Characterizing land use effect on shallow groundwater contamination by using self-organizing map and buffer zone.

Area of Science:

• Environmental Science
• Hydrogeology
• Water Quality Assessment

Background:

• Groundwater contamination by nitrate-nitrogen (NO₃-N) is a significant issue for rural drinking and domestic water supplies.
• Land use patterns are critical factors influencing the quality of shallow alluvial groundwater.

Purpose of the Study:

• To investigate the impact of diverse land use types on shallow alluvial groundwater quality in a South Korean rural area.
• To identify sources and patterns of nitrate-nitrogen (NO₃-N) contamination in groundwater.

Main Methods:

• Application of Self-Organizing Map (SOM), Principal Component Analysis (PCA), and Hierarchical Cluster Analysis (HCA) for data analysis.
• Utilizing a buffer zone (32.65 m radius) around wells to enhance spatial land use information accuracy.
• Classification of shallow groundwater into three clusters based on chemical constituents and land-use properties, including NO₃-N, Cl, and SO₄.

Main Results:

• Forests (44.9%) and rice fields (28.8%) dominate the land use, significantly impacting groundwater.
• Higher NO₃-N concentrations were observed in groundwater influenced by public facilities and livestock areas.
• Rice paddies showed NO₃-N contamination alongside chlorine (Cl) and sulfate (SO₄), linked to soil nutrients and residual salts.
• Variations in NO₃-N levels within the same land use type suggest diverse biochemical reactions and recharge pathways.

Conclusions:

• Land use type is a primary driver of nitrate-nitrogen (NO₃-N) contamination in rural groundwater systems.
• The integrated approach using SOM, PCA, and HCA, enhanced by a buffer zone, effectively classified groundwater quality.
• Improved SOM model prediction accuracy (approx. 10%) was achieved by incorporating a buffer zone based on the Cooper-Jacob equation.