Combining multi-isotopic and molecular source tracking methods to identify nitrate pollution sources in surface and...

Area of Science:

• Environmental Science
• Water Quality Management
• Isotope Hydrology

Background:

• Nitrate pollution is a significant threat to surface and groundwater quality.
• Accurate identification of nitrate sources is essential for implementing effective mitigation strategies.
• Traditional isotopic methods for nitrate source identification face limitations due to overlapping ranges and mixing.

Purpose of the Study:

• To enhance nitrate source identification by combining multi-isotopic analysis with fecal indicator bacteria (FIB) and microbial source tracking (MST).
• To assess the effectiveness of this integrated approach in groundwater and surface water samples in Catalonia, Spain.
• To evaluate the reliability of using literature-based isotopic values for anthropogenic sources.

Main Methods:

• Collected 149 groundwater, 39 surface water, and 18 wastewater treatment plant (WWTP) effluent samples.
• Performed multi-isotopic analysis (δ15N, δ18O, δ11B) on water samples.
• Utilized fecal indicator bacteria (FIB) and microbial source tracking (MST) techniques for biological characterization.

Main Results:

• The combined isotope and MST approach provided complementary and more reliable information on nitrate sources.
• Agreement between isotopic and MST data was observed in 79% of samples, particularly effective for surface water and organic groundwater pollution.
• Local isotopic characterization of WWTP effluents is recommended, as literature values may not accurately reflect site-specific conditions.

Conclusions:

• The integrated isotope and MST approach significantly improves the accuracy and reliability of nitrate source identification.
• This method is effective for tracing nitrate pollution in various water bodies, including surface water and groundwater influenced by organic matter.
• Accurate local characterization of potential pollution sources, like WWTPs, is crucial for robust interpretations and effective water resource management under regulations like the European Nitrate Directive.