Investigation of Vertical Distribution of Soil Elements at Central Part of Bangladesh Using Neutron Activation Analysis

Abstract

Soil is a mixture of minerals, plant and animal materials formed during a long process that may take thousands of years. The trace elements in soil are very important in aspects of both soil and environmental quality as well as the geological purposes. The soil and sediments have been extracted in the undisturbed state from Singair Upazila, Manikgonj district, Bangladesh; each of them extending from 1.5 feet (0.46m) up to about 27 feet (8.23m) of depth. The drilling cores were executed by wash borings method which were mainly composed of silty clay, very fine silty sand, fine to very fine sand, fine to medium sand and fine sand with mica layers at different depths. Nuclear reactor based Instrumental Neutron Activation Analysis (INAA) method has been used for analysis of concentrations of various trace elements in subsurface soil and sediments at various depths. Although the mean, median and standard deviation of trace elements concentration from the two study sites soil samples demonstrate same distribution characteristics of soil, but the analytical results of selected borehole sediment samples of contaminated areas shows that the vertical distributions of arsenic and iron do not follow any regular or particular pattern. They are randomly distributed over all layers and the correlations coefficients [R 2 =0.6568 (n=16), R 2 =0.4668 (n=18)] between total arsenic and iron in the core sediments are significant. Furthermore, a highly significant correlation was observed between Fe-Mn, Cr-Fe, Cr-Sc and Sc-Fe which indicates that they are closely associated with each other and variation in concentrations of one can influence the concentration of others.

Full text

International Journal of Environmental Protection Feb. 2013, Vol. 3 Iss. 2, PP. 5-13
- 5 -
Investigation of Vertical Distribution of Soil
Elements at Central Part of Bangladesh Using
Neutron Activation Analysis
Md. Saifur Rahman
*1
, Syed Mohammod Hossain
2
, Mohammed Jamal Uddin
3
1
Bangladesh Space Research and Remote Sensing Organization (SPARRSO), Agargaon, Sher-E-Bangla Nagar, Dhaka-1207,
Bangladesh
2
Institute of Nuclear Science and Technology, Atomic Energy Research Establishment, G.P.O. Box No. 3787, Dhaka-1000,
Bangladesh
3
Department of Environmental Sciences, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh
1
sfr_rahman@yahoo.com;
2
syed9495@yahoo.com;
3
jamaluddinrunu@gmail.com
Abstract-Soil is a mixture of minerals, plant and animal
materials formed during a long process that may take
thousands of years. The trace elements in soil are very
important in aspects of both soil and environmental quality as
well as the geological purposes. The soil and sediments have been
extracted in the undisturbed state from Singair Upazila,
Manikgonj district, Bangladesh; each of them extending from 1.5
feet (0.46m) up to about 27 feet (8.23m) of depth. The drilling
cores were executed by wash borings method which were mainly
composed of silty clay, very fine silty sand, fine to very fine
sand, fine to medium sand and fine sand with mica layers at
different depths. Nuclear reactor based Instrumental Neutron
Activation Analysis (INAA) method has been used for analysis
of concentrations of various trace elements in subsurface soil
and sediments at various depths. Although the mean, median
and standard deviation of trace elements concentration from
the two study sites soil samples demonstrate same distribution
characteristics of soil, but the analytical results of selected
borehole sediment samples of contaminated areas shows that
the vertical distributions of arsenic and iron do not follow any
regular or particular pattern. They are randomly distributed
over all layers and the correlations coefficients [R
2
=0.6568
(n=16), R
2
=0.4668 (n=18)] between total arsenic and iron in the
core sediments are significant. Furthermore, a highly
significant correlation was observed between Fe-Mn, Cr-Fe,
Cr-Sc and Sc-Fe which indicates that they are closely
associated with each other and variation in concentrations of
one can influence the concentration of others.
Keywords- Investigation; Trace Elements; Neutron
Activation Analysis, Correlation Analysis
I.
