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  • 1
    Digitale Medien
    Digitale Medien
    Specific heat of smoky quartz
    Amsterdam : Elsevier
    Physics Letters A 66 (1978), S. 389-391 
    Details
    ISSN: 0375-9601
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Physik
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(78)90069-5
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  • 2
    Digitale Medien
    Digitale Medien
    The distribution of phosphate in sediments and its relation with eutrophication of a Mediterranean coastal lagoon (1995)
    Springer
    Hydrobiologia 297 (1995), S. 29-41 
    Details
    ISSN: 1573-5117
    Schlagwort(e): organic phosphate ; inorganic phosphate ; phosphate fractionation ; sediment ; coastal lagoons ; eutrophication
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A major problem of the Mediterranean coastal lagoons is an excessive input of nutrients (i.e. N and P), causing eutrophic conditions in summer. The sediments of these lagoons can serve as a reservoir by fixing phosphate, or as a source when this phosphate is released under certain conditions. Knowledge of nutrient sources and fluxes is needed if coastal lagoons are to be protected against eutrophication. Therefore, we have evaluated the total pool of phosphate in the lagoon sediments, and the quantity of phosphate which may be released. Sediment profiles have been analysed at two stations of the ‘Lagune de Thau’ both in and outside the oyster-bank zone. A sequential fractionation, using chelating agents was performed to extract the inorganic (iron and calcium bound phosphate) and the organic phosphate fractions. A statistical analysis of the data set has revealed several significant factors which explain the fluctuations of the concentrations of each phosphate fraction. These factors are: the time of year (seasons), the depth (5 cm layers of sediment), and the site (station). A spatial and a temporal variation of the concentration of Tot-P was found. The largest variation between the two different zones appeared only in the first five cm of sediment. There is only a slight seasonal variation in the amount of phosphate at other depths at the two different zones. Season and station are the factors which control the variations in distribution of phosphate fractions. The spatial and temporal variations of the iron and calcium bound phosphate are explained by the redox potential and pH in the top layer of the sediment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00033499
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  • 3
    Digitale Medien
    Digitale Medien
    Seasonal variations of P compounds and their concentrations in two coastal lagoons (1993)
    Springer
    Hydrobiologia 253 (1993), S. 102-102 
    Details
    ISSN: 1573-5117
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00050730
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  • 4
    Digitale Medien
    Digitale Medien
    Seasonal variations of P compounds and their concentrations in two coastal lagoons (Herault, France) (1993)
    Springer
    Hydrobiologia 252 (1993), S. 45-59 
    Details
    ISSN: 1573-5117
    Schlagwort(e): phosphate ; sediment ; calcium ; iron ; coastal lagoons ; seasonal variations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract This article concerns seasonal variations in the phosphate concentrations in two coastal lagoons near Montpellier (Mediterranean coast, France). The o-P concentration in the overlying water is highest during summer. The role of the sediment, particularly that of the different P fractions in the sediment, is discussed. Significant variations, especially in the FeOOH ≈ P fraction, occur. For both Tot-Psed and the Fe00H≈P fraction a gradient from surface to bottom is observed, as well as a distinct decrease in the FeOOH≈P fraction in the surface sediments during summer and autumn. Variations in the FeOOH≈P fraction appear to be compensated by variations in the CaC03≈P fraction. These variations appear to be determined by the ferric hydroxide concentration. This compound represents only a small part (maximally 15%) of the total iron in the sediments and is related to the dissolved oxygen content of the immediately overlying water. Besides the fractions o-P, Fe(OOH)≈P, a large part of the CaC03≈P fraction is potentially bioavailable. A large proportion of the Tot-Psed is therefore bioavailable.[/p]
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00000127
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  • 5
    Digitale Medien
    Digitale Medien
    Phosphate mobility at the sediment–water interface of a Mediterranean lagoon (etang du Méjean), seasonal phosphate variation (1998)
    Springer
    Hydrobiologia 373-374 (1998), S. 203-216 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Phosphate ; sediments ; coastal lagoon ; seasonal variations ; P fractions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Méjean Lagoon (France) is a confined, shallow system, 0.7 m in depth, with a surface area of 747 ha. Its sediments have a fine granulometry and are evenly distributed. The bathymetry and hydrodynamic behaviour of the basin create two zones with restricted exchanges between them. The western part (60% of the total surface area) is rich in dissolved phosphate (〉 mg l-1 in summer) and receives the majority of the phosphate (P) inputs from the watershed. The heavy macroalgal population consists of Gracilaria throughout the year and Ulva in summer and autumn. Phytoplankton levels sometimes reach 100 µg l-1 of chlorophyll a. The sediment-water phosphate exchange varies with environmental conditions and macroalgal growth. P mobility was studied on the basis of these characteristics. Algal biomass and water characteristics were measured at 15-day intervals throughout 1993. A seasonal study was conducted in 1994 to investigate which P fractions in the sediment were involved in the exchanges. The springtime rise in temperature reactivated decomposition of the macroalgal biomass that had accumulated in autumn. The redox potential (EH) fell as a result of this biological activity, leading to a decrease in the inorganic P fractions. This P release accounts for the higher P water concentrations observed in the lagoon in summer. The mobility of P fractions shows that the P stored in the sediments plays an active role in the dynamics of the overlying water. Seasonal variations in these fractions explain the patterns of P storage and mobilization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017092226396
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