The chemistry of aqueous iron

Zusammenfassung Bei der Berechnung der L?slichkeiten des zwei-und des dreiwertigen Eisens müssen neben den Fe⁺² und Fe⁺³ Ionen auch die Eisen(II)- und Eisen(III)-Hydroxokomplexe ([Fe(OH)]⁺, [Fe(OH)]²⁺, [Fe(OH)₂]⁺, [Fe(OH)₃] (d), und [Fe(OH)₄]⁻) berücksichtigt werden. Die L?slichkeit des zweiwertigen Eisens in natürlichen (Bikarbonat enthaltenden) W?ssern ist in der Regel durch die L?slichkeitsgleichgewichte des Eisenkarbonats beschr?nkt, w?hrend die L?slichkeit des dreiwertigen Eisens durch die L?slichkeitsgleichgewichte des Eisen(III)-Hydroxyds bestimmt wird (Abbildungen 2 und 4). Die L?slichkeitsverh?ltnisse k?nnen durch Komplexbildung, vor allem mit organischen Basen, ver?ndert werden. Dreiwertiges Eisen hat eine viel st?rkere Tendenz, Hydroxokomplexe zu bilden, as zweiwertiges Eisen. Dementsprechend ist das hydratisierte Eisen-(III)-Ion eine so?rkere S?ure (im SinneBr?nsteds) als das Eisen-(II)-Ion. Die Oxydation von Eisen-(II) zu Eisen-(III) ist deshalb von einer Erniedrigung des pH-Wertes begleitet. Die Hydroxoeisen-(III)-Komplexe haben eine starke Tendenz, Polymerisationsreaktionen einzugehen, wobei im schwach sauren oder neutralen Bereich positiv geladene im alkalischen Bereich hingegen negative geladene Kolloidpartikel entstehen k?nnen. Die allf?llige Koagulation dieser Kolloide zu Eisenoxydhydrat ist vom Elektrolytgehalt abh?ngig und kann durch hydrophile organische Schutzkolloide verhindert werden. Zweiwertiges Eisen ist in Gegenwart von gel?stem Sauerstoff unbest?ndig und wird zu dreiwertigem Eisen oxydiert. Die Oxydationsgeschwindigkeit nimmt mit zunehmendem pH stark zu. Kupfer-, Platinsalze und Aktivkohle als Katalysatoren sowie Komplexbildner, welche mit dreiwertigem Eisen Komplexe bilden,beschleunigen die Autoxidation. Elektrodenpotential-pH-Diagramme (Abbildung 5) erm?glichen einen zusammenfassenden überblick über den Einfluss von Potential und pH auf die L?slichkeitsverh?ltnisse. Im Eisenkreislauf der Seen (Abbildung 7) kommt das Wechselspiel von Oxydation und Reduktion sowie von F?llung und L?sung eindrücklich zur Geltung.      

A simple direct interpretation method for an electrical sounding carried out over an inclined interface

Summary The potential field due to a point electrode, above an inclined interface, has been given in the form of a multiple integral, involving modified Bessel functions of the second kind (Skalskaya [9]²). From this formula it is only possible to derive formulae, from which type curves may be computed, for a limited number of cases. By considering the asymptotic expansion of the Hankel transform of this potential function, it is possible to derive results which will permit the complete interpretation of a Schlumberger sounding, carried out in the direction of strike; for an arbitrary angle of dip of the contact. The method of interpretation is suitable for use on a digital computer and has been found to give rapid and reliable results.     

Trace and platinum-group element geochemistry and the development of the Merensky unit of the Western Bushveld complex

Whole-rock samples of the Merensky Unit were analysed for major elements, Cu, Ni, Cr, Co, Eu, Th, U, Cs, and the platinum-group elements Pt, Pd, Rh, Ir and Au. There is a sympathetic variation of Cu, Ni, Co, and S throughout the sequence. Th and U abundances are highest around the Merensky Reef, and their distribution in the rest of the unit reflects the amount of mesostasis. Eu distribution is governed by primary plagioclase. Pt, Pd, Rh, Ir and Au (PM) are concentrated in the Merensky Reef. The relative proportions throughout the unit are Ir2 enrichment trends; interaction of these trends resulted in the Merensky Reef and its attendant mineralization.     

