Journal of Environmental Protection, 2010, 1, 389-400
doi:10.4236/jep.2010.14045 Published Online December 2010 (http://www.SciRP.org/journal/jep)
389
Water Quality and Heavy Metal Monitoring in
Water, Sediments, and Tissues of the African
Catfish Clarias gariepinus (Burchell, 1822) from
the River Nile, Egypt
Alaa G. M. Osman1,2*, Werner Kloas2
1Department of Zoology, Faculty of Science, Al-Azhar University (Assiut Branch), Assiut, Egypt; 2Leibniz-Institute of
Freshwater Ecology and Inland Fisheries, Berlin, Germany.
Received June 24th, 2010; revised July 19th, 2010; accepted July 30th, 2010.
ABSTRACT
Water quality of the river Nile and trace elements of the water, sediments and fish tissues were investigated in the cur-
rent work. Eighteen different sampling points were selected along the whole course of the River Nile from its spring at
Aswan to its estuaries at Rosetta and Damietta. Higher mean value of conductivity, alkalinity, chemical oxygen demand
(COD), total organic carbon (TOC), ammonia (NH3), nitrate (NO3), total solid (TS), sulphate (SO4), chloride (Cl), or-
thophosphate were recorded in the water of Damietta and Rosetta branches comparing to other sites. Also trace metals
in the water, sediments and tissues of Clarias gariepinus increased significantly (P < 0.05) from Aswan toward Dami-
etta and Rosetta branch. Such increase proves the presence of large quantities of organic and inorganic pollutants in
Rosetta and Damietta water. This was expected due to the fact that the water of such branches receives high concentra-
tions of organic and inorganic pollutants from industrial, domestic as well as diffuse agricultural wastewater. The
heavy metal residues in the tissues of Clarias gariepinus exhibited different patterns of accumulation and distribution
among the selected tissues and localities. It was evident from our study that, liver was the site of maximum accumula-
tion for the elements followed by gills while muscle was the over all site of least metal accumulation. Trace metals ac-
cumulations in fish liver at sites under investigation were detected in the following descending order: Zn > Fe > Cu >
Pb > Mn > Cr> Cd > Hg. In the gill tissues theses metals were accumulated in the following order Fe > Zn > Mn > Pb
> Cr > Cu > Cd> Hg. The low accumulation of metals in muscle may be due to lack of binding affinity of these metals
with the proteins of muscle. This is particularly important because muscles contribute the greatest mass of the flesh that
is consumed as food.
Keywords: Water Quality, Sediment, River Nile, Clarias gariepinus, Heavy Metals, Aquatic Pollution
1. Introduction
Water pollution is thus a cosmopolitan problem that
needs urgent attention and prevention [1-3]. It resulted
from many sources, e.g. accidental spillage of chemical
wastes, discharge of industrial or sewerage effluents,
agricultural drainage, domestic wastewater and gasoline
from fishery boots [2,4]. Water pollution is one of the
principal environmental and public health problems
Egyptian River Nile are facing [5]. The Nile is the donor
of life to Egypt and represents the principal freshwater
resource for the country, meeting nearly all demands for
drinking water, irrigation, and industry [6]. During its
transit through Egypt, the river Nile receives numerous
non-point and point source discharges [6]. Now, the
changes in Nile water quality are primarily due to a com-
bination of theses contaminants.
Water quality is a term used to express the suitability
of water to sustain various uses or processes [7]. The
quality of water may be described in terms of the con-
centration and state the organic and inorganic material
present in the water, together with certain physical char-
acteristics of the water [8]. The composition of surface
waters is dependent on natural factors in the drainage
basin and varies with seasonal differences in runoff
volumes, weather conditions and water levels. Human

Water Quality and Heavy Metal Monitoring in Water, Sediments, and Tissues of the African Catfish Clarias gariepinus
(Burchell, 1822) from the River Nile, Egypt
390
intervention also has significant effects on water quality
[8]. Some of these effects are the polluting activities,
such as the discharge of domestic, industrial, urban and
other wastewaters into the watercourse (whether inten-
tional or accidental) [9]. The principal reason for moni-
toring water quality has been the need to verify whether
the observed water quality is suitable for intended uses
[7]. However, monitoring has also evolved to determine
trends in the quality of the aquatic environment and how
the environment is affected by the release of contami-
nants, by other human activities, and/or by waste treat-
ment operations.
Sediments are one of the possible media in aquatic
monitoring. Apart from water, sediments are also respon-
sible of nutrients and pollutant transportation in aquatic
environment. Sediments are known to capture hydropho-
bic chemicals pollutants entering water bodies [10] and
slowly releasing the contaminant back into the water
column [7,10]. Therefore, ensuring a good sediment qual-
ity is crucial to maintain a healthy aquatic ecosystem,
which ensuring good protection of human health and
aquatic life. In addition to the physical and chemical rela-
tionships between sediments and contaminants, sediments
are of fundamental importance to benthic communities in
terms of providing suitable habitats for essential biologi-
cal processes. Therefore, sediments provide an essential
link between chemical and biological processes.
Fish accumulate toxic chemicals directly from the wa-
ter and through their diet, and contaminant residues may
ultimately reach concentrations hundreds or thousands of
times above those measured in the water, sediment and
food [11-13]. For this reason, monitoring fish tissue con-
tamination serves an important function as an early warn-
ing indicator of sediment contamination or related water
quality problems [14,15]. Monitoring fish tissue contami-
nation also enables us to detect concentrations of toxic
chemicals in fish that may be harmful to consumers, and
take appropriate action to protect public health and the
environment. Multiple factors including season, physical
and chemical properties of water can play a significant
role in metal accumulation in different fish tissues
[16,17]. It is therefore of great significance to evaluate
pollution effects on fish for both environmental protec-
tion and socio-economic reasons [18].
