International Journal of Marine Science 2015, Vol.5, No.58: 1-6
3
certified reference materials for sandy clay (CRM
049-050). There were no significant differences
(p<0.05) between determined and certified metal
concentrations.
2.4 Statistical Analysis
The results obtained were subjected to statistical
evaluation using Minitab © version 15. One-way
Analysis of variance (ANOVA) was used to evaluate
s i g n i f i c a n t difference in mean values of the trace
metals in the estuary. Mean separation was carried
out using the Turkey test. Correlations we re
performed in a pair wise fashion employing Pearson
correlation procedure.
3 Results
Trace metal concentrations in water are summarized
in Table 1 for the three stations. The general trend of
metals in water was in the following order:
Fe>Zn>Pb>Cd. The minimum and maximum mean
values (mg/L) for the metals in water ranged from
0.12 to 0.20 for iron; 0.06 to 0.09 for zinc; 0.01 to
0.02 for lead and 0.003 to 0.01 for cadmium. The
results of water samples showed variations in the
distributions of Fe, Zn, Pb and Cd. Significant
variations (P<0.05) occurred in Fe and Pb, while
variations in Zn and Cd were not significant across the
sampling stations.. Except for Cd, the mean values of
Fe, Zn and Pb in wet season (0.19, 0.10, and
0.01respectively) were comparatively higher than
those of dry season (0.14, 0.06 and 0.01 respectively)
(Figure 2). However, Fe, Zn and Cd showed
significant variations (P<0.05) in seasons except for
Pb which indicated no significant differences.
The spatial variations of metals in sediment are
presented in Table 2. Similar trend (Fe>Zn>Pb>Cd)
was observed in sediment. Except for iron, spatial
variation of heavy metals across all stations were not
significant (P>0.05). The concentrations of Fe ranged
from 0.09 – 3.6 mg/kg in sediment. The lower limit of
Fe in sediment was determined at station 1 and the
upper limit at station 2. Zn concentrations ranged from
0.01 in station 3 to 1.27 in station 2. Pb concentrations
ranged from 0.01 – 0.17 mg/kg in the sediment. The
lower limit of Pb was determined at station 1 and
upper limit at station 2. Concentrations of Cd ranged
from 0.001 – 0.08 mg/kg in sediment, with lower limit
determined at station 1 and upper limit at station 3.
Metal values obtained in dry season were relatively
higher than those in wet season. Fe, Zn, Pb and Cd
were 0.99, 0.51, 0.05 and 0.03 respectively for dry
season while the same metals were 0.19, 0.15, 0.02
and 0.01 in wet season (Figure 3).
The correlation coefficient between the metal levels in
water and sediments for the six (6) month is presented
in Table 3. High significance variation were obtained
at p<0.05. Fe in water showed a significant positive
relationship with Zn (r=0.67); Pb (r=0.68) and Cd
(r=0.713) and negative correction with other metals in
sediments. The relationship between Pb and Zn was
significantly positive (r=0.559) in water and (r=0.84)
in sediments. Cd on the other hand showed a
significant positive correlation with Zn (r=0.612) and
Pb (r=0.592) in water.
4. Discussions
Qua Iboe estuary is one of the estuaries in the Niger
delta of Nigeria that provides essential breeding and
nursery grounds for fishes in Gulf of Guinea. Despite
the significant role estuary plays, metals from
naturally occurring deposits, natural processes and
anthropogenic activities are in the estuaries. Metals
analyzed in sediments were higher than those in water
which confirmed that sediments are important sink for
toxic metals and tend to pose threats to aquatic life as
a result of re-suspension into the water column. It
shows that some trace metals that may not be detected
or in low concentration in the water column can be
observed in the sediments.
Iron which is the fourth most abundant element in the
Earth’s crust plays a role in many redox reactions in
metabolic functions in human. Concentration of iron
in water from this study was below the NIS maximum
permissible level for drinking water. No guideline
value for iron in drinking-water is proposed by WHO,
they stated that it was not of health concern at levels
found in drinking-water. However, concentration of
0.3 – 1.0 mg/l are satisfactory level but may cause
staining and objectionable taste, while Fe values of >
1.0 are unsatisfactory in drinking water (WHO, 2011).
The lowest concentration of Fe in sediment was
determined at station 1 and the highest level was at
station 2.
The could be as a result of anthropogenic
inputs such as the discharge of Fe-laden wastes and
