metal contamination of surface sediments of the sfax–chebba coastal line, tunisia
TRANSCRIPT
ORIGINAL ARTICLE
Metal contamination of surface sediments of the Sfax–Chebbacoastal line, Tunisia
Nedia Ghannem • Dorra Gargouri •
Mohamed Moncef Sarbeji • Chokri Yaich •
Chafai Azri
Received: 24 October 2013 / Accepted: 29 March 2014
� Springer-Verlag Berlin Heidelberg 2014
Abstract Concentrations of several heavy metals (Pb, Cr,
Cd, Cu, Zn and Fe) in surface sediment were determined to
investigate the distributions and the metallic pollution
status in Sfax–Chebba coastal area (southeast of Tunisia).
Sediment samples were collected from 20 locations, rep-
resenting three different site groups (i.e., site I: urban zone,
site II: pre-urban zone and site III: rural zone). Heavy metal
contents were analyzed by Atomic Absorption Spectrom-
etry. The obtained results showed that generally, heavy
metal concentrations in the coastal sediments near Sfax city
(urban zone) were higher than those at other stations
because of the anthropogenic activities. These concentra-
tions exceeded the threshold effect levels. This was con-
firmed by the chemometric approaches (enrichment factors,
geoaccumulation index and principal component analysis)
which showed a significant impact of multiple anthropo-
genic sources. Moderate to extremely severe enrichment of
sediments in terms of Pb, Cr, Cd, Cu and Zn were shown to
exist in site I. Severe enrichment by Cd was also observed
in other sites. Based on the geoaccumulation index, Pb, Cr,
Cd, Cu and Zn can be considered as unpollutants to
extreme pollutants.
Keywords Heavy metals � Sediment � Contamination �Chemometric methods � Sfax–Chebba coast
Introduction
Coastal areas are sites of discharge and accumulation of a
range of environmental contaminants, which ultimately
affects the sustainability of living resources and public
health (MacFarlane and Burchett 2000). Different urban,
industrial, and agricultural activities, as well as atmo-
spheric deposition (Yang et al. 2011) contribute to con-
tamination of aquatic environments.
Among environmental pollutants, heavy metals are of
particular concern due to their toxicity, wide source, non-
biodegradable properties, and their ability to accumulate for
long period of time (Dong et al. 2011). They can cause
harmful effects on both marine organisms and human pop-
ulations (Muhammad et al. 2000; Vallejuelo et al. 2010; Wu
and Zhang 2010). These metals are rapidly and efficiently
associated with the sediment via adsorption onto surface
particles, hydrolysis and co-precipitation. Adsorption is
usually the predominant process because metals have strong
affinities for iron and manganese hydroxides, particulate
organic matter, and a lesser extent to clay minerals. Conse-
quently, metals tend to accumulate in bottom sediments
(Rezayi et al. 2011). Only small portion of free metal ions can
be found dissolved in water (Sultan and Shazili 2009).
Marine sediments are good indicators for the assessment
of various contaminants in aquatic environments because
they act as major repository of metals, leading to the
contamination of coastal zone (Adams et al. 1992; Atgin
et al. 2000; Caccia et al. 2003). Furthermore, they show
less variation in time and area, allowing more consistent
assessment of spatial and temporal contamination (Krishna
et al. 2011). Therefore, the fate of heavy metals in sediment
has recently been the subject of extensive discussion (Ding
and Ji 2010; Kong et al. 2011; Sundaray et al. 2011; Tang
et al. 2010).