INTRODUCTION
Bangladesh, the world’s biggest delta landscape, is very
small compared to the large population. Although the
country does not have much forest, it is still lush green and
is noted for its unique landscape. It is not surprising that the
land and soil suffer numerous threats in sustaining their
fertility and quality. Due to catering for the exploiting
population agricultural production is intensified to radical
frontier. In this struggle for food self-sufficiency, nutrient
mining is a major concern. At the same time, diverse land
usage is removing land from agriculture to other uses like
industrial and social infrastructures. In addition, production
of waste products from different sources and their careless
disposal into agricultural land and water bodies are
becoming another major burning question.
In many countries researches on the base line
concentrations of trace elements in soils have been
conducted from the earlier periods. For instance, in USA,
researches have been conducted to provide a reliable data
base on concentrations of trace metals in soils. This is
necessary for the regulators to specify the maximum metal
concentration in wastes for land application. Similarity,
Norway, France, Poland, China, Japan, India and many other
developed countries have their own data base.
Unfortunately, existing data on baseline concentrations of
trace elements in soils of Bangladesh are inadequate for
determining the issue of cleaning up the polluted soils.
Trace elements find their way into humans and animals
either by direct absorption via air and drinking water or the
food chain. Plants absorb trace elements either via the root
system or foliar absorption. Whenever the trace elements
have abnormally low or high-level of concentration in soil,
have an adverse effect on environment.
Realizing the importance, an attempt has been made to
perform the following studies: i) to determine the amount of
arsenic and other trace elements in the soils and sediments
collected from the surface to various depths of Singair
Upazila (Manikganj district, Bangladesh) using INAA
technique; ii) to find a correlation of arsenic with other trace
elements. Correlation analysis has been used to identify the
source and the relations of common geogenic origin among
the measured elements, to examine the possible
relationships, to measure the variation in concentration of
each other, etc. Throughout the study, the baseline data of
the elemental status of the study area will be created that
will help to find out the geological origin of arsenic
contamination of our ground water. The application of
INAA technique ensures the production of quality baseline
data as the method is treated a ‘referee method’ to check the
accuracy of other analytical methods worldwide especially
for solid sample analysis. The INAA is treated as a referee
method due to the simplicity of sample preparation,

International Journal of Environmental Protection Feb. 2013, Vol. 3 Iss. 2, PP. 5-13
- 6 -
capability of analysis solid sample (no chemical treatment or
decomposition of sample is required like AAS, ICP-MS,
etc.) simultaneous multielement determination capability,
nearly matrix independent characteristics. However, as NAA
involved radioactive decay turn around time is
comparatively higher than other chemical methods for long-
lived elements.
II.
STUDY VICINITY
Singair Upazila (Manikganj district, Bangladesh) with an
area of 217.38 sq km, is bounded by Dhamrai and
Manikganj Sadar Upazilas on the north, Nawabganj (Dhaka)
Upazila on the south, Savar and keraniganj Upazilas on the
east, Manikganj Sadar Upazila on the west. Main rivers are
the Dhaleshwari, Ghazikhali and Kaliganga in Fig. 1
[3]
. The
study areas of Bakchor and Panishain villages of Singair
Upazila under Manikgonj district are chosen as they seem to
be arsenic affected. The INAA is a good choice to analyze
soils and sediments. So to realize the necessity of the point,
this work has been done using the 3 MW TRIGA Mark-II
research reactor in the Institute of Nuclear Science and
Technology (INST), Atomic Energy Research Establishment
(AERE), Savar, Dhaka.
Fig. 1 Study area in Bakchor and Panishain villages of Singair Upazila
under Manikgonj district of Bangladesh (Source: Ref
[3]
)
III.
EXPERIMENT
A. Boring Execution and Sample Collection
In the study area, two borings (one is up to 24 feet or 7.32 m
and another is up to 27 feet or 8.23 m, distance between these
two is about 1 Km) were executed in the field by the technical
assistance of the consulting firm. The method of wash borings
was followed in drilling the boreholes after driving the casing
pipe in Fig. 2
Fig. 2 Sample collection by wash borings
drilling
method
The soil samples in the undisturbed state have usually
been extracted from each of the 1.5 feet (0.46 m) depth up to
the depth of the investigation, along with the performance of
the Standard Penetration Test (SPT). The SPT includes
dropping of a hammer weighting 63.5 kg (140 lb) and falling
freely over a constant height of 30 inch along the drill pipe in
order to drive the sampler attached at the end of the same. The
SPT blow count value and bore logs descriptions are shown in
Tables I and II, against the respective interval of depth.
