Monte Carlo Simulation for Evaluating Spatial Dynamics and Ecotoxicological Hazards of Toxic Metals in Surface Water Impacted by Agricultural Runoff in the Sebou Basin, Morocco

Surface water is vital for environmental sustainability and agricultural productivity but is highly vulnerable to heavy metals (HMs) pollution from human activities. The focus of this research is to provide an analysis of ecological and human exposure to HMs in the Sebou Basin, an agriculturally significant region within Morocco's Gharb Plain. Using a multi-index integration approach, encompassing HM pollution indices, Human Health Risk Assessment (HHRA), Monte Carlo Simulation (MCS), multivariate statistical analysis (MSA), and Geographic Information Systems (GIS), twenty samples of surface water were taken and subjected to analysis. The results demonstrated notable spatial variability, with the northwestern, southwestern, and western parts of the Sebou Basin showing higher contamination levels. Cu exhibited the highest hazard quotient for ingestion, while Cr exceeded the hazard index (HI) threshold in both age categories. Statistical analysis uncovered strong associations, particularly between As and Cr, while principal component analysis (PCA) detected two key factors explaining 74.44% of the overall variability. Pollution indices classified all samples as highly contaminated (HPI > 30), with 65% categorized as "seriously affected" (MI > 6). The HHRA results indicated a heightened non-carcinogenic risk for children and carcinogenic risks exceeding acceptable thresholds (TCR > 10 ^− 4 ), with Ni presenting the highest risk (TCR = 2.32 × 10 ^− 3 for children). MCS results revealed that Cu and Cr pose potential risks, with Cu exceeding the safety threshold for ingestion in both adults and children. These results emphasize the urgent necessity for tailored strategies to reduce contamination and foster sustainable agricultural and environmental management practices.