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International Journal of Aquaculture, 2014, Vol.4, No.06
http://ija.sophiapublisher.com
39
Table 1 Concentration heavy metals ppm (µg/g) in muscle
tissues and gills of
O. niloticus
at two sampling points.
Fish (1)
Fish (2)
Heavy
metals
Muscle
Gills
Muscle
Gills
Cd
0.005
0.003
0.006
0.003
Cr
0.03
0.013
0.016
0.013
Ni
0.03
0.02
0.03
0.02
Pb
0.3
0.2
0.3
0.2
Cu
0.5
0.4
0.5
0.4
Zn
0.8
0.5
0.9
0.7
Fe
2.2
2
3.2
3
Sr
3.3
2.1
3.4
3
Figure 2 Mean metal (Sr, Fe, Zn, Cu and Pb) concentrations
(µg/g) in muscles and gills of fish collected from
sewage-treatment canals (1) and the White Nile (2) at the
discharge of sewage- treated waste water.
3.2 Concentration of heavy metals in water samples
The water samples at each sampling point were also
analyzed by using ICP-OES. The concentration of Fe
and Sr was very high in all sampling stations (Table 2).
The range of Fe was (10.6 – 11.6 ppm) with no
significant difference between the four sampling
stations, while the range of Sr was (6.32 – 7.86 pppm)
with increased concentration in station 4, the discharge
point of the treated waste-water (Figure 3). The
concentration Zn and Cu was very low and below the
detection limit in all sampling stations, while the
concentration of Ni, Cr and Cd was a pit higher. Lead
was detected in the four stations (0.11 – 0.2 ppm) with
the highest level in station 3, the discharge point of
industrial effluents.
The above data indicated the order of heavy metals
accumulation in fish muscles and gills was Sr > Fe >
Zn > Cu > Pb > Ni > Cr > Cd for samples of fish from
both points of collection, while the concentrations of
heavy metals in the water collected from four stations
through the waste-treatment canal had the order Fe >
Figure 3 Mean metal (Fe, Sr, Pb, Cr and Cd) concentrations
(µg/L) in water samples from four stations along the canals of
sewage-treatment.
Sr > Pb > Cr > Cd > Ni > Cu > Zn. The trend of
accumulation suggested deposition was maximum for
Sr and iron, and minimum for cadmium in the muscles
and gills of fish samples. In water samples, the
concentration of Fe and Sr was very high in St (1), the
beginning of the canal, where effluent from different
sources are discharged, then the level came down at St
(2), the end of the waste-water canal. At St (3) the
industrial effluents from the military factory are
released into the canal. This situation explains why the
concentrations of these metals were high at St (3), and
consequently, their levels in the water increase at St
(4), which is released into the White Nile. The water
condition was also very muddy caused by the effluent
discharge into the water.
Although some metals such as Zn and Cu were high in
the tissues and gills of the fish, they are very low and
below the detected limits in the water from where the
fish samples were collected. This however is in
agreement with a study in Turkey and
Malaysia,
where the concentration of heavy metals in fish was
high even the concentration of heavy metals in the
water was low (Ismaniza and Saleh, 2012). It was
reported that Ca, Mg, Fe, Cu, Zn and Pb exhibited
bio-accumulation from water to fish (Kalfakakon and
Akrida-Demertai, 2000; Irwandi and Farida, 2009).
They demonstrate that metal concentrations in fish are
higher than in water, which indicates the
bio-accumulation. The main reason is the long-term
disposal of sewage-treated water into the Nile, which
results in the accumulation of toxic heavy metals in
river water, and may adversely affect the growth of
various aquatic vertebrates and invertebrates including
fishes. Ayotunde and Offen (2012) found a level of