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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Adsorption 6 (2000), S. 93-104 
    ISSN: 1572-8757
    Schlagwort(e): adsorption refrigerator ; transient operation ; activated carbon ; methanol ; modeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Adsorption refrigerators are a particular type of refrigerator in which compression is avoided, and in a sense replaced by adsorption. No mobile parts are needed; the energy input, instead of being mechanical, is thermal and is used to achieve desorption. Such machines have a cyclic operation, made of successive adsorption/evaporation and of desorption/condensation steps. The transient operation of adsorption refrigerators is a relatively recent subject of research. The modeling of the adsorber is the key point of such studies, because of the complex coupled heat and mass transfer phenomena that occur during the cycle. The present work therefore presents a study of an annular type adsorber which is intended to account for transient temperatures observed experimentally. The equipment in which the experiments were performed and which uses alcohol adsorption on activated carbon is briefly described, and its operating cycle described, along with typical experimental observations of pressure and temperature transients. A model of the adsorber unit is proposed which accounts for the coupling of adsorption and heat transfer, and describes mass-transfer in the annular adsorbent layer as a global diffusional mechanism with temperature dependent parameters. This model correctly predicts, qualitatively and semi-quantitatively, the observed trends of the temperature changes. Finally, various aspects of the performances are discussed.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Plasma chemistry and plasma processing 20 (2000), S. 65-86 
    ISSN: 1572-8986
    Schlagwort(e): thermal plasma ; waste processing ; fly-ash vitrification ; optical emission spectroscopy ; volatilization ; lead ; modeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Results are presented of optical emission spectroscopy (OES) application asa control tool to improve fly-ash plasma vitrification. A twin-torch plasmasystem has been used for the fly-ash processing, and a new OES method hasexamined metallic vapors above the melt. The method allows the study ofnonhomogeneous optically thin plasmas exhibiting a symmetry plane withoutsophisticated tomographic systems. The dc arc torches are mounted above acold crucible filled with a synthetic glass. The arc intensity is from200 to 400 Å. Argon is introduced into the torches along the cathodeand the anode, while argon, oxygen or hydrogen are injected through thelance between the torches. Local plasma temperatures above the melt havebeen evaluated using measured relative intensities of spectral lines ofthe plasma-forming gas. Metallic vapor concentration in the plasma isdeduced from the intensity ratio of the metal–gas spectral lines. Leadoxide has been used to study heavy-metal behavior at the fly-ash plasmavitrification. Distribution of the lead along the crucible surface,depending on the plasma-forming gas composition as well as the concentrationevolution with time, have been examined. The elemental analysis of theresultant glass has been measured by scanning electron microscopy (SEM)with energy-dispersive spectrometry (EDS). A predictive model has beenadapted to simulate the noncongruent vaporization of heavy metals from themelt. According to the data obtained, steep variations of the volatility ofthe elements depend strongly on reducing properties of gases controllingthe plasma composition near the melted surface. In addition, the melttemperature and the redox potential of the gas phase are found to be themost critical parameters.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Plasma chemistry and plasma processing 20 (2000), S. 521-553 
    ISSN: 1572-8986
    Schlagwort(e): thermal plasma ; transferred arc ; fumed silica ; modeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract The volatilization of quartz in a transferred arc plasma followed byquench and recondensation is a promising route to the production offumed silica. In this work, an existing model of a transferred arcwas modified and combined with a newly developed model of a moltensilica anode to predict the behavior of a transferred arc evaporatoras a function of current and plasma gas flow rate. The model predictstemperature, current, and flow fields in both the plasma and anode aswell as evaporation rates. Although quantitative agreement withexperimental results was not possible because of insufficient propertydata for silica at high temperature, the results were within an orderof magnitude of those measured experimentally. The model developed isuseful for the design and scaleup of this type of reactor.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Transport in porous media 41 (2000), S. 105-116 
    ISSN: 1573-1634
    Schlagwort(e): flow ; integration ; Gassmann ; acoustics ; reservoir ; characterization ; modeling ; simulation ; Newton–Raphson
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract Integrated flow modeling is the combination of a traditional flow simulator with a petrophysical model. By combining a petrophysical model with a traditional flow model, it is possible to perform calculations that improve our ability to monitor fluid movement in porous media. This paper outlines the formulation of an integrated flow model IFLO and its multi-variable, Newton–Raphson IMPES solution procedure. The benefits of integrated flow modeling and the underlying principles involved in the integration of a flow model with a petrophysical model are presented. Results from the IFLO model are used to illustrate the principles.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Transport in porous media 38 (2000), S. 223-240 