N. Ghannem (&) � M. M. Sarbeji � C. Yaich
Department of Geology, National School of Engineers of Sfax,
Road Soukra, km 4, PB 1173, 3038 Sfax, Tunisia
e-mail: [email protected]
D. Gargouri � C. Azri
Department of Earth Sciences, Faculty of Science of Sfax,
Road Soukra, km 3,5, PB 1171, 3000 Sfax, Tunisia
123
Environ Earth Sci
DOI 10.1007/s12665-014-3248-z
The Sfax–Chebba coastal area (southeast of Tunisia)
represents an example of marine ecosystem whose biological
balances have been modified due to the particular marine
hydrodynamics of the gulf of Gabes and the anthropogenic
development, and in particular to the great industry settle-
ment of Sfax. Indeed, since the 1950s, the growing manu-
facturing industries, the population expansion and the rapid
urban development in Sfax city have resulted in industrial
and municipal wastewater, which can seriously affect sea-
water and marine sediments (Illou 1999; Mkawar et al. 2007
Choura et al. 2009; Gargouri et al. 2010; Ghannem et al.
2010; Chulli et al. 2012; Sahnoun et al. 2012).
In this context, the present study aims to (1) assess the
level of metal (Pb, Cr, Cd, Cu, Zn and Fe) concentrations in
surface sediments of Sfax–Chebba coast, (2) explore the
natural and anthropogenic input of heavy metals and (3)
discuss the pollution status on the area.
Materials and methods
Sampling and analysis surface sediment samples were
collected from 20 stations along the coastal area of Sfax–
Chebba (southeast of Tunisia) (Fig. 1). Such a coast is
characterized by semi-diurnal tide with amplitude about
1.4 m during spring tides and 0.3 m during neap tides
(Amari 1984). Tidal currents are generally very low;
however, they may be strong particularly at tidal channels.
The offshore swells are strongly dimmed during its prop-
agation by seagrass beds and shoals surrounding the Ker-
kennah archipelago. The swells are characterized by a high
variability of directions (W, NW, N to NE, E, S and SSE)
and velocities. E, NE and SE swell directions were dem-
onstrated dominant (Amari 1984).
In order to determine the distribution of metal contam-
ination in this coastal zone, the sampling stations were
divided into three site groups based on the possible
anthropogenic activities:
– Site I = Sfax-Sidi Mansour (Stations S1–S7: Urban zone,
densely populated area, commercial port, industrial park,
presence of the phosphogypsium deposit resulting from
old processing plants of NPK ‘‘phosphates’’).
– Site II = Haggouna-El Awabed (Stations S01–S03: Pre-
urban zone);
– Site III = El Louza-Chebba (Stations S001–S0010: rural
area and fishing activities).
Samples from each station were collected using an
Ekman grab. The top 5 cm of the sediment was removed
670000
670000
680000
680000
690000
690000
3850000 3850000
3860000 3860000
3870000 3870000
3880000 3880000
3890000 3890000
3900000 3900000N
Haggouna
el Louza port
port
el Awabed
S"10S"9S"8
S"7
S"6S"5
S"4
S"3
S"2
S"1
S'3
S'2
S'1
S7S6
S5S4
S3S2S1
Sidi Mansour
Sfax
Malloulech
Chebba
Port
Ouady EzzitPK4 canal
Site III
Site II
Site I
Tunisia
0 10Km
0 100Km
N
Fig. 1 Location of sampling sites in the coast from Sfax to Chebba
Environ Earth Sci
123
with an acid-washed spatula to prevent contamination.
Immediately after collection, samples were placed in
polyethylene bags, refrigerated, and transported to the
laboratory. Sediment samples were dried to a constant dry
weight at 60 �C, and sieved through a 63-lm stainless steel
sieve. Finer sediments contain more heavy metals than the
coarser ones. This enrichment is mainly due to surface
adsorption and ionic attraction (Szefer et al. 1996).
For the analyses of total Pb, Cr, Cd, Cu, Zn and Fe
concentrations in sediment samples, about 0.5–1.0 g of the
dried sediment were digested in a mixture of concentrated
acids (nitric acid, fluorhydric acid, and perchloric acid)
according to the EPA 3052 guideline (EPA 1996). The
digested samples were then diluted to 25 ml with double
distilled water, and filtered through Whatman filter paper
into acid-washed polyethylene sample bottles. After fil-
tration, the samples were determined for Pb, Cr, Cd, Cu, Zn
and Fe using an air–acetylene flame Atomic Absorption
Spectrometry (SHIMADZU HIC- 6A model) using Zee-
man Effect.
