Human Health and Ecological Risk Assessment of Heavy Metal Contamination in the Tigris River (Mosul, Iraq): A Spatial–Temporal Analysis Using CCME-WQI and HPI

River water quality assessments are commonly conducted under conventional anthropogenic pressures; however, the long-term environmental impacts of armed conflicts remain insufficiently understood. This study addresses this gap by evaluating the persistence of war-related heavy metal contamination and its associated human health risks in the Tigris River, Mosul, a post-conflict urban system. The results revealed that Cd, Pb, Cr, and Ni concentrations exceeded WHO guideline values across most sites, while Zn remained within acceptable limits. The highest contamination levels were observed in the central urban zone (Zone 3), which was directly affected by military activities. Hazard quotient (HQ) values for Cd and Pb exceeded the safe threshold (HQ > 1) at all sites, identifying them as dominant contributors to toxicity. The cumulative hazard index (HI) reached extremely high levels (>300 in 2022 and >200 in 2023), indicating severe non-carcinogenic health risks despite a slight temporal improvement. Spatially, contamination increased from upstream to downstream, with midstream and downstream areas acting as critical hotspots. Temporally, although pollutant levels declined in 2023, they remained significantly above safe limits, demonstrating limited natural recovery. Overall, the findings provide clear evidence of the long-term persistence of conflict-related contamination and its sustained risks to human health. This study highlights the need for targeted remediation strategies and offers a transferable framework for assessing water quality in conflict-affected river systems.: