Geochemical Fingerprinting of Rising Deep Endogenous Gases in an Active Hypogenic Karst System

The hydrothermal caves linked to active faulting can potentially harbour subterranean atmospheres with a distinctive gaseous composition with deep endogenous gases, such as carbon dioxide (CO2) and methane (CH4). In this study, we provide insight into the sourcing, mixing, and biogeochemical processes involved in the dynamic of deep endogenous gas formation in an exceptionally dynamic hypogenic karst system (Vapour Cave, southern Spain) associated with active faulting. The cave environment is characterized by a prevailing combination of rising warm air with large CO2 outgassing (>1%) and highly diluted CH4 with an endogenous origin. The δ13CCO2 data, which ranges from −4.5 to −7.5‰, point to a mantle-rooted CO2 that is likely generated by the thermal decarbonation of underlying marine carbonates, combined with degassing from CO2-rich groundwater. A pooled analysis of δ13CCO2 data from exterior, cave, and soil indicates that the upwelling of geogenic CO2 has a clear influence on soil air, which further suggests a potential for the release of CO2 along fractured carbonates. CH4 molar fractions and their δD and δ13C values (ranging from −77 to −48‰ and from −52 to −30‰, respectively) suggest that the methane reaching Vapour Cave is the remnant of a larger source of CH4, which was likely generated by microbial reduction of carbonates. This CH4 has been affected by a postgenetic microbial oxidation, such that the gas samples have changed in both molecular and isotopic composition after formation and during migration through the cave environment. Yet, in the deepest cave locations (i.e., 30 m below the surface), measured concentration values of deep endogenous CH4 are higher than in atmospheric with lighter δ13C values with respect to those found in the local atmosphere, which indicates that Vapour Cave may occasionally act as a net source of CH4 to the open atmosphere.

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Iron-mediated removal of ammonium from strong nitrogenous wastewater from food processing

Water Science & Technology ◽

10.2166/wst.2004.0783 ◽

2004 ◽

Vol 49 (5-6) ◽

pp. 421-431 ◽

Cited By ~ 11

Author(s):

V. Ivanov ◽

J.-Y. Wang ◽

O. Stabnikova ◽

V. Krasinko ◽

V. Stabnikov ◽

...

Keyword(s):

Food Processing ◽

Value Added ◽

Microbial Reduction ◽

Iron Hydroxides ◽

Microbial Oxidation ◽

Iron Reducing Bacteria ◽

Iron Oxidizing Bacteria ◽

Co Precipitation ◽

Reducing Bacteria ◽

Food Processing Wastewater

The combination of microbial reduction and further microbial oxidation of iron was applied to the treatment of food-processing wastewater and recovery of ammonium. Fe2+ ions were formed by iron-reducing bacteria under anaerobic conditions. Ammonium was recovered by co-precipitation with negatively charged iron hydroxides produced during oxidation of Fe2+ by iron-oxidizing bacteria under microaerophilic conditions. The value-added by-product of this process can be used as a slowly released ammonium fertilizer.

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Bispectral Analysis Measures Sedation and Memory Effects of Propofol, Midazolam, Isoflurane, and Alfentanil in Healthy Volunteers

Anesthesiology ◽

10.1097/00000542-199704000-00014 ◽

1997 ◽

Vol 86 (4) ◽

pp. 836-847 ◽

Cited By ~ 836

Author(s):

Peter S. Glass ◽

Marc Bloom ◽

Lee Kearse ◽

Carl Rosow ◽

Peter Sebel ◽

...

Keyword(s):

Drug Concentration ◽

Predictive Performance ◽

Pooled Analysis ◽

Loss Of Consciousness ◽

Measured Concentration ◽

Anesthetic Drugs ◽

Arterial Blood ◽

A Value ◽

Prediction Probability ◽

The Individual

Background The bispectral index (BIS), a value derived from the electroencephalograph (EEG), has been proposed as a measure of anesthetic effect. To establish its utility for this purpose, it is important to determine the relation among BIS, measured drug concentration, and increasing levels of sedation. This study was designed to evaluate this relation for four commonly used anesthetic drugs: propofol, midazolam, isoflurane, and alfentanil. Methods Seventy-two consenting volunteers were studied at four institutions. Volunteers were given either isoflurane, propofol, midazolam, or alfentanil. Each volunteer was administered a dose-ranging sequence of one of the study drugs to achieve predetermined target concentrations. A frontal montage was used for continuous recording of the EEG. At each pseudo-steady-state drug concentration, a BIS score was recorded, the participant was shown either a picture or given a word to recall, an arterial blood sample was obtained for subsequent analysis of drug concentration, and the participant was evaluated for level of sedation as determined by the responsiveness portion of the observer's assessment of the alertness/ sedation scale (OAAS). An OAAS score of 2 or less was considered unconscious. The BIS (version 2.5) score was recorded in real-time and the BIS (version 3.0) was subsequently derived off-line from the recorded raw EEG data. The relation among BIS, measured drug concentration, responsiveness score, and presence or absence of recall was determined by linear and logistic regression for both the individual drugs and, when appropriate, for the pooled results. The prediction probability was also calculated. Results The BIS score (r = 0.883) correlated significantly better than the measured propofol concentration (r = -0.778; P < 0.05) with the responsiveness score. The BIS provided as effective correlation with responsiveness score of the OAAS as did the measured concentration for midazolam and isoflurane. None of the volunteers given alfentanil lost consciousness and thus were excluded from the pooled analysis. The pooled BIS values at which 50% and 95% of participants were unconscious were 67 and 50, respectively. The prediction probability values for BIS ranged from 0.885-0.976, indicating a very high predictive performance for correctly indicating probability of loss of consciousness. Conclusions The BIS both correlated well with the level of responsiveness and provided an excellent prediction of the loss of consciousness. These results imply that BIS may be a valuable monitor of the level of sedation and loss of consciousness for propofol, midazolam, and isoflurane.

