Pollution Load Index (PLI) Qarun Lake EgyptQarun Lake is a remnant of the historic Moreis Lake; it is an enclosed lake receives the water through several drains mainly El-Bats and El-Wadi drains carrying agricultural wastewater mixed with domestic and industrial wastes to the lake, which increases the accumulation of pollutants, in particular, the heavy metals in the lake environment. The present study is concerning the levels, distribution pattern as well as the pollution indices of the heavy metals in Qarun Lake water. The sites facing the inlet of the drain showed the highest contents of the metal, recording 587. 55, 59.6, 61.92, 26.98, 50.72 and 3.63 µg/l for Fe, Mn, Zn, Cu, Ni, Cr, Pb and Cd respectively. On the other side the, Metal Index (MI) and Pollution Load Index (PLI) denotes that Qarun Lake is suffering from serious metal pollution for the aquatic life utilization because of the huge amount of wastes discharging into the lake which maybe leads to dangerous adverse impacts on the fish and other aquatic organisms. The study recommended that usage of biological and chemical treatment for wastewater discharging into the lake into to improve the water quality of the lake water.

Sediments act as a sink or source of pollution under various conditions. Moreover, they can serve as pollution indicators. The present research aims to evaluate sediment quality associated with its content in heavy metals and the potential ecological risk, focusing on the sub-branches of Nile River (Rayahs) in Egypt, including El-Tawfiky (RT), El-Menoufy (RM), El-Behary (RB), and El-Nassery (RN). According to the results, El-Rayahs sediments are characterized by an increasing sand fraction, followed by mud. Regarding heavy metals pollution, Cd registered the highest pollution ranking, whereas Fe, Mn, Zn, Pb, and Ni exhibited the lowest effect. Furthermore, the ecological risk for El-Rayahs sediments increases northward; however, most sites either showed slight pollution or did not record any degree of contamination, except the northern stretch of El-Behery (El-Mahmoudia Canal), which is a very high-polluted zone, with high ecological risk according to the contamination degree (Cd) and potential ecological risk (RI) indices.

Egyptian Journal of Botany http://ejbo.journals.ekb.eg/ 61 M ANZALA Lake, the largest Egyptian northern lake, suffers from continuous deterioration as it receives huge amounts of different wastes. This study evaluated the abiotic and biotic conditions of the lake water (e.g., physicochemical variables, bacterial communities, and phytoplankton structures and their biochemical contents) from 11 sites along the lake in winter and summer 2020. The results revealed that the increase in phytoplankton densities and chlorophyll (a) in winter combined with increased nutrient contents. The highest concentrations of the biochemical contents of phytoplankton and the highest enumerations of bacterial indicators were recorded during summer. The sites close to the inlets of drains recorded a complete depletion of oxygen and a high ammonia content. The highest phytoplankton standing crop was recorded in the middle sector of the lake. Despite the efforts of the Egyptian government to rehabilitate Manzala Lake since 2017, the results showed an increase in pollution levels at various sites and the continued deterioration of the lake's ecological status. These results confirm the importance of increasing the efforts to restore the environmental health status of the lake, primarily by treating wastewater before it is discharged into the lake.

Sediments are vital components of aquatic ecosystems, which trap and store various essential elements as well as harmful polluting substances. This is why sediment quality assessment is of great importance in measuring the quality, or pollution, of water bodies. In this study, the levels, ecological risk, and toxicity indices of 17 heavy metals (HMs) were evaluated in the sediments of the two lakes: Upper Wadi El-Rayan Lake (UWRL) and Lower Wadi El-Rayan Lake (LWRL). Both are important wetlands in Egypt used as agricultural drainage water reservoirs for Fayoum province. As revealed by the texture of the sediments, the sand represented the major sediment portion of the UWRL, while the mud was dominant in the LWRL. According to ecological risk assessment, the sediments of the two lakes suffer different degrees of metal pollution, mainly Cd, Pb, and Ni. Based on sediment quality guidelines, toxicity indices indicated different potential toxic effects of the studied HMs on benthic-dwelling organisms, but Ni and Ba had the highest potential biological risk. Results also revealed that the area facing the El-Wadi Drain is the most polluted due to its proximity to the water drainage entrance. However, LWRL is generally more polluted than UWRL. This is related to the shrinkage of water volume and lake area; it causes an increase in the concentration of metals in water, and thus an increase in the sedimentation rate of these metals into the bottom.