Road Traffic and Avalanches – Methods for Risk Evaluation and Risk Management

This paper considers the methods for risk analysis and management in connection with avalanches and road traffic. Examples with calculations of encounter probability and quantification of uncertainty are given, along with suggestions for risk management in Norway.     

Oxygen-exchange pathways in aluminum polyoxocations

Using molecular dynamics simulations and electronic structure methods, we postulate a mechanism to explain the complicated reactivity trends that are observed for oxygen isotope exchange reactions between sites in aluminum polyoxocations of the ε-Keggin type and bulk solution. Experimentally, the molecules have four nonequivalent oxygens that differ considerably in reactivity both within a molecule, and between molecules in the series: Al₁₃, GaAl₁₂, and GeAl₁₂ [MO₄Al₁₂(OH)₂₄(H₂O)₁₂ⁿ⁺(aq); with M = Al(III) for Al₁₃, n = 7; M = Ga(III) for GaAl₁₂, n = 7; M = Ge(IV) for GeAl₁₂, n = 8]. We find that a partly dissociated, metastable intermediate molecule of expanded volume is necessary for exchange of both sets of μ₂-OH and that the steady-state concentration of this intermediate reflects the bond strengths between the central metal and the μ₄-O. Thus the central metal exerts extraordinary control over reactions at hydroxyl bridges, although these are three bonds away.This mechanism not only explains the reactivity trends for oxygen isotope exchange in μ₂-OH and η-OH₂ sites in the ε-Keggin aluminum molecules, but also explains the observation that the reactivities of minerals tend to reflect the presence of highly coordinated oxygens, such as the μ₄-O in boehmite, α-, and γ-Al₂O₃ and their Fe(III) analogs. The partial dissociation of these highly coordinated oxygens, coupled with simultaneous activation and displacement of neighboring metal centers, may be a fundamental process by which metals atoms undergo ligand exchanges at mineral surfaces.     

A new approach to interpreting Rock-Eval S2 and TOC data for kerogen quality assessment

A simple method for application in source potential mapping is used to assess the original oil and gas potentials in source rock horizons based upon Rock-Eval potential (S₂) and total organic carbon (TOC) values. The method assumes that kerogens consist of mixtures of end-members with assigned hydrogen index values. Based on suggested algorithms, the average amounts of oil-prone, gas-prone and inert organic material over source rock intervals are determined in TOC units. The method uses regression lines from plots of remaining hydrocarbon potentials (S₂) versus total organic carbon (TOC), and “quick-look” transparent overlays are used to read the appropriate kerogen mixture.Mineral matrix effects during pyrolysis, when strong, can cause erroneous results. This effect which occurs for oil-prone kerogens and adsorptive minerals can cause problems particularly for lean samples (S₂ = 0–3 mg HC/g rock) whilst the errors for richer samples are less.The method is applied on three sections of Upper Jurassic organic-rich rocks from the Danish North Sea sector, which are at different maturity stages. One of these sections is dominated by gas-prone material, one is dominated by oil-prone material and the third section contains a mixture of oil- and gas-prone material.The method has been compared with other methods that split kerogens in oil and gas generating potential and has given reasonable results.Experience using the method and a presented example suggest that sedimentological, system tract information may be derived from S₂ to TOC cross-plots. A constructed modelling example suggests that the end-member concept used in this approach may be used in forward type source rock prediction models when combined with sedimentological models. The resulting S₂–TOC plots can be used in order to check the forward modelling results against observed values.     

Molecular simulation of the magnetite-water interface

This paper reports molecular dynamics simulations of the magnetite (001)-water interface, both in pure water and in the presence of a 2.3 molal solution of NaClO₄. The simulations are carried out using a potential model designed to allow the protonation states of the surface functional groups to evolve dynamically through the molecular dynamics trajectory. The primary structural quantities investigated are the populations of the surface functional groups, the distribution of electrolyte in the solution, and the surface hydrogen bonding relationships. The surface protonation states are dominated by extensive hydrolysis of interfacial water molecules, giving rise to a dipolar surface dominated by FeOH2+-OH₂-OH⁻ arrangements. Triply coordinated, more deeply buried, surface sites are inert, probably due to the relative lack of solvent in their vicinity. The electrolyte distribution is oscillatory, arranging preferentially in layers defined by the solvating water molecules. The presence of electrolyte has a negligible effect on the protonation states of the surface functional groups. Steady-state behavior is obtained for the protonation states of the surface functional groups and hydrogen-bonding network. Although the overall structure of the electrolyte distribution is fairly well established, the electrolyte distribution has not fully equilibrated, as evidenced by the asymmetry in the distribution from the top to the bottom of the slab.     

