Visualization of physicochemical parameters' behavior in leachate, baseliner, and surface water during dry and rainy...

Landfill leachate, a major environmental contaminant, is influenced by multiple factors and can migrate through landfill systems, spreading over considerable distances and polluting surrounding ecosystems. This study utilized Ball Mapper, a topological data analysis tool, to qualitatively explore hidden relationships between physicochemical parameters in leachate, surface water, and the baseliner, which can aid in pollution monitoring. The resulting Ball Mapper topological graphs uncovered behavioral similarities and relationships among parameters across different seasonal conditions. The analysis effectively revealed underlying patterns and interconnections by clustering parameters with similar behavior into the same nodes and linking those with hidden similarities. Additionally, Spearman correlation was used to validate the Ball Mapper output, the analysis showed that baseliner and surface water had a weak linear relationship with leachate, except for PO₄³ (r = 0.99), SO₄²⁻(r = 0.71), TSS (r = 0.82), and pH (r = 0.95) in surface water across seasons, which could be as a result of runoff, sediment transport, and environmental factors rather than direct leachate infiltration. The study also demonstrated that while seasonal variations in precipitation influenced leachate volume and pollutant concentrations, the landfill's engineered barriers effectively mitigated the potential environmental impact of leachate migration. Ball Mapper successfully showed the hidden behavior that traditional clustering methods may miss, highlighting its potential as a valuable tool for environmental monitoring.