A combination of biological monitoring (Bioaccumu-
lation) and measurements of water and sediment quality
can provide a good indication of conditions and potential
risks to the water body. The present paper is a part of a
detailed investigation entitled (Biomonitoring of the river
Nile pollution using biomarker responses in fishes). The
present part was aimed to study the heavy metal moni-
toring in water, sediments, and tissues of the African
catfish (Clarias gariepinus) as biomarkers in combina-
tion with quality of water collected from six different
sites along the whole course of the river Nile from its
spring at Aswan to its estuaries at Rosetta and Damietta.
2. Materials and Methods
2.1. Study Area
The program of monitoring had been planned and im-
plemented to know the quality of water and the influence
of the drained water on its aquatic life. Eighteen different
sampling points from six sites (three points for each sit)
were selected along the whole course of the river Nile
from its spring at Aswan to its estuaries at Rosetta and
Damietta (Figure 1).
Sites Corresponding points
Aswan Aswan city, Aswan dam, and Kom-Umbo.
Kena Armant, Qena, and Naj-Hamadi.
Assiut Sedfa, Assiut, and Qusia.
Beni-SuefAl-Fashen, Beni-Suef, and Al-Wasta.
Damietta Zefta, Mansoura, and Damitta.
Rosetta Cairo, Kafr-Elzeyat, and Rasheed.
2.2. Water Analysis
Water sample were collected bimonthly by polyvinyl
chloride Van Dorn bottle (5 L capacity) two meter depths
at the selected eighteen points along the whole course of
the river Nile during the period from July 2009 to Jun
2010. Water samples were kept into a one-litre polyeth-
ylene bottle in ice box and analyzed in the laboratory.
Some of the physicochemical parameters including the
electrical conductivity of the water samples (mS·cm-1),
pH, and water temperature (℃) were measured by using
water checker U-10 Horiba Ltd. The other water criteria
[Chemical oxygen demand (COD), Total Organic Com-
pound (TOC), Total solids (TS), Hardness (Hard), Major
cations (Ca, Mg), Ammonia (NH3) Nitrate (NO3) Ortho-
phosphate (O-PO4) Chloride (CL) Florid (F) Sulphate
(SO4), Alkalinity (Alkal) Phenolics (Phenol)] were mea-
sured according to the traditional manual methods [19].
Total Pb, Cu, Cr, Mn, Zn, Hg, Fe, Cd were measured
after digestion using Graphite Furnace AA (GFAA)
spectroscopy. A mixture of nitric acid and the material to
be analysed was refluxed in a covered Griffin beaker.
After the digestate has been brought to a low volume, it
was cooled and brought up in dilute nitric acid (3% v/v).
The sample was filtered, allowed settling and preparing it
for analysis. It is to be noted that, the results obtained for
most parameters in the river Nile water were relatively
closed to each other; therefore the averages were calcu-
lated by the end of the measurement period.

Water Quality and Heavy Metal Monitoring in Water, Sediments, and Tissues of the African Catfish Clarias gariepinus
(Burchell, 1822) from the River Nile, Egypt
391
Figure 1. Map showing the sampling sites which extend along the whole course of the river Nile from its spring at
Aswan to its estuary at Damietta and Rosetta branches.

Water Quality and Heavy Metal Monitoring in Water, Sediments, and Tissues of the African Catfish Clarias gariepinus
(Burchell, 1822) from the River Nile, Egypt
392
2.3. Sediment Analysis
Sediment samples from the selected sites were collected
bimonthly from the main course of the river Nile during
the period from July 2009 to June 2010. These were col-
lected by using Ekman dredge and kept frozen until ana-
lyzed. For total heavy metals, sediment samples were
allowed to defrost, then air-dried in a circulating oven at
30°C and sieved mechanically using a 2 mm sieve. For
the digestion of samples, 1 gram-sieved sediment was
digested with repeated addition of nitric acid and hydro-
gen peroxide. For Graphite Furnace AA (GFAA) analy-
sis, the resultant digestate was reduced in volume and
then diluted to a final volume of 100 mL. The elements
of concern (Fe, Mn, Zn, Cu, Pb, Cr and Cd) in the sam-
ples were determined by Atomic absorption spectropho-
tometer (AAS).
2.4. Tissues Analysis
Fresh fish samples (Clarias gariepinus) were collected
by using long line or nets from the selected sites during
the period from July 2009 to Jun 2010. Muscles, Gills,
gonads and Liver were transported in liquid nitrogen
container to the laboratory for chemical analysis. These
organs were washed with tap water (previously analyzed
for Pb and Cd) followed by bi-distilled water, then oven-
dried to constant weight at 105℃. The dried fish was
crushed and powdered in an agate mortar, then, they
were kept in polyethylene bottles for analysis. One gram
portions of fish tissues were digested by means of a mi-
crowave after addition of nitric acid and hydrogen per-
oxide. The results were calculated in milligram per kilo-
gram wet weight (mg/kg wet wt). Chemicals concentra-
tion were analysed according to German industrial stan-
dard, DIN 38406-6, (DEV, E6) with an Atomic Absorp-
tion Spectrometer using flame and graphite furnace tech-
nique.
2.5. Statistical Analysis
All values from chemical analyses were presented as
mean ± SD. Data obtained from the experiment were
subjected to one way analysis of variance (ANOVA) test
using the Statistical Package for the Social Sciences [20].
The correlation coefficients between the quality parame-
ter pairs of the water samples were calculated by the ap-
plication of Pearson correlation analysis [20] in order to
indicate the nature and the sources of the polluting sub-
stances.
3. Results and Discussion
3.1. Water Analysis
The results of means and SD of the studied physical and
chemical parameters for water samples in the selected
sex sites are given in Table 1.
Because of its great impact on aquatic life, water tem-
perature is an important component of a water quality
assessment [7]. Temperature is a critical water quality
parameter, since it directly influences the amount of dis-
solved oxygen that is available to aquatic organisms [19].
Temperature affects the distribution, health, and survival
of aquatic organisms. While temperature changes can
cause mortality, it can also cause sub-lethal effects by
altering the physiology of aquatic organisms [7]. Tem-
peratures outside of an acceptable window affect the
ability of aquatic organisms to grow, reproduce, escape
predators, and compete for habitat. Water temperature
showed a noticeable variation between different sites
with a lowest value (22.7℃) recorded at Aswan and a
highest one (25.3℃) at Damietta. Such variations be-
tween different sites were mainly due to different sam-
pling times.
