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Edku lagoon is one of the important aquaculture sectors in the Nile Delta of Egypt. Recently, the lagoon has become a sink of discharge wastewater from different anthropogenic sources. The present work aims to study physicochemical parameters, level of nutrients and heavy metal concentrations in water of the lagoon to assess the water quality and identify the potential pollution source(s). Water quality index (WQI), eutrophication index and multiple heavy metal pollution indices (HPI, HEI, PI and Cd) in addition to evaluation of human health risk (HQdermal) model were applied. The obtained data revealed that physicochemical parameter varied between 7.62 - 8.90 for pH, 1.2 - 12.2 g/l for salinity, 3.5 - 12.5 mg/l for dissolved oxygen, 1.3 - 1.9 mg/l for ammonia, 0.065 - 0.191 mg/l for nitrite, 0.217 - 0.915 mg/l nitrate, 0.198 - 0.527 mg/l for orthophosphate, and 51.32 - 102.7 µg/l for chlorophyll-a. The average concentrations of heavy metals were 0.439, 0.322, 0.290, 0.328, 0.059, 0.040, 0.00005 ppm for Fe, Mn, Zn, Cu, Pb, Cd and Hg, respectively. Based on WQI, the lagoon was classified as bad water, while EI result varied between eutrophic to mesotrophic. The pollution indices revealed to lagoon water is highly contaminated based on HPI, HEI and Cd and varied between slightly affected to seriously affected by heavy metals according to PI. Human health risk showed that, HQdermal for all metals except Cd lower than the unity. [ABSTRACT FROM AUTHOR]

Heavy metals contamination level and their ecological risk of the Burullus lagoon were estimated using four cores and twelve surficial sediment samples. The distributions maps of Fe, Mn, Zn, Hg, Cu, and Pb indicate an increase toward drains areas, whereas Cd rises toward the Boughaz El-Burullus. The geoaccumulation index (I geo) and contamination factor (CF) for heavy metal displayed the following order: Cd > Zn > Fe > Cu > Pb > Mn > Hg. The degree of contamination (C d) indicates a considerable degree of contamination for 81.25% of the studied stations, and the pollution load index (PLI) suggested deterioration in 100% of sediments. Regarding the potential ecological risk (RI), the metals were arranged as: Cd > Hg > Cu > Pb > Zn, with considerable risk at the eastern part. According to sediment quality guidelines (SQGs), Zn concentrations suggest frequently adverse impacts on biota while Cu and Cd indicating an occasional adverse impact. Periodic monitoring of heavy metals in aquatic organisms is recommended to assess their toxic risk. • Drains discharging enriched the lagoon sediments by heavy metals. • Most of the lagoon sediments indicate a considerable degree of contamination. • The sediments of the eastern part suggested considerable risk. • Zn, Cu and Cd concentrations are among the most serious metals for living organisms. • Anthropogenic activities were the primary source of heavy metal pollution. [ABSTRACT FROM AUTHOR]

A 19.5-m long Holocene sediment core (MZ-1) was retrieved from Manzala lagoon coast, the depocenter of the Nile Delta. AMS-dating shows the complete Holocene strata of MZ-1, mostly consisting of lagoon muds. The high-resolution dated geochemical elements (major and trace) and bio-markers (n-alkanes) of MZ-1 serve as effective hydroclimate proxies that oscillated during the Africa Humid Period (AHP). Our measurements show the highest value of diagnostic geochemical elements of provenance implications (e.g. Ti/Al, Zr/Al, Cr/Al) prior to 7.5 ka - Period I, indicating the peak period of the AHP, when the African monsoon was intense over the Nile watershed, mainly the East African Plateau (EAP). This is immediately followed by Period II ca. 7.5–4.5 ka, characterized by the highly variable hydroclimatic conditions when the Intertropical Convergence Zone (ITCZ) withdrew southwards. It is denoted by a sharp drop of many diagnostic elements, then succeeded by a gentle, but highly-fluctuated rise, especially the metallic elements Fe, Ti and Cr of basaltic origins of the Ethiopian Highlands. It ascribes to an instability of the hydroclimate in the Blue Nile watershed due to eastward shift of the Congo Air Boundary (CAB) during the AHP receding. In response, the biomarker (n-alkanes) showed remarkably high terrestrial derived primary productivity in Manzala lagoon during 7.5–4.5 ka, evidently reversal to the Early-Holocene marine-enhanced ecological setting. The high Nile floods triggered by unstable hydroclimate of the Nile watershed, particularly in the Ethiopian Highlands of Period II delivered much terrestrial organic matter to coast, making lagoon water less saline. Minor geo-elemental and biomarker fluctuations occurred after ca. 4.5 ka in response to the post-AHP termination in the upper Nile Basin. • Diagnostic geochemical elements were assigned to trace hydroclimate change in Nile watershed • 3 stages of paleo-hydroclimate change: peak stage >8.5–7.5 ka; recession stage ca. 7.5–4.5 ka; drying stage ca. 4.5 ka–recent • The highly-fluctuated hydroclimate pattern during ca. 7.5–4.5 ka was linked to the unstable AHP recession • High Nile floods of recession stage was responsible for less saline lagoonal ecology during the Early Holocene [ABSTRACT FROM AUTHOR]

The Holocene hydro-ecological and environmental change of the Nile Delta remains a knowledge gap. The study aimed to approach this objective by using multi-proxies of lipid biomarkers and bulk organic carbon (OC) in a well-dated MZ-1 core in Manzala lagoon off the Nile Delta. The data defined five distinctive stages at decadal-centennial scale. Stage I (ca. 8.2–7.7 ka) was characterized by remarkedly high reconstructed pH and low mean annual air temperature (the 8.2-ka cold event). The obviously low TOC and C/N, but higher short-chain n-alkanes indicated more marine OC deposition. This was followed by highly fluctuated organic geochemical proxies at Stage II (ca. 7.7–5.8 ka) indicating episodic but significant terrestrial OC input delivered by Nile floods during the African Humid Period (AHP, 11.0–5.4 BP). Subsequent increase in short- and medium-chain n-alkanes suggested macrophytes prevailing in the lagoon during Stage III (ca. 5.8–5.4 ka) with cooling-drying climate transitioned from the AHP. Stage IV (ca. 5.4–1.2 ka) witnessed decreased short-chain n-alkanes of marine origin and increased long-chain n-alkanes of terrestrial origin when the Nile climate entered into the mega-trend of aridification. Abnormal pulses of terrestrial OC with high TOC likely reflected the modified landscape due to early human occupation around the area. The highly fluctuated charcoal fluxes since ca. 6 ka implied such clearing-firing-aided land exploitation activity. The lagoon eco-setting was further affected by intensified anthropogenic-OC input after the latest millennium. Our study highlighted the land-ocean interactions on modulating the paleo-lagoonal ecology of the Nile Delta, which should be incorporated into healthy management in the Nile Delta. • Terrestrial OC delivered by immense episodic Nile floods significantly impacted the eco-setting of the Nile lagoon during 7.7-5.8 ka. • Reconstructed MAAT and pH suggested a climate transition from later AHP to mega-aridification with enhanced brackish ecology. • Buried OC documented freshwater-marine-human intervened ecological condition of the Nile Delta in the Holocene. [ABSTRACT FROM AUTHOR]