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Merlijn P. Janssens - One of the best experts on this subject based on the ideXlab platform.

  • Spatial Variation in Denitrification and N_2O Emission in Relation to Nitrate Removal Efficiency in a N-stressed Riparian Buffer Zone
    Ecosystems, 2006
    Co-Authors: Mariet M. Hefting, Roland Bobbink, Merlijn P. Janssens
    Abstract:

    Spatial variability in hydrological flowpaths and Nitrate-Removal processes complicates the overall assessment of riparian buffer zone functioning in terms of water quality improvement as well as enhancement of the greenhouse effect by N_2O emissions. In this study, we evaluated denitrification and nitrous oxide emission in winter and summer along two groundwater flowpaths in a Nitrate-loaded forested riparian buffer zone and related the variability in these processes to controlling soil factors. Denitrification and emissions of N_2O were measured using flux chambers and incubation experiments. In winter, N_2O emissions were significantly higher (12.4 mg N m^−2 d^−1) along the flowpath with high Nitrate Removal compared with the flowpath with low Nitrate Removal (2.58 mg N m^−2 d^−1). In summer a reverse pattern was observed, with higher N_2O emissions (13.6 mg N m^−2 d^−1) from the flowpath with low Nitrate-Removal efficiencies. Distinct spatial patterns of denitrification and N_2O emission were observed along the high Nitrate-Removal transect compared to no clear pattern along the low Nitrate-Removal transect, where denitrification activity was very low. Results from this study indicate that spots with high Nitrate-Removal efficiency also contribute significantly to an increased N_2O emission from riparian zones. Furthermore, we conclude that high variability in N_2O:N_2 ratio and weak relationships with environmental conditions limit the value of this ratio as a proxy to evaluate the environmental consequences of riparian buffer zones.

  • Spatial Variation in Denitrification and N2O Emission in Relation to Nitrate Removal Efficiency in a N-stressed Riparian Buffer Zone
    Ecosystems, 2006
    Co-Authors: Mariet M. Hefting, Roland Bobbink, Merlijn P. Janssens
    Abstract:

    Spatial variability in hydrological flowpaths and Nitrate-Removal processes complicates the overall assessment of riparian buffer zone functioning in terms of water quality improvement as well as enhancement of the greenhouse effect by N2O emissions. In this study, we evaluated denitrification and nitrous oxide emission in winter and summer along two groundwater flowpaths in a Nitrate-loaded forested riparian buffer zone and related the variability in these processes to controlling soil factors. Denitrification and emissions of N2O were measured using flux chambers and incubation experiments. In winter, N2O emissions were significantly higher (12.4 mg N m−2 d−1) along the flowpath with high Nitrate Removal compared with the flowpath with low Nitrate Removal (2.58 mg N m−2 d−1). In summer a reverse pattern was observed, with higher N2O emissions (13.6 mg N m−2 d−1) from the flowpath with low Nitrate-Removal efficiencies. Distinct spatial patterns of denitrification and N2O emission were observed along the high Nitrate-Removal transect compared to no clear pattern along the low Nitrate-Removal transect, where denitrification activity was very low. Results from this study indicate that spots with high Nitrate-Removal efficiency also contribute significantly to an increased N2O emission from riparian zones. Furthermore, we conclude that high variability in N2O:N2 ratio and weak relationships with environmental conditions limit the value of this ratio as a proxy to evaluate the environmental consequences of riparian buffer zones.

Mariet M. Hefting - One of the best experts on this subject based on the ideXlab platform.

