Spatial Distribution of Polychlorinated Biphenyls in Some Watercourses: A Study on Water Quality, Risk, and Effect on Macroinvertebrates

Abstract Continued monitoring of polychlorinated biphenyl (PCB) residues in inland watercourses contributes indirectly to Sustainable Development Goal 14 by preserving aquatic biodiversity and ecosystems. Therefore, the current work aims to monitor PCBs in water courses of Giza, Al-Qaliobiah, and Al-Gharbiah Egyptian Governorates and assess their risk using various tools. The highest water temperature was 32.2 °C et al.-Gharbiah during spring. pH values were natural throughout all seasons and sites, except Al-Qaliobiah, which showed alkaline water in the summer. Giza showed high DO in winter (7.75 mg/L), while Al-Qaliobiah and Al-Gharbiah peaked in autumn (5.04 and 6.41 mg/L, respectively). Six PCB congeners (52, 70, 101, 118, 138, and 180) were detected, and their levels exceeded the permissible limit in surface water. PCB-52 and 70 were the most dominant in all investigated governorates. The highest total PCBs were 126.10 and 132.40 µg/L in deep water at Giza and Al-Gharbiah, respectively, while in surface water et al.-Qaliobiah it was 111.90 µg/L. Most PCB congeners were lowest in winter, compared to spring and autumn, and this was inversely proportional to abundance of macroinvertebrates. Hilsenhoff Biotic Index (HBI) values showed relatively poor water quality, indicating significant organic pollution. All hazard quotient (HQ) values were greater than 1, and the carcinogenic risks exceeded the acceptable limits. Therefore, implementing monitoring programs and regulatory policies is vital to protect aquatic ecosystems and public health.