    ISSN: 1573-1634
    Schlagwort(e): NAPLs ; radon ; modeling ; monitoring ; partitioning ; tracer ; emanation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract The recently developed natural radon tracer method has potential as a rapid, low‐cost, nondestructive, and noninvasive method for quantifying NAPL contamination. In the subsurface, radon‐222 (radon) is produced by the decay of naturally occurring radium‐226 contained in the mineral fraction of aquifer solids. In groundwater radon occurs as a dissolved gas, with a half‐life of 3.83 days. In the absence of NAPL, the radon concentration in groundwater quickly reaches a maximum value that is determined by the mineral composition of the aquifer solids, which controls the rate of radon emanation. In the presence of NAPL, however, the radon concentration in the groundwater is substantially reduced due to the preferential partitioning of radon into the organic NAPL phase. A simple equilibrium model and supporting laboratory studies show the reduction in radon concentration can be quantitatively correlated with residual NAPL saturation. Thus, by measuring the spatial distribution in radon it may be possible to identify locations where residual NAPL is present and to quantify the NAPL saturation. When the basic processes of partitioning, radon emanation from the aquifer solids, and first‐order decay are incorporated into an advective/dispersive transport model, good agreement is obtained with the results of laboratory and field experiments. Model sensitivity analyses shows many factors can contribute to the radon concentration response, including the length of the NAPL zone, NAPL saturation, groundwater velocity, porosity, and radon emanation. Thus, care must be taken when applying the radon method to locate and quantify NAPL contamination in the subsurface.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Transport in porous media 41 (2000), S. 47-60 
    ISSN: 1573-1634
    Schlagwort(e): unsaturated flow ; peat ; filters ; septic ; modeling ; hydraulics ; soil moisture retention curve
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract Peat is an alternative filter medium for the treatment of various waste streams including septic tank effluent. The water holding capacity and adsorption capacity of peat make it a favorable filter medium over sand or gravel which are commonly used as the filter medium for the drainage field of septic systems. This paper presents the results of a field study to evaluate the hydraulics of a peat filter used to treat the septic tank effluent from a public school west of Ottawa, Canada. An experimental box was placed within the filter during its construction to provide access to the vertical profile of the peat layer. The filter is periodically pulsed with septic tank effluent, which is distributed over the top of the filter and flows vertically through the peat. The filter was instrumented with tensiometers and transducers to monitor the pore water pressures in response to a pulse of septic tank effluent. An in-depth study of the hydraulics of the system was completed. The soil moisture retention curve and the hydraulic conductivity as a function of density were determined in laboratory experiments. A one-dimensional unsaturated flow model was used to predict the pressure response due to a pulse. A comparison of the field and model results illustrates the impact of the density variations, and the corresponding hydraulic conductivity variations, on the model predictions. The compaction of the peat is an important design consideration for the filter since it directly impacts the flow characteristics and the hydraulic retention time within the filter.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Water resources management 14 (2000), S. 257-283 
    ISSN: 1573-1650
    Schlagwort(e): decision-making ; ecosystem management ; ecosystem protection ; ecosystem restoration ; modeling ; sustainable development
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie
    Notizen: Abstract Ecosystem Management (EM) is a new holistic approach to the management of natural resources. It integrates the scientificknowledge on ecological interrelationships and the complex socioeconomic and political frame of values, aiming at the long-term sustainability of a region, i.e., the ecosystem. Itincludes the human, biological and natural dimensions, and canregulate the internal structures and functions of the ecosystem,and the inputs and outputs from it, so that solutions to development and protection problems can be achieved and be socially well-accepted. It has been given attention since 1991,mainly in the U.S.A., where the existing legal framework formeda basis for EM. The former experience of programs based on the traditional methods of management, the goal of sustainable development stated by many governmental, public or private agencies, and the advent of scientific knowledge, permitted the development of a theoretical basis for EM. Today, a significant number of EM programs have been established and are in progressin the U.S.A. Here the concept, general principles and methodology of EM are reviewed, and the EM program in the Stateof Florida in the U.S.A. is presented, which is considered a successful case study. In addition, the examples of managementof two very important ecosystems in Northern Greece are critically presented for comparison, in order to evaluate if they have EM characteristics.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Water quality and ecosystem modeling 1 (2000), S. 193-222 
