Assessment of Metallic Pollution along with Geochemical Baseline of Soils at Barapukuria Open Coal Mine Area in Dinajpur, Bangladesh

Abstract

A total 42 (5 + 37) soil samples surrounding 4 km2 of Barapukuria open coal mine area were collected to determine the geochemical baseline and concentrations of different metals after digestion with aqua regia. The mean total concentration and geochemical baseline values of Cu, Zn, Pb, Cd and Cr in soil samples were 28.43, 44.83, 20.94, 0.19 and 55.79 μg g−1 , and 20.40, 32.80, 20.47, 0.12 and 42.69 μg g−1 , respectively. Out of 37 sampling stations, 92-100% locations had the values higher for Cu, Zn, Cd and Cr, while it was 65% for Pb, than that of the geochemical baseline value. The deposition of outlet fly ash and waste water may be responsible to increase metal concentrations in surface soils around the coal mining area. Copper, Zn, Cd, Cr and Pb concentrations upto carbonate bound fraction were 2.52-17.12, 2.62-40.67, 0, 1.47-17.62 and 4.53-16.10 μg g−1 , respectively. Zinc, Cu, Cd and Cr were the major pollutants in the surrounding soils of Barapukuria because these metals have contamination factor >1.0 for most sampling stations. Study also revealed moderate pollution level by these metals after calculated Igeo values. According to risk assessment code, although adjacent soils of Barapukuria are contaminated with Cu, Zn, Cd, Cr and Pb but these metals are relatively strongly bound to the soils and are of low risk (<10% for these metals) as regards to mobilization. The study results inferred that if proper attention is ignored, the concentration of metals will increase to intolerable limits that may have severe impacts on the soil environment.

Full text

*Corresponding Author
Asian Journal of Water, Environment and Pollution, Vol. 14, No. 4 (2017), pp. 77–88.
DOI 10.3233/AJW-170038
Assessment of Metallic Pollution along with Geochemical
Baseline of Soils at Barapukuria Open Coal Mine Area in
Dinajpur, Bangladesh
H.M. Zakir*, M.Y. Arafat and M.M. Islam
Department of Agricultural Chemistry, Faculty of Agriculture, Bangladesh Agricultural University
Mymensingh – 2202, Bangladesh
* zakirhm.ac.bau@gmail.com
Received April 26, 2017; revised and accepted September 6, 2017
Abstract: A total 42 (5 + 37) soil samples surrounding 4 km2 of Barapukuria open coal mine area were collected
to determine the geochemical baseline and concentrations of different metals after digestion with aqua regia.
The mean total concentration and geochemical baseline values of Cu, Zn, Pb, Cd and Cr in soil samples were
28.43, 44.83, 20.94, 0.19 and 55.79 µg g–1, and 20.40, 32.80, 20.47, 0.12 and 42.69 µg g–1, respectively. Out
of 37 sampling stations, 92-100% locations had the values higher for Cu, Zn, Cd and Cr, while it was 65%
for Pb, than that of the geochemical baseline value. The deposition of outlet y ash and waste water may be
responsible to increase metal concentrations in surface soils around the coal mining area. Copper, Zn, Cd, Cr and
Pb concentrations upto carbonate bound fraction were 2.52-17.12, 2.62-40.67, 0, 1.47-17.62 and 4.53-16.10 µg
g–1, respectively. Zinc, Cu, Cd and Cr were the major pollutants in the surrounding soils of Barapukuria because
these metals have contamination factor >1.0 for most sampling stations. Study also revealed moderate pollution
level by these metals after calculated Igeo values. According to risk assessment code, although adjacent soils of
Barapukuria are contaminated with Cu, Zn, Cd, Cr and Pb but these metals are relatively strongly bound to the
soils and are of low risk (<10% for these metals) as regards to mobilization. The study results inferred that if
proper attention is ignored, the concentration of metals will increase to intolerable limits that may have severe
impacts on the soil environment.
Key words: Geochemical baseline, metallic pollution, Barapukuria coal mine, Bangladesh.
Introduction
Mining activities are responsible for different types
of serious problem to the environment in all over
the world. Open pit type coal mining activities in
Barapukuria produce huge quantities of solid and liquid
wastes that may be contaminated with different metals.
