Spatiotemporal patterns and source attribution of nitrogen load in a river basin with complex pollution sources

Area of Science:

• Environmental Science
• Water Resource Management
• Ecosystem Pollution

Background:

• Eutrophication from excessive nutrient discharge poses a global environmental challenge.
• Identifying nitrogen (N) pollution sources and their contributions is crucial for effective control strategies in river basins.

Purpose of the Study:

• To simulate N loads from anthropogenic sources in the Upper Huai River basin using the SWAT model.
• To assess the performance of SWAT with daily versus hourly rainfall data for N load simulation.
• To examine spatiotemporal patterns and source attributions of total nitrogen (TN) and ammonia nitrogen (NH4-N) loads.

Main Methods:

• Utilized the process-based Soil and Water Assessment Tool (SWAT) model for N load simulation.
• Compared SWAT model performance using daily and hourly rainfall inputs.
• Analyzed spatiotemporal distribution and source contributions of TN and NH4-N loads.

Main Results:

• Hourly rainfall-driven SWAT model showed superior performance for TN and NH4-N load simulation.
• TN loads peaked in summer, with crop production as the primary contributor, followed by septic tanks and animal feedlots.
• Concentrated animal feedlot operations (CAFOs) were the dominant source of NH4-N loads basin-wide.

Conclusions:

• Shift focus from 'end-of-pipe' treatment to integrated, source-prevention strategies for N pollution control.
• Stakeholder involvement is essential for effective N load reduction.
• Targeted interventions for crop production and animal feedlots are necessary for TN and NH4-N management.