    ISSN: 1573-1669
    Schlagwort(e): Sediment transport ; modeling ; Upper Hudson River
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Two-dimensional, vertically-averaged hydrodynamic and sediment transport models were developed and applied as part of a PCB fate and transport modeling study of Thompson Island Pool (TIP), Upper Hudson River. Mechanistic formulations were used to simulate cohesive and non-cohesive suspended load transport; site-specific data were extensively used to determine model inputs. This modeling approach is compared and contrasted to non-mechanistic solids transport sub-models used in other contaminant fate studies. A minimum number of model parameters were adjusted to calibrate the sediment transport model using data collected during the 1994 spring flood. The model was validated during the 1997 spring flood and for a 22-year (1977–1998) period. Successful calibration and validation of the model showed that: (1) deposition and resuspension processes were realistically and accurately formulated in the model; (2) the model is an effective diagnostic tool for quantitatively evaluating net deposition and erosion from various areas of TIP; and (3) sediment transport results can be coupled with a PCB fate model with a high degree of confidence.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Water quality and ecosystem modeling 1 (2000), S. 271-309 
    ISSN: 1573-1669
    Schlagwort(e): zebra mussels ; modeling ; water quality ; Seneca River ; dissolved oxygen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The development, testing and application of a dynamic two-dimensional (longitudinal-vertical) mass balance model for dissolved oxygen (DO) and chlorophyll (Chl) for rivers is documented that for the first time accommodates both the oxygen demand and filtering effects of zebra mussels. The test system is a phytoplankton-rich section (∼ 15 km long) of the Seneca River, NY, that is believed to represent an upper bound of the impact of this exotic invader. Changes in common measures of water quality of the river brought about by the zebra mussel invasion are reviewed and related longitudinal patterns in DO, Chl, and Secchi disc transparency are documented. Model testing is supported by comprehensive measurements of DO, Chl, and various forcing conditions over a three-month period, and independent determinations of several model coefficients. Wide variations in the areal consumption rate of DO (ZOD; g·m−2·d−1) and filtering rate (m3·m−2·d−1) of zebra mussels, as determined through model calibration, occurred over the study period. Values of ZOD in areas with dense zebra mussel populations at times (e.g., 〉 50 g·m−2·d−1) were an order of magnitude greater than the sediment oxygen demand associated with organically enriched deposits. The value of determinations of these fluxes from model calibration procedures is evaluated within the context of the limitations of protocols presently available to support independent specification of these rates. Model analyses are conducted to evaluate the relative magnitude of source and sink processes for DO and Chl, the potential operation and implications of feedback from low DO levels on oxygen consumption by zebra mussels, and the sensitivity of model simulations to selected sources of uncertainty and variability. Model projections of oxygen resources of the river are presented in a probabilistic format in evaluating reductions in zebra mussel biomass that would be necessary to eliminate violations of standards and regain assimilative capacity.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of computational neuroscience 8 (2000), S. 19-50 
    ISSN: 1573-6873
    Schlagwort(e): neural networks ; modeling ; population density ; orientation tuning ; visual cortex
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Medizin , Physik
    Notizen: Abstract We explore a computationally efficient method of simulating realistic networks of neurons introduced by Knight, Manin, and Sirovich (1996) in which integrate-and-fire neurons are grouped into large populations of similar neurons. For each population, we form a probability density that represents the distribution of neurons over all possible states. The populations are coupled via stochastic synapses in which the conductance of a neuron is modulated according to the firing rates of its presynaptic populations. The evolution equation for each of these probability densities is a partial differential-integral equation, which we solve numerically. Results obtained for several example networks are tested against conventional computations for groups of individual neurons. We apply this approach to modeling orientation tuning in the visual cortex. Our population density model is based on the recurrent feedback model of a hypercolumn in cat visual cortex of Somers et al. (1995). We simulate the response to oriented flashed bars. As in the Somers model, a weak orientation bias provided by feed-forward lateral geniculate input is transformed by intracortical circuitry into sharper orientation tuning that is independent of stimulus contrast. The population density approach appears to be a viable method for simulating large neural networks. Its computational efficiency overcomes some of the restrictions imposed by computation time in individual neuron simulations, allowing one to build more complex networks and to explore parameter space more easily. The method produces smooth rate functions with one pass of the stimulus and does not require signal averaging. At the same time, this model captures the dynamics of single-neuron activity that are missed in simple firing-rate models.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Mitigation and adaptation strategies for global change 5 (2000), S. 123-142 