Furthermore, open pit mine system requires dewatering
and depressurization of the aquifers through continuous
pumping out of water to keep the mine pit dry and keep
secure working conditions (Zaman, 2009). Discharge of
contaminated water from such activities mix with both
surface and ground water, and deteriorate their quality
(Khan et al., 2005; Singh et al., 2008; Singh et al.,
2010; Zakir et al., 2013). This contaminated water is
also responsible for the degradation of soil and aquatic
environment by allowing heavy metals to seep into
the sites (Fang et al., 2003; Coulthard and Macklin,
2003; Xi-Jun et al., 2008). Discharge of untreated
mine water, y ash, waste water and efuents from
different industries are responsible for toxic metallic
contamination in water and agricultural soils. Higher

78 H.M. Zakir et al.
concentration of toxic metals in soils can harmfully
affect crop growth by interfering with metabolic
functions in plants (Monni et al., 2000; Pietraszewska,
2001) and cause changes in the composition of soil
microbial community (Giller et al., 1998; Kurek and
Bollag, 2004), adversely affecting soil characteristics.
Considerable amounts of potentially toxic metals get
into the food chain if crops are grown in such metal
contaminated soils (Agoramoorthy et al., 2009; Naaz
and Pandey, 2010).
Natural variations in concentration for an element in
the surcial environment may refer as its geochemical
baseline (Salminen and Tarvainen, 1997). But the
natural element concentration of a substance is known
as the geochemical background. The baseline represents
the on-the-spot measured concentration of an element
in some sites under anthropogenic activities. Natural
spatial variations in the Earth’s surface materials can
dene using baseline value which is very much useful
for policy makers and others interested in different
environmental issues (Darnley, 1997). The geochemical
baseline may be used as a reference standard to monitor
environmental changes in spite of either natural or
anthropogenic comparative standards or scales (Yanguo
et al., 2001). Hence, the purpose of baseline study is to
take the geochemical picture of an area. Environmental
changes in geochemical landscape can be monitored
using this in future (Eppinger et al., 2001). Usually,
in geochemical environment natural and human made
anomalies coexist. Hence, in environmental impact
appraisal it is important to differentiate anthropogenic
anomaly from natural variation (Chaffee et al., 1997;
Chaffee and Carlson, 1998). Geochemical baselines and
related indices can be used to distinguish anthropogenic
inuence from natural one. Therefore, in the present
study, soil samples collected from surrounding areas
of Barapukuria open coal mine area were analysed
to determine concentrations of different metals and
assess pollution level along with geochemical baseline
of metals.
Study Area
Barapukuria is one among the most important coal
production base of Bangladesh, which is located at
Phulbari Police Station in Dinajpur district. Geological
Survey of Bangladesh (GSB) rst discovered the mine
in 1985 and a treaty was signed between Petrobangla
and a Chinese consortium (M/S China National
Machinery Import and Export Corporation) in 1994, and
accordingly the physical works for implementation of
the project was commenced in June 1996. According to
Barapukuria Coal Mining Company Limited (BCMCL),
it has a proved area of 6.68 square kilometre. The
coaleld has a depth of coal deposit between 118 m and
509 m with an estimated reserve of coal as 390 million
metric ton. There are six coal containing seams (I to VI)
in Barapukuria and among those seams II, IV and VI
are more consistent and important. Furthermore, only
seam VI contained about 90% of the total demonstrated
reserve (Quamruzzaman et al., 2014). Presently coal is
extracted from the mine by multi-slice longwall method
and the thermal power plant, situated in the vicinity of
the study area, is the main user of the produced coal.
The main components of the geology of Barapukuria
coal mine basin are shown in Table 1 and Figure 1.
