Distribution and accumulation of heavy metals in Lake Manzala, Egypt

ABSTRACT Lake Manzala is the largest saline lake and the second largest one among all lakes in Egypt. Heavy metals' contamination is the most fundamental kind of contamination around the world, particularly in Lake Manzala. The purposes of this paper are investigating the relationship between contents of some heavy metals and major oxides of the Quaternary sediments of Lake Manzala islands as well as the correlation coefficient factor among them.Ten samples of both water and superficial bottom sediments had been representing the lake Manzala through summer, 2019 is covering the sources of pollution to carry out this study. Six heavy metals estimated to assess the environmental risk. The elements were analyzed through atomic absorption spectrometer. Concentration of heavy metals Fe> Zn> Pb; Fe> Mn> Zn> Pb> Cu> Cd in water and sediment is recorded within the southern and southeastern parts of the lake. Significant oxides' arrangement is SiO2> MgO> CaO> Na2O> A12O3> K2O> Fe2O3. Eco-toxicological of heavy metals' contamination was among the bottom sediments of Lake Manzala. Target hazard quotients (THQ) for individual metals are arranged within the order; Zn>Pb> Cu> Cd. Therefore, heavy metals should eliminate from the wastewater to protect the people and the environment.


Introduction
Millions of cubic meters of untreated domestic, industrial, and agricultural drainage waters are discharged annually into the lake [1]. These drains have an effect on the measure, and quality of the lake, threatens human health and cause a serious pollution problem.
These results led to the accumulation and distribution of contaminants like heavy metals within the lagoon sediments. Expected contamination of Lake Manzala with heavy metals has been reported [2]. Heavy metals include potentially toxic (Cd, Pb), probably essential and far from is essential (Cu, Zn, Fe, Mn) [3]. Häder et al. [4] declared provoking deleterious effects on environmental quality and ecosystem sustaina bility with the aid of human intervention. The primary relationship studies between environmental healthy and therefore, the ecosystems functioning of Lake Manzala done by Orabi and Osman [5]. Due to multiple waste discharges, there has been a greater metal concentration at the eastern and southeastern sites of Lake Manzala than permissible limits [6]. Sediments are considered an indicator of the degree of heavy metal contamination in water environment [7]. The heavy metals of anthropogenic origin occur within the ecosystem naturally by lithe-genie processes that have a tendency to be bio-available then grow to be toxic pollutants [8]. The aquaculture activities can effect by hydrological conditions of lake water and resulting in a decrease in fish productivity and lack of biodiversity [9].
The foremost aim of this research is to investigate the connection between the contents of some heavy metals and major oxides of the Quaternary sediments of Lake Manzala islands and coefficients of correlation factor among them.

Study area
Lake Manzala is one of the three mains Nile Delta wetland ecosystems, Egypt, lies between latitude 31°10 \ −31°40 \ N and longitude 31°50 \ −32°25 \ E ( Figure 1). It is rectangular and somewhat shallow with an average depth of about 100 cm.

Sampling and technique of study
The study was carried out on Lake Manzala through summer, 2019, to monitor and evaluate the levels of some heavy metals and major oxides in water and sediments. Ten samples of both water and superficial bottom sediments have been collected. The sample sites have  been chosen to cover sources of pollution near to discharges of most drains which consider the main source of pollution of the study area. Every one of the safeguards happened to limit dangers of the test tainting were followed during the assortment and treatment of tests. These samples have been chemically analyzed for the determination of their major oxides (Silica oxide SiO2, Aluminum oxide Al2O3, Ferric oxide Fe2O3, Magnesium oxide MgO, Calcium oxide CaO, Sodium oxide Na2O and Potassium oxide K2O) and a few heavy metals (Cu, Zn, and Pb, Fe, Mn and Cd). The study used the standard of the American Public Health Association (APHA) [11] for the collection, preservation and digestion technique. Heavy metals concentrations were measured using a graphite furnace atomic absorption spectrometer (Buck Scientific Company, USA) after the digestion technique. Calibration standards and quality control samples have been prepared freshly daily. The reference standard materials used to assess the precision and accuracy of the procedure. The study used analytical grade chemicals of certified standard solutions for the aim of sample preparation and its analysis.

Statistical analysis
It had been finished for all samples using the Statistical Package for the Social Sciences (SPSS) software program for Window version 16 [12]. The concentration of heavy elements presented as a mean and standard deviation (SD). Pearson's coefficient of correlation was calculated between different trace elements. For any of the used tests, results are considered as statistically significant if p-value ≤ 0.05, moderate significant ≤ 0.01, and highly significant ≤ 0.001.

Results
The concentrations of heavy metals in water samples and sediments of Lake Manzala were represented in Tables 1-2 and illustrated by graphs 1-2. Subsequent to the summarized study on the environmental status of studied heavy metals, which might cause risk on human health and environmental effects. Major oxides sequence is SiO2> MgO> CaO> Na2O> A12O3> K2O> Fe2O3 (Tables 3) and illustrated by graph (3). Average concentrations of heavy metals in water and sediment as compared with average EPA limits [13] have been; Fe> Mn> Zn> Pb> Cu> Cd (Table 4). Whereas, average concentrations of heavy metals of sediment samples in relation to sediment quality guidelines (SQGs) showed that Cd in sediments become rated non-polluted element. Sediment quality guidelines are unknown for Fe and Mn (Table 5). Pearson's correlation coefficients (r) between concentrations of heavy metals in water and in sediment of Lake Manzala showed that a significant direct correlation between Cu in sediment and in water as  Zn with P ≤ 0.05 (Table 6). Whereas, Pearson's correlation coefficients (r) between percent (%) of major oxides and concentrations of heavy metals in water and in sediment of Lake Manzala showed that Fe, Mn, Pb and Cd haven't any correlation with any of those major oxides ( Table 7). The calculated values of THQ are employed to precise the potential risk indicate that anglers are under threat (1.01) than the overall population (0.41) (Table 8), the health risk is calculated supported data documented by Hammed et al. [14].

