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Open accessJournal ArticleDOI: 10.1080/00206814.2020.1716400

Geochemistry of fluids discharged from mud volcanoes in SE Caspian Sea (Gorgan Plain, Iran)

04 Mar 2021-International Geology Review (Taylor & Francis)-Vol. 63, Iss: 4, pp 437-452
Abstract: A geochemical study was carried out on gas, water and mud samples from four mud volcanoes in Gorgan Plain, SE Caspian Sea (Iran) in order to investigate fluid primary sources and secondary processe...

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Topics: Mud volcano (70%)
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Open accessJournal Article
Abstract: According to WHO, the permissible limit of arsenic till 1993 was 0.05 mg. /L of drinking water. In 1993, WHO modified the maximum level and brought it down to 0.01 mg./L. According to the report of School of Environment Studies of Jadavpur University (1992-1993), West Bengal has 6 districts, affected by arsenic contamination of ground water. The present paper attempts to find out the vulnerability and impact of arsenic on human being. A detailed survey was conducted at Dahapara village of Murshidabad district to assess the present condition of the area giving emphasis on the identification of sources of arsenic pollution.

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367 Citations


Open accessBook
01 Jan 2014-
Abstract: Introduction.- The First Vertebrates, Jawless Fishes, the Agnathans.- The Earliest Jawed Vertebrates, the Gnathostomes.- Evolution of Modern Fishes: Critical Biological Innovations.- Tetrapods and the Invasion of Land.- Crucial Vertebrate Innovations.- The Dinosaur Integument.- Mammal-like Reptiles.- Reptiles Return to the Sea.

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Topics: Vertebrate (62%)

298 Citations



Journal ArticleDOI: 10.1016/J.CAGEO.2020.104595
John E. Snodgrass1, Alexei V. Milkov1Institutions (1)
Abstract: Investigations on the origin of natural gases traditionally involve manual plotting of values for various geochemical parameters on binary gas genetic diagrams and the comparison of these values with empirically defined gas genetic fields. However, these fields considerably overlap, and the accuracy and uncertainty on the derived origin are not quantified. To overcome these issues, we developed a web-based tool powered by a machine learning model that determines the origin of natural gases. The utilized large global dataset of natural gases (27,852 samples) includes 10,937 samples which we manually interpreted and labeled with one of the five gas origins (thermogenic, primary microbial from CO2 reduction, primary microbial from methyl-type fermentation, secondary microbial, and abiotic). The supervised machine learning model uses random forest algorithm to classify natural gas samples based on four features (geochemical parameters CH4/(C2H6+C3H8), δ13C–CH4, δ2H–CH4 and δ13C–CO2). The model determines the origin of gases in samples with unknown origin accompanied by model accuracy and the confidence score for each possible origin. The model is deployed on the website www.gasorigin.com with a simple user-friendly interface. The incorporation of more data, geochemical parameters (model features) and determination of post-generation processes are the subjects of future developments.

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8 Citations



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Open accessBook
01 Jun 1989-
Abstract: The chemical composition of natural water is derived from many different sources of solutes, including gases and aerosols from the atmosphere, weathering and erosion of rocks and soil, solution or precipitation reactions occurring below the land surface, and cultural effects resulting from human activities. Broad interrelationships among these processes and their effects can be discerned by application of principles of chemical thermodynamics. Some of the processes of solution or precipitation of minerals can be closely evaluated by means of principles of chemical equilibrium, including the law of mass action and the Nernst equation. Other processes are irreversible and require consideration of reaction mechanisms and rates. The chemical composition of the crustal rocks of the Earth and the composition of the ocean and the atmosphere are significant in evaluating sources of solutes in natural freshwater. The ways in which solutes are taken up or precipitated and the amounts present in solution are influenced by many environmental factors, especially climate, structure and position of rock strata, and biochemical effects associated with life cycles of plants and animals, both microscopic and macroscopic. Taken together and in application with the further influence of the general circulation of all water in the hydrologic cycle, the chemical principles and environmental factors form a basis for the developing science of natural-water chemistry. Fundamental data used in the determination of water quality are obtained by the chemical analysis of water samples in the laboratory or onsite sensing of chemical properties in the field. Sampling is complicated by changes in the composition of moving water and by the effects of particulate suspended material. Some constituents are unstable and require onsite determination or sample preservation. Most of the constituents determined are reported in gravimetric units, usually milligrams per liter or milliequivalents