Materials and Methodology
Collection and Preparation of Soil Samples
Total 37 soil samples were collected from the
surrounding area within a radius of 1 km from the origin
Table 1: Stratigraphic succession of the Barapukuria coal basin (after Quamruzzaman et al., 2014)
Age Group Formation Member Lithology Thickness (m)
Holocene Alluvium Silty clay 1.83
Pleistocene Barind clay
residuum
Clay and sandy clay 10.36
Pliocene Dupi tila Upper Sandstone, pebbly sandstone and clay/mudstone 126.82
Lower Sandstone, claystone and mudstone with silica
and white clay
Permian Gondwana Feldspathic sandstone, carbonaceous
sandstone and shale, ferruginous sandstone,
conglomerates and coal beds
457.32
Precambrian Basement
complex
Diorite, granodiorite, quartzdiorite, granite and
diorite gneiss
14.32

Assessment of Metallic Pollution along with Geochemical Baseline of Soils at Barapukuria Open Coal Mine Area 79
of Barapukuria coal mine. The sampling distance from
one station to another was at least about 100 m (Table
2). Soil samples were taken from 0-30 cm depth and
rapidly lled in airtight polythene bags. From each
location, about 500 g soil sample was collected and the
materials were oven dried at 50°C for 24 h. After drying,
soil particle size was homogenized by grinding in an
agate mortar. Then the samples were sieved (aperture
125 mm) and nally stored in glass bottles for chemical
analyses. Analytical reagent grade quality chemicals
and reagents were used during analysis. Before use, all
glass and plastic ware were soaked in 14% HNO3 for
24 hrs and the washing was completed with Millipore
water rinse.
Collection of Samples for Geochemical Baseline
Study
Five (5) fresh soil samples were collected from the
study area on the basis of an oral questionnaire to the
local people of the area. According to their statement,
ve sites were selected which fulll the criteria, such
as (i) the soil still is in its original condition; (ii) there
is no addition or deletion in the surface soil; (iii) the
lands remain fallow for at least last 20 (twenty) years;
Figure 1: Location of Barapukuria coal mine area, Dinajpur, Bangladesh showing the tectonic
elements and physiographic divisions of Bengal Basin (after Farhaduzzaman et al., 2012).

80 H.M. Zakir et al.
Table 2: Description of locations and basic properties of soil samples collected from Barapukuria open coal mine area,
Dinajpur, Bangladesh
Sample
ID
Location from the
mine
Distance from the
mine (m)
Land type pH EC
(µS cm–1)
Organic matter
(%)
1 North 100 Medium high land 6.92 74 1.49
2 North 200 Medium high land 6.75 30 1.76
3 North 350 Medium high land 6.84 28 1.75
4 North 700 Medium high land 6.92 29 1.64
5 North 850 Medium high land 6.87 20 1.57
6 North 1000 Medium high land 6.94 29 2.51
7 North-east 500 Medium high land 6.87 26 1.76
8 East 100 Medium high land 6.80 120 1.55
9 East 200 Medium high land 6.70 80 2.25
10 East 350 Medium high land 6.90 86 3.05
11 East 500 Medium high land 6.80 59 2.81
12 East 650 Medium high land 6.82 44 2.90
13 East 750 Medium high land 6.80 40 2.74
14 East 900 Medium high land 6.82 43 2.93
15 East 1000 Medium high land 7.09 276 3.05
16 South 100 Medium high land 6.81 135 0.68
17 South 200 Medium high land 6.90 387 2.35
18 South 350 Medium high land 6.89 200 3.22
19 South 500 Medium high land 6.92 51 2.18
20 South 650 High land 6.80 60 2.42
21 South 750 High land 6.78 65 2.43
22 South 850 High land 6.95 42 2.78
23 South 950 High land 6.77 50 1.76
24 South 1050 High land 6.88 70 1.87
25 West 150 Medium high land 7.05 75 1.75
26 West 250 Medium high land 6.89 96 1.85
27 West 400 Medium high land 6.82 78 2.17
28 West 550 Medium high land 6.87 63 2.51
29 West 750 Medium high land 6.88 70 2.32
30 West 850 Medium high land 6.70 120 2.15
31 West 1000 Medium high land 6.77 422 3.26
32 South-west 100 Low land 6.97 450 2.03
33 South-west 200 Low land 6.90 645 3.24
34 South-west 300 Low land 6.96 500 2.78
35 South-west 400 Low land 6.94 610 3.09
36 South-west 500 Low land 6.93 610 3.20
37 South-east 100 Low land 6.92 477 3.02
Mean 6.87 169 2.35
Range 6.70-7.09 20-645 0.68-3.26

Assessment of Metallic Pollution along with Geochemical Baseline of Soils at Barapukuria Open Coal Mine Area 81
and (iv) the soil is not contaminated by the local people.