EPA [13] Environmental Protection Agency limit for water and sediments a: not available data. SQG: sediment quality guidelines
The value of THQ Greater than 0.5, indicates high health risk Lower than 0.5, indicates low health risk

Discussion
Metals generally enter the aquatic environment through erosion of the geological matrix, or due to anthropogenic activities caused by industrial effluents, domestic sewage [15]. The mean concentration of the measured metals in the water and sediments was found to within the following sequence; Fe> Zn> Pb; Fe> Mn> Zn> Pb> Cu> Cd, as compared to Environmental Protection Agency (EPA) [13]. Depending on the SQG of EPA, sediments were classified as: low polluted, moderately polluted and heavily polluted [16]. Manzala sediments are often categorized as moderately polluted with Pb (8), Cu (5), and Zn (1) using SQGs. Cadmium in sediments was rated non-polluted element ( Table 5). During this investigation, the sediment quality guidelines (SQGs) developed for the aquatic ecosystem [17] became applied to estimate eco-toxicological sense of heavy metal contamination within the rock-bottom sediments of Manzala lagoon. There's a moderate significant direct correlation between Pb in sediment and in water as Fe and Mn with P ≤ 0.01. There's a highly significant direct correlation between Cd in sediment and in water with P ≤ 0.001 ( Table 6). Because of the local geological formations, there's a dominance of iron and manganese [18]. It's obvious that the heavy metals with direct correlation considered having similar sources as estimated by Dan et al. [19]. Table 7 indicates a significant correlation between A12O3 and Zn in water as MgO with Cu and in water at P ≤ 0.05. Iron, Mn, Zn, Pb, Cu and Cd have no correlation with any of the major oxides in sediment. Bai et al. [20], stated that through an equal physicochemical process or derived from similar sources, the much direct correlation results between metals and oxides redistributed in sediments. Therefore, an assessment of heavy metal contamination in sediment may be a crucial tool to assess the danger of the hydro-geochemical environment. Rock bottom concentration of lead recorded far away from drainage areas at a middle part of the lake. Whereas nearby world of urban extension, near an agricultural drain and at an eastern part of the lake whenever the economic region, absolutely the best concentration recorded. EPA [21] has classified Pb as being potentially hazardous and toxic to most sorts of life. Copper's content increases gradually, toward the southeastern part of the lake, especially nearby drains, whenever more agricultural wastes. At the drains and nearby industrial areas, it's noticeable that absolutely the best concentrations of zinc were observed as a result to direct discharge of economic wastes in these areas due to southeastern part. Through food, Zn may have eco-toxicological effects on humans [22]. Manganese values increased toward south due to dump the agricultural and industrial sewage which having a higher content of pesticide and heavy metals. This by means of Randa et al. [23], who reported that the southeastern region showed the worst water quality limits where the drain of Bahr el-Baqur. In addition, this could explain why the southeastern region of the lake hosted the foremost-deteriorated sites. Generally, absolutely the best concentrations of Pb, Cu and Zn had been found within the southeastern part of the lake. Abu Khatita et al. [1], pronounced that the foremost pollution source within the Lake, uncontrolled wastewater discharges via southern drains were inflicting a decrease of the salinity, dissolved oxygen and increase the concentration of alternative hydro-chemical parameters. THQ for individual metals are arranged within the order; Zn> Pb> Cu> Cd (Table 8). Fishermen inhabiting Lake Manzala affected by hepatic, cardiovascular, respiratory, gastrointestinal, urinary, and musculoskeletal evidence [24]. Different portability and bioavailability of different kinds of metals, and hence, the influence of anthropogenic sources cause different risk levels of various metals [25]. This through Tariq [26] who suggested that untreated wastewater have induced high gathering of heavy metals which may be providing wellness risk to the population. Green growth biomass is used for bio remediation of heavy metallic contaminated gushing by utilizing adsorption or via combination into the cells [27]. Likewise, incessant plant collection ought to be urged to assist with diminishing the relocation of heavy metals from the contaminated soils into the surrounding environment [28].

Conclusions
The above results confirmed that the lake is facing a serious threat of metal pollution. The main source for metal contamination in the wastewater effluents is via drains in southern and southeastern parts. To deteriorate the water quality aimed at a rise in accumulation of metals in fish tissues. Increasing awareness of pollution risk might support the implemented remediation programs to face the rapid deterioration regarding the importance of the lake ecosystem. Population awareness, especially anglers of health risk from the intake of the heavy metals through fish consumption. This paper provided  Table 7. Pearson's correlation coefficients (r) between % of major oxides and concentrations of analyzed heavy metals in water and in sediment of Lake Manzala. *, **, *** significant correlation at P ≤ 0.05, moderate significant ≤ 0.01, and highly significant ≤ 0.001 a framework for future research because of the presence of some heavy metals in the water and sediment of Lake Manzala also as possible ecotoxicological effects on the environment.