Assessment of Heavy Metal Pollution in Tilehbon River Sediments, Iran
In this study, four sediment samples on Tilehbon River
were chemically analyzed in order to determine the concentration, origin
and pollution intensity of heavy metals (Pb, Cr, Mn, N, Cd, Cu, Zn and
Fe). The concentration of these elements was determined by using inductively
coupled plasma atomic emission spectrometry (ICP-AES). Then a cluster
analysis has conducted using MVSP 3.1 software. The obtained results showed
that the concentration of heavy elements are transitive as compared with
the average concentration of these elements in ground surface and global
sediments and they controlled by geological units. Lime units play the
most important role to control the concentration of elements. Based on
Muller geochemical index, the sediments in Tilehbon River are not polluted.
Natural environment which is polluting by heavy elements is considered as a
universal problem. The heavy elements released in the environment as the result
of human activities, atmospheric depositions and erosions would finally enter
in to the aqua systems (Veena et al., 1997). Since,
heavy metals are toxic, stable in the environment and potential to combine with
the nutritive continuum. Thus, they are considered as one of the most significant
pollutant in aqua systems (Desya et al., 2002;
Smecka-Cymerman and Kempers, 2001).
Heavy metals are transferred into marine systems via rivers. Intensity and
amounts of metal entry into marines depend on their amounts in rivers sediments,
water and suspense ingredients (Chester, 2003). Because
of the importance of sediments to the overall quality of aquatic system, sediment
analysis is often included in environmental assessment studies (Adekola
and Eletta, 2007). Sediments can also be a potential reservoir of metals,
by releasing them to the water column under changing physical and chemical conditions
(Karbassi et al., 2007). Geochemical studies on
sediment conters of aqua systems such as rivers, estuary and river beds may
be an effective measure to find the origin and scatter pattern of elements and
to bio environmentally evaluate the current situation of an area (Paul,
2001). Methods of multivariate analysis have been widely used to identify
pollution sources and to apportion natural and anthropogenic contribution (Mico
et al., 2006).
Mining operation is an important industry in Iran. Many of them are near
rivers. It is essential to closely investigate the heavy metals concentrations
in river sediments in these regions of the country.
In this research, the concentration of heavy metals has investigated
via chemical analysis of Tilehbon River bed sediments and determining
the origin of heavy metals using cluster analysis. The old mine seeking
places in the watershed area of Tilehbon River can be counted as one of
the pollutant factors of this river.
MATERIALS AND METHODS
Study area is located at the west part of Baladeh Village in Mazandaran
Province and at 100 km distant from south-west of Sari. Baladeh region
with an approximate area of 11.8 km2 and a rectangular shape,
extends from east to west between the altitudes of 53° 3707 to
53° 4040 and latitudes of 36° 0845 to 36° 0735. Figure
1 shows the location of study area in Iran.
According to geology map of Kiasar with the scale of 1:100000, the regions
lithology contains shale, tuff and sandstone, green mica slits, dolomite
siltstone associated with coal layers, quaternary sediments and magmatism
|| Location of the study area and sampling points
Tilehbon is the main river in the study area and it flows from
east to west. Due to the low depth of Tilehbon River, all sediment samples
were directly collected from river bed using plastic dishes. Figure
1 shows the location of the sampling points. Sampling was done in
Weight of samples measured throughout the study area was 1 kg. All samples
were dried under the temperature of 70°C and passed through a 74 μm
mesh (equivalent to a No. 200 sieve). About 2 g of powdered sample was placed
in a Teflon beaker. The dry samples were then digested with HNO3/H2O2/
HCl and digestate made up to volume with Deionized water (Micó et
al., 2006). The concentration of Pb, Cr, Mn, Ni, Cd, Cu, Zn and Fe, were
determined by using ICP-AES (Carman et al., 2007).
Cluster analysis is a multivariable statistical method and it was used to find
the origin of heavy metals using analytical software of MVSP 3.1. The Weighted
Pair Group method (GWP) was used to identify clustering tendencies among the
samples (Davis, 1973; Karbassi, 1998;
Micó et al., 2006; Thevenot et al.,
2007). Cluster tree joins the alternatives of the same weight to create
bigger clusters then, their similarities could be evaluated. Mulers geochemical
index was used to measure the pollution intensity (Eq. 1).
