Spatio-temporal assessment and source identification of heavy metals in the Abou Ali River, North Lebanon

• Seasonal and spatial patterns of 12 heavy metals were assessed in Abou Ali River. • Six campaigns captured variability across wet, dry, and summer periods. • Statistical tests identified significant site and seasonal differences. • Fe, Mn, Pb, and Cd frequently exceeded WHO/EU guidelines at downstream sites. • Pearson correlations suggested common anthropogenic sources for multiple metals. Lebanese rivers face increasing contamination pressures, yet systematic assessments of heavy metal pollution remain scarce. The Abou Ali River, a vital resource for irrigation, hydropower, and local livelihoods in North Lebanon, has been especially vulnerable to untreated wastewater, industrial effluents, and solid waste dumping, but no comprehensive evaluation has been conducted to date. This study provides the first spatiotemporal analysis of 12 priority heavy metals (Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, Pb) in the Abou Ali River. A total of 96 surface-water samples were collected from 16 sites during six field campaigns (2015–2017) and analyzed using and analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Statistical tools, including ANOVA, Pearson correlation, and Principal Component Analysis (PCA), were applied to evaluate spatial and temporal variations and identify potential pollution sources. Results showed pronounced spatial heterogeneity, with upstream sites reflecting near-background levels, midstream sites influenced by agricultural and peri‑urban runoff, and downstream sites—particularly the estuary—showing severe contamination that exceeded WHO and EU guideline values for Fe, Pb, Cd, Zn, and Hg. Seasonal analysis further revealed higher concentrations during dry periods, underscoring the role of reduced dilution and continuous pollutant inputs. This study establishes the first systematic baseline for heavy metal contamination in the Abou Ali River, clarifies the dominant anthropogenic and geogenic sources, and provides a scientific foundation for water management, agricultural safety, and public health protection in North Lebanon. By generating the first systematic baseline dataset for heavy metals in the Abou Ali River, this study fills a critical knowledge gap in Lebanon, identifies contamination hotspots, and provides urgently needed evidence to guide water management, agricultural safety, and public health protection.