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  • 1
    Electronic Resource
    Electronic Resource
    The effect of nitrate in stream water on the relationship between gentrification and nitrification in a stream-sediment microcosm (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 18 (1987), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY 1. Microcosm experiments were carried out to simulate, in the laboratory, the conditions occurring at the water-sediment interface of a stream draining agricultural land. Constant boundary conditions were attained by passing synthetic 'stream water', saturated with dissolved oxygen and containing 1 mmol NO3−N dm−3 (or 1 mmol Cl− dm−3, control), once only over the sediment surface.2. Measurements were made of inorganic-N (nitrate, nitrite, ammonium), redox potential, potential denitrification and nitrification activities, and readily mineralizable carbon sediment profiles at three incubation times up to 24 days. The peaks in denitrification and nitrification activity moved down the profile with time in the nitrate-treated sediment, but stayed relatively stationary in the control treatment. Although the zone of nitrification was restricted to the top 2–3 mm of sediment in the control treatment, high fluxes of both dissolved oxygen and NH4−N maintained a high nitrifier activity within this zone for the duration of the experiment.3. Increases in denitrifier activity immediately below the nitrifier activity peak indicated that a coupled nitrification-denitrification sequence was operating in both the control and nitrate-treated sediment. The greater depth of nitrification when nitrate was present in the ‘stream water’ was attributed to a feedback mechanism in which enhanced denitrification in the sediment reduced the local demand for oxygen and permitted dissolved oxygen to diffuse further into the sediment. The progressively greater depth to which oxygen penetrated caused the contiguous peaks of potential nitrifier and denitrifier enzyme activity to migrate farther from the interface. However, diffusion rates of the reactants limited the depth to which these coupled reactions could extend.4. The possible effect of this feedback mechanism on the nitrate status of natural sediment-stream water systems is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1987.tb01309.x
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  • 2
    Electronic Resource
    Electronic Resource
    Spatial distribution of denitrifying activity in a stream draining an agricultural catchment (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 18 (1987), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY 1. A field study was made of the spatial distribution of denitrification activity in the sediment of the River Dorn, Oxfordshire, England.2. An assay of denitrifying enzyme activity was used to examine the distribution of denitrification with depth in cores of sediment representative of the types found in the stream. The maximum activity recorded in a predominantly silt sediment core was 5 times greater than that recorded in a sandy gravel core. In both fine sand and silt cores, peaks in denitrifier enzyme activity were shown to correspond to the limit of the nitrate diffusion front. At this depth the redox potential dropped rapidly from + 300 mV to 0 or less. Denitrifying enzyme activity in the stream water was negligible.3.In situdenitrification activity (I DA) measurements were carried out in an 800 m reach of the Dorn using the acetylene inhibition technique on small sediment cores. Concurrent measurements were also made of stream depth and velocity, nitrate concentration in the interstitial water, and the wet bulk density, loss on ignition, mineraliz- able carbon and total nitrogen contents of the sediment. Mineralizable carbon was the variable which showed the best correlation with I DA. Highest IDAs were associated with accumulations of fine-grained sediment at meander bends. Mean IDAs measured under flood conditions were significantly higher (P〈0.05) than those measured under baseflow. It was estimated that denitrification reduced the nitrate load in the River Dorn by 15% under summer baseflow conditions
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1987.tb01335.x
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  • 3
    Electronic Resource
    Electronic Resource
    Phosphorus Retention and Release Characteristics of Sewage-Impacted Wetland Sediments (1997)
    Springer
    Water, air & soil pollution 100 (1997), S. 163-179 
    Details
    ISSN: 1573-2932
    Keywords: iron ; natural wetlands ; phosphorus ; retention ; sediments ; sewage ; sorption-desorption ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Sediment deposited in traps positioned along a sewage-impacted wetland receiving phosphorus (P)-retaining reactants from natural wetland water was fractionated into different particle sizes, and the amount of P retained in these particle sizes was investigated. Subsamples of the sediments collected from different sites along the wetland system were also equilibrated with water at different water:sediment ratios and equilibration periods to investigate the extent of P released from these sediments under aerobic and anaerobic conditions. Results obtained showed that most of P deposited in sediments is in fine fractions (〈16 µm), particularly in sediments collected from confluence sites where water inflow from the natural wetland provides P-retaining reactants and from sites immediately below these confluence sites (postconfluence sites). The extent of P release from sediments depended on the aerobic-anaerobic conditions of the sediments, equilibration period, water:sediment ratio and the position of sites within the wetland. The rate of P released from sediments associated with an increase in equilibration period tended to be higher under aerobic than anaerobic conditions. Water:sediment ratio was found to be a more important factor in controlling the release of P from sediments under anaerobic than aerobic conditions. The amount of P released from the confluence and postconfluence sites was higher than that from other sites over a range of equilibration periods and water:sediment ratios under aerobic and anaerobic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018340028411
