PAHs in the sediments of the Shatt Al-Hillah River, Babylon, Iraq: Spatial and temporal distribution, pollution sources, human impacts, and treatment strategy

This study investigated the spatial and temporal distribution, sources, and human health risks of 16 priority polycyclic aromatic hydrocarbons (PAHs) in the sediments of the Shatt Al-Hillah River, Babylon, Iraq. The concentrations of PAHs ranged from 1713.29 to 9996.47 ng/g dry weight, with high molecular weight PAHs (five- and six-ring compounds) dominating across all seasons. Molecular diagnostic ratios and principal component analysis revealed that the primary sources of PAHs were mixed pyrogenic and petrogenic emissions, including vehicular exhaust, industrial discharges, and biomass combustion. The Incremental Lifetime Cancer Risk (ILCR) values for adults and children at all sampling sites and during all seasons exceeded the acceptable threshold of 1 × 10⁻⁴, indicating a significant carcinogenic risk. Sediment washing using Triton X-100 followed by treatment of the washing effluent with activated carbon (AC) derived from wheat straw achieved PAHs removal efficiencies between 74.87 % and 94.43 %. The AC exhibited high reusability across three cycles. These findings highlight the urgent need for environmental management strategies and demonstrate the potential of using agricultural waste-derived AC as an effective, low-cost, and sustainable solution for remediating PAH-contaminated sediments.