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Abstract El-Burullus Lake is a coastal Northern lagoon situated along the Mediterranean Sea, between the western Rosetta and the eastern Damietta branches of the River Nile. The lake is the second largest natural lake in Egypt with respect to area and production. It is the main source of fish production in all Egyptian lakes. Its production has increased gradually from 7,349 tonnes in 1963 to 67.577 tonnes in 2016, in addition to about 670.000 tonnes from the aquaculture processes around it, the production of the lake and its aquaculture ponds represented about 42.5 % from the total fish production in Egypt. Many sources of pollution affect and deteriorate the water quality of the Lake. Burullus lagoon is affected mainly by agricultural drainage water mixed with different types of wastes from fish farms (Terra Drain, Drain 7, Drain 8 and Drain 11), wastewaters effluents (Terra Drain, Drain 7 and El- Gharbia Drain) as well as domestic drainage water discharged mainly from El-Gharbia drain and drain 11. Agriculture drainage water accounts for 97% of the total inflow to the lake (3.9 billion m3 per year), followed by rain water (2%) and groundwater (1%). 16% of the lake’s water evaporates and 84% flows to the sea. Lake Burullus, one of the Mediterranean eutrophic lakes, is one of the major disposal areas for agricultural drainage water in Egypt. It receives approximately 4 billion m3 of drainage water per year from the Nile Delta agricultural lands. Twelve water samples were collected from different localities along El-Burullus Lake and nine samples from drains surrounded the Lake. Samples were collected seasonally, during the period of spring 2016 – winter 2017. The present study was designated to determine the pollution status of El-Burullus Lake by evaluation the water quality that may affect to a great extent the biological productivity of the Lake water, and to assess the levels of heavy metals (Fe, Mn, Zn, Cu, Ni, Cr, Pb, and Cd) in water of El- Burullus by determination of water quality index (WQI), metal quality indices (PI and MI), and eutrophication index to determine the suitability of aquatic life utililzations. The present work includes three chapters; a brief description of these chapters is given as follows: The first chapter is related to introduction of the thesis where the environmental status of El-Burulluse Lake is given from the historical background and the literature survey for physico-chemical studies of water. The second chapter contains the experimental parts including sampling techniques, description of the selected and investigated sampling stations and describing the methods applied to determine the physical and chemical parameters in water. The third chapter includes the obtained results, their discussion and data analysis during the period of study. The obtained results can be summarized as follows: 1- Water temperature depends upon the climatic conditions and sampling time collection. It ranged between (13.60-32.20°C) while the maximum water temperature was recorded at stations (9) during summer and the lowest water temperature value was recorded at stations (6) during winter. 2- Transparency was affected by domestic sewage, industrial and agricultural effluents and fluctuated between (15-70 cm) with maximum value was recorded at station (3) during winter and the minimum value recorded at station (4) during spring season. 3- Electrical conductivity depends on the concentration of total dissolved solids in the water body and it varies between (2.14-54.80 ms/cm). The maximum value was recorded at station (3) during summer while the minimum value was recorded at station (11) during summer. 4- The total solids (TS) content is a very useful parameter describing the chemical constituents of water. It is affected greatly by discharged effluents and the obtained values were in the range of (1.52-34.13 g/l) with maximum value during winter at station (3) and the minimum value recorded at station (11) during summer. 5- The total dissolved solids (TDS) increased at the stations considered as points of discharges. TDS values fluctuated between (1.44-34.10 g/l). The maximum value was recorded during summer at station (3) while the minimum value was recorded during summer at station (11) 6- The total suspended solids (TSS) also were affected by agricultural and domestic effluents discharged into El-Burulluse Lake and the obtained values were in the range of (32.86-94.12 mg/l). The maximum value of TSS was recorded during winter at station (6) while the minimum value was recorded during winter at station (3). 7- pH values were in the alkaline side (7.55-8.96). The maximum pH value recorded at station (9) during winter while the minimum value of pH recorded at station (11) during winter.8- Dissolved oxygen values (DO) ranged between (2.10-13.40 mg/l). The lowest values of DO concentrations found during winter at station (8) while the highest value of dissolved oxygen recorded in station (6) in summer. 9- The biological oxygen demand is a good indicator of organic pollution in water. Its values fluctuated between (5.82-29.16 mg/l). The maximum value recorded at station (8) during summer and the minimum value recorded at station (3) during winter. 10- The chemical oxygen demand values are of great importance where the BOD values cannot be determined accurately. COD values fluctuated between (10.29-48.51 mg/l). The maximum value of COD was recorded at station (5) during summer season and the minimum value was recorded at station (3) during summer. 11- Major anions showed elevated values in the most polluted areas along El-Burulluse Lake while the lowest values were recorded in the clear areas and the obtained results as follows: a) Carbonate values ranged between (0.1-14.6 mg/l). b) Bicarbonate values ranged between (133.6-376.4 mg/l). c) Chloride values ranged between (678.9-14663 mg/l). d) Sulphate values ranged between (144.5-3410 mg/l). 12- Major cations showed similar trends as major anions where elevated values were recorded in the polluted areas along El-Burulluse Lake while the lowest values were recorded in the clear areas and the results were as follows: a) Calcium concentrations varied between (43.7-409.2 mg/l). b) Magnesium values ranged between (63.3-1295.7 mg/l). c) Sodium values ranged between (433.4-10230 mg/l). d) Potassium values ranged between (15.9-375.01 mg/l). 