Integrated environmental assessment framework for evaluating and managing nitrogen contamination in complex fractured...

Area of Science:

• Environmental Science
• Hydrogeology
• Geochemistry

Background:

• Fractured crystalline bedrock aquifers are complex systems susceptible to contamination.
• Elevated nitrogen concentrations pose risks to groundwater quality and ecosystem health.
• Understanding contaminant sources and transport is crucial for effective groundwater management.

Purpose of the Study:

• To investigate the sources and hydrogeochemical evolution of elevated nitrogen in fractured bedrock aquifers.
• To integrate multiple disciplines to comprehensively assess groundwater contamination.
• To provide insights for sustainable groundwater management in similar geological settings.

Main Methods:

• A multidisciplinary framework integrating hydrochemical, isotopic, hydrogeological, geophysical, microbiological, and statistical approaches.
• Dual isotope analysis (δ15N/δ18O-NO3-) and Bayesian mixing models for source apportionment.
• Analysis of transmissivity contrasts and hydraulic connectivity between aquifer regions.

Main Results:

• Complete hydraulic disconnection between western and eastern aquifer regions with significant transmissivity contrasts.
• Western region showed high multi-contaminant signatures, while the eastern region had greater dilution capacity.
• 93.4% of nitrogen contamination originated from livestock waste (composted manure and manure slurry).

Conclusions:

• Physical heterogeneity in fractured bedrock aquifers governs contaminant transport and biogeochemical transformations.
• The integrated framework successfully identified contamination sources and hydrochemical evolution.
• Findings offer essential insights for sustainable groundwater management in fractured bedrock systems globally.