Integrated machine learning-bayesian receptor modelling framework for uncertainty-aware source apportionment in a...

Area of Science:

• Hydrogeology
• Environmental Chemistry
• Water Resource Management

Background:

• Coastal aquifers face complex fluoride contamination due to seawater intrusion, geology, recharge, and human activities.
• Seasonal variations and overlapping hydrogeochemical processes make evaluating fluoride sources challenging.
• Existing methods struggle to accurately apportion fluoride contributions in dynamic aquifer systems.

Purpose of the Study:

• To develop and apply an integrated, uncertainty-aware framework for identifying dominant groundwater fluoride processes.
• To quantify the relative contributions of different sources to fluoride contamination.
• To link fluoride sources to lithological and land use factors in a coastal aquifer.

Main Methods:

• A Bayesian-Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) receptor model was integrated with Self-Organizing Maps (SOM).
• Data-informed priors, prior-posterior checks, and No-U-Turn Sampler (NUTS) inference were used for uncertainty-aware source apportionment.
• Seasonal monitoring across 171 stations in an Indian coastal aquifer system provided the dataset.

Main Results:

• The Bayesian APCS-MLR model identified geogenic leaching as the primary fluoride source (89.14%) in the pre-monsoon season.
• Post-monsoon season showed a significant decrease in geogenic control (48.86%) with increased contributions from recharge-driven pH effects (16.13%) and ion exchange (3.83%).
• Lithology and land use were identified as key regulators, with fine-textured formations and croplands showing persistent geogenic influence, while aquaculture settings exhibited stronger post-monsoon anthropogenic impacts.

Conclusions:

• The study presents a robust, uncertainty-aware methodology for source apportionment in complex hydrogeochemical environments.
• Seasonal dynamics significantly alter fluoride sources, with recharge and land use playing crucial roles post-monsoon.
• The findings support informed groundwater management strategies for addressing fluoride contamination in coastal aquifers, aligning with Sustainable Development Goal 6.