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  • 4
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    Nitrate enhancement of nitrification depth in sediment/water microcosms (1988)
    Springer
    Details
    Publication Date: 1988-02-01
    Print ISSN: 0943-0105
    Electronic ISSN: 1432-0495
    Topics: Geosciences
    Published by Springer
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  • 5
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    The effect of storms on nitrification rates in a small stream (1985)
    Elsevier
    Details
    Publication Date: 1985-01-01
    Print ISSN: 0043-1354
    Electronic ISSN: 1879-2448
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Elsevier
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  • 6
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    The effect of prolonged exposure to acetylene on denitrification in a laboratory stream sediment system (1988)
    Elsevier
    Details
    Publication Date: 1988-06-01
    Print ISSN: 0043-1354
    Electronic ISSN: 1879-2448
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Elsevier
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  • 7
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    Phosphorus Removal Processes in a Wetland after a Decade of Receiving a Sewage Effluent (1992)
    Wiley
    Details
    Publication Date: 1992-10-01
    Print ISSN: 0047-2425
    Electronic ISSN: 1537-2537
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 8
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    Fractionation of Phosphorus in the Sediment of a Wetland after a Decade of Receiving Sewage Effluent (1992)
    Wiley
    Details
    Publication Date: 1992-10-01
    Print ISSN: 0047-2425
    Electronic ISSN: 1537-2537
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 9
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    Sources and sinks of nutrients in a New Zealand hill pasture catchment I. Stormflow generation (1988)
    Wiley
    Details
    Publication Date: 1988-04-01
    Description: The processes of stormflow generation were studied in a hill pasture catchment near Hamilton, New Zealand. Although rainfall was relatively evenly distributed throughout the year, stormflow was highly seasonal and over 65 per cent occurred during the winter. Three main processes contributing to stormflow were identified which could be related to soil type and physiographic position. On gleyed soils derived from rhyolitic colluvium, saturation overland flow was the dominant process. Hydrographs from ‘Whipkey’ throughflow troughs also indicated that there was a subsurface response (saturated wedge) from this soil type. On steeper convex slopes, more permeable soils were derived from weathered greywacke. The presence of ephemeral springs on the hillslopes and direct observation during storm events indicated that storm runoff was generated as return flow from this soil. It was noted that nitrate concentrations from subsurface sources were 5–10 times higher than surface runoff. This difference in concentration was utilized in a chemical mixing equation which partitioned stormflow sources. This was compared with the stormflow predicted from rain falling on to saturated areas. There was good agreement between the two models for winter‐spring events with respect to the volumes of surface runoff predicted, however the saturated areas model underestimated total stormflow. The results of the study are briefly discussed in terms of the potential for water quality management. Copyright © 1988 John Wiley & Sons, Ltd
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 10
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    Sources and sinks of nutrients in a New Zealand hill pasture catchment II. Phosphorus (1988)
    Wiley
    Details
    Publication Date: 1988-04-01
    Description: The management of the riparian zone has been suggested as a technique for controlling the amounts of phosphorus (P) entering watercourses draining pasture catchments. A study was therefore made of P entering a stream from various sources (rainfall, surface and subsurface derived runoff, direct fallout from aerial topdressing), with the object of providing a rational basis for the design of effective riparian management schemes. P entrained in surface runoff could account for virtually all of the P entering the stream during storms. Approximately 20 per cent of the annual P export from the catchment could be accounted for by direct aerial input of P to the stream during autumn fertilizer topdressing. More than 85 per cent of the P was exported from the catchment as particulate P. Stream sediment had higher P sorption capacities, and were enriched with P relative to the soils from which they were derived. There was a pronounced seasonal variation in sediment enrichment which could be predicted (r2 = 0.92) by the logarithm of the rainfall since fertilizer topdressing (LNFERT) and flood intensity. The amount of P lost in streamflow during any flood event was predicted (r2 = 0.94) by peak flow, seven day antecedent peak flow and LNFERT. Approximately 40 per cent of the 1.3 kg P ha−1 exported during 1981 occurred in four storms with recurrence intervals of more than three months. From a P budget compiled from nine events it was hypothesized that the stream acted as a net sink for P at baseflow and low‐medium intensity floods but was a source of P at higher flood intensities. It was concluded that P losses from hill pasture catchments could be reduced by avoidance of direct application of P fertilizer to the stream channel, and by fencing out stock from seasonally saturated areas during periods of saturation. The ultimate success of the latter technique would depend on whether buffer vegetation could retain accumulated P during extreme storm events. Copyright © 1988 John Wiley & Sons, Ltd
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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