317 research outputs found
Thermal alteration of organic matter in recent marine sediments. 1: Pigments
Sediment from Tanner Basin, the outer continental shelf off Southern California, was analyzed for photosynthetic pigments and their derivatives, namely carotenes and chlorins. Samples of the sediment were also exposed to raised temperatures (65, 100, 150 C) for various periods of time (1 week, 1 month, 2 months). Analysis of the heat-treated sediment revealed the presence of alpha-ionene and 2,6-dimethylnapthalene, thermal degradation products of Betacarotente. Chlorins were converted to nickel porphyrins of both DPEP and etio series. Possible mechanisms of these transformations are presented
Approximation of Biodegradation Rate Constants for Monoaromatic Hydrocarbons (BTEX) in Ground Water
Two methods were used to approximate site-specific biodegradation rates of monoaromatic hydrocarbons (benzene, toluene, ethylbenzene, and xylenes [BTEX]) dissolved in ground water. Both use data from monitoring wells and hydrologic properties of the aquifer to estimate a biodegradation rate constant that can be sued in ground water solute fate and transport models. The first method uses a biologically recalcitrant tracer in the ground water, associated with the hydrocarbon plume to normalize changes in concentration of BTEX under anaerobic conditions; attenuation of the tracer is attributed to dilution, sorption, and/or volatilization. Attenuation of BTEX in excess of the attenuation of the tracer is attributed to biodegradation, although other processes may affect the observed rate. The second method assumes that the plume has evolved to a dynamic steady-state equilibrium. A one-dimensional analytical solution to the advection-dispersion equation is used to extract the rate of attenuation that would be necessary to produce a steady-state plume of the configuration found at the site. Attenuation is attributed largely to biodegradation because the analytical solution removes the effects of sorption and dispersion and volatilization is assumed to be minimal
Solar System Processes Underlying Planetary Formation, Geodynamics, and the Georeactor
Only three processes, operant during the formation of the Solar System, are
responsible for the diversity of matter in the Solar System and are directly
responsible for planetary internal-structures, including planetocentric nuclear
fission reactors, and for dynamical processes, including and especially,
geodynamics. These processes are: (i) Low-pressure, low-temperature
condensation from solar matter in the remote reaches of the Solar System or in
the interstellar medium; (ii) High-pressure, high-temperature condensation from
solar matter associated with planetary-formation by raining out from the
interiors of giant-gaseous protoplanets, and; (iii) Stripping of the primordial
volatile components from the inner portion of the Solar System by super-intense
solar wind associated with T-Tauri phase mass-ejections, presumably during the
thermonuclear ignition of the Sun. As described herein, these processes lead
logically, in a causally related manner, to a coherent vision of planetary
formation with profound implications including, but not limited to, (a) Earth
formation as a giant gaseous Jupiter-like planet with vast amounts of stored
energy of protoplanetary compression in its rock-plus-alloy kernel; (b) Removal
of approximately 300 Earth-masses of primordial gases from the Earth, which
began Earth's decompression process, making available the stored energy of
protoplanetary compression for driving geodynamic processes, which I have
described by the new whole-Earth decompression dynamics and which is
responsible for emplacing heat at the mantle-crust-interface at the base of the
crust through the process I have described, called mantle decompression
thermal-tsunami; and, (c)Uranium accumulations at the planetary centers capable
of self-sustained nuclear fission chain reactions.Comment: Invited paper for the Special Issue of Earth, Moon and Planets
entitled Neutrino Geophysics Added final corrections for publicatio
High resolution profile of inorganic aqueous geochemistry and key redox zones in an arsenic bearing aquifer in Cambodia
Arsenic contamination of groundwaters in South and Southeast Asia is a major threat to public health. In order to better understand the geochemical controls on the mobility of arsenic in a heavily arsenic-affected aquifer in northern Kandal Province, Cambodia, key changes in inorganic aqueous geochemistry have been monitored at high vertical and lateral resolution along dominant groundwater flow paths along two distinct transects. The two transects are characterized by differing geochemical, hydrological and lithological conditions. Arsenic concentrations in groundwater are highly heterogenous, and are broadly positively associated with iron and negatively associated with sulfate and dissolved oxygen. The observed correlations are generally consistent with arsenic mobilization by reductive-dissolution of iron (hydr)oxides. Key redox zones, as identified using groupings of the PHREEQC model equilibrium electron activity of major redox couples (notably ammonium/nitrite; ammonium/nitrate; nitrite/nitrate; dissolved oxygen/water) have been identified and vary with depth, site and season. Mineral saturation is also characterized. Seasonal changes in groundwater chemistry were observed in areas which were (i) sandy and of high permeability; (ii) in close proximity to rivers; and/or (iii) in close proximity to ponds. Such changes are attributed to monsoonal-driven surface-groundwater interactions and are consistent with the separate provenance of recharge sources as identified using stable isotope mixing models
Chapter 15 Magnetic Properties of Soils
Iron-containing minerals, i.e., magnetic minerals, constitute an intimate part of a soil. These can be derived from the parent rock from which the soil developed, or can be formed in situ, or can be deposited from the atmosphere, originating from natural or anthropogenic sources. Recently, measurement of the magnetic properties of soils have found an increased use in detecting pollution, as a substitute of more time-consuming chemical techniques. The current chapter provides a brief background of the basic concepts of magnetism in order to define the parameters that are used in studies of contamination of soils. A detailed discussion is provided about the various classes of magnetic materials together with the methods that are used to measure magnetic parameters. The effects of several factors such as the presence of iron oxides, mineralogy, and grain size on the magnetic parameters are discussed, as well as, the dependence of the soil magnetic susceptibility on parent lithology, climate, oxidation/reduction, organic matter, topography, sediment source, particle size, and time. The relation between soil contamination, by heavy metals and organic pollutants, and the magnetic properties of soils are detailed based on recent scientific findings. Finally, the function of magnetic bacteria in the presence of contaminants and their impact on natural soil remediation as well as the measurement of a soil\u27s magnetic properties is discussed
Baedeker's Northern France
It is based on personal acquaintance with the country described, a great part of which has been repeatedly explored with the view of assuring accuracy and freshness of information. A short account of the ordinary routes from London to Paris will be found in connection with the French seaports at which the passengers land.Northern France, from Belgium and the English channel to the Loire, excluding Paris and its environs : handbook for travelers
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