The Integrated Use of Heavy-Metal Pollution Indices and the Assessment of Metallic Health Risks in the Phreatic Groundwater Aquifer—The Case of the Oued Souf Valley in Algeria

In this research, contamination levels and the spatial pattern identification, as well as human and environmental health risk assessments of the heavy metals in the phreatic groundwater aquifer of the Oued Souf Valley were investigated for the first time. The applied methodology comprised a combination of heavy-metal pollution indices, inverse distance weighting, and human health risk assessment through water ingestion on samples collected from (14) monitoring wells. The contamination trend in the phreatic aquifer showed Al > B > Sr > Mn > Fe > Pb > Ni > Cr > Ba > Cu > Zn. Similarly, the enrichment trend was Al > B > Sr > Mn > Ni > Pb > Cr > Ba > Cu > Zn. Ecologically, most of the analyzed metals reflected a low potential ecological risk, except for two wells, S13 and S14, which represented a considerable and high ecological risk in terms of Pb. According to the applied grouping method, the samples in the first group indicated a lower risk of contamination in terms of heavy metals due to their lower concentration compared to the second group. This makes the area containing the second group’s samples more vulnerable in terms of heavy metals, which could affect urban, preurban, and even agricultural areas. All of the samples (100%) indicated the possibility of potential health risks in the case of children. While six samples showed that the non-cancer toxicity risk is considered low, the rest of the samples had high Hazard Index (HI) values, indicating the possibility of health risks occurring in the case of adults. The constructed vertical drainage system is acting as a supporter and accelerator of the pollution levels in the shallow groundwater aquifer. This is due to its contribution to the penetration of different pollutants into this aquifer system, depending on the residence time of the water, which appears to be long within the drainage system.