From each location three soil samples were collected
upto 60 cm depth and mixed together to get a composite
sample. These samples were used to obtain geochemical
baseline data. Special attention was given for these
samples during processing and analysis to avoid any
sorts of contamination.
Determination of Basic Properties of Soil Samples
The pH and electrical conductivity (EC) were measured
in 1:2.5 soils to water ratio by using a sensION +
PH3 basic benchtop pH meter and sensION + EC5
portable conductivity meter, respectively. Prior to pH
determination, the suspension was allowed to stand
overnight. The wet oxidation method of Walkley and
Black (1934) was used to measure the organic carbon
(OC) present in soil samples.
Determination of Heavy Metals Concentration
in Soil Samples
Total concentrations of heavy metals (Cu, Zn, Pb, Cd
and Cr) in soil samples were determined by using an
atomic absorption spectrophotometer (AAS) (Shimadzo,
AA7000, Japan). The instrument was equipped
with single elements hollow-cathode lamps at the
wavelengths of 324.8, 213.9, 283.3, 228.8 and 357.9
nm, respectively, which was operated at maximum
sensitivity with an air-acetylene ame. Lamp intensity
and bandpass of AAS were used according to the
manufacturer’s recommendations. Exactly 1.00 g of
powdered soil sample was digested with aqua regia
(HNO3: HCl = 1: 3) to determine total concentration
of metal. On the other hand, for the determination of
metal up to carbonate bound fraction, exactly 1.00 g of
powdered soil sample was taken into 200 mL conical
ask followed by the addition of 20 mL of 0.11M
acetic acid. Then the content was stirred for 16 hours
at room temperature (Rauret et al., 1999). All chemicals
and reagents were of analytical reagent grade quality
(Merck, Germany).
Mineralogical Study of Soils
Two (2) air-dried, pulverised and sieved soils, regardless
of the constituent particle size were used in the
mineralogical study. Among these two samples, one
was polluted for most of the metals studied (sample
# 8), and the other was fresh soil sample (collected
for geochemical baseline study). The study was
completed using a D8 Advance Bruker AXS (Berlin,
Germany) X-ray diffractometer (XRD), and technical
specications required for optimal operation were set
according to the manufacturer’s recommendations. The
analyzing radiation was Cu K-alpha with wavelength
of 1.5406 Å (0.15406 nm). X-ray diffractograms were
collected on powder samples within the 2θ range
[2°-70°], with counting for 2s. each 0.02°. The X-ray
diffraction was then attached to the advanced diffract
plus evaluation software through the computer.
Determination of Geoaccumulation Index (Igeo)
The geoaccumulation index (Igeo) values were calculated
for Cu, Zn, Pb, Cd and Cr using formula as introduced
by Muller (1969), which is modied as follows for the
present study,
Igeo = log2 (Cn/Bn)
where Cn is measured concentration of metal in the soil,
and Bn is the geochemical baseline for the same element
which is directly measured in soils of the present study,
and due to this reason, the factor 1.5 introduced by
Muller (1969) was omitted from the above equation.
According to Muller (1969), there are seven grades
or classes of the geoaccumulation index. Class 0
(practically uncontaminated/unpolluted): Igeo < 0; Class
1 (Uncontaminated to moderately contaminated): 0 <
Igeo < 1; Class 2 (moderately contaminated): 1 < Igeo <
2; Class 3 (moderately to strongly contaminated): 2 <
Igeo < 3; Class 4 (strongly contaminated): 3 < Igeo < 4;
Class 5 (strongly to extremely contaminated): 4 < Igeo
< 5; Class 6 (extremely contaminated): Igeo > 5, which
is an open class and comprises all values of the index
higher than Class 5.
Assessment of Pollution Load Index (PLI)
The pollution load index (PLI) was measured in
this study for the surface soils of Barapukuria open
coal mine area in Dinajpur, Bangladesh. According
to Tomlinson et al. (1980), the PLI for a single site
is the nth root of n number of multiplied together
contamination factor (CF) values. The CF and PLI are
the quotient obtained as follows:
CF = CMetal concentration/CBaseline concentration
of the same metal
and
PLI for a site = nth √CF1 × CF2 . . . × CFn,
where n equals the number of contamination factors and
sites, respectively. A number of contamination factors
will be calculated for different heavy metals at each
site. To calculate a site pollution index, the ve highest
contamination factors were selected and then deriving
the fth root of the ve factors multiplied together. A

82 H.M. Zakir et al.
zone or area index can also be calculated in exactly
the same way such as site pollution index (Tomlinson
et al., 1980).
