Sediments equilibrium model

MacKenzie and Garrels equilibrium models. Most marine clays appear to be detrital and derived from the continents by river or atmospheric transport. Authigenic phases (formed in place) are found in marine sediments (e.g. Michalopoulos and Aller, 1995), however, they are nowhere near abundant enough to satisfy the requirements of the river balance. For example, Kastner (1974) calculated that less than 1% of the Na and 2% of the K transported by rivers is taken up by authigenic feldspars. 

Tipping E., 1994, WHAM - a chemical equilibrium model and computer code for waters, sediments and soils incorporating a discrete site/electrostatic model of ion-binding by humic substances. Computers and Geosciences 20,973-1023. 

The First-Order Kinetic Model. Karickhoff (1, 68) has proposed a two-compartment equilibrium-kinetic model for describing the solute uptake or release by a sediment. This model is based on the assumption that two types of sorption sites exist labile sites, S, which are in equilibrium with bulk aqueous solution, and hindered sites, Sjj, which are controlled by a slow first-order rate process. Conceptually, sorption according to this model can be considered either as a two-stage process ... 

It is not widely appreciated that the major aspects of core histone interactions were well understood even before the development of the nucleosome model. Evidence for strong H2A H2B dimer interactions and an FI3 H4 tetramer was available in the early seventies (see Ref. [1], Chapter 2). By 1978, the rigorous sedimentation equilibrium studies from Moudrianakis laboratory had elucidated the thermodynamics of octamer formation [7]. What was missing, of course, was any structural information concerning these interactions. This was overcome by arduous X-ray diffraction studies, culminating in the elegantly detailed structures we have today [15,17,18], see also Flarp et al., this volume, p. 13. We now know how the core... 

D. Two-box sediment/water model combined with three-phase equilibrium (Table 23.7) ... 

By comparing the actual composition of sea water (sediments + sea -f- air) with a model in which the pertinent components (minerals, volatiles) with which water has come into contact are allowed to reach true equilibrium, Sillen in 1959 epitomized the application of equilibrium models for portraying the prominent features of the chemical composition of this system. His analysis, for example, has indicated that contrary to the traditional view, the pH of the ocean is not buffered primarily by the carbonate system his results suggest that heterogeneous-equilibria of silicate minerals comprise the principal pH buffer systems in oceanic waters. This approach and its expansion have provided a more quantitative basis for Forchbammer s suggestion of 100 years ago that the quantity of the different elements in sea water is not proportional to the quantity of elements which river water pours into the sea but is inversely proportional to the facility with which the elements in sea water are made insoluble by general chemical actions in the sea. 

The equilibrium model allows certain inferences to be drawn concerning the geochemical environment which might have existed when sediments were formed, from knowledge of the thermodynamic properties of these sediments today. Thus, one can speculate about the evolution of the lithosphere, hydrosphere, and atmosphere, by assuming that equilibrium states were approached at various stages in geological history. 

Figure 1. The true system (right) of 1 liter of sea water with the corresponding 0.6 kg. sediments and 3 liters air. On the left, the equilibrium model with the same amounts of the various components at true equilibrium (with the exception of N2 (20)...

Figure 13 illustrates the use of sedimentation equilibrium analysis to assess, in a complementary manner to SEC (see Section 13.2.5.3, Figures 11 and 12), whether the oligomerization state of a model coiled coil was responsive to single amino acid substitutions at one a position along the amphipathic a-helical strands. 

Thomann, R.V., J.P. Connolly, and T.F. Parkerton. 1992. An equilibrium model of organic chemical accumulation in aquatic food webs with sediment interaction. Environ. Toxicol. Chem. 11 615-629. Thurston, R.V. and P.C. Gehrke. 1993. In Fish Physiology, Toxicology, and Water Quality management. Proceedings of an International Symposium, Sacramento, California, USA, September 18-20,1990. R.C. Russo and R.V. Thurston, Eds., p. 95. Environmental Research Laboratory Office of Research and Development. EPA, Athens, Georgia. EP/600/R-93/157. 

Table 11.2 Results of chemical equilibrium modelling of the contribution of ferrous iron phases to the proportion of iron (in %) extracted from an anoxic freshwater sediment from the Elbe River near Hamburg (Germany) by the first two acetate buffer steps of a modified Tessier sequential extraction scheme...

The fate and distribution of 4-nitrophenol in different environmental compartments were assessed with a nonsteady-state equilibrium model (Yoshida et al. 1983). The model predicted the following distribution air, 0.0006% water, 94.6% soil, 0.95% sediment, 4.44% and biota, 0.00009%. Therefore, only a very small fraction of this compound released from various sources is expected to... 

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