The analytical data quality was guaranteed through the
implementation of laboratory quality assurance and quality
control methods, including the use of standard operating
procedures, calibration with standards, analysis of reagent
blanks, recovery of known additions and analysis of rep-
licates. All analyses were carried out in triplicate, and the
results were expressed as the mean.
The detection limits (mg/l) were 0.041 for Pb, 0.015 for
Cr, 0.004 for Cd, 0.010 for Cu, 0.003 for Zn and 0.013 for
Fe. Data reported in this study are calculated as dry weight.
Sediment quality assessment
Enrichment rate of sediment can be calculated by the
Eq. (1) as described by Yaboue (1991).
Tð%Þ ¼ CðXÞSitea � CðXÞSiteb
CðXÞSitea�100 ð1Þ
where T(%): enrichment rate of sediments for Site a (in our
case ‘‘urban area’’ or ‘‘pre-urban area’’) with respect to that
of Site b selected as rural area; CðXÞSitea: concentration of a
selected heavy metal ðX) in the sediment sampled in the
urban (pre-urban) area; CðXÞSiteb: concentration of the
selected heavy metal ðX) in the sediment sampled in the
rural area.
Due to the absence of Tunisian guidelines for coastal
sediments, Pb, Cr, Cd, Cu and Zn concentrations were
compared with the China sediment quality assessment
guidelines (i.e., the threshold effect levels or TEL) (Jun-
hong et al. 2011).
The TEL, as defined by MacDonald et al. (1996), is
the upper limit of the range of sediment contaminant
concentrations dominated by no effect data entries. Within
this range, concentrations of sediment-associated contami-
nants are not considered to represent significant hazards to
aquatic organisms. The TEL can be calculated by the fol-
lowing Eq. (2):
TEL ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
EDS � Lð Þ � NEDS � Mð Þp
ð2Þ
where (EDS-L) is the 15th percentile concentration in the
effect data set, and (NEDS-M) is the 50th percentile con-
centration in the no effect data set. An elaborate description
of the numerical sediment quality assessment guidelines
and the TEL development can be found in MacDonald
(1994) and Macdonald et al. (1996).
In order to assess the impact of the anthropogenic
activities related to the abundance of trace metals in the
studied sediments, the computation of enrichment factor
(EF) is required.
A normalization procedure using Al or Fe is a powerful
tool to evaluate the anthropogenic input of trace metals in
the sediments (Nolting et al. 1999; Selvaraj et al. 2004).
In this study, the geochemical normalization was
obtained using Fe. This element is widely used as a crustal
reference (Feng et al. 1998; Schiff and Weisberg 1999;
Mucha et al. 2003; Zhou et al. 2007; Zhang et al. 2007).
According to Ergin et al. (1991), the metal EF can be
calculated as following Eq. (3):
EF ¼Cx=CFeð Þsample
Cx=CFeð Þcrust or background
ð3Þ
where (Cx/CFe) sample is the ratio of concentration of the
element being tested (Cx) to that of Fe (CFe) in the sedi-
ment sample, and (Cx/CFe)crust or background is the same ratio
in unpolluted baseline samples.
EF values were interpreted as suggested by Birch
(2003).
EF \ 1 indicates no enrichment, EF \ 3 is minor
enrichment, 3 \ EF \ 5 is moderate enrichment,
5 \ EF \ 10 is moderately severe enrichment,
10 \ EF \ 25 is severe enrichment, 25 \ EF \ 50 is very
severe enrichment, and EF [ 50 is extremely severe
enrichment.
The geoaccumulation index (Igeo) introduced by Muller
(1981) may contribute to the estimation of the degree of the
sediment contamination.
This index can be determined from the following
Eq. (4):
Igeo ¼ Log2
Cn
1:5Bn
� �
ð4Þ
where Cn is the measured concentration of element n, Bn is
the background concentration value (average crust) of the
element n, and 1.5 is the background matrix correction
Environ Earth Sci
123
factor that is included to correct possible background value
variations due to lithogenic effects.
