Identifying heavy metal contamination hotspots in agricultural soils: an IDW-based ecological and health risk assessment

To assess the contamination of agricultural soils by heavy metals (HMs) in the Kebir-Rhumel basin of northeastern Algeria, soil samples from a depth of 0-20 cm were analyzed for metal concentration (Cd, Cr, Cu, Pb, and Zn). Pollution levels and ecological risks were evaluated using several indices, including the contamination factor (C_f), contamination degree (C_d), ecological risk factor (Er) and potential ecological risk index (PERI). These metrics specifically targeted soils irrigated with river water. Human health risks were assessed using the hazard index (HI) and carcinogenic risk (CR) indices based on ingestion exposure pathways for adults and children. The concentration of heavy metals in the agricultural soils of the Kebir-Rhumel basin followed this order: Zn > Cr > Pb > Cu > Cd. The average concentrations of Cd, Cr, Cu, Pb, and Zn were 0.84, 60.83, 39.26, 58.01, and 93.71 µg.g^-1, respectively. Notably, pollution levels of Pb, Cd, and Cu were particularly concerning with concentrations exceeding background levels at 85%, 75% and 70% of sampling sites, respectively. Health risk assessments indicated that the average hazard index (HI) and hazard quotient (HQ) values were below 1. However, the carcinogenic risk (CR) and total carcinogenic risk (TCR) for Cd, Cr, and Pb were higher for children compared to adults. TCR mean values were about 4.93E - 05 and 4.61E - 04 for both adults and children, with chromium identified as the primary contributor to carcinogenic risk. Both CR and TCR exceeded the acceptable carcinogenic risk threshold of 1.0E - 04, potentially posing carcinogenic risks through extended exposition. Overall, these findings highlight significant concerns regarding soil quality in this region. This study can guide the development of effective strategies for monitoring, mitigating and managing the levels of heavy metals in agricultural soils, thereby ensuring the safeguarding of the human health.