Protecting the North-East Atlantic: enhancing synergies by institutional interplay

This article examines the interplay between three different international institutions on marine pollution in the North Sea and the wider North-East Atlantic: the International North Sea Conferences (INSC), the OSPAR-Convention and preceding conventions as well as the European Union (EU). It argues that interplay between these institutions have proved synergetic in two ways. First, the INSC-process has speeded up decision-making within OSPAR and the EU by means of leadership, change in membership and institutional arrangements. Second, OSPAR and the EU have subsequently facilitated domestic implementation of the North Sea Conference Declarations by means of higher authoritativeness and enforcement competence. These three institutions have fulfilled different functions all of which are needed to make international environmental cooperation effective.     

The allocation of scarce natural resources: The case of fisheries

This article addresses the question of allocation of living marine resources among countries. We examine the principles for distribution emanating from the global rules for ocean governance, review state practice, and consider some distributional effects of conservation measures. We find that it is difficult to ascertain the influence of the distribution principles with any greater degree of precision. The principles vary with regard to their ease of operationalization. Further, state practice shows that distributional principles serve to define the scope for a range of different distributional outcomes, but their relative importance remains elusive. Thus, distributional outcomes cannot be explained in terms of these principles alone. A measure of politics is always at play.     

Ab initio calculation of the carbon isotope signatures of amino acids

Carbon isotope compositions for the 20 standard amino acids are calculated using high-level molecular orbital and density functional theory methods. In agreement with measurements of the isotopic compositions of amino acids in a cyanobacterium [Macko, S.A., Fogel, M.L., Hare, P.E., Hoering, T.C., 1987. Isotope fractionation of nitrogen and carbon in the synthesis of amino acids by microorganisms. Chemical Geology 65, 79–92] the calculations give heavy signatures for aspartic acid + asparagine, serine, glutamine + glutamic acid and light signatures for leucine and isoleucine. The relative intramolecular enrichment of ¹³C in carboxyl groups is often much less than measured [Abelson, P.H., Hoering, T.C., 1961. Carbon isotope fractionation in formation of amino acids by photosynthetic organisms. Proceedings of the National Academy of Sciences, USA 47, 623–632]. Fractionations predicted from density functional calculations often differ by several per mil from those predicted from molecular orbital calculations.     

Speleothem preservation and diagenesis in South African hominin sites implications for paleoenvironments and geochronology

Plio‐Pleistocene speleothems from australopithecine‐bearing caves of South Africa have the potential to yield paleoenvironmental and geochronological information using isotope geochemistry. Prior to such studies it is important to assess the preservation of geochemical signals within the calcitic and aragonitic speleothems, given the tendency of aragonitic speleothems to recrystallize to calcite. This study documents the geochemical suitability of speleothems from the principal hominin‐bearing deposits of South Africa. We use petrography, together with stable isotope and trace element analysis, to identify the occurrence of primary aragonite, primary calcite, and secondary calcite. This study highlights the presence of diagenetic alteration at many of the sites, often observed as interbedded primary and secondary fabrics. Trace element and stable isotopic values distinguish primary calcite from secondary calcite and offer insights into geochemical aspects of the past cave environment. δ¹³C values of the primary and secondary calcites range from +6 to −9‰ and δ¹⁸O values range from −4 to −6‰. The data are thus typical of meteoric calcites with highly variable δ¹³C and relatively invariant δ¹⁸O. High carbon isotope values in these deposits are associated with the effects of recrystallization and rapid outgassing of CO₂ during precipitation. Mg/Ca and Sr/Ca ratios differ between primary and secondary calcite speleothems, aiding their identification. Carbon and oxygen isotope values in primary calcite reflect the proportion of C₃ and C₄ vegetation in the local environment and the oxygen isotope composition of rainfall. Primary calcite speleothems preserve the pristine geochemical signals vital for ongoing paleoenvironmental and geochronological research. © 2009 Wiley Periodicals, Inc.     

A large wet snow avalanche cycle in West Greenland quantified using remote sensing and in situ observations

Natural Hazards - On 11 April 2016 we observed high slushflow and wet snow avalanche activity at the environmental monitoring station Kobbefjord in W-Greenland. Snow avalanches released as a result...