Statistical analysis
Correlation matrix and multivariate statistical analysis
including principal component analysis (PCA) were per-
formed using the ITCF statistical software package
(STATIT-CF 1987) to evaluate associations among the
investigated variables in the samples and to identify the
most common pollution sources.
Results and discussion
Heavy metal concentrations in studied superficial
sediments are presented in Table 1
Metal concentrations of Pb, Cr, Cd, Cu and Zn in sediments
were found to be higher in stations from S1 to S7, located
in the vicinity of Sfax city. Pb concentration (125.2 mg/kg)
and Cr (196.9 mg/kg) were, respectively, found highest
downstream PK4 and ‘‘Ouady Ezzit’’ canals (two principal
anthropogenic effluents). High concentrations of Cd, Cu
and Zn (36; 81.4 and 2,077.3 mg/kg, respectively) were
found around the phosphogypsum dump resulting from old
processing plants of NPK ‘‘phosphates’’. The minima of Cr
(1.5 mg/kg), Cd (0.1 mg/kg) and Zn (3.6 mg/kg) were
observed in station S’’1 (site III), and the minima of Pb
(0.2 mg/kg) and Cu (0.9 mg/kg) in stations S’1 and S’3
(site II). Port activities and industrial effluents of El Louza
as well as fishing boats activities along the coast contribute
to important levels in some stations of Cr (in site II and III),
Cd, Cu and Zn (in station S’’2, site III).
Heavy metals distribution among the three site groups
can be seen in Fig. 2. The mean concentrations (in mg/kg
dry weight) of Pb, Cr, Cd, Cu, Zn and Fe from the three
sites were, respectively, 28.3, 62.4, 10, 17, 398 and 8,822.5
from site I and 1.7, 57.6, 0.7, 4.5, 32.1 and 8,827 from site
II and 2.1, 41, 1.3, 5.7, 24.1 and 8,816.1 from site III.
Table 1 Heavy metals
concentrations (mg/kg dry
weight) in surface sediments
from the coast of Sfax–Chebba
nd not determineda Martin and Whitfield (1983)b Rais (1999)c Boudjellal et al. (1993)d Ahdy and Khaled (2009)
Site Station Metal
Pb Cr Cd Cu Zn Fe
I S1 20.2 1.6 36 2.6 2,077.3 8,825
S2 25.8 185.8 20.5 81.4 281.9 8,817
S3 125.2 21.3 6.8 8.1 270.1 8,826
S4 9.8 nd 1.8 6.5 47.7 8,820
S5 11 196.9 1.9 6.3 41.6 8,822
S6 4.9 9.9 2.1 4.8 40.4 8,830
S7 1.2 20.9 0.8 9.2 26.9 8,817.6
II S01 2.7 8.3 0.5 1 27.1 8,831.6
S02 2.3 14.5 0.8 2.7 59.9 8,824.8
S03 0.2 149.9 0.8 9.9 9.3 8,824.5
III S001 0.6 1.5 0.1 nd 3.6 8,816.3
S002 4.5 50.2 6.5 15.3 85.4 8,814.7
S003 2.4 57.2 0.9 11.3 11.6 8,815.9
S004 nd 97.5 0.8 7.9 23.4 8,816.3
S005 1.4 21.2 0.7 2 27.9 8,813.2
S006 1.6 105 0.3 4.5 14.0 8,812.5
S007 0.7 20.4 0.8 2.7 22.2 8,819.6
S008 2.5 20.8 0.6 2 20.8 8,821.2
S009 nd 25 0.9 1.5 5.1 8,816.9
S0010 7.1 11.4 0.9 10.4 26.5 8,814
Range 0.2–125.5 1.5–196.9 0.1–35.9 1–81.4 3.6–2,077.3 8,812.5–8,831.6
Crust averagea 16 71 0.2 32 127 35,900
Golf of Tunisb 112 nd 7 79 226 –
Bay of Algerc 93 63 1.10 79 256 –
Egyptian
Mediterranean Sea
(range)d
20.7–35.6 16.24–34.2 0.5–0.9 26.5–33.3 26.3–112.1 –
Environ Earth Sci
123
Lower metals concentration in sites II and III were
observed, probably due to low anthropogenic activities in
the area. The coastal area was mostly dominated by man-
grove. Human population inhabited these sites was also
limited. The concentrations of heavy metal in the studied
sediment samples followed the order of sites I [ II [ III
for Cr and Zn. Concentrations of Pb, Cd and Cu showed the
following order: I [ III [ II, while Fe showed no clear
pattern as for other metals (Fig. 2). The mean metal
concentrations in sediment from stations closed to Sfax city
(site I) exceeded the crust average values (Martin and
Whitfield 1983). Mean concentrations of all metals (except
for Cd) were below crust average in sites II and III.
