Seasonal and regional variations of five heavy metals in water, sediments and fishes inhabiting Lake Qarun, Egypt

INTRODUCTION

Lake Qarun is located in the western desert in the deepest part of Fayoum depression and lies 83 Km south west of Cairo. Lake Qarun attracts attention of many researchers because of its historical and scientifically importance to study its unique ecosystem. The description of the lake ecosystem, climatic conditions and sources of pollution were previously published (Authman and Abbas 2007; Hussein et al., 2008; Abdel Satar et al., 2010; Ibrahim and Ramzy, 2013; Tayel et al., 2013). For example, Authman and Abbas, (2007) reported that most of agricultural drainage water reaches the lake by two main drains, El-Batts and El-Wadi. There are minor drains poured its drainage water into the lake by means of hydraulic pumps but in small amounts.

The present study was conducted to get recent information about the seasonal and regional distribution of heavy metals in the lake components (Water, sediments and inhabiting fishes). So, on the basis of previous and current results, one can allow the buildup of a meaningful database that can be used for comparative assessment and trend delineation. 

MATERIALS AND METHODS

Study Area

Six stations or sites were selected to cover eastern, middle and western sectors of Lake Qarun (two sites / sector). The selection was determined by using Geographic Position System model 53. Fig. (1) shows the sampling locations.

Sampling

Samples of lake water, sediments and fish were collected during the period from October, 2015 to September, 2016. Surface water samples were collected by Ruttner bottle water sampler with capacity of 1-2 L. Samples for dissolved oxygen were collected in oxygen bottle (300 ml capacity). The other water samples were collected in polyethylene bottles for measuring other physicochemical parameters and heavy metals concentrations. Sediments samples were collected using Van Veen type, grab. Three fish species (Tilapia zillii, Solea solea andMugilsp.) which are the most common fishes in the lake and widely consumed were caught. A total number of 180 adult fish of each species were collected per season with the help of local fishermen, then dissected freshly and their parts were stored on ice.  

Measurements

Air and water temperatures were measured directly by using mercury thermometer graduated to 100°C. Hydrogen ion concentration (pH) was measured directly by using pH-meter model (Jenway 3150) after calibration with buffer solution. Salinity of water was determined by using salino-meter (Beckman; model RSAS) after calibration. Dissolved oxygen, biological oxygen demand, nitrite, nitrate concentrations were determined according to (APHA, 1995). Concentrations of heavy metals in water, sediments and fish were measured using inductively coupled plasma optical emission spectrophotometer (model 3400 DV, Perkin Elmer, Shelton, USA) according to standard methods of  (APHA, 1995). Statistically, results were expressed in tables as mean ± S.D. Data were analyzed by using correlation coefficient for environmental factors and the interaction between the concentration of heavy metals in both water, sediment and target organs according to Bailey (1981).

Fig. 1. Map of Lake Qarun showing the sampling location.

RESULTS AND DISCUSSION

Physicochemical parameters of lake water

Table (1) shows seasonal variation of many physicochemical parameters obtained from the six sites of the lake during the four studied seasons. Air and water temperature was measured in the field and showed significant differences among seasons. They increased during summer, while winter sustained the lowest values at most sites. Air and water temperature ranged between 24 - 36, 18 - 33°C, respectively. These values are in the neighborhood of those obtained previously (Afifi, 2015 and Ragab, 2017). Afify et al. (2019) reported that there is no clear thermal stratified recorded in the lake due to shallowness of the lake (̴ 4 m depth is average) and it is considered being homoeothermic in nature. Changes in water temperature may ulter or inhibit normal growth and development of certain organisms including fishes (Salem, 2006).

Lake water showed moderately an alkaline character with pH values ranging between 8.15 - 8.95 which is in the neighborhood of that obtained by Khalilet al. (2017) and in the range of permissible limits (WHO, 1993). Lake water salinity were 35.05, 46.35‰ for the minimum and maximum value, respectively. Abdel Satar et al. 2010 reported that salinity in 1953 was 21.94%. this value was fluctuated from increase and decrease thereafter depending on the rate of evaporation, amount of drained waters and consumption of lake salts by Egyptian company of salts and minerals (EMISAL). The values of lake water salinity listed in Table (1) are approximately the same as obtained lay Ragab (2017). Thus, Haroon et al. (2018) cited that lake Qarun is considered saline water.