TABLE I BORE LOG DESCRIPTION IN SOIL OF BH
-1
Bore hole Log-1
D: 23/03/08, Time: 1pm
Vill : Bakchor
Thana : Singair
Dist : Manikgonj
Boring
Depth (ft) Litho Symbol
Color Lithology
0-1.5
Brown Silty Clay
1.5-3 Brown Silty Clay
3-4.5 Gray Silty Clay
4.5-6 Gray Silty Clay
6-7.5 Gray Silty Clay
7.5-9 Gray Silty Clay
9-10.5 Gray Silty Clay
10.5-12 Gray Silty Clay
12-13.5 Gray Silty Clay
13.5-15 Gray Silty Clay
15-16.5 Gray Silty Clay
16.5-18 Gray Silty Clay
18-19.5 Gray Very fine silty sand
19.5-21 Gray Fine to very fine sand
21-22.5 Gray Fine to medium sand
22.5-24 Gray Fine to medium sand
Bakchor
Panishain

International Journal of Environmental Protection Feb. 2013, Vol. 3 Iss. 2, PP. 5-13
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TABLE II BORE LOG DESCRIPTION IN SOIL OF BH
-2
Bore hole Log-2
D: 24/03/08, T: 11.55 am.
Vill : Panishain
Thana : Singair
Dist : Manikgonj
Chandonpur Govt. Primary School
Boring
Depth (ft) Litho Symbol
Color Lithology
0-1.5 Brown
Silty clay
1.5-3 Gray Silty clay
3-4.5 Gray Silty clay
4.5-6 Gray Silty clay
6-7.5 Gray Silty clay
7.5-9 Gray Silty clay
9-10.5 Gray Silty clay
10.5-12 Gray Silty clay
12-13.5 Gray Silty clay
13.5-15 Gray Silty clay
15-16.5 Gray Very fine silty sand
16.5-18 Gray Very fine silty sand
18-19.5 Gray Very fine silty sand
19.5-21 Gray Fine to very fine sand
21-22.5 Gray Fine to medium sand
22.5-24 Gray Fine to medium sand
24-25.5 Gray Fine sand with mica
25.5-27 Gray Fine sand with mica
B. Sample Preparation
Soil samples were weighted, cleaned and dried in an oven at
70°C until having constant weight. The dried soil samples were
gently ground and homogenized in an agate mortar and stored as
stock sample. From the stock sample about 100 mg was packed
into ultra clean irradiation type small polyethylene envelopes
and then heat shield in Fig. 3.
Fig. 3 Samples were packed and prepared to transfer in a vial before irradiation
The standard reference material (SRM) IAEA-SL-1,
IAEA Soil-7 and NIST coal fly ash (1633b) were taken into
the same kind of ultra clean polyethylene irradiation
envelopes of same size and their weight were determined.
Two sets of samples and standards were prepared. For the
first set, soil samples of 16 numbers together with the
standard references were packed into four layers inside the
high density polyethylene irradiation tube in such a way that
the first layer consisted of four samples, second layer
consisted of one sample and three standards; each of third
and four layers consisted of four samples. In order to
monitor the neutron flux gradient within the sample stack,
foils of IRMM Al–0.1%Au were placed at the top, bottom
and in the middle position of the stack in Fig. 4 (A set). For
the second set, 24 soil samples together with the standard
references were packed into four layers in such a way that
each of the first, second and fourth layer was consisted of
six samples, third layer consisted of three samples and three
standards in Fig. 4 (B set).
