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  • 1
    Publication Date: 2021-10-15
    Description: Cities are the drivers of socioeconomic innovation and are also forced to address the accelerating risk of failure in providing essential services such as water supply today and in the future. Here, we investigate the resilience of urban water supply security, which is defined in terms of the services that citizens receive. The resilience of services is determined by the availability and robustness of critical system elements or “capitals” (water resources, infrastructure, finances, management efficacy, and community adaptation). We translate quantitative information about this portfolio of capitals from seven contrasting cities on four continents into parameters of a coupled system dynamics model. Water services are disrupted by recurring stochastic shocks, and we simulate the dynamics of impact and recovery cycles. Resilience emerges under various constraints, expressed in terms of each city's capital portfolio. Systematic assessment of the parameter space produces the urban water resilience landscape, and we determine the position of each city along a continuous gradient from water insecure and nonresilient to secure and resilient systems. In several cities stochastic disturbance regimes challenge steady-state conditions and drive system collapse. While water insecure and nonresilient cities risk being pushed into a poverty trap, cities which have developed excess capitals risk being trapped in rigidity and crossing a tipping point from high to low services and collapse. Where public services are insufficient, community adaptation improves water security and resilience to varying degrees. Our results highlight the need for resilience thinking in the governance of urban water systems under global change pressures.
    Keywords: 333.9 ; systems dynamics modeling ; coupled natural-human-engineered systems (CNHES) ; adaptive capacity ; water management ; stochastic shocks ; Capital Portfolio Approach (CPA)
    Language: English
    Type: map
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Environmental science & technology 19 (1985), S. 975-979 
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 67 (1982), S. 35-43 
    ISSN: 1573-5036
    Keywords: Agro-ecosystems ; Mathematical models ; N-cycling ; Simulation modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Resumen Los modelos de simulación del comportamiento en agro-ecosistemas difieren en dos características: (i)entereza o minuciosidad conceptual, en términos del número de procesos que considera, y (ii)el nivel de detalle en el cual cada proceso es modelado. Estas características del modelo son determinadas por los objetivos para los cuales el modelo es diseñado y por el grado acutal del conocimiento de los procesos incluídos en el modelo. Los niveles de entereza conceptual y de detalle en un modelo determinan las aplicaciones potenciales para las cuales dicho modelo puede ser utilizado. Las aplicationes pueden ser orientadas a la investigación, manejo o planificación. Un modelo adecuado para una aplicación determinada debería tener un nivel apropiado de entereza y detalle para lograr el objetivo establecido. Los criterios de ayuda en la selección y evaluación de los modelos de simulación del nitrógeno para una aplicación particular incluyen: (i) la disponibilidad de facilidades computacionales, (ii) las escalas espacial y temporal de aplicación, (iii) el uso deseado de las simulaciones, (iv) la disponibilidad de datos de entrada al modelo, y (v) los ámbitos de confianza asociadas con las salidas del modelo.
    Notes: Abstract Available simulation models for describing nitrogen behavior in agro-ecosystems vary in two characteristics:(i) conceptual completeness in terms of the number of processes considered, and(ii) thelevel of detail at which each process is modeled. These model characteristics are determined by both the objectives that the model is designed to meet and the current state-of-the-art understanding of the various processes included in the model. The levels of conceptual completeness and detail in a model govern the potential applications for which the model may be used. Applications of models may be research-oriented, management-oriented, or planning-oriented. A model suitable for a given application should have an appropriate level of completeness and detail to accomplish the stated objective. Criteria to aid in the selection and evaluation of nitrogen simulation models for a particular application include: i) the availability of computational facilities, ii) the spatial and temporal scales of application, iii) the intended use of the simulations, iv) the availability of model input data, and v) the confidence regions associated with the model output.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 106 (1988), S. 159-169 
    ISSN: 1573-5036
    Keywords: allophane ; first-order kinetics ; mineralization ; nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrogen mineralization kinetics of Costa Rican soils developed from volcanic ash were investigated. Two aspects of the aerobic incubation method proposed by Stanford and Smith (1972) were examined: the addition of—N nutrient leaching solution, and air-drying samples prior to incubation. Net cumulative N mineralized over 210 days was analyzed in terms of three kinetic models of N mineralization: single term, first-order (FO); two term, first-order (DFO); and combined first-order, zero-order (FOZ). Net cumulative N mineralization was significantly increased both by air-drying and by—N nutrient solution addition. The effect of air-drying was to induce a ‘flush’ of mineralization during the first 30 to 45 days of incubation, while the effect of the—N nutrient solution was more apparent after that time. The 16 mineralization curves generated were qualitatively similar. The FO model provided the worst fit with the data and deviated from it in a consistent manner. Both the DFO and the FOZ models fit the data closely but the precision of parameter estimation using the DFO model was relatively poor. The first-order term of the FOZ model was interpreted as accounting for pretreatment effects (e.g., air-drying) and the zero-order term as describing the ‘basal mineralization rate’ of the soil. The success of the zero-order term in describing mineralization over long times suggests that incubation methods cannot be used to isolate a ‘mineralizable fraction’ of soil organic N.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 317 (1996), S. 31-40 
