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  • 1
    Electronic Resource
    Electronic Resource
    Response of lakes to the reduction of phosphorus load (1991)
    Springer
    Aquatic ecology 24 (1991), S. 165-170 
    Details
    ISSN: 1573-5125
    Keywords: eutrophication ; nutrient loading ; individual lakes ; management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract On occasion of the publication of a book (H. SAS, ed.) a discussion of the predictability of the response of eutrofied lakes on a reduced external phosphorus loading is presented. Whereas the OECD study examines the correlations between nutrient loading and indicators for eutrofication for groups of lakes, the book discusses the direction of the response on reduction of the phosphorus loading for individual lakes. Although this is a valuable analysis that can increase the insight in the mechanisms controlling lake responses, neither the OECD study nor this book yield sufficiently unquestioned data that can be used directly in a a management framework. The relationships between loading and inlake concentration and between phosphate concentration and chlorophyll are discussed in some detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02260434
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Iron content of sediment and phosphate adsorption properties (1993)
    Springer
    Hydrobiologia 253 (1993), S. 311-317 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; sediment ; iron ; aluminum ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphorus can occur in sediments in different forms and accordingly its availability varies. The distinction between the phosphorus fractions is made with two chemical extraction methods; an ammonium oxalate-oxalic acid extraction and an extraction according to Hieltjes & Lijklema (1980). The iron and aluminum liberated with the ammonium oxalate-oxalic acid extraction method is linearly correlated (r 2 = 0.73) with the phosphorus liberated in the first two steps of the Hieltjes and Lijklema extraction by: P = 0.035 (Fe + Al) + 0.001 (P, Fe and Al in mmol g−1). The iron and aluminum (hydr)oxides are very important fractions in the sediment adsorption capacity for phosphorus. The phosphorus sorption capacity (PSC) is 0.080 mol P (mol (Fe + Al))−1 and the adsorption constant (k) is 11.9 µmol P l−1. Here it is assumed that iron and aluminum (hydr)oxide have the same affinity for phosphorus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00050751
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Modelling sediment transport in shallow lakes — interactions between sediment transport and sediment composition (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 153-166 
    Details
    ISSN: 1573-5117
    Keywords: Resuspension ; sedimentation ; sediment transport ; shallow lakes ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In shallow, wind exposed lakes, the light conditions, the cycling of nutrients, heavy metals and organic micro-pollutants and changes in the local composition of the sediment top layer can be dominated by resuspension/erosion of bottom sediment and sedimentation of suspended solids. A 2 dimensional model for Sediment Transport, Resuspension and Sedimentation in Shallow lakes (STRESS-2d), based on an existing transport model, is discussed. In the model, mass balance equations for the water compartment and the bottom sediment are solved numerically. Up to 7 sediment fractions can be taken into account, each having a specific set of resuspension/erosion and sedimentation parameter values. Several options for modelling the changes in the bottom sediment composition are available. A simulation experiment for Lake Veluwe (The Netherlands), in which model options with and without the distinction of sediment fractions were used, showed that using sediment fractions to account for the variability in the sediment composition leads to an improvement of the model results, particularly the simulated phosphorus sediment-water exchange fluxes. For Lake Ketel (The Netherlands) two options for modelling changes in the bottom sediment composition are compared. It is shown that an option in which a thin water-sediment layer on top of the more consolidated bottom sediment is simulated provides an improvement in the simulation of the suspended solids concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026208
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Sorption of phosphate by sediments as a result of enhanced external loading (1993)
    Springer
    Hydrobiologia 253 (1993), S. 249-261 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; sediments ; adsorption ; dispersion ; solid-phase diffusion ; Al-hydroxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In artificial test ditches, originally poor in nutrients, the effects of enhanced external loading with phosphorus were studied. An important term in the mass balance of phosphorus is retention by sediment. Parameters concerning the uptake of phosphorus by the sandy sediment of a ditch have been measured or were obtained from curve-fitting and were used in a mathematical model to describe diffusion into the sediment and subsequent sorption by soil particles. On a time scale of hours uptake of phosphorus from the overlying water by intact sediment cores could be simulated well with a simple diffusion-adsorption model. Mixing of the overlying water resulted in an enhanced uptake rate caused by an increased effective diffusion coefficient in the top layer of the sediment. Laboratory experiments revealed that after a fast initial adsorption, a slow uptake process followed that continued for a period of at least several months. This slow sorption can immobilize a substantial part of the phosphorus added. It may physically be described as an intraparticular diffusion process, in which the adsorbed phosphate penetrates into metaloxides, probably present as sand grain coating, and thereby reaches sorption sites not immediately accessible otherwise. The total sorption capacity of the soil particles is ca. 3.3 times the maximum instantaneous surficial adsorption capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00050746
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  • 5
    Electronic Resource
    Electronic Resource
    Nutrient dynamics in shallow lakes: effects of changes in loading and role of sediment-water interactions (1994)
    Springer
    Hydrobiologia 275-276 (1994), S. 335-348 
    Details
    ISSN: 1573-5117
    Keywords: nutrients ; loading ; load reduction ; lakes ; productivity ; resilience ; nutrient pools ; sinks ; limiting nutrient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The transport and cycling of nutrients through the various pools in water, soil and sediment is controlling the long term and short term productivity of water bodies. An understanding of the size of these pools and the fluxes between them is essential for the assessment of the usefulness of management measures resulting in reduced external input and the anticipated resilience of the system towards changes in trophic character. Large pools, such as phosphorus in surficial sediments and nitrate in groundwater have a potential for prolonged stimulation of productivity. Diffuse sources, fluxes towards sinks, competition between biota and adsorbents for sparse nutrients, feedback mechanisms, non-linearities and shifts among prevailing processes are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026724
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Considerations in modeling the sediment-water exchange of phosphorus (1993)
    Springer
    Hydrobiologia 253 (1993), S. 219-231 
    Details
    ISSN: 1573-5117
    Keywords: sediment ; water ; phosphorus ; models ; temporal scales ; spatial scales
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The potential to release accumulated phosphorus from sediments has been the major motive to study and to model the fate of this nutrient in sediments. For the dynamics of the sediment-water interaction the sizes of the pools involved and the rates of conversion/transport from one pool to another are of primary interest. As the sediment pools for phosphate are generally much larger than the pools in the water column, a rather slow adjustment of the sediment to management measures will occur. For the analysis of management measures it is obvious that the gradual change in sediment composition must be taken into account. Only for rather short periods the sediment composition can be assumed to be constant; this may be appropriate for studies of e.g. the annual cycle. The sediment-water interaction is a complex resultant of physical, chemical and biological processes, including: physical processes: advection due to seepage or consolidation, pore-water diffusion, transport and mixing of solids by resuspension, sedimentation and bioturbation. chemical processes: adsorption and desorption, dissolution and (co)precipitation, inclusion. biological processes: mineralization of a wide range of organic compounds by various (micro)organisms, each with their own nutrient requirements and electron acceptors. Aspects which are discussed and need to be considered in application of a model in research or management are the level of aggregation and detail that is required and may still be practical, the spatial and temporal scales which are applicable for the processes mentioned and their influence upon the numerical dispersion and model stability, the availability of data for calibration/validation and the resolution of the analytical techniques. These aspects are not independent however. Frequently models are not functional because they contain details which are either unnecessary or suggest a feigned accuracy which is not justified by analytical and experimental resolution of system characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00050744
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    Paper (German National Licenses)
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