Conditional analysis for petroleum resource evaluations

Conditional analysis is an essential component for evaluation of petroleum resources. Such analysis attempts to answer the questions: for the input data and a given play potential, what is the most likely number of pools and their sizes? An example is provided to illustrate the usage and application of this conditional method of analysis. This example demonstrates that the method can be used as a feedback mechanism to challenge the underlying geological concepts of the play; and to yield more certain predictions if additional information is given. Consequently, the method will enhance the reliability of the estimates of petroleum resources.     

Evaluation of acid-producing sulfidic materials in Virginia highway corridors

Road construction through sulfidic materials in Virginia has resulted in localized acid rock drainage (ARD) that threatens water quality, sedimentation, integrity of building materials, and vegetation management. Geologic formations associated with acid roadcuts were characterized by potential peroxide acidity (PPA), expressed as calcium carbonate equivalence (CCE), and total sulfur (total-S) in order to develop a statewide sulfide hazard rating map. The geologic formations were grouped into four categories based on potential acid-producing severity: i) Tabb formation (PPA<6 Mg CCE/1000 Mg; S<0.2%); ii) Ashe formation (PPA<18 Mg CCE/1000 Mg; S<2.0%); iii) Chesapeake Group, Lower Tertiary deposits, Millboro shale, Marcellus shale, and Needmore Formation (PPA<60 Mg CCE/1000 Mg; S<2.6%), and; iv) Chattanooga shale and Quantico slate (PPA<99 Mg CCE/1000 Mg; S<3.9%). Sulfide hazard analysis should be an essential step in the pre-design phase of highway construction and other earth-disturbing activities.     

Pilot-scale field model tests for detecting landfill leachate intrusion into the subsurface using a grid-net electrical conductivity measurement system

The grid-net electrical conductivity measurement system for detecting exact locations of landfill leachate intrusion in the subsurface was developed in this study. Laboratory and pilot-scale field model tests were performed to evaluate the direct application of a grid-net electrical conductivity measurement system for the detection of landfill leachate. A significant increase in electrical conductivity of soil was observed by adding landfill leachate. This can be explained as an increase in electrical conductivity of pore fluid due to an increase in leachate constituents as charge carriers. In pilot-scale field model tests, leachate intrusion locations were accurately identified at the initial stage of landfill leachate release by the grid-net electrical conductivity measurement system. The electrical conductivity of the subsurface before leachate injection lay within a small range of 24.8–43.0 S/cm. The electrical conductivity values in detected points were approximately ten times more than the conductivity values of the subsurface without landfill leachate intrusion. The results in this study indicate that the grid-net electrical conductivity measurement method has a possible application for detecting locations of landfill leachate intrusion into the subsurface at the initial stage, and thus has great potential in monitoring leachate leakage at waste landfills.     

Use of an artificial neural network for analysis of the susceptibility to landslides at Boun,Korea

The purpose of this study was to develop landslide susceptibility analysis techniques using artificial neural networks and to apply the resulting techniques to the study area of Boun in Korea. Landslide locations were identified in the study area from interpretation of aerial photographs and field survey data. A spatial database of the topography, soil type, timber cover, geology, and land cover was constructed and the landslide-related factors were extracted from the spatial database. Using these factors, the susceptibility to landslides was analyzed by artificial neural network methods. The results of the landslide susceptibility maps were compared and verified using known landslide locations at another area, Yongin, in Korea. A Geographic Information System (GIS) was used to analyze efficiently the vast amount of data and an artificial neural network turned out to be an effective tool to analyze the landslide susceptibility.