When compared to metal concentrations in sediments
from other inshore sectors of the Mediterranean Sea, con-
centrations of Pb, Cr, Cd, Cu and Zn in Sfax–Chebba coast
sediments were found higher (Table 1). This result indi-
cated heavy metal contamination of the studied sediments.
Pb
0
10
20
30
40
50
60
70
80
Cr
0
20
40
60
80
100
120
140
160
Cd
0
5
10
15
20
25
Cu
0
5
10
15
20
25
30
35
40
45
50
Zn
0
200
400
600
800
1000
1200
1400
Fe
0
2000
4000
6000
8000
10000
I II III I II III
I II III I II III
I II III I II III
Co
nce
ntr
atio
n (
mg
/kg
)
Co
nce
ntr
atio
n (
mg
/kg
)
Co
nce
ntr
atio
n (
mg
/kg
)
Co
nce
ntr
atio
n (
mg
/kg
)
Co
nce
ntr
atio
n (
mg
/kg
)
Co
nce
ntr
atio
n (
mg
/kg
)
Fig. 2 Mean metal concentrations
(mg/kg) in sediments of each site
group
Environ Earth Sci
123
The computed enrichment rates of heavy metals [by
Eq. (1)] showed that the urban area is more enriched in
terms of Pb, Cr, Cd, Cu and Zn (Fig. 3). In such area, these
metals are characterized by higher rates varied between 4.5
and 94 %.
The values of TEL for each metal and also the number
of samples exceeding TEL are presented in Table 2. As
shown in Table 2, Metal concentrations of the aforemen-
tioned metals exceeded the TEL values for surface sedi-
ment samples. Moreover, it was revealed that
approximately 14, 29, 100, 14 and 43 % of the sediment
samples in site I for Pb, Cr, Cd, Cu and Zn, respectively,
had concentrations exceeding the TEL values for superfi-
cial sediments (Fig. 4). In site II, 34 and 67 % of the
sediment samples for Cr and Cd, respectively, had con-
centrations exceeding the TEL values. For Pb, Cu and Zn,
the concentrations do not exceed the TEL values. In site III,
only Cr and Cd had concentrations exceeding the TEL
values (30 and 70 %, respectively).
The computed metal enrichment factors in the studied
sediments with respect to average crust (Martin and
Whitfield 1983) showed that the EF of Pb ranges from 0.05
to 31.8, EF of Cr from 0.1 to 11.3, EF of Cd from 2.2 to
731.8, EF of Cu from 0.1 to 10.3 and EF of Zn from 0.1 to
66.5. The highest EF values were observed in stations near
the Sfax city with high anthropogenic activities, whereas
the lowest values were found in stations from site II and
site III. Some stations from site II and site III showed
important EF values of Cr and Cd. This significant
enrichment is related to the impact of dispersed anthropo-
genic sources along the coastline of the pre-urban and rural
areas. Among the site groups, EFs for all metals studied
were higher in site I when compared to other sites (Fig. 5).
The EF mean values for Pb, Cr, Cd, Cu and Zn were,
respectively, 7.2, 3.6, 202.9, 2.2 and 12.8 for site I; 0.4, 3.3,
13.9, 0.6 and 1 for site IIl; 0.5, 2.4, 25.6, 0.7 and 0.8 for site
III.
