Wyniki wyszukiwania - Biblioteka Nauki

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: Lake Nasser

Sortuj według:

Ogranicz wyniki do:

Comprehensive assessment of water and sediment quality in Lake Nasser, Egypt, using various potential risk indices

100%

Abdel-Satar A. M. , Salem S. G. , El-Sayed S. M. , Goher M. E. , Abdelaziz G. S. , Al-Afify A. D. G.

Oceanological and Hydrobiological Studies

2024

tom Vol. 53, No. 1

40--60

Lake Nasser is a freshwater lake that supplies over 95% of Egypt’s freshwater budget. Therefore, the quality of water in the lake is critical for its conservation. In addition to assessing the metal pollution load, the quality of water and sediment in the lake was assessed by collecting water and sediment samples for metal content analysis. Lake Nasser is a warm monomictic water body with a single circulation cycle in the cold months. Dissolved oxygen content in bottom water samples often dropped significantly to levels below international guidelines, reflecting reduced rates of photosynthetic activity. Although 50% of the lake’s water samples contained Pb concentrations slightly above the World Health Organization’s (WHO) limit for drinking water, the metal pollution index did not exceed the critical level and was classified as low metal water pollution. Based on the geoaccumulation index (I-geo), the enrichment factor (EF) and the pollution load index, the sediments of Lake Nasser are practically uncontaminated with metals. Ni has the highest EF and I-geo values, while Ni and Cd contributed the most to the ecological risk and toxic risk index. The obtained results revealed that Cd and Ni in the sediments may pose a threat to organisms living in Lake Nasser.

Phytoplankton response to changes of physicochemical variables in Lake Nasser, Egypt

72%

Hussian A.-E. M. , Napiorkowska-Krzebietke A. , Toufeek M. E. F. , El-Monem A. M. A. , Morsi H. H.

Journal of Elementology

2015

tom 20

nr 4

Seasonal and spatial changes of phytoplankton in relation to environmental variables affecting the water quality were investigated along the main channel of Lake Nasser throughout 2013. In total, 104 phytoplankton species, belonging to 7 classes, were identified. Phytoplankton assemblages were dominated by Bacillariophyceae, Cyanophyceae and Chlorophyceae, whereas Dinophyceae, Euglenophyceae, Chrysophyceae and Cryptophyceae were infrequent. Cyclotella glomerata, C. ocellata and Aulacoseira granulata represented the most abundant species among Bacillariophyceae. Cyanophyceae was dominated by Planktolyngbya limnetica and Eucapsis minuta, and Chlorophyceae by Ankistrodesmus fusiformis and Staurastrum paradoxum. The water column was thermally stratified during summer, while being mixed throughout winter. Phytoplankton features and physicochemical variables were analyzed with the principal component analysis. Electrical conductivity and water temperature were the most common factors negatively controlling phytoplankton density. Phytoplankton density was positively associated with NO3, whereas it was negatively correlated with PO4 and HCO3. Cyanophyceae were strongly adapted to the environmental variables and NO2 was limiting their growth. Chlorophyceae were more dependent on PO4 than NO3. The vertical distribution of Chl a was associated with the summer thermal stratification and its concentration increased southwards. Chl a was affected by NO2 and linked to Chlorophyceae. The regional variations of phytoplankton reflected its response to varying environmental conditions. The annual average of the trophic state index indicated eutrophic waters of Lake Nasser.