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W, ffect of the drains effluent on the variations of trace metals and inorganic anions and cations of water were studied in the southern sector of Lake Manzalah during four successive seasons (1999-2000). The study revealed that an obvious depletion of dissolved oxygen has occurred in addition to a high increase in COD and BOD in the area which received the urban and agricultural wastes from Bahr El-Bagar drain. The concentrations of the nutrient salts showed a wide fluctuation and abrupt changes due to irregular influx of different wastes. Also, high and abnormal concentrations of ammonia, nitrate and orthophosphate were recorded. The levels of trace metals in lake water were high in areas received domestic and agricultural effluents. INTRODUCTION Lake Manzalah is the largest and most productive among all the Egyptian brackish lakes. It is located in the north-eastern extremity of the Nile Delta. The total area of the lake is about 872 Km of which only 778 Km represent open water with an average depth of about 140 cm; The area of the lake has been steadily decreased in size since records started in the early 1900s where it was estimated as 1647 Km. Land reclamation in the west and the south of the lake is the main cause of this decrease. . Now, the lake is considered as a sink for disposing industrial and human wastes. A total amount of about 7500 million cubic meters of untreated industrial, domestic and drainage water as well as agrochemical (fertilizers and biocides) is discharged annually into the lake through seven main drains (Ibrahim et aL, 1997a). Hadous, 18 Amaal M. Abdel Satar Ramsis and Bahr El-Bagar drains contribute about 75% of the total annual drainage water into the southern sector of the lake. Consequently, the quality of water in the lake basin has been affected by many factors; the most significant of which are the location of the drains and the quality of their water inflow. The appearance of the pollution problem in the lake started since 1967 by closing of the inlets, which connected the lake with the sea. This situation led to the continuous disappearance of the marine fishes from the lake. Khaii! (1990) stated that the salinity and nutrients are important factors, which affect and still affect the ecology of lake Manzaiah. The increase in nutrients and freshwater discharges has changed the fish community from a brackish (mixed species) to a freshwater (Tilapia) dominated one (Khalil and Salib, 1986). Ibrahim et aL (1997a) recorded three species of bottom fauna at the southern sector of lake compared by 16 species at sea-lake connection and added that the low number of species encountered is probably due to the high level of water pollution. Previous studies on biological characteristics of the lake have been issued by Dowidar et ah (1990); El-Serafy and AbdelBaky (1990); Aboul Ezz and Abdel-Razek (1991); Ibrahim etal (1997b); Abdel-Baky et al (1998); Fishar (1999a,b) and Sabae (2000). The aim of the present study was to follow up the variations in water quality and trace metals in the southern sector of the lake in addition to the inflowing drains to assess the extent of eutrophication condition in Lake Manzaiah. MATERIAL AND METHODS The sampling stations were chosen to cover the southern sector of Lake Manzaiah and its inflowing drains. Water of study area is subjected to pollution via several and rather complicated routes; airong them domestic and agricultural discharges are the most significant. Hadous-Ramsis drain has typical agricultural drainage water, which would be of moderate quality for agricultural use. However, water from Bahr El-Bagar, is quite differentBahr ElBagar serves as a wastewater stabilizing facility for Cairo sewage, allowing this wastewater to become biologically degraded into nutrient-rich by the time it reaches the lake. Environmental studies on the impact of the drains effluent upon the southern sector of Lake Manzalah, Egypt The present study was extended from autumn 1999 to summer 2000. Six stations were determined to cover the area of investigation. Additional stations were chosen inside both HadousRamsis and Bahr El-Bagar drains. The locations of sampling stations are presented in Pig. (1). Water samples were taken from the surface layer by using poly vinyl chloride Van Dorn bottle. Samples were preserved in an ice-box and returned immediately to be analysed. The chemical parameters were analysed according to the methods described in APHA 1995. Salinity was calculated by multiplying the value of chlorosity by 1.80655 (Jacobosen and Kimdsen, 1940). For total trace metals, the samples were acidified with concentrated nitric acid (pH<2) and then digested by nitric-perch lurk acid mixture (APHA, 1995). The total metal concentrations were determined by using Hitachi model 170-30 with graphite atomizer (GA-2) atomic absorption spectrophotometer. RESULTS AND DISCUSSION The present results showed a noticeable seasonal trend of temperature (17.6-24.6 and 25.0-30.5 °C during cold and hot seasons, respectively). However, the variations in water transparency and conductivity were almost local without clear-cut seasonal trends (Table 1). Generally, the decrease of transparency in the studied area may be due to increase in phytoplankton abundance, as the water acquired a characteristic greenish color. E.G. showed positive correlation with Na, K, Ca and Mg (r0.66, 0.86, 0.57 and 0.75. respectively) and with P 0 4 \ S04 ' and NH3 (r= 0.45, 0.62 and 0.65. respectively). Slightly acidic pH values were recorded at station 4 during autumn and in Bahr El-Bagar drain during autumn and winter seasons (Table 1). The relative decrease of pH may be attributed to the bacterial and fungal action in the sediment. These activities give rise to methane and hydrogen sulphide release as well as the formation of organic acids and other break down products (Elewa and Ghallab, 2000). The values of dissolved oxygen (DO) ranged between 0.0 to 5.9 mgl" with remarkable seasonal and site variations (Table 2). The highest values were recorded during winter and the 20 Amaal M. Abdd Satar lowest during summer. Obvious depletion of DO was recorded at discharge point of Bahr Ei-Bagar into the lake and inside the drain itself. This may be attributed to the effect of pollution by sewage and agricultural wastes discharged, as well as, biochemical decomposition of orgaric matter. This is supported by the increase in COD at this station. As a general the highest values of COD and BOD were observed at station 4 due to the high load of organic matter from Bahr Ei-Bagar drain during the different seasons (Table 2). The bicarbonate concentrations of the lake (210.0-528.2 mgl") indicate their high productivity and consequently favorable condition for fish production (Table 3). The salinity showed large fluctuation (614-3074 mgl") at different stations with abrupt increase at the areas affected by domestic waste (Table 3), Thus, the fluctuation in salinity plays a key role in establishing the distribution and dynamics of the chemical water quality also, has a strong influence on the distribution of biological species (Ueda et al, 2000). Statistically, salinity shows significant correlation at p<0.05 with Na, K, Ca and Mg (r= 0.66, 0.86, 0.57 and 0.75, respectively) and with P04~, S04" and NH3 (r= 0.48, 0.64 and 0.66, respectively). The high increase in sulphate concentrations during different seasons at station 4 and Bahr El-Bagar drain may be due to the bacterial oxidation effect of detrital organic phase present in domestic sewage (Table 3). Obviously, there was an increase in the concentration of eutrophication key elements (P and N). Nitrate content exhibited an extremely wide range of variation (1.71-821.09 jigl) (Table 4). This is mainly due to domestic wastes and agricultural runoff beside fertilizers, which are considered one of the sources of nutrients, (Macdonald et aL, 1995). The depletion of nitrite at station 4 may be principally due to the its reduction to ammonia as well as, its uptake by phytoplankton in the surface water as reported by Elewa et al. (1995). Ammonia concentrations are present in excess (1.13-20.35 mgl" ) with relatively higher values at station 4 than other station (Table 4). These high values are attributed to the domestic and agricultural wastes, where ammonia and bicarbonate are the final products of the bacterial decomposition of organic matter (AbdelSatar, 1998). The main factor that affects the toxicity of ammonia at this station is the dissolved oxygen depletion, as the decrease in Environmental studies on the impact of the drains effluent upon the southern sector of Lake Manzalah, Egypt dissolved oxygen increase the toxicity as reported by Deai ei at. (1991). The present results showed significant positive correlation between ammonia and E.C, (r = 0.65, at p<0.05), which proved, that the ionized form is predominate in the lake water. The orthoand total phosphate concentrations were varied in the range of 249.32-1399.56 \x%\ and 0.486-2.066 mgl", respectively (Table 5). The observed high concentrations of phosphorus content at station 4 may be due to the domestic wastes discharged from Bahr EIBagar drain into this station, which contain high amount of phosphorus resulting from the organic matter degradation (Muscu** and Wither, 1996). The high anthropogenic inputs of nutrients has led to a deteriorating water quality and caused serious problems (Yoshimural et a/., 2000) A negative significant correlation between both orthophosphate with dissolved oxygen exists (r= -0.71 at p<0.05). This suggests that under aerobic conditions, the phosphate concentration is decreased due to the consumption by rooted hydrophytes and phytoplankton as mentioned by Olsen and Sommerfeld(1977). There are decrease in the silicate concentration during hot seasons (0.93-5.55 mgl") compared with high values recorded during cold seasons (10.29-16.34 mgl") for all stations (Table 5). This is related t

ENVIRONMENTAL STUDIES ON THE IMPACT OF THE DRAINS EFFLUENT UPON THE SOUTHERN SECTOR OF LAKE MANZALAH, EGYPT