  • Spatial Variation in Denitrification and N_2O Emission in Relation to Nitrate Removal Efficiency in a N-stressed Riparian Buffer Zone
    Ecosystems, 2006
    Co-Authors: Mariet M. Hefting, Roland Bobbink, Merlijn P. Janssens
    Abstract:

    Spatial variability in hydrological flowpaths and Nitrate-Removal processes complicates the overall assessment of riparian buffer zone functioning in terms of water quality improvement as well as enhancement of the greenhouse effect by N_2O emissions. In this study, we evaluated denitrification and nitrous oxide emission in winter and summer along two groundwater flowpaths in a Nitrate-loaded forested riparian buffer zone and related the variability in these processes to controlling soil factors. Denitrification and emissions of N_2O were measured using flux chambers and incubation experiments. In winter, N_2O emissions were significantly higher (12.4 mg N m^−2 d^−1) along the flowpath with high Nitrate Removal compared with the flowpath with low Nitrate Removal (2.58 mg N m^−2 d^−1). In summer a reverse pattern was observed, with higher N_2O emissions (13.6 mg N m^−2 d^−1) from the flowpath with low Nitrate-Removal efficiencies. Distinct spatial patterns of denitrification and N_2O emission were observed along the high Nitrate-Removal transect compared to no clear pattern along the low Nitrate-Removal transect, where denitrification activity was very low. Results from this study indicate that spots with high Nitrate-Removal efficiency also contribute significantly to an increased N_2O emission from riparian zones. Furthermore, we conclude that high variability in N_2O:N_2 ratio and weak relationships with environmental conditions limit the value of this ratio as a proxy to evaluate the environmental consequences of riparian buffer zones.

  • Spatial Variation in Denitrification and N2O Emission in Relation to Nitrate Removal Efficiency in a N-stressed Riparian Buffer Zone
    Ecosystems, 2006
    Co-Authors: Mariet M. Hefting, Roland Bobbink, Merlijn P. Janssens
    Abstract:

    Spatial variability in hydrological flowpaths and Nitrate-Removal processes complicates the overall assessment of riparian buffer zone functioning in terms of water quality improvement as well as enhancement of the greenhouse effect by N2O emissions. In this study, we evaluated denitrification and nitrous oxide emission in winter and summer along two groundwater flowpaths in a Nitrate-loaded forested riparian buffer zone and related the variability in these processes to controlling soil factors. Denitrification and emissions of N2O were measured using flux chambers and incubation experiments. In winter, N2O emissions were significantly higher (12.4 mg N m−2 d−1) along the flowpath with high Nitrate Removal compared with the flowpath with low Nitrate Removal (2.58 mg N m−2 d−1). In summer a reverse pattern was observed, with higher N2O emissions (13.6 mg N m−2 d−1) from the flowpath with low Nitrate-Removal efficiencies. Distinct spatial patterns of denitrification and N2O emission were observed along the high Nitrate-Removal transect compared to no clear pattern along the low Nitrate-Removal transect, where denitrification activity was very low. Results from this study indicate that spots with high Nitrate-Removal efficiency also contribute significantly to an increased N2O emission from riparian zones. Furthermore, we conclude that high variability in N2O:N2 ratio and weak relationships with environmental conditions limit the value of this ratio as a proxy to evaluate the environmental consequences of riparian buffer zones.

Alan R Hill - One of the best experts on this subject based on the ideXlab platform.

  • Groundwater Nitrate Removal in riparian buffer zones: a review of research progress in the past 20 years
    Biogeochemistry, 2019
    Co-Authors: Alan R Hill
    Abstract:

    This review evaluates research in the past 20 years focusing on groundwater Nitrate Removal in the riparian zones of agricultural watersheds. Studies have reported a large range in the magnitude of groundwater and Nitrate fluxes to buffers in different hydrogeologic settings. An earlier focus on buffers with shallow subsurface flow has expanded to include sites with deep flow paths and groundwater-fed overland flow. Nitrate Removal efficiency and the width required for Removal have been linked to riparian sediment texture and depth to an impervious layer. Denitrification has been identified as the dominant mechanism of Nitrate Removal based on evidence that this process occurs at depth in many buffers which contain buried organic-rich deposits. Several studies have assessed the cumulative effect of riparian buffers on Nitrate Removal at the watershed scale. Despite considerable research progress areas of uncertainty still remain. Buffers with coarse-textured sediments located in landscapes with upslope sand aquifers have received most attention. In contrast, few sites have been analysed in weathered bedrock and glacial till landscapes. Many studies have reported Nitrate Removal efficiency based on Nitrate concentrations rather than measuring groundwater fluxes which assess the magnitude of Nitrate Removal. More information is needed on interactions between riparian hydrological flow paths and biogeochemical processes. Further research is recommended on the effect of riparian zone Nitrate Removal at the watershed scale and long-term monitoring with respect to buffer restoration, the ability to sustain Nitrate Removal and responses to land use and climate change.