    ISSN: 1573-1596
    Schlagwort(e): Kyoto Protocol ; GHG ; mitigation strategies ; economiccosts ; modeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Geographie
    Notizen: Abstract The Kyoto Protocol requires the U.S.to reduce the rate of emissions of six greenhousegases (GHG) to 93% of their 1990 rate and to achievethis target by the 2008 to 2012 commitment period. This study assesses the magnitude of change needed inthe U.S. economy and, specifically, in the U.S. energysector, to achieve and maintain the target establishedby the Kyoto Protocol. A simple carbon (C)emissions-energy model is explained in this analysisusing four key variables. Current and future trendsin C emissions are explained by: the carbon/energy(C/E) ratio, Gross Domestic Product growth, energyprices and an energy trend variable. Potential GHGmitigation policy actions affect C emissionsindirectly by affecting at least one of these keyvariables. The analysis concludes that reducingfossil energy use in the U.S. to meet the Kyoto GHGemissions reduction target would be very costly. Technological progress that reduces C emissions wouldnot be fully sufficient without prematurely abandoningproductive capital equipment. Energy price increasesof about 14% per year, or declines in economic growthof almost 5% per year, could reduce energy demand andassociated C emissions enough to achieve the terms ofthe Kyoto Protocol.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Earth, moon and planets 89 (2000), S. 135-160 
    ISSN: 1573-0794
    Schlagwort(e): C/1995 O1 (Hale-Bopp) ; 19P/Borrelly ; 46P/Wirtanen ; comets ; modeling ; nucleus ; observations ; rotation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract We review several techniques used to retrieve rotational parameters from observations. The spin period of a dozen of comets retrieved with these techniques are summarized. We describe how the spin period of comet Hale-Bopp (C/1995 O1) has been calculated with a high accuracy (11.30–11.34 h). Although several authors converged to a spin axis orientation at (α,δ) = (275 ± 15°, -55 ± 5°), detailed studies indicate that the dust jets morphology in 1996–1997 may be incompatible with this orientation. Comet 19P/Borrelly has been recently observed by the Deep Space 1 spacecraft. At the same time, its spin axis orientation and period have been determined by several authors to be respectively (α,δ) = (225 ± 15°, -10 ± 10°)and 26h. These two comets are likely to be in (or close to) a principal axis spin state. We discuss new modeling of the spin state of comet 46P/Wirtanen, the target of the Rosetta mission. The model involves a three-dimensional shape and thermal model, from which the torque of the non gravitational force is calculated at each time step. The moments of inertia are computed for each irregular shape. The results from numerical integrations show that this comet can remain in a principal axis spin state during more than 10 orbits if the spin period does not get above∼6 h. If the spin period increases, its nucleus gets rapidly into excited spin states. It shows that even small and very active short-period comets are not necessarily in non principal axis spin states. In the last section, the consequences of recent observations and modeling of the rotational parameters of comet nuclei are discussed, and unsolved problems are presented.
    Materialart: Digitale Medien
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  • 13
    ISSN: 1573-1839
    Schlagwort(e): virtual reality ; modeling ; constructionism ; astronomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Allgemeine Naturwissenschaft , Technik allgemein
    Notizen: Abstract In this manuscript we describe an introductory astronomy course for undergraduate students in which we moved from the large-lecture format to one in which students were immersed in a technologically-rich, inquiry-based, participatory learning environment. Specifically, undergraduate students used 3-D modeling tools to construct virtual reality models of the solar system, and in the process, build rich understandings of various astronomical phenomena. For this study, primarily naturalistic inquiry was used to gain a holistic view of this semester-long course. These data are presented as two case studies focusing on: (1) the role of the teacher in this participatory learning environment; (2) the particular dynamics that formed in each group; (3) the modeling process; (4) the resources used, specifically student-developed inscriptions; and (5) the role of technology and whether learning the technology interfered with learning astronomy. Results indicated that VR can be used effectively in regular undergraduate university courses as a tool through which students can develop rich understandings of various astronomical phenomena.