Conductivity is the ability of the water to conduct an
electrical current, and is an indirect measure of the ion
concentration [19]. The more ions present, the more
electricity can be conducted by the water. The major salts
that contribute to the measurement of conductivity are
the positively charged ions calcium and magnesium.
Other ions that contribute to conductivity to a smaller
degree are sulfate, chloride, carbonate, bicarbonate, ni-
trate, and phosphate [7]. Electrical conductivity showed
lowest values at Aswan (0.24 mS·cm-1) and the highest
value were recorded at Rosetta (0,63 mS·cm-1) followed
by Damietta (0.53 mS·cm-1) with a remarkable increase
from Aswan to Damietta and then Rosetta branch. Such
increase may be due to the disposal of domestic and in-
dustrial effluent in the water of Damietta and Rosetta
branches.
The pH measurement is one of the most important and
frequently used tests in water chemistry (APHA, 1995).
PH is a measure of the concentration of hydrogen ions in
the water. This measurement indicates the acidity or al-
kalinity of the water. Naturally occurring fresh waters
have a pH range between 6 and 8. The pH of the water is
important because it affects the solubility and availability
of nutrients, and how they can be utilized by aquatic or-
ganisms. According to the present results PH seems to be
constant all over the river Nile. All the PH values were in
alkaline side (7.8 to 8.4). The relatively lowest pH of
some sites can be attributed to the discharge of effluents
which loaded with a large amount of organic acids.
Total solids (TS) are a measure of the amount of par-
ticulate solids that are in solution. This is an indicator of
nonpoint source pollution problems associated with
various land use practices. They are the direct measure-

Water Quality and Heavy Metal Monitoring in Water, Sediments, and Tissues of the African Catfish Clarias gariepinus
(Burchell, 1822) from the River Nile, Egypt
393
Table 1. Mean and SD of some physical and chemical parameters of the water samples collected from six sites along the whole
course of the river Nile from its spring at Aswan to its estuary at Damietta and Rosetta branches.
Aswan Kena Assiut Beni-Suef Damietta Rosetta
Locality
Parameter (Unite) Mean ± SD Mean ± SDMean ± SD Mean ± SDMean ± SD Mean ± SD
Permissible
limit
PH (Unit) 7.8 ± 0.248 8.01 ± 0.4058.15 ± 0.1878.27 ± 0.2738.40 ± 0.442 8.223 ± 0.449 7-8.5
Conductivity (Ms·cm-1) 0.25 ± 0.029 0.27 ± 0.07010.28 ± 0.0860.33 ± 0.07220.37 ± 0.099 0.57 ± 0.115 -
Temperature (℃) 22.68 ± 2.218 23.71 ± 3.15223.33 ± 4.67123.64 ± 4.23925.29 ± 5.661 24.52 ± 4.441 Over 5℃
Chemical oxygen demand (ppm) 10.58 ± 3.616 9.16 ± 3.041910.63 ± 2.1797.87 ± 2.1538.59 ± 2.509 18.00 ± 10.37510
Total organic carbon (ppm) 5.65 ± 2.876 5.89 ± 1.9255.73 ± 0.9184.93 ± 2.5755.20 ± 2.635 8.61 ± 6.055 -
Total solid (ppm) 198.87 ± 14.08 212.66 ± 23.70227.75 ± 16.297259.5 ± 44.33305.25 ± 55.959 411.25 ± 85.66500
Hard (ppm) 123.7 ± 15.756 134.4 ± 23.26140.36 ± 29.316127.56 ± 23.84147.83317.101 162.25 ± 25.53-
Magnesium (ppm) 11.86 ± 4.672 14.97 ± 7.98914.34 ± 7.5213.92 ± 6.29215.32 ± 5.255 16.43 ± 3.887 -
Calcium (ppm) 29.89 ± 6.423 25.76 ± 4.101529.21 ± 7.06228.12 ± 7.2434.05 ± 10.639 38.31 ± 12.3742-
Ammonia (pp m) 0.105 ± 0.158 0.008 ± 0.001450.019 ± 0.0110.012 ± 0.00980.044 ± 0.0487 0.14 ± 0.091 0.5
Nitrate (ppm) 0.80 ± 0.396 0.76 ± 0.38680.50 ± 0.2050.72 ± 0.6271.134 ± 1.131 2.04 ± 2.271 45
Chlorides (ppm) 7.052 ± 1.443 8.56 ± 1.89610.03 ± 2.5815.28 ± 5.10322.41 ± 4.929 40.54 ± 6.722 -
Florid (PPm) 0.28 ± 0.146 0.31 ± 0.13830.38 ± 0.1630.31 ± 0.1250.30 ± 0.0971 0.37 ± 0.0737 0.5
Ortho phosphate (ppm) 0.01 ± 0.0198 0.03 ± 0.03810.09 ± 0.0900.03 ± 0.0340.13 ± 0.066 0.21 ± 0.1871 -
Sulphate (ppm) 34.16 ± 13.299 45.33 ± 15.3747.95 ± 14.1145.25 ± 15.8151.00 ± 12.759 68.12 ± 11.4261200
Alkalinity (ppm) 96.2 ± 31.43 103.49 ± 25.943102.93 ± 54.42798.26 ± 25.86115.24 ± 38.266 124.25 ± 47.83120-150
Phenol (ppm) 0.01 ± 0.0227 0.01 ± 0.01980.01 ± 0.01570.01 ± 0.00980.02 ± 0.0178 0.04 ± 0.0227 0.02
Pb (ppm) 0.012 ± 0.0154 0.021 ± 0.01430.024 ± 0.0170.016 ± 0.0090.03 ± 0.041 0.06 ± 0.078 0.05
Cd (ppm) 0.004 ± 0.0046 0.002 ± 0.00240.006 ± 0.0070.002 ± 0.0020.02 ± 0.023 0.012 ± 0.01790.1
Zn (pp m) 0.21 ± 0.1736 0.12 ± 0.10170.30 ± 0.4650.34 ± 0.4570.45 ± 0.689 0.69 ± 0.952 1
Cu (ppm) 0.030 ± 0.0272 0.022 ± 0.02450.030 ± 0.02610.031 ± 0.02760.032 ± 0.0321 0.054 ± 0.02781
Cr (ppm) 0.003 ± 0.0025 0.006 ± 0.00580.005 ± 0.00570.006 ± 0.00500.045 ± 0.0643 0.088 ± 0.15490.05
Fe (ppm) 0.19 ± 0.176 0.22 ± 0.19550.34 ± 0.32650.46 ± 0.39370.41 ± 0.2733 0.49 ± 0.4494 1
Hg (ppm) 0.0000 ± 0.001 0.0004 ± 0.00050.0005 ± 0.00110.0000 ± 0.00090.002 ± 0.0017 0.003 ± 0.00130.001
Mn (ppm) 0.033 ± 0.0277 0.0651 ± 0.06850.045 ± 0.0210.058 ± 0.0600.071 ± 0.0851 0.099 ± 0.14660.5

Water Quality and Heavy Metal Monitoring in Water, Sediments, and Tissues of the African Catfish Clarias gariepinus