Based on the interpretation suggested by Birch (2003),
sediments in site I were categorized as moderately to
extremely severe enriched. Minor enrichment of Cu was
only observed in site I. No enrichments of Pb, Cu and Zn
were distinguished in sites II and III, while severe enrich-
ment by Cd was observed in site II and III. For the Cr, EF
values showed moderate enrichment in site II and minor
enrichment in site III.
Site I had the highest anthropogenic activities when
compared to the other stations, as mentioned earlier. Sites
II and III, where the anthropogenic activities is low,
showed the lowest EF values indicating less anthropogenic
inputs into the studied sites.
The results of computed geoaccumulation index (Igeo)
values are regrouped in Table 3. This index consists of
seven classes in relation to pollution extent. In site I, sed-
iments can be considered as unpolluted to strongly polluted
by Pb, whereas in the other sites, sediments are unpolluted
by this metal. For the Cr, the quality of sediments varies
from unpolluted to moderately polluted in sites I and II and
unpolluted in site III. According to Igeo values of Cd,
sediments can be considered as moderate to extreme pol-
luted for site I, from unpolluted to moderately polluted for
site II and from unpolluted to strongly polluted for site III.
Site I can be considered as unpolluted to moderately pol-
luted by Cu. The Igeo for Zn indicated strong contamination
in some stations from site I. However, no contamination by
this metal was detected in sites II and III.
Results of the descriptive study presented above were
refined by a PCA. Person’s correlation analysis was applied
to test the relationship among the heavy metals analyzed.
The correlation matrix showed that in overall stations Cd
and Zn, on one hand, and Cu and Cr on other hand, were
highly correlated with each other showing a strong positive
association (r = 0.92; p \ 0.05) and (r = 0.58; p \ 0.05),
respectively, while Pb, Cr, Cd, Cu and Zn were not
-100
-80
-60
-40
-20
0
20
40
60
80
100
Pb Cr Cd Cu Zn Fe
Enr
iche
men
t ra
te (
%)
Fig. 3 Enrichment rate for selected heavy metals
Table 2 Trace element concentrations (mg/kg dry weight) compared to marine sediment quality standards
Class Pb Cr Cd Cu Zn References
China sediment quality assessment guidelines TEL 30.2 52.3 0.68 18.7 124 Junhong et al. (2011)
Number of surface samples (site I) exceeding TEL/number of samples 1/7 2/7 7/7 1/7 3/7
Number of surface samples (site II) exceeding TEL/number of samples 0/3 1/3 2/3 0/3 0/3
Number of surface samples (site III) exceeding TEL/number of samples 0/10 3/10 7/10 0/10 0/10
Environ Earth Sci
123
correlated with Fe as seen in Table 4. The high correlation
obtained between Cd and Zn and between Cu and Cr in
surface sediments of Sfax–Chebba coast suggests common
pollution sources of these metals. In contrast, lack of cor-
relations with Fe reflects an anthropogenic contribution of
these metals.
The PCA applied to all metal concentrations resulted
essentially in three principal components. The threshold of
significance considered for p \ 0.05 is equal to 0.423 after
the student test (n = 20). The significant correlations
between selected parameters (variables) and the compo-
nents represent approximately 65 % of the total variance.
The contribution of the first, second and third PCs of the
total variance are 36.29 and 17 %, respectively. Over the
1 9 2 factorial plane (presenting the maximum of inertia),
one can clearly show three distinct groups (Fig. 6):
– The first group (G1), which is negatively displayed
over axis 2, is representative of Fe. It is representative
of the natural component.
– The second group (G2), which is positively displayed
over axis 1, is representative of Cd, Zn and Pb. These
metals present among each other highly significant
positive correlation coefficients. This group did not
show any correlations with the first group, testifying the
impact of anthropogenic sources.
– The third group (G3), which is positively displayed over
axis 2, is articulated around Cr and Cu. Those metals (Cr
and Cu) showed significant positive correlation coeffi-
cients, but they did not show any correlations with
metals of the first and second groups. This clearly shows
the impact of other anthropogenic sources.