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  • 14
    ISSN: 1573-2959
    Schlagwort(e): modeling ; New York City ; risk assessment ; watershed monitoring
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The International Life SciencesInstitute (ILSI) Risk Science Institute (RSI) convenedan expert panel of scientists to developrecommendations for a comprehensive monitoring programfor the Croton and Catskill/Delaware watersheds, whichprovide drinking water to New York City's residents. This effort was conducted as part of efforts topreserve and enhance the quality of New York City'sreservoir system through a watershed protectionprogram. The panel developed recommendations for astrategic framework on which to construct a monitoringprogram. As part of this activity, the paneldetermined whether existing monitoring activities weredeficient and, where activities were deficient, thepanel developed recommendations for additionalinformation that should be collected.The panel recommended the development and use of anintegrated approach to watershed monitoring, whichdraws on modeling, risk-based planning and analysis,statistical sampling and design, and basic compliancemonitoring. The approach should be designed toprovide an assessment of natural and anthropogenicsources of stress to the system as well as anassessment of water quality trends in response tostresses acting in concert, both over the long termand over the five-year New York City Memorandum ofAgreement (MOA) assessment time frame. It should alsoprovide an assessment of the human health andenvironmental risks posed by a variety of stressors,and the impact of management actions implemented toameliorate stressors.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Water, air & soil pollution 120 (2000), S. 139-167 
    ISSN: 1573-2932
    Schlagwort(e): base saturation ; clay soils ; loess soils ; modeling ; nutrient uptake ; soil acidification ; weathering
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract To assess the impact of acid deposition on forestedloess and clay soils in the Netherlands, changes inbase saturation and soil solution concentrations weresimulated with the dynamic soil acidification modelReSAM for 38 loess soils and 16 clay soils. Theselected locations represent the range in geographicalposition and diversity in parent material occurring inforested loess and clay soils in the Netherlands. Twodeposition scenarios were used for the period1992–2050: a business as usual scenario (BAU) and ascenario in which deposition was reduced according topresent Dutch policy plans (MV-3). A comparison ofsimulated and measured soil solution concentrationsand base saturation in 1992/1993 showed that the modelsimulated concentrations and base saturation in theloess soils quite good. However, the model tended tooverestimate acidification in the top (0–10 cm) of theclay soils. Despite the reasonable agreement betweenmeasured and simulated data some uncertainty in thevalidity of the model predictions remains because timetrends to validate the model were not available. Themodel predicted a small but ongoing acidificationduring the BAU scenario in the loess soils asindicated by a decline in median base saturation andpH in the topsoil in 2050. Present policy plans (MV-3)lead to a slight recovery of the base saturation in2050 and a decline in Al concentrations. In the claysoils a strong decline in base saturation is simulatedin the topsoil, whereas an increase in base saturationis predicted for the subsoil.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Applied mathematics and mechanics 21 (2000), S. 19-26 
    ISSN: 1573-2754
    Schlagwort(e): structure ; optimization ; topology optimization ; modeling ; dual programming ; O223 ; TU323
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Mathematik , Physik
    Notizen: Abstract Topology optimization design of continuum structures that can take account of stress and displacement constraints simultaneously is difficult to solve at present. The main obstacle lies in that, the explicit function expressions between topological variables and stress or displacement constraints can not be obtained using homogenization method or variable density method. Furthermore, large quantities of design variables in the problem make it hard to deal with by the formal mathematical programming approach. In this paper, a smooth model of topology optimization for continuum structures is established which has weight objective considering stress and displacement constraints based on the independent-continuous topological variable concept and mapping transformation method proposed by Sui Yunkang and Yang Deqing. Moreover, the approximate, explicit expressions are given between topological variables and stress or displacement constraints. The problem is well solved by using dual programming approach, and the proposed element deletion criterion implements the inversion of topology variables from the discrete to the continuous. Numerical examples verify the validity of proposed method.
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  • 17
    ISSN: 1573-2932
    Schlagwort(e): adsorption ; arsenic ; chromium ; copper ; iron-oxide-coated sand ; modeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract The adsorption of copper, chromate, and arsenate (CCA)onto iron-oxide-coated sand (IOCS) was examined insingle-metal and mixed-metal systems. Copper andarsenate were strongly adsorbed or formed inner-spheresurface complexes with the IOCS surface while chromatewas weakly adsorbed or formed an outer-sphere surfacecomplex with the IOCS surface. Copper adsorption byIOCS slightly increased in the presence of arsenatebut was not affected by the presence of chromate. Arsenate adsorption was not affected by the presenceof copper and/or chromate. Chromate adsorptionincreased in the presence of copper by the combinationof electrostatic effects and possiblesurface-copper-chromate ternary complex formation. The presence of arsenate significantly decreasedchromate adsorption due to competition for adsorptionsites and electrostatic effects. Using inner-spheresurface complexation constants for copper and arsenateand outer-sphere surface complexation constants forchromate, the triple-layer model (TLM) was successfulin describing adsorption of copper, chromate, andarsenate in single-solute systems. The modelindicated that each metal uses a different number ofadsorption sites. For CCA metals-IOCS systems, theequilibrium constants determined from single-solutesystems were not able to predict adsorption frommulti-solute systems. The TLM does not currentlyaccount for the heterogeneity of oxide surface sitesand the formation of ternary complexes and/or solidphases that do not exist in single-solute systems.
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