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A statistical approach to estimate nitrogen sectorial contribution to total load
B Grizzetti1, F Bouraoui, G de Marsily
1Joint Research Centre of the European Commission, Institute for Environment and Sustainability, Soil & Waste Unit, TP 460, 1-21020 Ispra (VA), Italy. bruna.grizzetti@jrc.it
Summary
This study developed a statistical model to pinpoint nitrogen sources in rivers. Agriculture is the primary contributor (71%) to river nitrogen transport, followed by point sources (24%) and atmospheric deposition (5%).
Area of Science:
- Environmental Science
- Hydrology
- Water Quality Management
Background:
- Nitrogen pollution in rivers is a significant environmental concern, impacting aquatic ecosystems and water resources.
- Understanding the sources and pathways of nitrogen transport is crucial for effective water quality management.
- Existing methods for source apportionment often lack the spatial resolution and comprehensive consideration of basin characteristics.
Purpose of the Study:
- To develop and validate a source apportionment methodology for nitrogen river transport.
- To quantify the contribution of punctual and diffuse nitrogen sources to riverine export.
- To investigate the influence of basin characteristics on nitrogen retention and export.
Main Methods:
- Development of a statistical, non-linear regression model relating nitrogen transport rates to spatially referenced sources and basin characteristics.
- Inclusion of key nitrogen sources: applied fertilizer, atmospheric deposition, and point discharges.
- Integration of basin characteristics: winter rainfall, average air temperature, topographic wetness index, and dry season flow.
- Model calibration and validation in a 8913 km2 area of East Anglia, UK.
Main Results:
- Agriculture was identified as the dominant source, contributing an estimated 71% to the total nitrogen load.
- Point sources accounted for approximately 24% of the exported nitrogen.
- Atmospheric deposition contributed around 5% to the riverine nitrogen export.
- The model successfully estimated source contributions and highlighted the influence of basin factors on nitrogen retention.
Conclusions:
- The developed statistical model provides a robust methodology for nitrogen source apportionment in river systems.
- Agricultural practices are the most significant driver of nitrogen pollution in the studied region.
- Basin characteristics play a critical role in modulating nitrogen retention and export, informing targeted management strategies.