribution of Archaeal Methanotrophs That Couple Anaerobic Oxidation of Methane with Sulfate Reduction

SUMMARY In marine anaerobic environments, methane is oxidized where sulfate-rich seawater meets biogenic or thermogenic methane. In those niches, a few phylogenetically distinct microbial types, i.e., anaerobic methanotrophs (ANME), are able to grow through anaerobic oxidation of methane (AOM). Due to the relevance of methane in the global carbon cycle, ANME have drawn the attention of a broad scientific community for 4 decades. This review presents and discusses the microbiology and physiology of ANME up to the recent discoveries, revealing novel physiological types of anaerobic methane oxidizers which challenge the view of obligate syntrophy for AOM. An overview of the drivers shaping the distribution of ANME in different marine habitats, from cold seep sediments to hydrothermal vents, is given. Multivariate analyses of the abundance of ANME in various habitats identify a distribution of distinct ANME types driven by the mode of methane transport. Intriguingly, ANME have not yet been cultivated in pure culture, despite intense attempts. Further advances in understanding this microbial process are hampered by insufficient amounts of enriched cultures. This review discusses the advantages, limitations, and potential improvements for ANME laboratory-based cultivation systems.

Relationship between vertical depth of the kickoff point of a fracking operation and methane concentrations in groundwater resources

There is a problem with hydraulic fracturing and water contamination. Despite Safe Drinking Water Act regulations, risk to water resources remains in areas of water acquisition, chemical mixing, well injection, produced water handling, and wastewater disposal and reuse. This problem has negatively impacted some relying on groundwater resources surrounding hydraulic fracturing operations because of inadequate information (e.g. unmapped faults, abandoned/unfilled wells, unknown mechanisms of risk, etc.). Perhaps a study which investigates the correlation between the vertical depth of the kickoff point (point at which fracking fluids are dispersed underground in vertical wells) and thermogenic methane concentrations in groundwater resources could remedy this situation by filling a gap in the research and identifying a potential risk to groundwater resources. The question: to what extent does the vertical depth of the kickoff point in a fracking operation correlate to thermogenic methane concentrations in groundwater resources?