    ISSN: 1573-5117
    Keywords: benthic organism ; diffusion ; mixing ; sediments ; tritium ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Increased inputs of nutrients into the waters of Lake Okeechobee has raised concern that the lake is becoming hypereutrophic. One aspect in understanding the overall cycling and dynamics of the nutrients in the system is the effect of benthic organisms on solute transport. Various diffusional models have been used to approximate the effect of benthic organisms on solute transport within sediments using diffusion coefficient values which represent the pooled contributions of molecular diffusion (D s ) and enhanced solute mixing due to macrobenthos activity (D i ). The objective of this study was to investigate the impact of benthic activity on solute transport by measuringD s (i.e., no benthic activity) and an apparent-dispersion or mixing coefficientD m (i.e., with benthic activity) for the four major sediment types of Lake Okeechobee, Florida using a reservoir technique. This method involved monitoring the depletion of a conservative tracer (tritiated water) from the overlying water (reservoir) resulting from transport into sediments using disturbed sediments repacked in cores (3.2 cm diam.) and undisturbed cores (3.2 to 12 cm diam.) obtained from the lake. Additional estimates ofD m andD s were also obtained by measuring tracer concentration profiles in the sediment cores at the end of a specified diffusion period. Molecular diffusion coefficients (D s ) measured forrepacked cores of sand, littoral, mud and peat sediments ranged from 0.90 to 1.29 cm2 d−1, and estimates ofD s were slightly higher in undisturbed cores without benthic organisms.D m values for undisturbed cores of mud, sand and littoral sediments having macrobenthic populations ranged from 2.09 to 24.78 cm2 d−1; values that were 1.6 to 15 times higher than those in sediments without benthic activity. Undisturbed cores of varying diameter from mud sediments had similar estimates ofD m for tritium; however, the undisturbed cores with larger diameters from littoral sediments yielded larger estimates ofD m , reflecting the heterogeneity of benthic population densities and activity. Therefore,D s estimates may not adequately represent transport processes for mud, sand and littoral sediments of Lake Okeechobee; hence careful consideration should be given to the role of benthic organisms in the overall transport of solutes across the sediment-water interface.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 192 (1990), S. 279-279 
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 159 (1988), S. 177-188 
    ISSN: 1573-5117
    Keywords: eutrophic lake water ; nitrogen flux ; anaerobic sediment ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen flux from sediment of a shallow lake and subsequent utilization by water hyacinth (Eichhornia crassipes [Mart] Solms) present in the water column were evaluated using an outdoor microcosm sediment-water column. Sediment N was enriched with 15N to quantitatively determine the movement of NH4-N from the sediment to the overlying water column. During the first 30 days. 48% of the total N uptake by water hyacinth was derived from sediment 15NH4-N. This had decreased to 14% after 183 days. Mass balance of N indicates that about 25% sediment NH4-N was released into the overlying water, but only 17% was assimilated by water hyacinth. NH4-N levels in the water column were very low, with very little or no concentration gradients. NH4-N levels in the interstitial water of the sediment were in the range of 30–35 mg L−1 for the lower depths (〉 35 cm), while in the surface 5 cm of depth NH4-N levels decreased to 3.2 mg L−1. Simulated results also showed similar trends for the interstitial NH4-N concentration of the sediment. The overall estimated NH4-N flux from the sediment to the overlying water was 4.8 µg cm−2 day−1, and the soluble organic N flux was 5.8 µg N cm−2 day−1. Total N flux was 10.6 µg N cm−2 day−1.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic solutes ; Enthalpy and entropy changes ; Eluent composition effects ; Surface area effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chromatographic retention of several nonpolar solutes by three reversed-phase liquid chromatography (RPLC) supports was measured at several temperatures with binary mixtures of methanol/water and acetonitrile/water as the mobile phase. These data were used to estimate enthalpy and entropy changes (ΔH sorp o and ΔS sorp o ) associated with solute retention. The dependence of these two thermodynamic parameters on organic solvent content (θ) in the mobile phase, solute hydrophobic surface area (HSA), and bonded n-alkyl chain length (Nc) of the RPLC support was evaluated. The differences noted in the two solvent mixtures were attributed to: (1) the manner in which solvent surface tension changes with increasing θ, and (2) the differences in the interaction of methanol and acetonitrile with the bonded alkyl chains.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 1979-03-01
    Print ISSN: 0361-5995
    Electronic ISSN: 1435-0661
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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