Ecological and Human Health Hazards Evaluation of Toxic Metal Contamination in Agricultural Lands Using Multi-Index and Geostatistical Techniques across the Mnasra Area of Morocco's Gharb Plain Region

Abstract

Heavy metal (HM) contamination in agricultural soils is a pressing environmental concern with significant ecological and human health implications. This research focused on assessing the ecological and health hazards posed by HMs (arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn)) in agricultural land within Morocco's Mnasra area in the Gharb Plains. A total of thirty surface soil samples were taken from selected sites and analyzed using a multi-index integration approach, multivariate statistical analysis (MSA), and geostatistical techniques. The results showed substantial variability in HM concentrations, with As exceeded safety limits in 75% of samples, while Cd surpassed regulatory thresholds in 62% of cases. The geo-accumulation index (I_geo) indicated moderate to strong contamination for As, while the enrichment factor (EF) and contamination factor (CF) highlighted significant contributions from anthropogenic activities. As and Cd pose the highest ecological risks, with RI values of 4623.77 and 909, respectively. The pollution load index (PLI) ranged from 1.29 to 4.43, with 60% of soil samples classified under moderate pollution. The human health risk assessment (HHRA) identified potential non-carcinogenic risks, particularly for children, with a hazard index (HI) exceeding the critical threshold (HI > 1) for Cr (1.24) and Pb (1.11). Statistical analysis revealed strong correlations among certain metals, suggesting common sources. Geostatistical analysis identified spatial hotspots, especially near landfills and intensive farming areas. The results provide essential guidance for stakeholders involved in agricultural land management, underlining the importance of focused remediation measures and the continuation of research efforts.