  • A Landscape-based Approach to Estimate Riparian Hydrological and Nitrate Removal Functions
    Journal of the American Water Resources Association, 2006
    Co-Authors: P Vidon, Alan R Hill
    Abstract:

    : This study evaluates a conceptual model developed for riparian zones in Ontario, Canada, that links landscape hydrogeological characteristics to riparian ground water hydrology and Nitrate Removal efficiency. Data from a range of riparian sites in the United States and Europe suggest that the riparian zone types identified in the model are consistent with patterns of riparian hydrology and Nitrate flux and Removal in many humid temperate landscapes. These data also support the view that a riparian width of less than 20 m is often sufficient for effective Nitrate Removal unless riparian sediments are coarse grained or Nitrate transport occurs mainly in surface-fed ground water seeps. This study assesses the possibility of using topographic, soil, surficial geology, and vegetation maps to determine landscape attributes linked by the model to riparian zone hydrological functioning and Nitrate Removal efficiency. Although mappable data can help in determining broad classes of riparian zones, field visits are necessary to determine non-mappable riparian attributes such as seeps, organic horizons, and permeable sediment depth in the riparian zone. This research suggests that the conceptual model could be used for landscape management purposes in most temperate landscapes with minor modifications and that the hydrological component of the model could be adapted for contaminants other than Nitrate.

  • Landscape controls on Nitrate Removal in stream riparian zones
    Water Resources Research, 2004
    Co-Authors: P Vidon, Alan R Hill
    Abstract:

    [1] We examined how landscape hydrogeologic characteristics influence groundwater Nitrate Removal by eight stream riparian sites on glacial till and outwash landscapes in southern Ontario, Canada. During high water table periods in 2000–2002, mean NO3−-N input concentrations from adjacent cropland to the riparian sites ranged from 0.15 to 44.7 mg L−1. Seven of the eight sites had a mean Nitrate Removal efficiency of >90%. This Removal occurred within the first 15 m of the riparian zone at three sites with loamy sand and sandy loam soils overlying a shallow confining layer at 1–2 m. However, at four of five sites with more conductive sand and cobble sediments the width required for 90% Nitrate Removal varied from >25 m to a maximum of 176 m at a site with a confining layer at 6 m. Sites linked to an extensive thick (>6 m) upland aquifer with a slope gradient of >15% at the riparian perimeter had high Nitrate inputs throughout the year and were large Nitrate sinks. Sites with gentle topography (

  • landscape controls on Nitrate Removal in stream riparian zones
    Water Resources Research, 2004
    Co-Authors: P Vidon, Alan R Hill
    Abstract:

    [1] We examined how landscape hydrogeologic characteristics influence groundwater Nitrate Removal by eight stream riparian sites on glacial till and outwash landscapes in southern Ontario, Canada. During high water table periods in 2000–2002, mean NO3−-N input concentrations from adjacent cropland to the riparian sites ranged from 0.15 to 44.7 mg L−1. Seven of the eight sites had a mean Nitrate Removal efficiency of >90%. This Removal occurred within the first 15 m of the riparian zone at three sites with loamy sand and sandy loam soils overlying a shallow confining layer at 1–2 m. However, at four of five sites with more conductive sand and cobble sediments the width required for 90% Nitrate Removal varied from >25 m to a maximum of 176 m at a site with a confining layer at 6 m. Sites linked to an extensive thick (>6 m) upland aquifer with a slope gradient of >15% at the riparian perimeter had high Nitrate inputs throughout the year and were large Nitrate sinks. Sites with gentle topography (<4–5%) and <2 m of permeable sediments were minor Nitrate sinks because of small Nitrate inputs that were limited to the late autumn-spring period. A conceptual model linking landscape hydrogeologic characteristics to riparian zone Nitrate Removal capacity is developed to understand and predict the effectiveness of riparian buffers at the landscape scale.

