Methane in aquifers and alluvium overlying a coal seam gas region: Gas concentrations and isotopic differentiation.

The detection and attribution of methane in aquifers overlying oil and gas reservoirs has recently gained increasing attention internationally. The Surat Basin, in the Great Artesian Basin (GAB), Australia, hosts a coal seam gas (CSG) reservoir, with feedlots, town water supply, mines and agriculture that extract groundwater from aquifers that underly and overly the gas reservoir. This study aimed to use a multi-isotopic approach to differentiate biogenic methane generated in situ in GAB aquifers and the Condamine Alluvium, from the biogenic CSG produced from the underlying Walloon Coal Measures reservoir, to understand if gas had migrated or not. Dissolved methane (0.001 to 160 mg/l) and total methane concentrations (up to 91,818 ppmv) were measured using closed sampling methods and were higher than from open direct fill sampling (<0.001 to 25.4 mg/l), especially in gassy bores that contain dissolved methane above 10 to 13 mg/l. The CSG production waters and a gassy overlying aquifer bore had the most depleted water isotopes, and also the most enriched δ13C-DIC indicating strong methanogenesis. The majority of aquifers have isotopic signatures (δ13C-DIC, CH4 and CO2) indicating in situ methane production by primary CO2 reduction or fermentation, distinct from secondary microbial CO2 reduction in the CSG reservoir. Fractionation factors support methane production mainly via CO2 reduction, with fermentation in a subset of aquifer samples. The gas wetness parameters (636 to 20,000) are consistent with mainly microbial gases, with low dissolved ethane (max 0.04 mg/l). The majority of aquifer and alluvium samples in this study are consistent with in situ methane production, not migration, however in several gassy bores the methane source could not be clearly identified. This study is broadly applicable to understanding methane sources in aquifers overlying CSG reservoirs.

The influence of hydrogeological disturbance and mining on coal seam microbial communities.

The microbial communities present in two underground coal mines in the Bowen Basin, Queensland, Australia, were investigated to deduce the effect of pumping and mining on subsurface methanogens and methanotrophs. The micro-organisms in pumped water from the actively mined areas, as well as, pre- and post-mining formation waters were analyzed using 16S rRNA gene amplicon sequencing. The methane stable isotope composition of Bowen Basin coal seam indicates that methanogenesis has occurred in the geological past. More recently at the mine site, changing groundwater flow dynamics and the introduction of oxygen in the subsurface has increased microbial biomass and diversity. Consistent with microbial communities found in other coal seam environments, pumped coal mine waters from the subsurface were dominated by bacteria belonging to the genera Pseudomonas and the family Rhodocyclaceae. These environments and bacterial communities supported a methanogen population, including Methanobacteriaceae, Methanococcaceae and Methanosaeta. However, one of the most ubiquitous micro-organisms in anoxic coal mine waters belonged to the family 'Candidatus Methanoperedenaceae'. As the Archaeal family 'Candidatus Methanoperedenaceae' has not been extensively defined, the one studied species in the family is capable of anaerobic methane oxidation coupled to nitrate reduction. This introduces the possibility that a methane cycle between archaeal methanogenesis and methanotrophy may exist in the anoxic waters of the coal seam after hydrogeological disturbance.

Body composition in nonalcoholic cirrhosis: the effect of disease etiology and severity on nutritional compartments.

BACKGROUND/AIMS: Previous studies of body composition in cirrhosis have either measured only one body compartment, used alcoholic subjects, or not corrected body composition for physical characteristics. The aim of this study was to perform a detailed analysis of body composition in subjects with nonalcoholic cirrhosis. METHODS: Simultaneous measurements of total body potassium and total body water were performed and values of body cell mass and body fat were corrected for physical characteristics. RESULTS: Child's class C patients had a significantly lower mean total body potassium index (i.e., percent observed value/expected value) and body fat index than class A or B patients. Eighty-one percent of class C patients had simultaneous reductions in body fat and body cell mass, and 71% of patients with class A disease had a significant reduction in either or both compartments. Nine patients showed the pattern of tissue loss seen with short-term starvation. Fourteen patients showed the pattern of tissue loss seen in physiological stress. CONCLUSIONS: Severe liver disease is characterized by significant reductions in body fat and body cell mass, most class A patients have a significant reduction in some nutritional compartments, and the pattern of tissue loss may reflect mechanisms of tissue wasting.

Distribution of body water in patients with cirrhosis: the effect of liver transplantation.

We compared total body water and intracellular-extracellular distribution of body water between male patients with mild liver disease without ascites (n = 9), male patients with severe liver disease and gross ascites (n = 6) and a group of age-, sex-, height- and weight- matched controls (n = 6). In addition, we documented the effects of liver transplantation on intracellular, extracellular and total body water in 12 patients (6 men and 6 women) by means of deuterium oxide dilution and whole-body potassium counting. We saw no significant difference in total body water between the healthy controls, patients without ascites and patients with ascites (46.5 +/- 9.2 kg, 45.4 +/- 6.6 kg and 50.4 +/- 5.1 kg, respectively), although, as expected, extracellular water was increased in patients with ascites compared with healthy controls and cirrhotic patients without ascites (36.9 +/- 6.5 kg vs. 25.4 +/- 4.4 kg, p = 0.005; and 36.9 +/- 6.5 kg vs. 27.0 +/- 5.3 kg, p = 0.002, respectively). We found no difference between non-ascitic patients and healthy controls (25.4 +/- 4.4 kg vs. 27.0 +/- 5.3 kg). However, intracellular water was significantly reduced in patients with severe liver disease compared with that in controls (13.6 +/- 3.3 kg vs. 21.5 +/- 4.2 kg, p = 0.005) or patients without ascites (13.6 +/- 3.3 kg vs. 18.3 +/- 2.9 kg, p = 0.01). The reduction of intracellular water appears to be due to loss of body cell mass.(ABSTRACT TRUNCATED AT 250 WORDS)