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  • 1
    Electronic Resource
    Electronic Resource
    Improved methods for the measurement of dissolved and particulate organic carbon in fresh water and their application to chalk streams (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 4 (1974), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The development and use of an improved automatic system for the accurate measurement of dissolved organic carbon (D.O.C.) in fresh waters is described. The method, which covers the range 0-25 mgl−1 D.O.C., is based on the oxidation of organic carbon to carbon dioxide by U.V. radiation. The carbon dioxide produced is measured by a non dispersive infra-red gas analyser (I.R.G.A.). The I.R.G.A. is also used in the semi-automatic measurement of particulate organic carbon (P.O.C.) by a combustion method which allows very low concentrations to be measured using samples of 200 ml or less.Results of surveys of two river systems indicate that D.O.C. concentrations of less than 2.0 mg l−1 are typical in unpolluted chalk streams. D.O.C. concentrations of streams draining acid heathland were found to be significantly higher (3-5.5 mg l−1).D.O.C. concentration was found to increase rapidly during a spate, in a river draining areas of mixed underlying geology. The throughput of D.O.C. during the twenty-five to fifty spates which occur annually in the river could amount to 20-30% of the annual flux of D.O.C.P.O.C. concentration in chalk spring waters (0.03–0.04 mg l−1) were found to be higher than expected from preliminary estimates using membrane filtration techniques.The relevance of the measurement of D.O.C. and P.O.C. flux to estimates of the energy budgets of stream ecosystems is discussed and published methods for the automatic measurement of D.O.C. are reviewed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1974.tb00109.x
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  • 2
    Electronic Resource
    Electronic Resource
    Importance of dissolved organic matter produced by duckweed (Lemna minor) in a southern English river (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 17 (1987), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The quantity of dissolved organic carbon (DOC) released by axenic Lemna minor cultures in the laboratory has been determined by an absolute method and by 14C labelling.2. Good agreement was obtained between the two methods and from 1.1% to 2.6% of the total carbon fixed was released.3. The DOC produced by L. minor has been analysed by ultrafiltra- tion and compared with a similar analysis of DOC in natural river water.4. The results of ullrafiltration analyses indicate that the proportion of low molecular weight (〈1000 Daltons) material in DOM produced by axenic L. minor is significantly greater than is found in its natural habitat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1987.tb01052.x
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of within-stream disturbance on dissolved nutrient levels during spates (1982)
    Springer
    Hydrobiologia 91-92 (1982), S. 447-462 
    Details
    ISSN: 1573-5117
    Keywords: rivers ; artificial spates ; nutrients ; D.O.C. ; B.O.D.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In rivers, variations in concentrations of many dissolved nutrients occur during spates. Increases are usually attributed to concentrated point or non-point inputs, and decreases to dilution associated with rainfall. Increased discharge disturbs sediments and benthic communities, but the effects of such disturbance on nutrient levels are difficult to isolate. Measurements of nutrient levels over three artificial spates revealed that substantial variations in dissolved organic carbon, dissolved phosphate, silicate, nitrate, and potassium levels could result from increased discharge in the absence of allochthonous inputs. Variations were closely related to peaks in suspended solids concentration or water height. Increases in biochemical oxygen demand and suspended bacteria also occurred. Variations in phosphate and silicate could be accounted for by a balance between release of ‘sediment interstitial water’ and exchange processes involving suspended and freshly exposed sediment. An increase in nitrate, during one spate, was probably due to a reduction in the effect of benthic denitrification. Small peaks in dissolved organic matter concentration were detected over each spate. We propose that within-stream disturbance is a factor which may contribute to variations in dissolved nutrient concentration during the rising hydrograph in natural spates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00940133
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of within-stream disturbance on dissolved nutrient levels during spates (1982)
    Springer
    Hydrobiologia 91-92 (1982), S. 447-462 
    Details
    ISSN: 1573-5117
    Keywords: rivers ; artificial spates ; nutrients ; D.O.C. ; B.O.D.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In rivers, variations in concentrations of many dissolved nutrients occur during spates. Increases are usually attributed to concentrated point or non-point inputs, and decreases to dilution associated with rainfall. Increased discharge disturbs sediments and benthic communities, but the effects of such disturbance on nutrient levels are difficult to isolate. Measurements of nutrient levels over three artificial spates revealed that substantial variations in dissolved organic carbon, dissolved phosphate, silicate, nitrate, and potassium levels could result from increased discharge in the absence of allochthonous inputs. Variations were closely related to peaks in suspended solids concentration or water height. Increases in biochemical oxygen demand and suspended bacteria also occurred. Variations in phosphate and silicate could be accounted for by a balance between release of ‘sediment interstitial water’ and exchange processes involving suspended and freshly exposed sediment. An increase in nitrate, during one spate, was probably due to a reduction in the effect of benthic denitrification. Small peaks in dissolved organic matter concentration were detected over each spate. We propose that within-stream disturbance is a factor which may contribute to variations in dissolved nutrient concentration during the rising hydrograph in natural spates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000043
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  • 5
    Electronic Resource
    Electronic Resource
    The influence of within-stream disturbance on dissolved nutrient levels during spates (1982)
    Springer
    Hydrobiologia 91-92 (1982), S. 447-462 
    Details
    ISSN: 1573-5117
    Keywords: rivers ; artificial spates ; nutrients ; D.O.C. ; B.O.D.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In rivers, variations in concentrations of many dissolved nutrients occur during spates. Increases are usually attributed to concentrated point or non-point inputs, and decreases to dilution associated with rainfall. Increased discharge disturbs sediments and benthic communities, but the effects of such disturbance on nutrient levels are difficult to isolate. Measurements of nutrient levels over three artificial spates revealed that substantial variations in dissolved organic carbon, dissolved phosphate, silicate, nitrate, and potassium levels could result from increased discharge in the absence of allochthonous inputs. Variations were closely related to peaks in suspended solids concentration or water height. Increases in biochemical oxygen demand and suspended bacteria also occurred. Variations in phosphate and silicate could be accounted for by a balance between release of ‘sediment interstitial water’ and exchange processes involving suspended and freshly exposed sediment. An increase in nitrate, during one spate, was probably due to a reduction in the effect of benthic denitrification. Small peaks in dissolved organic matter concentration were detected over each spate. We propose that within-stream disturbance is a factor which may contribute to variations in dissolved nutrient concentration during the rising hydrograph in natural spates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02391959
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  • 6
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    The influence of within-stream disturbance on dissolved nutrient levels during spates (1982)
    Springer
    Details
    Publication Date: 1982-07-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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  • 7
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    The influence of within-stream disturbance on dissolved nutrient levels during spates (1982)
    Springer
    Details
    Publication Date: 1982-07-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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    PAPER CURRENT
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