Dissolved oxygen (DO) was found to be fluctuated and ranged between 7.65 and 13.68 mg/L which is in the range of permissible limits (WHO, 1993). However, the range of Do obtained by Shaaban et al. (2016) and Khalil et al. (2017) were less than that listed in Table (1) Adequate dissolved O₂ is vital for the survival of aquatic organisms and is therefore an important variable in the assessment and monitoring of water quality. The relatively low concentration of DO recorded could be attributed to the fall in water temperature, phytoplankton blooming and exhaustion of DO for oxidation of huge amounts of organic matter discharged into the lake (Tayel et al., 2013). The results for BOD (which is the amount of DO required to degrade certain amount of organic matter present in water) were ranged from 3.85 - 11.1 mg/L. which is in the neighborhood of that obtained by Khalil et al. (2017). The high concentration of BOD may be due to the high load of wastes discharged into the lake (Saad et al., 2011).

The obtained values of nitrite ranged between 6.90-30.46 µg/L which are above the permissible limits many times. Approximate value of nitrite was obtained by Sadrin et al. (2016). Nitrite is considered the major pollutant threaten the health of aquatic organisms and its high level may be attributed to the decomposition of organic matter present in waste water by nitrosomonas bacteria which oxidize ammonia to nitrite (Saad et al., 2011). Nitrate concentration fluctuated within the range of 186.80 to 584.50 µg/L and these values are higher than the corresponding values of nitrite due to fast conversion of NO₂ to NO₃ by nitrifying bacteria (Abdel Satar et al., 2010). Nitrate is relatively non-toxic to fish and its level is below the permissible limit. The low values in nitrate concentration might be due to uptake of nitrate by phytoplankton and its reduction by denitrifying bacteria and biological denitrification (Abdo, 2002). Statistical analysis indicated a strong positive correlation between water and air temperatures, pH with air and water temperatures, Salinity with air & water temperatures as well as pH value. Also, positive correlation between BOD with DO (Table, 2).   

Table 1. Seasonal variations of many physicochemical parameters (Mean ± S.D.) of Lake Qarun water at different sectors, during the period from autumn, 2015 to summer, 2016.

Table 2. Correlation coefficient of the environmental factors in the water of Lake Qarun.

Heavy metals

Among the myriad pollutants released into aquatic eco-systems, heavy metals have received considerable attention due to their toxicity, long-term persistence, bioaccumulation and biomagnification at various trophic levels (Ololade et al., 2008).

Metals in Lake Qarun water occur in particulate or soluble form. Soluble species include labile and non-labile fractions. The labile metal compounds are the most dangerous to fish.

The presence of metals in the lake may be due to surplus discharges from agriculture drainage, sewage and various industrial effluents released into the lake, beside diverse natural processes such as erosion and weathering. However, anthropogenic activities remain the main cause of metal existence in lake water.

Seasonal variations of many heavy metals concentrations in water and sediment of Lake Qarun during the period from Autumn 2015 to Summer, 2016 are presented in Table (3).

Metals concentrations in lake water and sediments followed an abundance of Fe > Mn ≅ Zn > cu > Cd. Cd and Cu concentrations in lake water are below the permissible limits, while Fe, Mn and Zn concentrations are above the permissible limits (U. S. EPA., 2006).

Table (3) indicate that seasonal and regional variations affected the distribution of heavy metals in lake water and sediments. Generally, eastern sector showed an increased values of heavy metals (especially Mn and Zn concentrations) than other sectors. Similar findings were recorded by Ali and Fishar (2005) who reported that Fe & Mn are observed onto the surface of suspended particles. Therefore, their concentrations increased in the east lake side where the organic matter are more drained from El-Batts drain. Previous studies (Abdel Satar et al., 2010 and Abou El-Gheit et al., 2012) have confirmed the existence of lofty heavy metal pollutions in Lake Qarun water, however, the level of many metals in the current study exceeded the earlier reports indicating recent and increasing pollution events in the lake. Table (4) shows the correlation coefficient between some heavy metals in water and sediment of the lake. It is clear that, there are strong positive correlation between the concentration of iron and copper in the lake water, in addition to the same trend between the concentration of manganese in the water and cadmium, iron in the sediment. Furthermore, a strong positive correlation was showed between the concentration of zinc in the water and all the measured metals in the sediment, plus the concentration of each metal in the sediment with other metals.