Risk Assessment Code (RAC)
The metals in the soil are bound with different strengths
to the different fractions. The risk assessment code
(RAC), as proposed by Perin et al. (1985), mainly
applies the sum of exchangeable and carbonate bound
fractions for assessing the availability of metals in soils.
If a soil sample can release in these fractions less than
1% of the total metal it will be considered safe for the
environment; 1-10% low risk; 11-30% medium risk;
31-50% high risk and more than 50% of the total metal
has to be considered very high risk/dangerous, which
can easily enter into the food chain.
Results and Discussion
Basic Properties of Soils
Results on pH, EC and organic matter of soils collected
from Barapukuria open coal mine area are presented
in Table 2. The pH value around the study area ranged
from 6.70-7.09 with an average value as 6.87. The
increase in acidity of agricultural soils due to application
of coal mine water seems possible for deposition of
basic cation in soils from the coal mine water whose
basic cation content was considerably high. Maiti and
Ghose (2005) reported that the pH vary from 4.9 to
5.3 in a mining dump site, which is located in Central
Coaleld Limited’s (CCL), North Karanpura, Ranchi,
India. The EC value around the study area varied
greatly from 20-645 µScm–1 and the average value
was 169 µScm–1 (Table 2). The variation of EC among
the sampling sites might be due to the effect of place,
slope, soil condition, irrigation, drainage and others.
The amount of organic matter among the sampling
locations ranged from 0.68 to 3.26% with a mean value
of 2.35%. According to Callesen et al. (2003), the
quantitative relationship between soil organic matter
and temperature, textural class and precipitation has
been documented. In general soil organic carbon pool
is increased both due to precipitation and temperature,
and the increase with mean annual temperature was
more pronounced for coarse-textured soils than for
medium-textured soils.
Assessment of Geochemical Baseline of Metals
Environmentally geochemical baseline is the basis for
distinguishing anthropogenic from natural inuence.
Metallic concentration and basic soil properties obtained
from collected fresh soil samples are presented in Table
3 and their average value is treated as geochemical
baseline data for the study area. The mean total
concentration of Cu, Zn, Pb, Cd and Cr in soil samples
were 20.40, 32.80, 20.47, 0.12 and 42.69 µg g–1,
respectively. The geochemical baselines of elements
depend on geological background, sample collection,
sample grain size and sample treatment (Salminen and
Gregorauskiene, 2000; Miko et al., 1999).
Metal Status in Soils of Barapukuria
Coal Mine Area
Mining activities are the potential source of metals
for surrounding environment of Barapukuria. Total
concentrations of different metals along with the mean
concentration of geochemical baseline value collected
from different locations of Barapukuria open coal mine
area are presented in Figure 2. Total concentration of
Cu, Zn, Pb, Cd and Cr in soil samples varied from
20.28-49.77, 31.64-72.69, 15.14-32.69, 0.155-0.288
and 40.95-75.82 µg g–1, with the mean value of 28.43,
44.83, 20.94, 0.19 and 55.79 µg g–1, respectively. Out
of 37 sampling stations, all locations had the values
higher for Cu and Cd, 34 sites for Zn, 36 stations for
Cr and 24 locations for Pb than that of the geochemical
Table 3: Geochemical baseline values of metals and basic properties of fresh soils of Barapukuria open coal mine
area, Dinajpur, Bangladesh
Sample ID Metal concentration (µg g–1 ± SD)pH EC
(µS cm–1)
Organic matter
(%)
Cu Zn Pb Cd Cr
1
2
3
4
5
21.46±1.4
22.31±2.2
17.95±1.2
19.11±2.1
21.16±2.0
32.52±1.6
33.71±2.3
31.22±1.3
32.35±2.6
34.21±2.8
21.01±2.1
21.05±1.6
19.13±1.8
20.12±1.6
21.02±1.2
0.144±0.02
0.101±0.01
0.150±0.02
0.124±0.01
0.105±0.01
43.41±4.1
43.72±3.8
40.95±2.0
42.51±2.2
42.87±3.4
6.79
6.85
6.80
6.86
6.90
76
23
20
16
18
1.01
0.14
1.16
1.75
1.24
Mean 20.40 32.80 20.47 0.124 42.69 6.84 30.6 1.06

Assessment of Metallic Pollution along with Geochemical Baseline of Soils at Barapukuria Open Coal Mine Area 83
baseline value. Mobility and bioavailability of metals
are determined primarily by pH and are enhanced
under acidic conditions (when pH < 4.5). Other factors
controlling mobility of metals in soils include solubility
reactions, sorption reactions and redox conditions
(Smith, 2007). But the soils of Barapukria coal mine
area had pH > 4.5 (Table 2), so metals present in the
study area are not so mobile.