where, Igeo is geochemical aggregation indicator or pollution intensity indicator,
Cn is Sediment metal concentration, Bn is metal concentration in
the shale (Müller, 1979; Gonzalez-Macias et al.,
2006). The factor of 1.5 is placed in the equation due to the probability
of difference between the primary densities of sediments as the result of earth
RESULTS AND DISCUSSION
Based on the results shown in Table 1, the mean concentration
of Pb, Cr, Mn and Ni in Tilehbon River sediments are higher than the mean metal
concentrations that are typical of aquatic sediments and crust samples from
around the globe (Bowen, 1979). Similar results have been
reported from several global locations (Liu et al.,
2003). Zn and Cu concentration are located between the global sediment and
Earthcrust mean concentration. Cu concentration in river sediments is similarity
to other system influenced by mines, such as the Mandovi estuary in India (Alagarsamy,
2006). Concentration of Zn is similar to the river-estuary of system Marabasco
(Marmolejo-Rodríguez, 2007). Measurements of Cd are similar to Earthcrust
and other world systems near to mine, such as sediments of Tinto and Odiel rivers,
Spain (Morillo et al., 2002). Also, River sediments
did not show a significant Fe enrichment. Therefore, in Tilehbon may be defined,
in general, as a natural system, according to the Cd and Fe background level
reported for the Earth crust (Marmolejo-Rodríguez, 2007).
|| Concentration of heavy metals in Tilehbon river- surficial
|*Bowen (1979). Concentration of the all
elements are in mg kg-1, except Fe
|| Dendrogram of metals in Tilehbon river bed sediment
using cluster analysis
units contain different concentration of heavy metals, Thus comparing them with
global sediments and earth crust mean concentration may not be an effective
procedure; for instance. Iron concentration is lower than them concentration.
As can be seen in Fig. 2, cluster analysis has used
to statistically interpret the heavy metals relationships and to find
their origins. Cluster analysis is composed of two branches (A and B).
Branch A consists of such elements as Copper, Iron, Nickel, Cadmium and
Plumb, therefore, control factors in this branch are similar. While branch
B includes Manganese, Zinc and Chromium. The close relations among these
three elements indicate their similar behaviors in the nature. There exists
a very weak relationship between these two branches which is a meaningful
negative relation; thus, it can be concluded that the elements of branches
A and B originates from different sources.
As it is shown in cluster analysis, dendrogram of sediments in Tilehbon
River was composed of two branches. Copper, Plumb, Iron, Nickel, Cadmium
and are presented at branch A (Fig. 2). There is a very
significant relationship between the elements in this branch (except for
Copper). Since Iron is known as an earth index in cluster analysis, thus
it can be concluded that Nickel, Cadmium and Plumb are also originated
from the earth. This conclusion is somehow true for Copper. Based on the
results of complete segregation of elements (Table 1),
there are lower densities of Iron in Tilehbon River sediments as compared with the averages of global sediments and ground surface,
which shows the role of geology to control heavy metal densities. Three elements
including Manganese, Chromium and Zinc are presented at branch B. The significantly
close relationships among these three elements indicate their similar behavior
in the nature. Due to lacking an indicator in this branch, their origin could
not be found. However, a very weak and negative relationship exits between branch
of A and B. Thus, it could be concluded that Manganese, Chromium and Zinc are
not originated form the earth and earth materials make their densities thinner.
Mulers geochemical index was used to measure the pollution intensities in
studying area (Muller, 1979). The Igeo is
associated with a qualitative scale of pollution intensity, samples may be classified
as unpolluted (0≤Igeo≤1), unpolluted to moderately polluted
(1≤Igeo≤2), moderately polluted (2≤Igeo≤3),
moderate to strongly polluted (3≤Igeo≤4), strongly to extremely
polluted (4≤Igeo≤5) and extremely polluted (Igeo≥6)
(Muller, 1979; Farkas et al.,
2007). Following this classification the sediments collected during sampling
can be unpolluted with Pb, Cr, Mn, Ni, Cd, Cu, Zn and Fe. As the results of
this study, pollution intensity of heavy metals in Tilehbon River is classified
as not polluted area. Pollution intensities are measured as follows:
Cr and Ni (0)<(0.1) Mn and Pb>(0.2)Cd<(0.4) Fe and Zn<(0.7)Cu
Based on the results of this study, the measured concentrations are transitive
comparing the averages of global sediments and Earth crust. However,
heavy metals concentrations were significantly different through various
geological units and making a comparison between the measured concentration
and the averages of ground surface and Earth crust may not reach the
desired results. Finally, the mining operation of Tilehbon basin has not
caused negative impact in the surficial sediments of Tilehbon River until
now. The measured concentration in this study can be used in future studies.
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