(Burchell, 1822) from the River Nile, Egypt
394
ment of particle concentration that quantifies the diffrac-
tion of light caused by particles in the water [7]. TS con-
centrations have been recommended by the US EPA as
useful indicators of water quality and are important
measurements for a number of reasons. Increased TS are
frequently indicators of erosion. This fine material can
clog the gills of fish and serve as a carrier of pollutants
and pathogens. Total solid showed a significant (P < 0.05)
increase from Aswan to Damietta and Rosetta. The low-
est value of TS was recorded at Aswan (198.8 ppm). The
highest values were recorded at Rosetta (411.25 ppm)
(Table 1). The increase in TS values in the water of Da-
mietta and Rosetta branches are probably due to the
phytoplankton blooming which always associated with
lower level of dissolved oxygen.
The chemical oxygen demand (COD) is used as a
measure of oxygen equivalent of the organic matter con-
tent of a sample that is susceptible to oxidation by strong
chemical oxidants. The chemical oxygen demand (COD)
and total organic compounds (TOC) showed a remark-
able fluctuation with a slight increase from Aswan to
Rosetta (Table 1). The lowest value of COD and TOC
were recorded at Beni-Suef (7.87 and 4.9 ppm respec-
tively). The highest values of both parameters were de-
tected at Rosetta (Table 1). The value of COD in Rosetta
branch, Assiut and Aswan was higher than the permissi-
ble limits. This increase was due to the presence of
higher organic matter concentration in theses areas. This
may be due to the discharge of industrial effluents into
the Nile by some non-compliant factories in these areas,
in addition to the discharge of municipal wastewater (un-
treated and detergent-carrying wastewater) and other
wastes into the river.
Water hardness was understood to be a measure of the
capacity of water to precipitate soap. Soap is predicated
chiefly by the calcium and magnesium ions present [7].
Water hardness was slightly increased from Aswan to
Rosetta and Damietta recording the highest value at
Rosetta (162.3 ppm) (Table 1). Table 1 shows that Ca
and Mg nearly have the same distribution as water hard-
ness. The concentrations of magnesium showed low val-
ues (11.8-16.4 ppm) comparing to calcium concentra-
tions (2.7-38.3 ppm) (Table 1).
The fluoride ion is necessary for teeth health. So it is
very important to keep its concentration in drinking wa-
ter between 0,8 and 1,00 ppm. The detected concentra-
tions of fluoride are still lower than the required limits in
all sites ranging from 0.28 to 0.37 ppm. So it is not rec-
ommended to use this water directly as a drinking water.
We have to add the fluoride to the optimum levels
(0,8-1.00 ppm) for dental health. According to the pre-
sent results fluoride did not have a specific trend of in-
crease or decrease. It fluctuated from Aswan to Damietta
recorded the lowest value at Aswan and the highest one
at Assiut (Table 1). This increase was due to the pres-
ence of phosphate fertilizer factories in this site. Chloride
is the most common inorganic anion found in water and
wastewater. High chloride content may indicate pollution
by sewage or industrial wastes. The distribution of (Cl)
was similar to those of the cations (Ca and Mg) showing
a minor increase from Aswan to Damietta and Rosetta
(Table 1).
Nitrate and ammonia are the most common forms of
nitrogen in aquatic systems [19]. Ammonia is excreted
by animals and produced during decomposition of plants
and animals, thus returning nitrogen to the aquatic sys-
tem. It is also one of the most important pollutants caus-
ing lower reproduction and growth. Ammonia can easily
pass through the membranes of the gills, causing nervous
system toxicity and even death. Ammonia was recorded
in a very low concentration in all sites (Table 1) re-
cording the highest value at Rosetta (0.14 ppm). Nitrate
is often the limiting element restricting biological pro-
ductivity of Nile water [7]. The values of nitrate fluctu-
ated within a wide range and showed low levels during
the whole period of investigation (Table 1). The highest
value of Nitrate was recorded at Rosetta. Higher concen-
tration of nitrate in water of Rosetta branch can create a
large oxygen demand and cause algae to grow in large
quantity. Dead algae can cause oxygen depletion prob-
lems which in turn can kill fishes and other aquatic or-
ganisms. This result also can explain the detection of the
higher concentration of orthophosphate in the water of
Rosetta and Damietta branches. Orthophosphate is gen-
erally considered to be the primary nutrient limiting algal
and plant growth in fresh waters. Orthophosphate
(O-PO4) was detected in low values especially in the
upper Egyptian sites (Aswan and Kena). The highest
concentrations were detected at Rosetta (0.21 ppm) fol-
lowed by Damietta (0.13 ppm) (Table 1).