According to Zhai et al. (2009), the strength of
contamination of a metal in a coal mining area depends
on its concentration in coal, its performance during
the combustion of coal and nally its mobility in
surface soils. They also stated the Morupule power
station in Botswana has experienced of more than 30
years of coal mining and more than 20 years of coal
combustion activities and reported that the deposition
of outlet y ash from the coal-red power plant has
increased some heavy metals concentrations in surface
soils around the power station. The Barapukuria coal
power plant is also a coal-red power station, which
consumed approximately 450 thousand tonnes of coal
in a year (BPDB, 2012). High volatile bituminous coal
of Barapukuria is mainly formed by: moisture 10%, ash
12.4%, volatile matter 29.2%, xed carbon 48.4% and
total sulphur 0.53% (BCMCL, 2016). So the deposition
of outlet y ash from the power plant may increase
metal concentrations to the surrounding soils.
The trace element behaviour is mainly controlled
by their vaporization or condensation temperatures
during combustion in the coal based power station, and
the ner particles of y ash possess most of the trace
elements (Linak and Wendt, 1994). Coal that contained
higher concentration of heavy metals, had stronger
small particle association during coal combustion and
were less mobile in surface soils, showed stronger
contaminations in soils around the plant (Zhai et al.,
2009). However, the average metal levels in soils of
Barapukuria open coal mine area were relatively lower
compared with several other mining areas in the world
(Table 4). So it can be inferred from the study results
that the soils of the area has not so far polluted yet, but if
it is continued, the concentration of metals will increase
to unbearable limits, which may create severe impacts
on the soil environment as well as to the food chain.
Mineralogical Composition of Soils
Additional independent information on the mineralogical
composition of the soil sampling site 8 (polluted for
most of the metals studied) and another sample of
geochemical baseline was obtained by XRD analysis
and the results are presented in Table 5. Quartz has
the strongest peak in both the samples at d = 3.35 and
4.26 Å. The next strongest peak was for calcite (d =
1.82 Å) in both the samples. Several clay minerals
such as micas and illites, chlorites and kaolinite
(diffracted peaks at d = 9.89, 1.54, 14.12, 3.56, 2.28
and 1.98 Å) were common in both soils but the peak
intensities for site 8 were comparatively stronger than
the geochemical baseline sample. Besides this feldspar
(anorthite), feldspar/chlorite and bayerite, and iron oxide
and hydroxide group minerals, specically magnetite
and goethite were also common in both soil samples.
It is apparent from Table 4 that the peak intensity for
sampling site 8 was dominant for most of the clay,
carbonate and hydroxide minerals. Several study reports
stated that the presence of different clay minerals are
likely to be the major host of heavy metals in soils
(Islam et al., 2000; Sharmin et al., 2010; Zakir et al.,
2014; Zakir et al., 2015).
Table 4: Average metal concentrations (µg g–1) in collected soil samples of Barapukria open coal
mining area, Dinajpur, Bangladesh compared with other mining areas of the world
Metal HMAaFHCMAbPMAcLCMGdMSSeMCCfSMSgPresent study
Cu 11.2 66.1 34.49 110.51 34- 570 35.4 20- 62* 28.43
Zn 28.5 113.8 78.86 107.06 110- 4023 65.0 100- 250* 44.83
Pb 23.7 20.8 29.32 17.86 27- 2847 22.8 60- 90* 20.94
Cd 0.05 0.10 nd 1.56 Trace to 2.4 nd 0.7- 2.0* 0.19
Cr 29.5 85.26 81.61 37.99 nd 125.2 nd 55.79
HMA = Huainan mining area in China; FHCMA = FuXin-Haizhou coal mining area in China; PMA = Panzhihua mining area in China;
LCMG = Lignite coal mine at Gujarat, India; MSS = Mining sites soil in South Morocco; MCC = Morupule colliery coalmine in Botswana;
SMS = Soils of mining sites in France; nd = not determined and * = With moderate geochemical anomaly.
a Yao et al. (2010); b Xi-Jun et al. (2008); c Yanguo et al. (2002); d Ladwani et al. (2012); e Boularbah et al. (2006), f Zhai et al. (2009);
g Baize and Paquereau (1997).

84 H.M. Zakir et al.
Figure 2: Metal concentrations (μg g–1) in soils collected from Barapukuria open coal mine area in Dinajpur, Bangladesh
along with geochemical baseline concentration.

Assessment of Metallic Pollution along with Geochemical Baseline of Soils at Barapukuria Open Coal Mine Area 85
Table 5: Mineralogical constituents of soil sampling site
8 (polluted for most of heavy metals studied) and the
geochemical baseline
Minerals Angle
(2θ)
d-value
(Å)
Peak intensity (%)
Sample
ID 8
Geochemical
baseline
Quartz 26.59 3.35 100.0 100.0
20.77 4.26 25.8 19.5
Feldspar 27.45 3.23 4.4 6.8
24.04 3.67 3.3 4.2
23.02 3.75 2.6 3.9
21.18 4.14 – 2.7
Feldspar/
chlorites
31.93 2.82 1.7 2.7
Anorthite 28.54 3.19 3.8 3.9
Micas and
illites
8.93 9.89 4.4 0.6
Chamosite 12.37 7.09 2.5 2.0
Chlorites 60.02 1.54 9.3 5.9
6.21 14.12 1.9 0.1
24.92 3.56 2.1 –
Biotite/chlorites 19.83 4.46 2.7 3.1
36.46 2.46 8.5 6.0
Kaolinite 39.51 2.28 8.3 5.3
45.63 1.98 4.9 2.0
Muscovite 35.08 2.57 2.3 2.7
Goethite 37.08 2.43 8.5 2.4
Bayerite 40.35 2.23 4.9 4.6
Calcite 50.16 1.82 11.9 8.1
Magnetite 35.07 2.53 2.3 2.7
Assessment of Pollution Level
Index of Geoaccumulation (Igeo)
The geoaccumulation index (Igeo) was used to assess
metal pollution in soils of Barapukuria open coal mine
area in Dinajpur, Bangladesh. The calculated Igeo for
metals of soils of the study area and their corresponding
contamination intensity are illustrated in Figure 3.
Out of 37 locations, 92-100% sites showed positive
Igeo values (0 < Igeo < 2) and exhibited Igeo class 1-2,
indicating moderately polluted soil quality for Cu, Zn,
Cd and Cr. On the other hand, 59% (22 sites) locations
showed positive Igeo values (0 < Igeo < 1) and exhibited
Igeo class 1, indicating unpolluted to moderately polluted
soil quality for Pb. Finally, it can be inferred from the
Igeo calculation that the soils of Barapukuria open coal
mine area are moderately polluted by Cu, Zn, Cd and
Cr, and the source of pollution at the study area are
coal mining activities and its use at nearby coal-red
power station.
Figure 3: Geoaccumulation index (Igeo) of metals at
different sampling sites of Barapukuria open coal mine
area in Dinajpur, Bangladesh.
Pollution Load Index (PLI)
While computing the contamination factor (CF) for
pollution load index (PLI) of soils of the study area,
average geochemical baseline value for each metal
obtained by this study was considered as background
concentration (Figure 4). The concept of a baseline
is a fundamental issue to the formation of a PLI
(Tomlinson et al., 1980). The PLI values ranged from
1.14 to 1.84 for soil samples collected from 37 locations
of Barapukuria open coal mine area. According to
Tomlinson et al. (1980) the PLI provides a simple and
comparative means for assessing a site quality. If a PLI
value is zero that indicates perfection, a value of one
(1.0) represents only baseline levels of pollutants, and
values >1.0 would indicate progressive deterioration of
the site. So, it can be inferred from Figure 4 that the
PLI for all sampling sites had value higher than 1.0,
which indicates progressing worsening of soil quality
by several metals at Barapukuria open coal mine area.