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Microbial role in N2O-NO2 production and CH4 oxidation under active hypogenic settings

10.5194/egusphere-egu2020-21141 ◽

2020 ◽

Author(s):

Tamara Martin-Pozas ◽

Soledad Cuezva ◽

Valme Jurado ◽

Raul Perez-Lopez ◽

Cesareo Saiz-Jimenez ◽

...

Keyword(s):

Nitrogen Oxides ◽

Phylogenetic Analyses ◽

Lower Troposphere ◽

Mitigation Strategies ◽

Active Faulting ◽

Near Surface ◽

Cave Sediments ◽

New Findings ◽

Gaseous Composition ◽

Nitrogenous Gases

The hydrothermal caves linked to active faulting have subterranean atmospheres with a distinctive gaseous composition containing deep endogenous gases, such as carbon dioxide, methane and nitrogen oxides (NOx). Ascending fluids through associated near-surface hydrothermal processes can mobilize endogenous gases into the Critical Zone and, ultimately, to the lower troposphere. Nitrogen oxides are polluting gases and can have adverse effects on human health, especially inhaled NO2. They also catalyse ozone (O3) production in the lower layers of the atmosphere and the greenhouse effect, when they react with volatile organic compounds. The largest source of NOx emissions is anthropogenic. The rest is produced naturally by microbial processes in soil and water, by lightning, volcanic activity, storms, etc. Production of N2O and NO2 is associated with soil and other active-geothermal ecosystems, far less is known about the sources and sinks of these gases within subterranean locations. Here, we report high N2O and NO2 concentrations detected along a hypogenic system associated with an active faulting (Vapour Cave, southern Spain), which enables direct gas exchange with the low-atmosphere. These anomalous concentrations of N2O and, NO2 are about ten and five times higher than the typical atmospheric background, respectively. Gaseous composition analyses of subterranean atmosphere were conducted by high precision field-deployable CRDS and FTIR spectrometers for measuring in situ the target tracer gases (NO2, N2O, CH4, CO2) and &#948;13C of both carbon-GHGs. DNA extraction, sequencing and phylogenetic analyses were conducted to characterize the microbial community of cave sediments. The results showed that N2O and NO2 emission depends on the activity of nitrification by ammonia oxidizing microorganisms (such as members of the family Nitrosomonadaceae and phylum Thaumarchaeota) and/or as a result of incomplete denitrification by heterotrophic denitrifying bacteria (such as Bacillus, Acinetobacter and Cupriavidus) from this hydrothermal and hypoxic ecosystem. On the other hand, CH4 concentrations and &#948;13CH4 vary along the cave (with the deep), in deepest cave locations CH4 values are higher with lighter &#948;13C values in comparison with the more superficial areas, which indicates a deep endogenous origin of methane. However, in areas near the entrance we observe lower concentrations of methane and heavier &#948;13C values (CH4<1 ppm and &#948;13C close to &#8722;30&#8240;), as a result of methane oxidation by denitrifying methanotrophs of the NC10 phylum during gas migration from the deepest areas to the surface.These new findings reveal the sourcing of these nitrogenous gases into the upper vadose zone of a hypogenic/geothermal ecosystem, and its potential release to the lower troposphere. A better understanding of biogeochemical processes controlling the production of nitrogenous gases in subterranean environments will be useful to identify and characterize new possible sources, reservoirs and sinks of greenhouse gases (CO2, CH4, N2O and NOx) in order to calculate more accurately the budgets and for the design of new mitigation strategies of these gases.

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THE PYRITIZATION OF BASIC FERRIC SULFATES IN ACID SULFATE SOILS: A MICROBIOLOGICAL INTERPRETATION

Canadian Journal of Soil Science ◽

10.4141/cjss76-048 ◽

1976 ◽

Vol 56 (4) ◽

pp. 393-406 ◽

Cited By ~ 11

Author(s):

K. C. IVARSON ◽

R. O. HALLBERG ◽

T. WADSTEN

Keyword(s):

Elemental Sulfur ◽

Sea Water ◽

Desulfovibrio Desulfuricans ◽

Parent Material ◽

Microbial Reduction ◽

Acid Sulfate Soils ◽

Microbial Oxidation ◽

Acid Sulfate ◽

X Ray ◽

Sulfate Soils

The aim of this investigation was to suggest a mechanism whereby the basic ferric sulfates, which occur in acid sulfate soils as a result of the microbial oxidation of pyrite in the original sedimentary parent material, can be microbiologically transformed back to pyrite when the soils are flooded. Three basic ferric sulfates were tested and it was found that in the presence of lactate and Desulfovibrio desulfuricans, 10 g of each mineral were reduced within 12 wk to mackinawite (FeS). Additional incubation, to a total of 33 wk, resulted in no further sulfidation. However, in the presence of elemental sulfur, the sulfidation process resumed and mackinawite was soon transformed into greigite (Fe3S4) and then, following an aging process of increased temperature and pressure, pyrite (FeS2) was produced. Under simulated flooding conditions of sea water and decomposing seaweed, the sulfates were converted to a black X-ray amorphous sulfide which is known to change to mackinawite and/or greigite. The ability of H2S-oxidizing bacteria to form elemental sulfur in sedimentary pyrite-forming systems is reviewed and interpreted as a factor in producing the necessary sulfur. Basic aluminum sulfates were stable to microbial reduction. The X-ray pattern for ammoniojarosite was refined.

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