Alkalinity of water is its acid-neutralizing capacity. It
is the sum of all titratable bases [19]. It is taken as an
indication of the concentration of carbonate, bicarbonate
and hydroxide content in water. Alkalinity was fluctuated
within a very narrow ranges recording highest values at
Rosetta (124.3 ppm) followed by Damietta (115.2 ppm).
The concentrations of phenolics were recoded in very
low values in all sites recording the lowest value at As-
siut and Beni-Suef (0.01 ppm). The highest concentration
of phenolics was recorded at Rosetta (0.04 ppm) (Table
1). The concentration of phenolics was higher than the
permissible limits in Rosetta and Damietta branches.
Heavy metals enter rivers and lakes from a variety of
sources. The rocks and soils directly exposed to surface

Water Quality and Heavy Metal Monitoring in Water, Sediments, and Tissues of the African Catfish Clarias gariepinus
(Burchell, 1822) from the River Nile, Egypt
395
water are the largest natural sources [19]. In addition to,
the discharge of various treated and untreated liquid
wastes to the water body can introduce large amounts of
trace metals for rivers. Total trace metals exhibited dif-
ferent behavior, with constant or increasing concentra-
tions up river. Pb values were fluctuated within a narrow
range (0.01 to 0.06 ppm) and it was very low in all Upper
Egyptian sites ranging from 0.01 to 0.02 (Table 1). The
highest values were recorded in the water of Rosetta
(0.06 ppm). The lead concentration was higher than the
permissible limit in the water of Rosetta Branch. Cd ex-
hibited a wide range of variation between 0.002 and 0.02
ppm (Table 1). The highest value was recorded at Dami-
etta (0.02 ppm). Down stream sites recording a very high
Cd concentration comparing to the up stream sites (Ta-
ble 1). The cadmium level was higher than the permissi-
ble limits in Rosetta and Damietta branches. Zinc con-
centrations fluctuated between 0.12 and 0.69 ppm. The
maximum values were recorded at Rosetta (Table 1).
Copper concentration ranged from 0.02 to 0,05 ppm
(Table 1). The lowest concentration of Cr was recorded
at Aswan (0.003 ppm) and the highest one was recorded
at Rosetta (0.088 ppm). The chromium in the Rosetta
branch was higher than the permissible limit. Fe recorded
the highest values at Rosetta (0.46 ppm) and the lowest
value at Aswan (0.19 ppm) (Table 1). Hg seems to be
very rare in the Egyptian river Nile water and it was re-
corded only in some sites along the river Nile (Table 1).
The concentration of Mercury was higher the permissible
limits in the Rosetta and Damietta branches. Mn concen-
trations ranged from 0.033 ppm to 0.099 ppm. It showed
a slight increase from upto downstream sites. The maxi-
mum value was recorded at Rosetta (0.14 ppm) (Table 1).
Generally, the increase in heavy metals concentrations in
the Nile water might be attributed to the direct inputs
from different sources (industrial wastes and atmospheric
inflow of dust containing car exhaust). In addition, the
increase in density of boats and ship, which discharge its
effluent directly to the Nile containing high amount of Pb
in both the dissolved and particular phases [21,22].
3.2. Sediments Analysis
Results of heavy metal analysis of sediments from the
selected sites are presented in Table 2. The sediment
existing at the bottom of the water column plays a major
role in the pollution scheme of the river system by heavy
metals [23]. They reflect the current quality of the water
system and can be used to detect the presence of con-
taminant that does not remain soluble after discharge into
water. The concentrations of the selected heavy metals in
sediments samples were very high in all sites comparing
to the concentration of the same heavy metals in water
samples from same sites. Low-level discharges of a con-
taminant may meet the water quality criteria, but long-
term partitioning to the sediments could result in the ac-
cumulation of high loads of pollutants [24]. Therefore,
the determination of heavy metals in the sediments is
fundamental to realize the toxic pollutants in the river
sediment [25]. The concentrations of lead (Pb) exhibited
a wide range of variation ranging from 3.1 to 76.9 mg/kg.
Pb was very low in the sediment of Aswan and Kena
comparing to its concentration in the sediment of Dami-
etta and Rosetta (Table 2). The concentration of lead was
higher than the permissible limit in Rosetta Branch.
Cadmium (Cd) exhibited narrow range of variation
ranging from 0.4 to 0.7 mg/kg. The lowest concentration
was recorded at Aswan and the highest one was recorded
at Damietta and Rosetta. In general the concentrations of
Cd were fluctuated between sites but they still showed
slightly increased from Aswan toward Damietta and
Rosetta (Table 2). The level of Cadmium was higher
than the permissible limit in all sites except in the sedi-
ment of Aswan and Kena.
Copper (Cu) and Chromium (Cr) exhibited a wide
range of variation ranging from 0.03 to 0.05 mg/kg for
Cu and from 8.8 to 17.6 mg/kg for Cr. The highest con-
centration for Cu was recorded in the sediment of Rosetta
and the lowest one was recorded in the sediment of Kena.
For Cr the highest concentration was recorded at Assiut
and lowest one was recorded at Rosetta (Table 2). Man-
ganese (Mn) and Zinc (Zn) concentrations represented
the second highest metals in the sediment after iron.
They nearly had the same concentration and the same
distribution (Table 2). Such concentrations were ranged
from 139.8 to 351.8 mg/kg for Mn and from 91.5 to 307
mg/kg for Zn. The concentration of the Zinc was higher
than the permissible limits in Rosetta and Damietta
branch and also in Beni-Suef. Fe showed higher values at
all sites comparing to other heavy metals ranging from
379.4 to 698.7 mg/kg, indicating that this metal is natu-
rally high in the sediments. Hg was recorded in very low
concentrations through the whole course of the river Nile
and it was completely not detected in the sediment at
Aswan (Table 2). Such concentrations seem to be con-
stant in all sites. The wide ranges of metal concentrations
which recorded for some heavy metals may be attributed
to variations in mud percent and increase in heavy metals
rich urban effluents draining into river.