Fig. 4 Sample, standard and flux monitor foils arrangements inside the high
density polyethylene tube for irradiation
C. Irradiation of Samples
Two independent irradiations were performed for
irradiations of two sets of sample at the irradiation position
of G19 of the TRIGA reactor core. For loading and
unloading the rabbit tube, the pneumatic transfer system was
used. In both cases the irradiation was performed for 8
minutes at 2 MW reactor power with thermal neutron flux ~
1.5×10
13
n/ cm
2
/sec.
After the end of irradiation, the tube was unloaded and
all the irradiated samples were kept in a lead castle for one
day as a waiting time to decay the short lived nuclides.
Afterwards the emitted γ-rays from the studied, reference
and the monitor samples were counted by means of a high
resolution HPGe detector (resolution at FWHM is 1.92 keV
at 1,332.5 keV of
60
Co) associated with other electronic
accessories.
D. Gamma Ray Spectra Acquisition and Analysis
The acquisition of γ-spectra for all irradiated samples
was done by the High Purity Germanium (HPGe) detector.
For the case of first irradiated samples, three independent
measurements were performed by allowing various decay
intervals in order to identify different nuclides: (1) after the
decay time of 24 hours for the determination of Mn with a
measuring time of 5 minutes; (2) after the decay time of 3–6
days, with a measuring time of 1.39 h to 2.23 h for the
determination of U, La, As, Sb, Na, and K; (3) after a decay
110+111+112+
113+F-3
Soil7+SL1+
1633b+105
F1+101+102
+103+104
F-2+106+107+
108+109
1
st
layer
2
nd
layer
3
rd
layer
218+219+220+
114+115+116
207+208+209+
212+213+214
201+202+203+
204+205+206
215+216+217+
SL-1+Soil7+1633b
4
th
layer
B set of sample A set of sample

International Journal of Environmental Protection Feb. 2013, Vol. 3 Iss. 2, PP. 5-13
- 8 -
time of 3 weeks for the determination of Th, Eu, Cr, Cs, Sc,
Fe and Co with a measuring time of 1.1 h. The Al – 0.1%
Au monitor foils were measured after 1 week of irradiation.
The measurements of short lived elements in the samples
and standards were carried out on the 2 cm of the detector
and long lived elements in the samples and standards were
carried out on the surface of the detector due to the low
activity of the product nuclides. The γ-spectra for all kind of
samples and standards were achieved by Canberra HPGe
detector coupled with Genie 2000 VDM acquisition
software in Fig. 5.
Fig. 5
The gamma ray spectrum of a soil sample achieved by Canberra HPGe detection coupled with Genie 2000 acquisition software
E. Concentration Calculation
The relative standardization approach is applied to
calculate the concentration of elements in the investigated
sample using the following relation:
dardsin
elementofcontents
dardsthein
cpscorrectedDecay
samplethein
cpscorrectedDecay
sample
Wtan
tan
)( ×=
F.
Background Problem
Interfering background in gamma spectra originates
either from within the sample being counted (Compton-
produced) or from the environment. The background effect
is very important for the present work, in detecting gamma
rays by High Purity Germanium (HPGe) detector. For
extremely weak samples, the environmental background
becomes more significant as the magnitude of the
background ultimately determines the minimum detectable
radiation level, it becomes most significant in those
applications involving weak radiation sources having
activity. As the HPGe detector used in the present
experiment is well surrounded with a very good and
effective shielding, the background effect is negligible.
There was no gamma line found in the background spectrum
at our investigated energy.
G.
Neutron Flux Gradient Measurement
Neutron flux gradient within the irradiation tube was
determined by irradiating 3 IRMM Al – 0.1% Au foils
placed at the bottom, middle and top of the tube. All these 3
samples were counted at the sample geometry of HPGe
detector for the determination of their specific activity at the
end of irradiation. By comparing their decay corrected
specific activity, the neutron flux gradient was determined
and implemented to calculate the concentration using
relative method. In extreme case the neutron flux gradient
varied only 5% with the irradiation tube.
IV.
RESULTS AND DISCUSSION
A.
