Changes in portlandite morphology with solvent composition: Atomistic simulations and experiment

The second edition of The Biomarker Guide is a fully updated and expanded version of this essential reference. Now in two volumes, it provides a comprehensive account of the role that biomarker technology plays both in petroleum exploration and in understanding Earth history and processes. Biomarkers and Isotopes in the Environment and Human History details the origins of biomarkers and introduces basic chemical principles relevant to their study. It discusses analytical techniques, and applications of biomarkers to environmental and archaeological problems. The Biomarker Guide is an invaluable resource for geologists, petroleum geochemists, biogeochemists, environmental scientists and archaeologists.

The Biomarker Guide

Electromagnetically induced transparency1,2,3 is a quantum interference effect that permits the propagation of light through an otherwise opaque atomic medium; a ‘coupling’ laser is used to create the interference necessary to allow the transmission of resonant pulses from a ‘probe’ laser. This technique has been used4,5,6 to slow and spatially compress light pulses by seven orders of magnitude, resulting in their complete localization and containment within an atomic cloud4. Here we use electromagnetically induced transparency to bring laser pulses to a complete stop in a magnetically trapped, cold cloud of sodium atoms. Within the spatially localized pulse region, the atoms are in a superposition state determined by the amplitudes and phases of the coupling and probe laser fields. Upon sudden turn-off of the coupling laser, the compressed probe pulse is effectively stopped; coherent information initially contained in the laser fields is ‘frozen’ in the atomic medium for up to 1 ms. The coupling laser is turned back on at a later time and the probe pulse is regenerated: the stored coherence is read out and transferred back into the radiation field. We present a theoretical model that reveals that the system is self-adjusting to minimize dissipative loss during the ‘read’ and ‘write’ operations. We anticipate applications of this phenomenon for quantum information processing.

Observation of coherent optical information storage in an atomic medium using halted light pulses

Hydrothermal technologies are broadly defined as chemical and physical transformations in high-temperature (200–600 °C), high-pressure (5–40 MPa) liquid or supercritical water. This thermochemical means of reforming biomass may have energetic advantages, since, when water is heated at high pressures a phase change to steam is avoided which avoids large enthalpic energy penalties. Biological chemicals undergo a range of reactions, including dehydration and decarboxylation reactions, which are influenced by the temperature, pressure, concentration, and presence of homogeneous or heterogeneous catalysts. Several biomass hydrothermal conversion processes are in development or demonstration. Liquefaction processes are generally lower temperature (200–400 °C) reactions which produce liquid products, often called “bio-oil” or “bio-crude”. Gasification processes generally take place at higher temperatures (400–700 °C) and can produce methane or hydrogen gases in high yields.

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Thermochemical biofuel production in hydrothermal media: A review of sub- and supercritical water technologies

The rapid increase of carbon dioxide concentration in Earth’s modern atmosphere is a matter of major concern. But for the atmosphere of roughly two-and-half billion years ago, interest centres on a different gas: free oxygen (O2) spawned by early biological production. The initial increase of O2 in the atmosphere, its delayed build-up in the ocean, its increase to near-modern levels in the sea and air two billion years later, and its cause-and-effect relationship with life are among the most compelling stories in Earth’s history.

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The rise of oxygen in Earth’s early ocean and atmosphere

CO 2 reduction processes occurring during experimental serpentinization of olivine at 300 °C and 500 bar confirm that ultramafic rocks can play an important role in the generation of abiogenic hydrocarbon gas. Data reveal that conversion of Fe(II) in olivine to Fe(III) in magnetite during serpentinization leads to production of H 2 and conversion of dissolved CO 2 to reduced-C species including methane, ethane, propane, and an amorphous carbonaceous phase. Hydrocarbon gases generated in the process fit a Schulz-Flory distribution consistent with catalysis by mineral reactants or products. Magnetite is inferred to be the catalyst for methanization during serpentinization, because it has been previously shown to accelerate Fischer-Tropsch synthesis of methane in industrial applications involving mixtures of H 2 and CO 2 . The carbonaceous phase was predominantly aliphatic, but had a significant aromatic component. Although this phase should ultimately be converted to hydrocarbon gases and graphite, if full thermodynamic equilibrium were established, its formation in these experiments indicates that the pathway for reduction of CO 2 during serpentinization processes is complex and involves a series of metastable intermediates.

Reduction of CO2 during serpentinization of olivine at 300 °C and 500 bar

Hydrothermal alteration of basalt by seawater under seawater-dominated conditions

Low temperature basalt alteration by sea water: an experimental study at 70°C and 150°C

Alteration of the oceanic crust: Implications for geochemical cycles of lithium and boron

Progressive heating of seawater to 350 degrees C causes it to become increasingly acid and depleted in Ca, Mg, and SO4, because anhydrite and a previously undescribed magnesium oxysulfate are precipitated. Observed composition changes and calculation of activities of dissolved species reveal a progressive increase of HSO4-, HCl, and MgOH+ and decrease of HCO3-, C03-, and CaHCO3+ at temperatures above 150 degrees C. The pH at experimental conditions drops to 3.3, while the buffer capacity of seawater increases from 0.24 meq/pH at 25 degrees C to 54 meq/pH at 350 degrees C. Theoretical solubilities of brucite, anhydrite, magnesite, dolomite, and calcite were compared to ion-activity products. Comparison of solution composition with theoretical solubilities indicates that carbonate minerals were supersaturated with increasing temperature. The solution composition indicates equilibrium saturation with anhydrite at temperatures of 150 degrees C.

William E. Seyfried

Papers

Reduction of CO2 during serpentinization of olivine at 300 °C and 500 bar

Hydrothermal alteration of basalt by seawater under seawater-dominated conditions

Low temperature basalt alteration by sea water: an experimental study at 70°C and 150°C

Alteration of the oceanic crust: Implications for geochemical cycles of lithium and boron

Hydrothermal chemistry of seawater from 25 degrees to 350 degrees C