Combining stable isotopes and spatial stream network modelling to disentangle the roles of hydrological and biogeochemical processes on riverine nitrogen dynamics
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View abstract on PubMed
Summary
This summary is machine-generated.Agricultural nitrogen loss is complex. This study used isotopes and modeling to show wet seasons mobilize fertilizer nitrogen, while dry seasons involve diverse sources and enhanced denitrification, highlighting the need for adaptive nutrient management.
Area Of Science
- Environmental Science
- Biogeochemistry
- Hydrology
Background
- Intensive agriculture alters watershed hydrology and biogeochemistry, causing water quality degradation and biodiversity loss.
- Quantifying nitrogen (N) sources and sinks in agricultural watersheds is challenging due to heterogeneous N transformation and transport processes.
Purpose Of The Study
- To investigate watershed hydrology, nitrogen (N) transformation, and nitrate (NO3-) sources in the Cannon River Watershed, Minnesota.
- To differentiate N sources and understand N cycling under contrasting wet and dry hydrological conditions using stable isotopes and spatial stream network modeling.
Main Methods
- Utilized stable isotopes of water and nitrate (NO3-).
- Employed spatial stream network modeling (SSNMs).
- Analyzed data under contrasting wet and dry seasonal conditions.
Main Results
- Wet seasons exhibited elevated riverine NO3- concentrations, driven by high watershed wetness and near-surface N mobilization, with reduced denitrification due to shorter water travel times.
- Dry seasons showed lower NO3- concentrations and stronger denitrification signals, with deep groundwater as the primary water source and longer water travel times promoting denitrification.
- Fertilizer N was the dominant NO3- source in the wet season (98.2±1.3%), while the dry season showed mixed sources (64.4% fertilizer, 26.0% soil N, 9.5% manure/sewage).
Conclusions
- Hydrologic connectivity and water travel time significantly influence N loss and transformation processes in agricultural watersheds.
- Findings underscore the importance of considering drainage water management and groundwater N accumulation for effective nutrient management strategies.
- Adaptive measures are crucial for controlling N pollution in agricultural watersheds, particularly in karst regions with high connectivity.
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