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6,062 Citations


Journal ArticleDOI: 10.1016/S0009-2541(99)00092-3
Michael J. Whiticar1Institutions (1)
30 Sep 1999-Chemical Geology
Abstract: The diagenetic cycling of carbon within recent unconsolidated sediments and soils generally can be followed more effectively by discerning changes in the dissolved constituents of the interstitial fluids, rather than by monitoring changes in the bulk or solid organic components. The major dissolved carbon species in diagenetic settings are represented by the two carbon redox end-members CH4 and CO2. Bacterial uptake by methanogens of either CO2 or “preformed” reduced carbon substrates such as acetate, methanol or methylated amines can be tracked with the aid of carbon ( 13 C / 12 C ) and hydrogen ( D/H≡ 2 H/ 1 H ) isotopes. The bacterial reduction of CO2 to CH4 is associated with a kinetic isotope effect (KIE) for carbon which discriminates against 13 C . This leads to carbon isotope separation between CO2 and CH4 (eC) exceeding 95 and gives rise to δ 13 C CH 4 values as negative as −110‰ vs. PDB. The carbon KIE associated with fermentation of methylated substrates is lower (eC is ca. 40 to 60, with δ 13 C CH 4 values of −50‰ to −60‰). Hydrogen isotope effects during methanogenesis of methylated substrates can lead to deuterium depletions as large as δ D CH 4 =−531‰ vs. SMOW, whereas, bacterial D/H discrimination for the CO2-reduction pathway is significantly less (δDCH4 ca. −170‰ to −250‰). These field observations have been confirmed by culture experiments with labeled isotopes, although hydrogen isotope exchange and other factors may influence the hydrogen distributions. Bacterial consumption of CH4, both aerobic and anaerobic, is also associated with KIEs for C and H isotopes that enrich the residual CH4 in the heavier isotopes. Carbon fractionation factors related to CH4 oxidation are generally less than eC=10, although values >20 are known. The KIE for hydrogen (eH) during aerobic and anaerobic CH4 oxidation is between 95 and 285. The differences in C and H isotope ratios of CH4, in combination with the isotope ratios of the coexisting H2O and CO2 pairs, differentiate the various bacterial CH4 generation and consumption pathways, and elucidate the cycling of labile sedimentary carbon.

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Topics: Isotopes of carbon (59%), Carbon (55%), Acetate fermentation (53%) ... show more

2,273 Citations


Journal ArticleDOI: 10.1139/E81-019
Abstract: Maps of the paleography of Iran are presented to summarize and review the geological evolution of the Iranian region since late Precambrian time On the basis of the data presented in this way reconstructions of the region have been prepared that take account of the known major movements of continental masses These reconstructions, which appear at the beginning of the paper, show some striking features, many of which were poorly appreciated previously in the evolution of the region They include the closing of the 'Hercynian Ocean' by the northward motion of the Central Iranian continental fragment(s), the apparently simultaneous opening of a new ocean ('the High-Zagros Alpine Ocean') south of Iran, and the formation of 'small rift zones of oceanic character' together with the attenuation of continental crust in Central IranWith the disappearance of the Hercynian Ocean, the floor of the High-Zagros Alpine Ocean started to subduct beneath southern Central Iran and apparently disappeared by Late Cretaceou

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Topics: Continental crust (53%), Continental fragment (53%)