Table (5) shows the concentration of heavy metals in different organs of the three studied fish species. Regardless the fish species, the lower concentrations of metals were recorded in fish muscles, while the higher values were in the liver. These findings are in agreement with those obtained previously (Mohamed and Gad 2008; Ibrahim and Ramzy 2013; Omar et al., 2013).  High concentration of metals in the liver are related to its detoxification, transformation and storage of toxic materials. Furthermore, metals are bound in liver to specific polypeptides, i.e., metallothioneins (Jezierska 2001). Data listed in Table (5) indicate that fish liver and kidney contained considerable amounts of heavy metals, so it is advisable to throw down the fish viscera before human consumption. The lowest bioaccumulated of heavy metals in muscles may be correlated with low fat-content and little blood supply to the muscular tissue. Statistically, Table (6) indicates a positive correlation between the concentration of Cd in the sediment and it's concentration in the gills of S. solea. For M. cephalus there are strong positive correlations between Cu & Zn in the sediment with their concentrations in the gills. Same trend was found between Fe & Mn concentrations in the sediment and their concentration in the kidney of the same sp. There for, data listed in Table 5 & 6 indicate that Mugil sp. Seemed to be more contaminated with metals than Tilapia and Soliea sp. Ali and Fishar (2005) reported that the concentrations of trace metals in fish samples indicated that Solea sp. seemed to be more contaminated than other fish species followed by Mugil sp. and Tilapia sp.

The difference in the pattern of metals distribution in the three studied fish species might be a result of their difference in many factors such as, feeding habitats, habitats, ecological needs, metabolism and physiology (Arellano et al., 1999).

Data listed in Tables 3 and 5 indicate that concentrations of metals in sediments and fishes are more than their corresponding concentrations in water. For example, Zn concentrations in water, sediments and Tilapia fishes are 250 µg/L, 44.60 µg/g and 57.72 µg/g, respectively, which means that Zn concentrations in sediments and in Tilapia fish is about 178 and 230 times more than that found in water.

Heavy metals when discharged into water can enter the food chain, bioaccumulated in fish tissue and hence become threat to man.

Ravera et al., 2003 postulated that pollutants concentrations in the organism are the result of the past as well as the recent pollution level of the environment in which the organism lives, while the pollutants concentrations in the water only indicate the situation at the time of sampling.

CONCLUSIONS

From the above findings, it is clear that, Lake Qarun is suffering from various pollution types which leads to affect water and aquatic organisms in the lake, furthermore, some of studied metals exceed the permissible limits with the great dangerous impact on fishes and human health. Distribution of heavy metals in the organs of studied fish species might be a result of many factors such as, feeding habitats, metabolism and physiology.  Gills act as the target organ for cadmium and manganese, while copper, iron and zinc prefers accumulate in the liver than other organs. It is recommended that, water quality of the lake must be protected and improved as soon as possible. The following measured may be suggested and taken into consideration. First, a prior treatment for industrial wastewater must be enforced contentiously and domestic sewage must be treated before discharging. Second, the agriculture waste must be managed to reduce the pollutions in the lake.

Table 3. Seasonal variations of some heavy metals concentrations in the water and sediment of Lake Qarun, during the period from autumn, 2015 to summer, 2016.

Note: Overall mean of Zn conc. in lake water = (321+230+199)/3 = 250 μg/L ≅ 0.25 μg/g; Overall mean of Zn conc. in lake sediment = (63.5+34.0+36.4)/3 = 44.6 μg/g

Table 4. Correlation coefficient between some heavy metals in the water and sediment of Lake Qarun.

Table 5. Seasonal variations of some heavy metals concentrations (μg/g wet wt.) in the target organs of T. zillii, S. solea and M. cephalus collected from Lake Qarun during the period from autumn, 2015 to summer, 2016.

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