Trace Elements Concentration in Soil
Trace elements act as metalloenzymes and perform
important metabolic functions. These elements may be
integral parts of the enzyme-protein molecule and they are
involved in vitamins and hormones. Any functions, i.e.,
deficiency or excess in their normal level in living cells may
cause the physiological disorders and may lead to various
diseases. The contamination of water supply and food with
trace metals arising from various sources may have, in long
run, deleterious effects on health and welfare of human
population of a country. This concern has stimulated
increasing interest in the study of trace elements related to
soil and their movement in the environment.
La-140, 487 keV
Sc-46, 889 keV
K-42, 1524.6 keV
La-140, 1596 keV
Na-24, 1369 keV
Fe-59, 1292 keV
Sc-46, 1120 keV
Fe-59, 1099 keV

International Journal of Environmental Protection Feb. 2013, Vol. 3 Iss. 2, PP. 5-13
- 9 -
Table III represents the concentration of trace metals in
the sub surface soil of the Bakchor bore log samples. The
average concentrations of U, La, Sb, As, K, Na, Th, Cr, Sc,
Fe, Co are 3.70, 43.29, 0.22, 4.73, 24314.30, 2972.32, 23.28,
71.88, 12.22, 39390.09, 20.26 mg/kg, respectively. Table IV
represents the concentration of trace metals in the sub
surface soil of the Panishain bore log samples. The average
concentrations of U, La, Br, Sb, As, Mn, Na, K, Th, Cr, Sc,
Fe, Co are 2.92, 44.04, 6.07, 0.09, 3.84, 601.48, 14643.86,
21750.94, 22.36, 104.53, 1.97, 7622.67, 10886.65
mg/kg,
respectively. The average concentrations of U, La, As, k and
Th are almost same of the two villages but the median
concentration of Na in Panishain soil sample is higher than
Bakchor soil sample.
TABLE III COMPOSITIONS OF SOME TRACE ELEME NTS
(
IN MG
/
KG
)
OF SOILS
AND SEDIMENTS OF BAKCHOR STUDY AREA
Trace
Elements
Min Max Mean Median SD
U 0.00 5.11 3.70 4.17 1.59
La 27.06 61.07 43.29 43.69 8.09
Sb 0.00 0.57 0.22 0.24 0.22
As
0.00 12.48 4.73 4.71 2.96
K
16847.10 32718.30
24314.30
23760.91
5262.99
Na 10.38 19515.38
2972.32 13.21 6470.14
Th 14.42 35.89 23.28 23.00 5.46
Cr 0.00 101.65 71.88 85.38 31.79
Sc 7.87 16.41 12.22 12.00 2.78
Fe
22458.16 55181.06
39390.09
39594.83
11336.55
Co
0.00 87.09 20.26 17.48 19.17
TABLE IV COMPOSITIONS OF SOME TRACE ELEME NTS
(
IN MG
/
KG
)
OF SOILS
AND SEDIMENTS OF THE PANISHAIN STUDY AREA
Trace
Elements
Min Max Mean Median SD
U 0.00 6.23 2.92 3.66 2.13
La 30.03 55.80 44.04 45.00 7.20
Br 0.00 28.16 6.07 2.27 7.79
Sb 0.00 0.73 0.09 0.00 0.22
As
1.67 9.90 3.84 3.51 2.00
Mn
348.36 947.67 601.48 612.62 126.32
Na 11215.03 16319.17
14643.86
15097.09
1403.87
K 16845.11 26148.91
21750.94
21824.72
2745.09
Th 16.41 30.35 22.36 22.60 3.27
Cr 0.00 149.22 104.53 100.14 35.42
Sc
0.83 5.32 1.97 1.76 1.10
Fe
6081.35 8373.30 7622.67
7805.48 654.13
Co 8437.73 13084.62
10886.65
10923.42
1371.68
The mean, median and standard deviation of trace metals
concentration from the two study sites soil samples in Tables
III and IV demonstrates same distribution characteristics of
soil and the Pearson correlation coefficients in Tables V and
VI among most trace elements are almost same. Thus, the
trace metals concentrations mainly inherited from parent
materials because the soils are young with relatively little
weathering impacts
[14]
.
B.
