Coupling cross-validated geoscientific evidence and indigenous knowledge to understand contaminant dynamics affecting a land-based community in Northern Ontario.

Chronic environmental contamination inequitably affects Indigenous communities across Canada, including a First Nation (FN) near a major industrial city in northwestern Ontario. Motivated by reports of elevated blood cancer rates and widespread pollution in this FN, we developed an environmental monitoring framework that synthesizes geoelectrical, hydrogeological, and geochemical data, alongside numerical modelling of groundwater flow and contaminant transport, with Indigenous Knowledge, community priorities, and lived experiences. Structured around five interlinked layers-Foundational, Diagnostic, Process, Validation, and Communication-this framework is the core of the study, supporting the integration of diverse knowledge sources across spatial and temporal data scales. Geoelectrical surveys reveal a leachate plume migrating northeast from an industrial landfill toward the FN community. Hydrogeochemical data indicates a correlation between concentrations of heavy metals, low resistivity and high induced polarization anomalies. Other pollution sources in peripheral areas contribute to elevated levels of heavy metals and carcinogenic hydrocarbons in groundwater, soils, and sediments. Groundwater flow simulations (1990-2030), constrained by site-specific geological and hydrometeorological data, show that rainy periods accelerate contaminant migration, overwhelming mitigation systems and increasing exposure risks. Indigenous oral histories and environmental observations ground technical findings in lived experience, reinforcing their interpretation and guiding research priorities. This study yields time-evolution environmental threat maps and predictive contaminant transport models. These outcomes support risk assessment and inform locally actionable mitigation and remediation strategies, contributing to more effective spatial-temporal environmental monitoring and advancing Indigenous health equity in rural and remote Canadian settings.