3.3. Tissues Analysis
Table 3 shows the mean and SD values of the tested
heavy metals in African catfish organs. Knowledge of

Water Quality and Heavy Metal Monitoring in Water, Sediments, and Tissues of the African Catfish Clarias gariepinus
(Burchell, 1822) from the River Nile, Egypt
396
Table 2. Mean and SD of the concentrations of the selected heavy metals of the sediment samples collected from six sites along
the whole course of the river Nile from its spring at Aswan to its estuary at Damietta and Rosetta branches.
Aswan Kena Assiut Beni-Suef Damietta Rosetta
Locality
Metal Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD
Permissible
limit*
Pb (mg/kg) 3.1 ± 2.619 3.1 ± 2.342 4.4 ± 2.402 11.5 ± 11.518 6.9 ± 4.864 46.9 ± 23.509 35
Cd (mg/kg) 0.4 ± 0.256 0.5 ± 0.232 0.6 ± 0.354 0.6 ± 0.256 0.7 ± 0.414 0.7 ± 0.502 0.6
Zn (mg/kg) 101.1 ± 58.2 91.5 ± 27.77 100.2 ± 37.58 126.6 ± 32.73 179.8 ± 76.2 307 ± 99.19 123
Cu (mg/kg) 0.030 ± 0.027 0.024 ± 0.024 0.030 ± 0.0261 0.027 ± 0.0282 0.032 ± 0.0321 0.054 ± 0.0278 35.7
Cr (mg/kg) 8.8 ± 1.564 11.1 ± 14.417 17.6 ± 24.931 10.3 ± 10.342 9.1 ± 11.549 8.7 ± 8.438 37.3
Fe (mg/kg) 397.053 ± 291.9 379.44 ± 238.63 496.55 ± 333.45 536.483 ± 351.21632.133 ± 393.87 698.74 ± 287.17-
Hg (mg/kg) 0.0000 ± 0.001 0.0004 ± 0.0004 0.0009 ± 0.001 0.0010 ± 0.001 0.0020 ± 0.001 0.0033 ± 0.001 0.17
Mn (mg/kg) 210.36 ± 151.86 159.84 ± 122.70 273.35 ± 261.033221.72 ± 198.72351.79 ± 299.66 269.96 ± 204.093-
*Canadian Environmental Quality Guidelines
heavy metal concentrations in fish is important with re-
spect to nature of management and human consumption
of fish. In the literature, heavy metal concentrations in
the tissue of freshwater fish vary considerably among
different studies [26-28], possibly due to differences in
metal concentrations and chemical characteristics of wa-
ter from which fish were sampled, ecological needs, me-
tabolism and feeding patterns of fish and also the season
in which studies were carried out. In the river, fish are
often at the top of the food chain and have the tendency
to concentrate heavy metals from water [14]. Therefore,
bioaccumulation of metals in fish can be considered as an
index of metal pollution in the aquatic bodies [26,29,30]
that could be a useful tool to study the biological role of
metals present at higher concentrations in fish [31]. Bio-
accumulation is the ability of an organism to concentrate
an element or a compound from food chain and water to
a level higher than that of its environment. Bioaccumula-
tion is the resultant process of many interactions within
the compartments of the organisms. Metals uptake and
their toxicity in aquatic fauna are influenced by many
factors such as pH, hardness of water, alkalinity, tem-
perature etc. Metals exist in a variety of states and their
toxicity depends on its nature and chemical forms
whether it is in ionic form or in an oxidized or reduced
state in combination with other organic substances and
other metals [32].
Copper is an essential part of several enzymes and is
necessary for the synthesis of haemoglobin [33], but very
high intake of Cu can cause adverse health problems.
The concentration of the copper exhibited a wide range
of variation between different tissues and between dif-
ferent sites (Table 3). The highest concentration was
recorded in the liver comparing to other tissues for all
sites. The highest concentration was recorded in the liver
of fish collected from Rosetta (31.9 mg/kg) and the low-
est one was recorded in the muscles of fish collected for
Kena (1.01 mg/kg). The distribution of the copper was in
the order of L > GL > G > M. The elevation of copper
accumulation in this study may be due to industrial and
sewage wastes. Also, it may be due to elevated metal–
binding protein synthesis as recorded by [33]. Copper
toxicity in fish is taken up directly from the water via
gills [34]. The present study showed similar accumula-
tion of copper in the gills. Effects of high concentrations
of copper on fish are not well established; however, there
is evidence that high concentrations in fish can experi-
ence toxicity [35]. Copper can combine with other con-
taminants such as ammonia, mercury and zinc to produce
an additive toxic effect on fish [33].
Manganese functions as an essential constituent for
bone structure, reproduction and normal functioning of
the enzymes system [36]. It is toxic only when present in
higher amount, but at low level is considered as micro-
nutrient [36]. A wide range of variation was recorded for
Mn between different tissues and different sites. The
highest concentration of Mn was recorded in the gills of
fishes from nearly all sites (Table 3). The highest con-
centration was recorded in the gill of fish collected from
Rosetta (17.37 mg/Kg) followed by Damietta (16.68
mg/Kg). The lowest concentration of Mn was detected in
the gonad of fishes collected from Assiut (Table 3). Cr

Water Quality and Heavy Metal Monitoring in Water, Sediments, and Tissues of the African Catfish Clarias gariepinus
(Burchell, 1822) from the River Nile, Egypt
397
Table 3. Mean and SD of the concentration of the selected heavy metals in different tissues of the African catfish Clarias
gariepinus collected from six sites along the whole course of the river Nile from its spring at Aswan to its estuary at Damitta
and Rosetta branches.