2,078 Citations


Journal ArticleDOI: 10.1038/NATURE02134
Ian M. Head1, D. Martin Jones1, Steve Larter1Institutions (1)
20 Nov 2003-Nature
Abstract: At temperatures up to about 80 °C, petroleum in subsurface reservoirs is often biologically degraded, over geological timescales, by microorganisms that destroy hydrocarbons and other components to produce altered, denser 'heavy oils'. This temperature threshold for hydrocarbon biodegradation might represent the maximum temperature boundary for life in the deep nutrient-depleted Earth. Most of the world's oil was biodegraded under anaerobic conditions, with methane, a valuable commodity, often being a major by-product, which suggests alternative approaches to recovering the world's vast heavy oil resource that otherwise will remain largely unproduced.

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Topics: Petroleum (55%)

1,023 Citations


Reference BookDOI: 10.1007/978-3-540-77587-4
01 Jan 2010-
Abstract: VOLUME 1: HYDROCARBONS, OILS AND LIPIDS: DIVERSITY, PROPERTIES AND FORMATION Part 1 Diversity and Physico-Chemical Characteristics, Part 2 Formation and Location, Part 3 Transfer from the Geosphere to Biosphere, Part 4 Environmental Chemistry, Part 5 Biochemistry of Biogenesis, Part 6 Genetics of Biogenesis , Part 7 The Microbes (Section Editor: Terry Mcgenity), Part 8 Methanogenic Communities VOLUME 2: MICROBIAL UTILIZATION OF HYDROCARBONS, OILS AND LIPIDS Part 1 Introduction: Theoretical Considerations, Part 2 Biochemistry of Aerobic Degradation , Part 3 Biochemistry of Anaerobic Degradation, P art 4 Enzymology , Part 5 Genetics (the Paradigms) (Section Editor: Victor De Lorenzo), Part 6 Functional Genomics (the Paradigms) (Section Editor: Victor De Lorenzo), Part 7 Cellular Ecophysiology: Problems of Hydrophobicity, Bioavailability , Part 8 Cellular Ecophysiology: Uptake, Part 9 Cellular Ecophysiology: Problems of Solventogenicity, Solvent Tolerance, Part 10 Cellular Ecophysiology: Problems of Feast or Famine VOLUME 3: MICOBES AND COMMUNITIES UTILIZING HYDROCARBONS, OILS AND LIPIDS Part 1 The Microbes (Section Editor: Terry Mcgenity), Part 2 Microbes Utilizing Non-Hydrocarbon Components of Fossil Fuels, Part 3 Microbial Communities Based on Hydrocarbons, Oils and Fats: Natural Habitats, Part 4 Microbial Communities Based on Hydrocarbons, Oils and Fats: Anthropogenically-Created Habitats VOLUME 4: CONSEQUENCES OF MICROBIAL INTERACTIONS WITH HYDROCARBONS, OILS AND LIPIDS Part 1 Introduction , Part 2 Applications: Organics Degradation, Part 3 Applications: Biomonitoring, Part 4 Applications: Fuel Production , Part 5 Applications: Chemicals Production, Part 6 Global Consequences of the Consumption and Production of Hydrocarbons, Part 7 Human-Animal-Plant Health and Physiology Consequences of Microbial Interactions with Hydrocarbons and Lipids , Part 8 The Future VOLUME 5: EXPERIMENTAL PROTOCOLS AND APPENDICES Part 1 Study Systems (Section Editor: Jan Roelof Van Der Meer), Part 2 Analytical Procedures (Section Editor: Jan Roelof Van Der Meer), Part 3 Microbiology and Community Procedures (Section Editor: Jan Roelof Van Der Meer), Part 4 Biochemical Procedures (Section Editor: Jan Roelof Van Der Meer), Part 5 Genetic and System Procedures (Section Editor: Jan Roelof Van Der Meer), Part 6 Application Procedures (Section Editor: Jan Roelof Van Der Meer), Part 7 Appendices

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1,016 Citations


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20214
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20141
19951
19901