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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 24 (1990), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 〈list xml:id="l1" style="custom"〉1 The concentrations of total and dissolved (〈0.2 μm) Fe, Mn, Cu, Co, Zn and Al in the Dutch reservoir, the Tjeukemeer, were recorded fortnightly between 1984 and 1986.2 Due to its reservoir function, the Tjeukemeer receives water that is relatively rich in Fe and Mn from its peaty drainage area in winter. In summer, water that is relatively rich in Cu and Zn from lake IJsselmeer, which is flushed by a tributary of the River Rhine, flows into the lake. Therefore trace metal loads, as estimated from annual mean concentrations and hydraulic data, are climate-dependent.3 In wet years, such as 1985, the annual Fe, Mn, Cu and Zn loads may be 3.1,0.2,0.001 and 0.009 gm−2, respectively. In dry years, such as 1984 and 1986, the Fe and Mn loads may be less than one quarter while the Cu and Zn loads may double. Especially in wet years comparable Cu and Zn inputs occur by deposition.4 Despite the dependence of trace metal loads on the climate-dependent water regime. Principal Component Analysis indicated no strong relation between the total Cu, Co, Zn and Al concentrations in lake water and hydrological tracers such as Cl− and UV absorbance. Instead, wind speed appeared to be more strongly connected with the dynamics of these metals. Thus in the shallow Tjeukemeer, internal trace metal loading due to wind-induced resuspension starts to dominate the contributions of external loads to the total metal concentrations at wind speeds exceeding 3ms−1.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 229 (1992), S. 59-71 
    ISSN: 1573-5117
    Keywords: humic substances ; aquatic ecosystems ; biogeochemistry ; acidification ; eutrophication ; UV radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Humic substances (HS) are the main constituent of the organic carbon pool in stained aquatic ecosystems. HS absorb visible and ultraviolet (UV) light, have acid-base properties and metal and nutrient binding abilities. Based on these characteristics, UV irradiation, pH and the trophic status of aquatic ecosystems will influence the impact of HS on element cycling in surface waters. With climatic change and environmental pollution, UV irradiance, acidification and eutrophication may increase further. In this paper impacts of UV irradiation, pH and eutrophication on the structure, properties and biodegradation of aquatic HS are discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic ecology 25 (1992), S. 183-189 
    ISSN: 1573-5125
    Keywords: Adsorption ; iron(III) ; manganese dioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The adsorption of iron(III) onto hydrous manganese dioxide was studied in the model water of Lake Tjeukemeer, The Netherlands, as a function of pH under the condition where no precipitation of iron(III) hydroxide occurs. Adsorption isotherms obtained in the pH range 3.5–5.0, fitted the Langmuir equation. Langmuir constants were strongly pH-dependent and increased with an increase in pH. Especially, the value for the conditional adsorption binding constant for iron(III), log B, was relatively high compared to that for copper in natural water. The extent of iron(III) adsorbed was more affected by the surface loading at lower pH. According to the Kurbatov plot, the average number of protons released to solution per mole of iron(III) adsorbed was estimated to be 2.2.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5117
    Keywords: fen lakes ; hydrology ; eutrophication ; productivity ; element cycling ; recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Most relatively large (〉 250 ha) and shallow (〈 2 m), Dutch lakes originate from large-scale peat mining. Originally, their water tables were regulated by natural processes such as evapotransporation, precipitation, drainage and seepage (up and downwards). These lakes used to be oligo to mesotrophic, and the phytoplankton consisted mainly of diatoms and green algae. However, 30 years ago filamentous cyanobacteria were also present. Owing to the intensification of agriculture in the surroundings of the lakes, their management developed more and more towards a man-made reservoir function. This management resulted in inflow of eutrophic water from the agricultural areas in winter. In summer the lakes were increasingly used as a water supply. This supply is compensated by water imported mainly from the River Rhine. The impacts of this reservoir function on the limnology of the Dutch fen lakes are discussed with the Tjeukemeer, the Loosdrechtse Plassen and the Reeuwijkse Plassen as examples. All these lakes have become typical eutrophic waters with high turbidity, dominance of filamentous cyanobacteria and bream and complete loss of submerged macrophytes. Finally, methods and results of manipulation procedures to restore these waters are discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic ecology 24 (1991), S. 145-151 
    ISSN: 1573-5125
    Keywords: Ultrafiltration ; Size distribution ; speciation ; aluminium ; dissolved organic carbon ; humic substances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chemical equilibrium calculations treating humic substances as the simple diprotic phtalic acid, predicted no Al-humus at pH〉6.5 in humic lake water. However, dissolved (〈200 nm) organic carbon (DOC) and dissolved Al appeared to be linearly (r=0.597, P〈0.001) correlated in samples from five different humic surface waters in The Netherlands with a DOC range of 10–36 mg.l−1 and a (mean) pH range of 6.85–8.47. Yet, organic carbon (Corg) and Al did no exhibit similar size distributions between 5 and 200 nm revealed by ultrafiltration. Averaged 25% of the Corg and 〉50% of the Al occurred in the fraction 〈5 nm. Only in this fraction the Corg and Al were linearly correlated (r=0.515, P〈0.001). This result suggests the presence of organic ligands in the DOC pool of humic waters having smaller molecular sizes and higher Al stability constants than the humic substances used to model aquatic Al speciation.
    Type of Medium: Electronic Resource
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