13- The nutrient salts concentrations depend on the Lake effluents and phytoplankton community at different locations. a) Nitrite values fluctuated between (14.25-247.92μg/l). b) Nitrate concentrations fluctuated between (36.29-1241.09 μg/l). c) Ammonia concentrations ranged between (115.95-11350.04μg/l). d) DIN ranged between (275-11563 μg/l) e) While the DON concentration fluctuated between (204.5-1146.1 μg/l) f) PON ranged between (208.1-4080.5 μg/l) g) TDN concentration ranged between (507.6-12371.7μg/l). h) TN concentrations ranged between (1001.5-16452.2μg/l). i) orthophosphate concentrations fluctuated between (11.6-413.3 μg/l), the dissolved organic phosphorus (DOP) ranged between (6.79-176.1 μg/l), the dissolved inorganic phosphorus (TIP) ranged between (13.64-434μg/l), the total particulate phosphorus (TPP) included POP which ranged between (4.1-176.1 μg/l) and PIP which ranged between (1.8-44.8), While the total phosphorous concentrations fluctuated between (24.55-796.2 μg/l) j) The silicate concentrations ranged between (1.4-24 mg/l). 14- The heavy metal concentrations increased at station (8), due to wastes of drain (8&9) which are contain agricultural, domestic and industrial wastes. The heavy metals results can be summarized as: a) The iron concentrations fluctuated between (240.4-700.4 μg/l). b) The manganese concentrations fluctuated between (18.-87.4 μg//l). c) The copper concentrations fluctuated between (2.5-8.4 μg/l). d) The zinc concentrations fluctuated between (36.8-83.7 μg/l). e) The nickel concentrations fluctuated between (9-22.2 μg/l). f) The chromium concentrations fluctuated between (9.2-20 μg/l). g) The lead concentrations fluctuated between (20.4-71.3 μg/l). h) The cadmium concentrations fluctuated between (0-5.3 μg/l). 15- According to the Oregon Water Quality Index (OWQI), the present results indicate that Lake Burullus are classified during all season as very poor for fishing utilization at all station. .the minimum annual value (1.7) was recorded at station (8) this indicate that this station is lower water quality as it received water from drain 8,9 which contain industrial ,domestic and agricultural waste water . 16. El-Burullus Lake water suffers from obviously different contamination grades with the measured metals for different utilizations. Mn , Fe, Zn, Cu and Cr exhibit a slightly pollution effect at various locations according to the aquatic life criteria, Cd show slightly to moderately pollution effects at the most studied sites for aquatic life utilizations. while Pb show seriously pollution effects at the most studied sites for aquatic life utilizations but Ni recorded no pollution effects at all stations along the Lake 17- Metal index indicate that all the selected stations along the Lake are seriously threatened with metal pollution for drinking and aquatic life usages, (MI ≥ 1).18- The trophic status throughout the lake varied spatially and temporally. result indicate that the mean value of trophic state index ranged between (73.29-86.1) the minimum value 73.29 was recorded at station(3) this may attributed to that station receives water from the sea through El-Boughaz out-let. While the maximum value 86.1was recorded at station (8) this may attributed to that the station (8) receive wastewater drainage from Drain 9 and Drain 8. . from the above mentioned results we can conclude the following: 1- The abnormal values of different physical and chemical parameters were recorded at stations affected by different wastes (agricultural, industrial and domestic) discharged into the Lake at the area under investigation. 2- The results revealed that water of El-Burullus Lake Contain high concentration of nutrient due to uncontrolled discharge of untreated sewage and agricultural wastes 3-the Lake is largely fed by drainage water which effect on the characteristics of the Lake that cause the Lake to be hyper eutrophic 4-the water is brackish with a high EC near El-Boughaz out-let as this part receives water from the sea and slightly low in western part near Brimbal out-let as this part receives water from the Nile 5-station (8) is the most polluted as it receives water from drain 8 and drain 9 that contain domestic, agricultural and industrial wastes. 6- Increasing amounherefor Lake Burullus are classified during all season as very poor for fishing utilization at all station of dissolved inorganic nitrogen, phosphate and silicate concentrations causes higher phytoplankton count, diversity index and chlorophyll-content.7- Continuous release of wastewater from the southern drains is much greater than seawater discharge into the lagoon. This situation has eventually accelerated eutrophication of the water body due to the increased nutrient inflow to the lake. 8-The dissolved oxygen of the lagoon is generally high, particularly at the western side. The eastern most section of the lagoon, which receives the greatest wastewater effluents from four drains (Drain 7; Nasser Drain; El- Gharbia Drain; and El-Burullus East Drain) containing sewage and agricultural waste, exhibits the minimal dissolved oxygen content. 9- The eastern and southern sides of the Burullus Lagoon are much polluted than the northern and western sides. The primary reason is the occurrence of many drains carrying sewage and agricultural waste at these sides. from the above mentioned results we can recommend and offer the following: 1-control discharge of drainage and sewage water in to the lake or at least minimize the usage of fertilizers in agricultural lands, or treatment of drainage water is essential to hurry its recovery and improving water quality. 2- Continues environmental studies must be done to determine the current status of water quality and to assess the chemical and biological pollution of water of El-Burullus Lake as well as animal pests, plant plankton and fish in it. 3-Strict application of laws concerning the protection of environment, in particular the law 4 of 1994. 4-Constructing measuring units for controlling and detection biomass and environmental balance of the Lake for its present explorating and future prediction. These units give the policy makers the scientific supported vision that will lead to promotion plans for the present and sustainable development. |