Aswan Kena Assiut Beni-Suef Damietta Rosetta
Parameters
Localities
Organs Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD
Liver 10.64 ± 2.49 5.50 ± 4.34 6.51 ± 2.35 11.25 ± 0.68 5.08 ± 2.05 31.92 ± 11.19
Gills 4.14 ± 2.81 3.22 ± 3.04 5.08 ± 4.02 4.19 ± 4.15 3.65 ± 4.31 9.631 ± 2.91
Gonads 2.85 ± 1.93 2.79 ± 0.35 4.49 ± 1.87 8.15 ± 1.62 1.81 ± 1.34 6.02 ± 1.45
Cu (mg/kg)
Muscles 3.75 ± 2.98 1.01 ± 0.42 3.70 ± 2.51 3.90 ± 2.68 4.19 ± 4.06 5.48 ± 0.71
Pattern L > GL > M > G L > GL > G > ML > GL > G > ML > G > GL > ML > M > GL > G L > GL > G > M
Liver 5.45 ± 3.05 7.71 ± 2.21 12.94 ± 8.37 3.84 ± 3.077 15.98 ± 6.67 15.43 ± 5.89
Gills 7.59 ± 1.93 10.15 ± 3.493 12.67 ± 8.26 7.42 ± 5.03 16.68 ± 2.517 17.37 ± 4.91
Gonads 8.18 ± 2.25 5.51 ± 1.49 3.38 ± 1.83 5.96 ± 3.34 5.406 ± 1.68 13.857 ± 3.089
Mn (mg/kg)
Muscles 4.79 ± 2.96 7.57 ± 4.85 5.223 ± 3.612 4.27 ± 4.09 14.14 ± 1.85 14.796 ± 4.12
Pattern G > GL > L > M GL > L > M > GL > GL > M > GGL > G > M > LGL > L > M > G GL > L > M > G
Liver 6.59 ± 1.357 8.51 ± 1.866 5.32 ± 3.75 3.74 ± 4.29 5.37 ± 0.963 6.99 ± 1.74
Gills 6.51 ± 1.34 6.72 ± 1.17 4.37 ± 3.579 4.29 ± 3.7 4.22 ± 1.77 8.46 ± 3.33
Gonads 5.63 ± 2.38 6.11 ± 2.89 5.24 ± 3.32 6.28 ± 8.35 2.38 ± 1.1 6.32 ± 1.59
Cr (mg/kg)
Muscles 2.37 ± 0.823 4.97 ± 2.71 4.50 ± 3.8 4.83 ± 3.477 3.84 ± 1.75 5.47 ± 1.79
Pattern L > GL > G > M L > GL > G > ML > G > M > GLG > M > GL > LL > GL > M > G GL > L > G > M
Liver 42.48 ± 14.74 65.09 ± 3.88 58.59 ± 15.24 55.29 ± 27.06138.98 ± 23.44 178.84 ± 20.94
Gills 35.38 ± 7.59 20.65 ± 1.62 56.39 ± 12.51 30.36 ± 17.46109.8 ± 83.69 112.13 ± 58.89
Gonads 30.69 ± 12.7 19.43 ± 22.48 44.27 ± 8.52 28.39 ± 4.45 83.28 ± 28.35 78.59 ± 13.97
Zn (mg/kg)
Muscles 32.57 ± 10.79 11.62 ± 6.917 51.224 ± 12.1547.32 ± 7.54 71.85 ± 25.89 62.49 ± 36.3
Pattern L > GL > M > G L > GL > G > ML > GL > M > GL > M > GL > GL > GL > G > M L > GL > G > M
Liver 13.8 ± 3.50 9.45 ± 4.92 6.1 ± 2.78 5.51 ± 2.52 15.32 ± 2.01 20.73 ± 8.48
Gills 7.31 ± 2.04 7.59 ± 2.74 5.60 ± 4.54 7.286 ± 9.84 14.61 ± 4.49 22.57 ± 8.13
Gonads 8.06 ± 3.17 9.29 ± 5.79 5.84 ± 3.2 1.89 ± 1.77 13.96 ± .72 12.17 ± 6.75
Pb (mg/kg)
Muscles 7.11 ± 4.71 7.48 ± 1.97 5.895 ± 3.96 6.72 ± 4.42 14.51 ± 2.00 14.10 ± 4.93
Pattern L > G > GL > M L > G > GL > ML > M > G > GLGL > M > L > GL > GL > M > G L > GL > M > G
Liver 4.92 ± 0.36 0.89 ± 0.06 0.57 ± 0.28 0.79 ± 0.23 1.09 ± 0.47 1.10 ± 0.54
Gills 0.62 ± 0.19 0.77 ± 0.1 0.71 ± 0.24 0.43 ± 0.17 0.90 ± 0.60 0.60 ± 0.13
Gonads 0.28 ± 0.16 0.62 ± 0.14 0.53 ± 0.34 0.52 ± 0.27 0.88 ± 0.15 0.76 ± 0.33
Cd (mg/kg)
Muscles 0.66 ± 0.06 0.49 ± 0.108 0.20 ± 0.058 0.354 ± 0.28 0.78 ± 0.32 0.55 ± 0.19
Pattern L > M > GL > G L > GL > G > MGL > L > G > ML > G > GL > ML > GL > G > M L > G > GL > M
Liver 51.72 ± 12.11 62.42 ± 8.51 52.54 ± 4.82 109.82 ± 11.197110.85 ± 13.99 115.08 ± 17.77
Gills 49.55 ± 6.13 44.04 ± 9.62 40.19 ± 7.02 91.43 ± 17.4478.71 ± 25.24 83.39 ± 39.21
Gonads 38.66 ± 6.44 47.24 ± 10.76 44.12 ± 7.17 83.99 ± 23.7655.13 ± 30.94 76.26 ± 21.92
Fe (mg/kg)
Muscles 26.49 ± 2.45 38.09 ± 6.75 27.67 ± 6.52 85.29 ± 11.7766.84 ± 22.51 80.59 ± 20.31
Pattern L > GL > G > M L > G > GL > ML > G > GL > ML > GL > G > ML > GL > M > G L > GL > M > G
Liver 0.0012 ± 0.0011 0.0016 ± 0.000840.008 ± 0.014 0.0099 ± 0.00830.019 ± 0.023 0.069 ± 0.11
Gills 0.00042 ± 0.00057 0.00088 ± 0.0010.004 ± 0.006 0.0051 ± 0.00440.015 ± 0.019 0.029 ± 0.015
Gonads 0.00017 ± 0.00018 0.00021 ± 0.000290.0011 ± 0.00060.0046 ± 0.00450.013 ± 0.022 0.008 ± 0.0049
Hg (mg/kg)
Muscles 0.00087 ± 0.00087 0.00017 ± 0.000110.00067 ± 0.000690.0012 ± 0.00150.0046 ± 0.0065 0.015 ± 0.0054
Pattern L > M > GL > M L > GL > G > ML > GL > M > GL > GL > G > ML > GL > G > M L > GL > M > G

Water Quality and Heavy Metal Monitoring in Water, Sediments, and Tissues of the African Catfish Clarias gariepinus
(Burchell, 1822) from the River Nile, Egypt
398
has a special pattern of distribution among tissues and
sites. The highest level of Cr was detected in the liver of
fish collected from Kena and the lowest concentration
was recorded in the muscles of fishes collected from
Aswan (Table 3).