Correlation Analysis and Vertical Distributions of As,
Fe and Mn
If an aquifer has a porosity of 25% and the sediment
contains say 1 mg As kg
-1
of labile As, the complete
dissolution of that As would lead to a groundwater As
concentration of 7950
µ
g As
L
-1
, far in excess any drinking
water standard
[7]
. The loss of only 0.1
µ
g/g of As from the
solid phase can enrich the groundwater by 200
µ
g/l
[5]
.The
concentrations of arsenic are also plotted as a function of
different selected parameters. The correlations coefficients
[R
2
=0.6568 (n=16), R
2
=0.4668 (n=18)] between total
arsenic and iron in the core sediments are significant in Fig.
6. Besides this, the As/Mn and Fe/Mn containing minerals in
the same layers in Fig. 7 (Panishain village) is controlled the
distribution of arsenic. There also show strong correlations
[R
2
=0.821, R
2
=0.542 (n=18)] between total arsenic-
manganese and iron-manganese respectively in the core
sediments.
Fig. 6 Profile showing the relationship between the concentrations of As
with Fe of (a) Bakchor and (b) Panishain bore logs
Fig. 7 Profile showing the relationship between the concentrations of (a) As
with Mn and (b) Fe with Mn of Panishain bore logs
Correlation analysis of arsenic and other elements of soil
samples from the sub soil were carried out using the
Pearson’s correlation method from SPSS statistical software.
Correlation coefficients ranged in value from –1 (a perfect
negative relationship) to +1 (a perfect positive
relationship).The most significant linear correlation is
counted at the correlation coefficient >±0.7 shown in Table
V and VI.
TABLE V PEARSON CORRELATION OF BOREHOLE
-1
U La Sb As K Na Th Cr Sc Fe Co
U 1
La
0.45
1
Sb
0.39
0.25
1
As
0.68
0.28
0.71
1
K 0.21
0.19
0.38
0.27
1
Na
-0.89
-0.28
-0.44
-0.63
-0.24
1
Th
0.74
0.73
0.20
0.48
0.20
-0.65
1
Cr
0.68
0.51
0.57
0.63
0.72
-0.69
0.58
1
Sc
0.68
0.24
0.41
0.55
0.77
-0.70
0.54
0.79
1
Fe
0.72
0.23
0.55
0.81
0.62
-0.69
0.53
0.81
0.90
1
Co
-0.40
-0.27
-0.07
-0.01
-0.13
0.21
-0.31
-0.32
-0.06
-0.03
1
y = 57.182x + 381.81
R
2
= 0.821
0
200
400
600
800
1000
0 2 4 6 8 10 12
As (mg/kg)
M n (m g /k g )
(a)
y = -3.8123x + 9915.7
R
2
= 0.542
0
2000
4000
6000
8000
10000
0 200 400 600 800 1000
Fe (mg/kg)
M n ( m g / k g )
(b)
y = 3103.4x + 24707
R
2
= 0.6568
0
20000
40000
60000
80000
0 5 10 15
As (mg/kg)
F e ( m g / k g )
(a)
y = -223.28x + 8480.4
R
2
= 0.4668
0
2000
4000
6000
8000
10000
0 2 4 6 8 10 12
As (mg/kg)
F e (m g / k g )
(b)

International Journal of Environmental Protection Feb. 2013, Vol. 3 Iss. 2, PP. 5-13
- 10 -
TABLE VI PEARSON CORRELATION OF BOREH OLE
-2
U La Br As Sb Mn Na K Th Cr Sc Fe Co
U 1
La -0.16 1
Br -0.55 -0.05 1
As 0.57 -0.42 -0.36 1
Sb 0.42 -0.03 -0.24 0.85 1
Mn 0.53 -0.49 -0.23 0.91 0.69 1
Na -0.14 0.31 -0.06 -0.72 -0.73 -0.78 1
K 0.65 -0.41 -0.49 0.79 0.55 0.81 -0.52 1
Th 0.20 0.38 0.07 -0.30 -0.10 -0.37 0.45 -0.53 1
Cr 0.33 -0.18 -0.12 0.50 0.47 0.43 -0.30 0.30 0.19 1
Sc 0.56 -0.38 -0.35 1.00 0.87 0.90 -0.73 0.78 -0.29 0.50 1
Fe -0.10 0.29 -0.09 -0.68 -0.71 -0.74 1.00 -0.48 0.45 -0.28 -0.70 1
Co 0.65 -0.41 -0.49 0.80 0.55 0.81 -0.52 1.00 -0.53 0.30 0.78 -0.48 1
Presence of organic matter in the aquifer sediments of
the Bengal Basin has been reported in several studies
[1, 9, 10]
.
