Abstract

Chemical pollution of water is the contamination of water by foreign matter that deteriorates the quality of the water. Pollution of water by heavy metals are dangerous because they tend to cause Bioaccumulation that means an increase in the concentration of a chemical in a biological organism over time, compared to the chemical's concentration in the environment. Chemical pollution of Manzala lake was studied in 4 main localities, Kapoty, Bashtier, Mataryia and Gamil areas which receives high load of sewage, agricultural and industrial wastes from different sources. Heavy metals, such as Zn, Pb, Cd and Hg were estimated in water and fish samples, to reveal high pollution of lake Manzala with such toxic elements, where Zn, reached 800µg/L. Pb,195 µg/L. Cd 45 µg/L and. Hg, 5000 µg/L in water samples.

1. Introduction

Lake Manzala is a shallow costal lake that consisting of thirty basins with depths ranging from 0.7 to 3m in depth, the deepest areas resting in the navigation canal ^{1, 2}.

Creation of canals and drains such as the Bahr El-Bakar drain, the Sirw drain, the Ramsis drain and the Hadous drain has created a eutrophic condition and low salinity levels in the lake. The areas around the drain outlets in the south and west are characterized by brackish water and the areas in the northeast, near the sea outlets, are saline ^{1, 3}.

Although the lake is still considered as the largest of the Egyptian Delta Lakes, its area has been gradually decreased. Extensive land reclamation during the last century has reduced the lake surface area to less than half of its original size. In the 1900's, its area was estimated at 1,709.4 km2. By the end of the previous century, the area of the lake was estimated to be 1000 km2. The area of the open water is only 742.8 km2 due to the presence of a large number of islets in the lake. During the last decade, the reclamation is progressing at an accelerating pace where land had subsequently been created and islands enlarged ^{1, 4}.

Sources of heavy metals can be represented as follows ⁵.

Heavy metal toxicity can result in damaged or reduced mental and central nervous function, lower energy levels, and damage to blood composition, lungs, kidneys, liver, and other vital organs. Long-term exposure may result in slowly progressing physical, muscular, and neurological degenerative processes that mimic Alzheimer's disease, Parkinson's disease, muscular dystrophy, and multiple sclerosis. Allergies are not uncommon and repeated long-term contact with some metals or their compounds may even cause cancer ⁵.

2. Materials and Methods

Water samples were taken from Kapoty, Bashtier , Mataryia and Gamil outlet areas. The selected sites are host to significant populations around the lake and receive various types of pollutants which negatively affect the condition of the lake and human health.

El-Kapoty Area Samples were taken from the end of the junction canal, which connects the Suez Canal with Lake Manzala; the main source of pollution in this area comes from the city of Port-Said. Effluents such as sewage water and industrial wastes from multiple factories are disposed of in this area of the Lake. This site is close to El-Kapoty village, a fishing village in Port-Said, where they dispose of raw sewage directly into the Lake water. El-Bashtier Area is considered a midpoint between the El-Kapoty and the Mataryia areas; it receives water currents from different directions resulting in high water levels. The depth reaches three meters and is part of the navigation canal. The area has many islets which are inhabited by people who work in fishing and raise animals, El-Mataryia area is considered the fresh-water part of the Manzala Lake; however, it receives high amounts of different types of pollutants. Untreated sewage from the El Dakahlyia governorate empties here as well as 6 million m3/ day of industrial and agricultural waste from the El-Siwr, Hadous, Ramsis and Bahr El-Bakar drains. The drains empty into the El Genka reservoir, a part of the lake that is characterized by vast vegetation composed of reeds and other aquatic plants like the water hyacinth, this area is particularly important for fishing, especially the fishing of Tilapia spp. Gamil outlet is considered the adjoining part of the lake with seawater coming from Mediterranean sea (Figure 1).

Water samples from each site were taken in clean sterile one liter glass bottles and transported from the lake to the laboratory within six hours. The bottles were kept in ice bags and ice jackets for direct examination.

Physicochemical characteristic of each water sample were evaluated in the field. The temperature of the water samples was determined by using a mercury thermometer. The pH values were determined using a recombination of a pH electrode (Eil Series 1180) and a pH meter (Eill, Model 7030), which was calibrated against pH 4, 7 and 9 buffers. The levels of dissolved oxygen in the water samples were determined using the Oxygen Meter model YSI 58. The chemical analysis to determine the total suspended solids (TSS), ammonia, nitrates, Sulphates, Alkalinity, calcium, magnesium and chloride levels were done using the recommended standard methods of water analysis( mg/L) ⁶.

Heavy metals i.e. Lead, Mercury, Cadmium and Zinc were determined by Atomic Absorption Spectrophotometry.

3. Results

Table 2 shows the physicochemical parameters of El-Kapoty area. The temperature ranged between 17 and 30. The pH of the water was found to be slightly alkaline throughout the year with a range of 7.5 to 8.17. Salinity was ranged between 16 to 29. Dissolved oxygen (DO) was ranged between 3.13 to 6.19 mg/l. Total suspended solids (TSS) was ranged between 75 to 180 mg/l. Total dissolved solid (TDS) was ranged between 8240 to 31406 mg/l. Ammonia concentration was ranged between 0.91 to 44.8 mg/l. Nitrate concentration was ranged between 1.05 to 8.96 mg/l.

Table 3 shows the physicochemical parameters of El-Gamil outlet. The temperature ranged between 19 and 29. The pH of the water was found to be slightly alkaline throughout the year with the range of 7.52 to 8.42. Salinity was ranged between 9 to 25. Dissolved oxygen (DO) was ranged from 4.45 to 6.1 mg/l. Total suspended solids (TSS) was ranged between 81 to 350 mg/l. Total dissolved solid (TDS) was ranged between 6418 to 33480 mg/l. Ammonia concentration was ranged between 0 to 2.5 mg/l. Nitrate concentration was 0 mg/l throughout the year.

Table 4 shows the physicochemical parameters of El-Bashtier area. The temperature ranged between 15 and 31. The pH of the water was found to be slightly alkaline throughout the year with a range of 7.4 to 8.91. Salinity was ranged between 5 to 12. Dissolved oxygen (DO) was ranged between 4.85 to 5.2 mg/l. Total suspended solids (TSS) was ranged from 19 to 80 mg/l. Total dissolved solid (TDS) was ranged between 3653 to 14600 mg/l. Ammonia concentration was ranged between 1.46 to 4.76 mg/l. Nitrate concentration was ranged between 0 to 0.17 mg/l

Table 5 shows the physicochemical parameters of El-Mataryia area. The temperature ranged between 15 and 30. The pH of water was found to be slightly alkaline throughout the year with a range of 7.59 to 7.85. Salinity was ranged between 4 to 5. Dissolved oxygen (DO) was ranged between 3.9 to 8.45 mg/l. Total suspended solids (TSS) was ranged between 30 to 60 mg/l. Total dissolved solid (TDS) was ranged between 1578 to 3800 mg/l. Ammonia concentration was ranged between 0 to 4.48 mg/l. Nitrate concentration was ranged between 0 to 4.2 mg/l.

Table 6 shows the Heavy metal concentration by µg/L; in Kapoty area, zinc (Zn) was ranged between 400 to 1700, lead (Pb) was ranged between 50 to 195, Cadmium (Cd) was ranged between 9 to 44, Mercury(Hg) was ranged between 700 to 5000. In El-Gamil outlet, zinc (Zn) was ranged between 300 to 800, lead (Pb) was ranged between 110 to 195, Cadmium (Cd) was ranged between 5 to 26, Mercury (Hg) was ranged between 700 to 2000. In Bashtier area, zinc (Zn) was ranged between 300 to 750, lead (Pb) was ranged between 90 to 145, Cadmium (Cd) was ranged between 5 to 22, Mercury (Hg) was ranged between 700 to 1400. Finally in Mataryia area, zinc (Zn) was ranged between 300 to 850, lead (Pb) was ranged between 80 to 110, Cadmium (Cd) was ranged between 9 to 14, Mercury (Hg) was ranged between 700 to 1400.

4. Discussion

Lake of Manzala is considered one of the most polluted lakes in the northern coast of Egypt, due to a high load of pollutants from different sources. This in line with the data obtained in this study where physic-chemical analysis of water samples exceeds the limits of national and international legislations.

The physic-chemical analysis of water in Manzala Lake in this study such as temperature, total dissolved solid (TDS), pH, salinity, dissolved oxygen (DO) was agreed with study of Physicochemical Properties of Manzala Lake that done by ⁷ in Manazala lake

Increasing the levels of heavy metals in Manzala Lake in this study is in line with the data obtained by ⁸ who study heavy metal residues in some fishes from Manzala Lake and approved that there is high levels of heavy metals in fish.

Some metals in some areas have maximum values during summer and the lowest level in winter as mercury in kapoty, El-Gamil, Mataryia but not all metals agree with this rule as zinc in kapoty and this in contrast with ⁹ who study the assessment of heavy metals concentrations in water, plankton and fish of Lake Manzala and approved that all metals attained their maximum values during summer, while the lowest level in winter.

The high levels of toxic metals in Lake of Manzala especially in the east northern cost could be because of the increasing volume of industrial complexes in port-said Governorate. This metal pollution negatively affects the marine life directly and human being indirectly through the assimilation of polluted seafood.

References