Zinc is an essential element and is a common pollutant
as well. Mining smelting and sewage disposal are major
source of zinc pollution. Fish take it up directly from
water, especially by mucous and gills [36]. The relatively
higher zinc concentration in the liver of the different fish
species may be due to the role of zinc as an activator of
numerous enzymes present in the liver [33]. Zn was ac-
cumulated mainly in the liver of fishes collected from all
sites. Such results were previously reported by [37]. The
highest level was recorded in the liver of fishes collected
from Rosetta followed by Damietta (Table 3).
Lead is non-essential element and higher concentra-
tions can occur in aquatic organisms close to anthropo-
genic sources. It is toxic even at low concentrations and
has no known function in biochemical processes [36]. In
all sites except Beni-Suef the highest lead level was de-
tected in the liver of C. gariepinus followed by gills. The
highest concentration was recorded in the tissues of
fishes collected from Rosetta followed by Damietta. In
contrast to the present results, [37] reported the gill as
highly Pb-accomulated organ in C. gariepinus. Lead was
found to inhibit the impulse conductivity by inhibiting
the activities of monoamine oxidase and acetylcholine
esterase to cause pathological changes in tissue and or-
gans. The increase of lead level is due to the discharge of
industrial, sewage and agricultural wastes in the investi-
gated area. The high level of lead may be attributed to
high lead concentration in water [38].
According to the present result the Cd accumulated
mainly in the liver followed by gills of fishes collected
from the selected sites. The highest concentration was
detected in liver of fish collected from Aswan. Cd is
highly toxic non-essential heavy metal and it dose not
have a role in biological processes in living organisms.
Thus even in low concentration, Cd could be harmful to
fishes. High accumulation of cadmium in liver may be
due to its strong binding with cystine residues of metal-
lothionein [38].
With different magnitude the Fe and Hg accumulated
mainly in the liver of fishes collected from all sites. The
highest concentrations of both metals were recorded in
the tissues of fishes collected from Rosetta followed by
Damietta. Iron is an abundant and important element,
unsurpassed by any other heavy metals in the earth’s
crust [36]. The increase of iron accumulation in fish liver
in this study may be related to the increase of total dis-
solved iron in Nile water and consequently increase the
free metal iron concentration and thereby lead to an in-
crease in metal uptake by different organs [38]. [33] ob-
served accumulation of iron ligand protein (Hemosidrin)
scattered in liver section of fish exposed to high iron
concentration. Trace metals accumulations in fish liver at
sites under investigation were detected in following de-
scending order: Zn > Fe > Cu > Pb > Mn > Cr> Cd > Hg.
In the gill tissues these metals were accumulated in the
following order Fe > Zn > Mn > Pb > Cr > Cu > Cd> Hg.
The lower concentration of Cu in the gill than that of
livers was possibly due to lower binding affinity of Cu
on the gill surface. Gills which are in direct contact with
water accumulated some amount of heavy metals. The
accumulation of such metals in the gills may be due to
adsorption to the gill surfaces and dependent on the
availability of proteins to which these metals may bind.
The low accumulation may be due to development of
some defensive mechanism such as excessive mucous
secretion and clogging of gills. Gonad and muscle were
found to accumulate small amounts of most heavy metals
and might have received it through circulation. It is sug-
gested that the low accumulation of metals in gonad and
muscle may be due to lack of binding affinity of these
metals with the proteins of gonad and muscle. This is
particularly important because muscles contribute the
greatest mass of the flesh that is consumed as food.
4. Conclusions
Higher mean value of conductivity, alkalinity, COD,
NH3, NO3, TS, SO4, Cl, orthophosphate and trace metals
in the water, sediments and fish tissues collected from
Damietta and Rosetta sites comparing to the other sites
prove the presence of large quantities of organic and in-
organic pollutants in Rosetta and Damietta water.
This was expected due to the fact that the water of
such branches receives high concentrations of organic
and inorganic pollutants from industrial, domestic as well
as diffuse agricultural wastewater [38]. The heavy metal
residues in the tissues of Clarias gariepinus exhibited dif-
ferent patterns of accumulation and distribution among the
selected tissues and localities. In fish, gills are considered
to be the dominant site for contaminant uptake because
of their anatomical and/or physiological properties that
maximize absorption efficiency from water [39]. How-
ever, it was evident from our study that, liver was the site
of maximum accumulation for the elements while muscle
was the over all site of least metal accumulation. The
higher levels of trace elements in liver relative to other
tissues may be attributed to the affinity or strong coordi-
nation of metallothionein protein with these elements
[40].

Water Quality and Heavy Metal Monitoring in Water, Sediments, and Tissues of the African Catfish Clarias gariepinus
(Burchell, 1822) from the River Nile, Egypt
399
5. Acknowledgements
This work was supported by Science and Technology
development fund (Project ID 448). I would like to thank
Mr. K. AbEl-Fadel, A. Gad El-Rab, M. Nassar, and A.
Moustafa for their support during sampling and analysis
processes.
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