Roland Bobbink - One of the best experts on this subject based on the ideXlab platform.

  • Spatial Variation in Denitrification and N_2O Emission in Relation to Nitrate Removal Efficiency in a N-stressed Riparian Buffer Zone
    Ecosystems, 2006
    Co-Authors: Mariet M. Hefting, Roland Bobbink, Merlijn P. Janssens
    Abstract:

    Spatial variability in hydrological flowpaths and Nitrate-Removal processes complicates the overall assessment of riparian buffer zone functioning in terms of water quality improvement as well as enhancement of the greenhouse effect by N_2O emissions. In this study, we evaluated denitrification and nitrous oxide emission in winter and summer along two groundwater flowpaths in a Nitrate-loaded forested riparian buffer zone and related the variability in these processes to controlling soil factors. Denitrification and emissions of N_2O were measured using flux chambers and incubation experiments. In winter, N_2O emissions were significantly higher (12.4 mg N m^−2 d^−1) along the flowpath with high Nitrate Removal compared with the flowpath with low Nitrate Removal (2.58 mg N m^−2 d^−1). In summer a reverse pattern was observed, with higher N_2O emissions (13.6 mg N m^−2 d^−1) from the flowpath with low Nitrate-Removal efficiencies. Distinct spatial patterns of denitrification and N_2O emission were observed along the high Nitrate-Removal transect compared to no clear pattern along the low Nitrate-Removal transect, where denitrification activity was very low. Results from this study indicate that spots with high Nitrate-Removal efficiency also contribute significantly to an increased N_2O emission from riparian zones. Furthermore, we conclude that high variability in N_2O:N_2 ratio and weak relationships with environmental conditions limit the value of this ratio as a proxy to evaluate the environmental consequences of riparian buffer zones.

  • Spatial Variation in Denitrification and N2O Emission in Relation to Nitrate Removal Efficiency in a N-stressed Riparian Buffer Zone
    Ecosystems, 2006
    Co-Authors: Mariet M. Hefting, Roland Bobbink, Merlijn P. Janssens
    Abstract:

    Spatial variability in hydrological flowpaths and Nitrate-Removal processes complicates the overall assessment of riparian buffer zone functioning in terms of water quality improvement as well as enhancement of the greenhouse effect by N2O emissions. In this study, we evaluated denitrification and nitrous oxide emission in winter and summer along two groundwater flowpaths in a Nitrate-loaded forested riparian buffer zone and related the variability in these processes to controlling soil factors. Denitrification and emissions of N2O were measured using flux chambers and incubation experiments. In winter, N2O emissions were significantly higher (12.4 mg N m−2 d−1) along the flowpath with high Nitrate Removal compared with the flowpath with low Nitrate Removal (2.58 mg N m−2 d−1). In summer a reverse pattern was observed, with higher N2O emissions (13.6 mg N m−2 d−1) from the flowpath with low Nitrate-Removal efficiencies. Distinct spatial patterns of denitrification and N2O emission were observed along the high Nitrate-Removal transect compared to no clear pattern along the low Nitrate-Removal transect, where denitrification activity was very low. Results from this study indicate that spots with high Nitrate-Removal efficiency also contribute significantly to an increased N2O emission from riparian zones. Furthermore, we conclude that high variability in N2O:N2 ratio and weak relationships with environmental conditions limit the value of this ratio as a proxy to evaluate the environmental consequences of riparian buffer zones.

Mika Sillanpää - One of the best experts on this subject based on the ideXlab platform.