Degradation of this organic matter could drive the sequence
of redox reactions in the aquifer and may, thereby enhance
arsenic mobilization
[2, 8, 11]
. Analytical results of selected
boreholes sediment samples of contaminated areas (Bakchor
and Panishain villages) show in Fig. 8 that the vertical
distribution of arsenic and iron has not followed any regular
or particular pattern but is rather randomly distributed over
all layers. The drilling cores are mainly composed of silty
clay, very fine silty sand, fine to very fine sand, fine to
medium sand and fine sand with mica layers at different
depths in Fig. 8. Arsenic concentrations in medium sand are
relatively lower than those of clay, fine sand and silt but
they contain considerable amount (1.6–3.5mg/kg) of arsenic
in Fig. 8 depending on the amount of reddish iron-oxide fine
particles found on the sand grains.
Fig. 8 Vertical profile used for analysis of As with Fe in [l] Bakchor and [ll] Panishain village; [lll] As with Mn and [lV] Fe with Mn in Panishain village along
with the stratigraphic column of the sequence sampled by the bore logs soil sample
Silty clay
Very fine silty sand
Fine to very fine sand
Fine to medium sand
Fine sand with mica
As conc.
Fe conc.
0
2000
4000
6000
8000
10000
1.5 3 4. 5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
Fe (mg/kg)
0
200
400
600
800
1000
Mn (mg/kg)
[lV
]
0
2
4
6
8
10
12
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
As (mg/kg)
0
100
200
300
400
500
600
700
800
900
1000
Mn (mg/kg)
[lll]
0
2
4
6
8
10
12
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
As (mg/kg)
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Fe (mg/kg)
[ll]
0
2
4
6
8
10
12
14
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24
Depth (ft)
As (mg/kg)
0
10000
20000
30000
40000
50000
60000
Fe (mg/kg)
[l]

International Journal of Environmental Protection Feb. 2013, Vol. 3 Iss. 2, PP. 5-13
- 11 -
The overall variation of arsenic concentration
(Bakchor:0.00–12.48 mg/kg; Panishain: 1.67- 9.90mg/kg)
with depth (27ft) can be attributed to the different flood
cycles sedimentation pattern and fluvio-deltaic sedimentary
profiles of the major rivers in these areas in the recent past
and also to the post-depositional as well as early diagenetic
nature of organic matter. The strong relationship between
total arsenic and iron contents may be a result of the
presence Fe-(hydr)oxides and the homogeneous distribution
of arsenic on metal (hydr)oxides
[13]
.
C.
Spatial Distribution of Arsenic with Ferrous
Profiles of the As and Fe distribution at different depths
with important parameters related to release it into soil are
shown in Fig. 9. Considerable variability is noted in the
levels of Fe (22458.16 to 55181.06 mg/kg and 6081.35 to
8373.30) with As in the soil samples as a function of depth.
In Bakchor bore log, high concentration of arsenic is
observed at 6ft depth (12.48 mg/kg), similarly, the highest
concentration of Fe is observed at 1.5ft depth (55181.06
mg/kg) in Fig. 9 (a). On the other hand, the lowest
concentration of As and Fe is found at 22.5 ft depth in Fig. 9
(a). In Panishain bore log, the highest concentration of As is
observed at 12 ft depth and Fe is observed at 22.5 ft depth in
Fig. 9 (b).
Fig. 9 Profile showing the distribution of As with Fe of
(a) Bakchor and (b) Panishain according to depth of bore logs
D.