Conclusion
This study has been performed to assess the contamination
state of the Sfax–Chebba coastal line. From the geo-
chemical analysis viewpoint, the studied heavy metals (i.e.,
Pb, Cr, Cd, Cu, Zn and Fe) showed an important spatial
variation and significant inter-level enrichments, especially
for Cr, Cd, Cu, and Zn. It was also found that those metal
concentrations exceeded the TEL, especially in stations
near Sfax city (site I). The same behavior was observed for
metal enrichment factors (EF) and geoaccumulation index
(Igeo), further testifying the significant metallic pollution.
Those results allowed the classification of the site I sedi-
ments as moderately to extremely severe enriched by Pb,
Cr, Cd and Zn.
The statistical analysis of data by PCA showed that
anthropogenic inputs derived from industrial developments
and habitations are among the contamination sources that
directly impacted the coastal sediments of study area.
Study area appeared affected on one hand by anthropo-
genic sources emitting Cd, Zn and Pb, and on other hand it
seemed to be affected by other multiple anthropogenic
sources emitting Cr and Cu.
Although sediment contamination of ‘‘Sfax–Chebba’’
coastal line by heavy metals concerned especially the urban
area of the northern coast of Sfax city, it may possibly be
extended to rural area if significant and effective strategies
of management are not adopted.
0
1
10
100
1000
Pb Cr Cd Cu Zn
Enr
iche
men
t F
acto
r (E
F)
EF site I
EF site II
EF site III
Fig. 5 Mean enrichment factor (EF) for analyzed metals in different
sites
0
20
40
60
80
100
Pb Cr Cd Cu Zn
TE
L e
xcce
din
g r
ate
(%)
Site I
Site II
Site III
Fig. 4 TEL exceeding rate
Environ Earth Sci
123
It is strongly recommended to perform an in-depth study
of the heavy metal impact on biological resources of the
Sfax coastal line.
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Table 3 Geoaccumulation index Muller’s classification and ranges of heavy metals in surface sediments of Sfax–Chebba coast
Muller scale (Muller 1981) This study
Igeo value Class Quality of sediment Metal Site Igeo range Quality of sediment
B0 0 Unpolluted Pb I -4.3 to 2.4 From unpolluted to strongly polluted
II -7 to -3.2 Unpolluted
II -14.6 to -1.8 Unpolluted
0–1 1 From unpolluted to moderately polluted Cr I -16.7 to 0.9 From unpolluted to moderately polluted
II -3.7 to 0.5 From unpolluted to moderately polluted
II -6.1 to -0.02 Unpolluted
1–2 2 Moderately polluted Cd I 1.4 to 6.9 From moderately to extremely polluted
II 0.6 to 1.4 From unpolluted to moderately polluted
II -1.5 to -4.4 Unpolluted
2–3 3 From moderately to strongly polluted Cu I -4.2 to 0.8 From unpolluted to moderately polluted
II -5.6 to -2.3 Unpolluted
II -15.6 to -1.6 Unpolluted
3–4 4 Strongly polluted Zn I -2.8 to 3.4 From unpolluted to strongly polluted
II -4.3 to -1.7 Unpolluted
II -5.7 to -1.2 Unpolluted
4–5 5 From strongly to extremely polluted
[5 6 Extremely polluted
Table 4 Pearson’s coefficient correlations for all analyzed metals
Pb Cr Cd Cu Zn Fe
Pb 1
Cr -0.03 1
Cd 0.27 0.08 1
Cu 0.18 0.58 0.36 1
Zn 0.21 -0.14 0.92 -0.01 1
Fe 0.27 -0.16 0.15 -0.24 0.23 1
Significant values (p \ 0.05) are shown in bold
Fe
Zn
Cu
Cd
Cr
PbAxis 1
Anthropogenic components
Axis 2
Natural component
Fig. 6 Projection of variables (metal concentrations) in the (1 9 2)
factorial plane
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