Risk Assessment Code (RAC)
The code as applied to the present study revealed that
2.52-17.12, 2.62-40.67, 1.47-17.62 and 4.53-16.10%
of total Cu, Zn, Cr and Pb with a mean value of 5.37,
8.25, 9.58 and 6.68%, respectively of the study sites
either is adsorb, exchangeable or carbonate bound
(Table 6). Hence, overall area comes under the low
risk category indicating lower availability from which
these metals cannot be easily leached out for the aquatic

86 H.M. Zakir et al.
environment. But out of 37 locations, 4 for Pb, 14 for
Cr, 5 for Cu and 7 for Zn had >10% of total metal in
upto carbonate bound fraction and therefore those sites
come under the medium risk category, which can easily
enter into the food chain. Due to their inherent toxicity
and availability, metals can pose serious problem to
the ecosystem and can be remobilized by changes in
environmental conditions such as pH, redox potential,
salinity etc. (Salomons, 1995). On the other hand, 0%
of total Cd was found in the same fraction indicating
no risk category or trace amount of availability of this
metal to the aquatic environment (Table 5). However, it
can be concluded from the RAC study that the metals
investigated are relatively strongly bound to the soils of
Barapukuria and are of low risk (<10% of total metal
in upto carbonate bound fraction) category for their
mobilization.
Table 6: Average metal percentage in upto carbonate
bound fraction of soils collected from Barapukuria open
coal mine area and risk assessment code (RAC)
Metal Average percentage of
metal in up to carbonate
bound fraction
Level of
risk on the
basis
of RAC
Range Mean
Copper (Cu) 2.52-17.12 5.37 Low risk
Zinc (Zn) 2.62-40.67 8.25 Low risk
Chromium (Cr) 1.47-17.62 9.58 Low risk
Lead (Pb) 4.53-16.10 6.68 Low risk
Cadmium (Cd) 0 0 No risk
Conclusion
The present study determined the geochemical
baseline and evaluated the heavy metal contents
in soils of Barapukuria open coal mine area in
Dinajpur, Bangladesh. The mean geochemical baseline
concentration of Cu, Zn, Pb, Cd and Cr in soil samples
were 20.40, 32.80, 20.47, 0.12 and 42.69 µg g–1,
respectively. Out of 37 sampling stations, all locations
had the values higher for Cu and Cd, 34 sites for Zn,
36 stations for Cr and 24 locations for Pb than that of
the geochemical baseline value, which may lead to a
potential danger for the environment at the study area.
The PLI and Igeo calculations indicate that the quality of
soils of Barapukuria open coal mine area is deteriorating
and are moderately polluted by Cu, Zn, Cd and Cr. The
study results also signify that the sources of pollution at
the area are coal mining activities and its combustion
at nearby coal-red power station.
Comparing the metal concentration with the other
mining areas of the world, it can be concluded that
the soils of the study area has not so far polluted yet,
but if the activity is continued by ignoring protective
measures, the concentration of metals will increase to
intolerable limits, which may create severe impacts
on the soil environment and nally to the food chain.
Although the association of these metals are relatively
strongly bound to the soils of the study area and under
low risk category for their mobilization after the risk
assessment code, it is highly appreciable to monitor
Figure 4: Contamination factor (CF) for each metal at
each sampling site along with pollution load index (PLI)
of soils in Barapukuria coal mine area in Dinajpur,
Bangladesh.

Assessment of Metallic Pollution along with Geochemical Baseline of Soils at Barapukuria Open Coal Mine Area 87
metal concentrations in surface soils routinely in future
and accordingly to take necessary initiative by the local
authority and government of Bangladesh.
Acknowledgement
This work was partially supported by the Ministry of
Science and Information & Communication Technology,
Government of the Peoples Republic of Bangladesh
under Special Allocation for Science and Technology
for the nancial year 2010-11; Research Grant no. #
39.009.002.01.00.020.2010/ES-14/1822/1(4).
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