Spatial Distribution of Other Trace Elements
It is therefore apparent that the As distribution in soil is
not only controlled by depth but also depend on subsurface
geology
[1]
. This means that one should expect the soil and
sediments with fine silt and clay contents to be relatively
high in arsenic concentration. The variations of the
concentrations of As and Fe in the soil are probably the
result of biodegrading of organic matter in subsurface
sediments
[4, 6, 9, 12]
.
Among the other parameters, concentrations of U(0.00 to
5.11 mg/kg), La(27.06 to 61.07 mg/kg), Sb(0.00 to 0.57
mg/kg), K (16847.10 to 32718.30 mg/kg), Na(10.38 to
19515.38 mg/kg), Th(14.42 to 35.89 mg/kg), Cr(0.00 to
101.65 mg/kg), Sc(7.87 to 16.41 mg/kg), Fe(22458.16 to
55181.06 mg/kg), Co(0.00 to 87.09 mg/kg), are observed in
the Bakchor soil sample in Fig. 10 (a – j).
Fig. 10 Profile showing the distribution of (a) U, (b) La, c) Sb, (d) K, (e)
Na, (f) Th, (g) Cr, (h) Sc, (i) Fe and (j) Co with depth of Bakchor bore log
In Panishain soil sample, the concentrations of U(0.00 to
6.23 mg/kg), La(30.03 to 55.80 mg/kg), Br(0.00 to 28.16
0
10000
20000
30000
40000
50000
60000
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24
Depth (ft)
Fe (mg/kg)
i
0
10
20
30
40
50
60
70
80
90
100
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24
Depth (ft)
Co (mg/kg )
j
0
2
4
6
8
10
12
14
16
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5
Depth (ft)
Na (mg/kg)
e
0
5
10
15
20
25
30
35
40
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24
Depth (ft)
Th (mg/kg)
f
0
2
4
6
8
10
12
14
16
18
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24
Depth (ft)
Sc (mg/kg)
h
0.00
20.00
40.00
60.00
80.00
100.00
120.00
1.5
3
4.5
6
7.5
9
10.5
12
13.5
15
16.5
18
19.5
21
22.5
24
Depth (ft)
Cr (mg/kg)
g
0
1
2
3
4
5
6
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24
Depth (ft)
U (mg/kg)
a
0
10
20
30
40
50
60
70
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24
Depth (ft)
La (mg/kg)
b
0.00
0.10
0.20
0.30
0.40
0.50
0.60
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24
Depth (ft)
Sb (mg/kg)
c
0
7000
14000
21000
28000
35000
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5
Depth (ft)
K (mg/kg)
d
0
2
4
6
8
10
12
14
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24
Depth (ft)
As (mg/kg)
(a)
0
2
4
6
8
10
12
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
As (mg/kg)
0
10000
20000
30000
40000
50000
60000
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24
Depth (ft)
Fe (mg/kg)
(b)
0
2000
4000
6000
8000
10000
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25. 5 27
Depth (ft)
Fe (mg/kg)

International Journal of Environmental Protection Feb. 2013, Vol. 3 Iss. 2, PP. 5-13
- 12 -
mg/kg), Sb(0.00 to 0.73 mg/kg), Mn(348.36 to 947.67
mg/kg), Na(11215.03 to 16319.17 mg/kg), K(16845.11 to
26148.91 mg/kg), Th(16.41 to 30.35 mg/kg), Cr(0.00 to
149.22 mg/kg), Sc(0.83 to 5.32 mg/kg), Fe(6081.35 to
8373.30 mg/kg) and Cr(8437.73 to 13084.62 mg/kg) are
observed in Fig. 11 (a – l).
Fig. 11 Profile showing the distribution of (a) U, (b) La, (c) Br, (d) Sb, (e) Mn, (f)
Na, (g) K, (h) Th, (i) Cr, (j) Sc, (k) Fe and (l) Co with depth of Panishain bore log
E.
Correlation Analysis of Other Investigated Elements
It was observed that trace elements are most closely
associated with each other. Strong positive correlation was
observed for Cr-Fe, