Assessment of potentially toxic elements in water and sediments in the drainage network of Lake Mariout, Egypt

The present work investigated the distribution and assessment of potentially toxic elements (PTEs) in the water and surface sediments of both Qalaa and Umum Drains. The water samples were taken from eighteen sampling sites covering the downstream part of the two drains before reaching Lake Mariout Main Basin (LMMB) and Lake Mariout Fishery Basin (LMFB) during the summer period. The samples collected were analyzed for Cu, Cd, Zn, Co, Ni, Mn, Fe and Al. Pollution loading index (PLI), enrichment factor (EF), contamination factor (CF), Geo accumulation index (Igeo) and sediment quality guidelines (SQGs) were calculated as a criterion of possible contamination. Qalaa Drain is characterized by a low pH value of 6.93 compared to the other waters in the studied areas. The lowest Cl was always recorded in the water of Qalaa Drain with an average of 0.65 g Cl/L. The water of Umum Drain, LMMB and LMFB are continually aerated with O2 concentration, compared to the Qalaa drain, which constantly carries H2S. The outcomes revealed that the concentrations of the dissolved metals are at suitable levels according to U.S. Environmental Protection Agency (USEPA). Fe and Al are the two abundant metals in the sediment of the four studied areas. The order of abundance of the metals in the sediments of the present study areas was Fe > Al > Zn > Mn > Cu > Ni > Co > Cd. For the sediments, only cadmium and zinc concentrations in all sites during the study period exceeded the average shale rock concentration. According to the examined indices, the level of contamination in Qalaa Drain ranges from considerable to extremely high. Additionally, the four examined regions have higher Cu and Zn contents than SQGs.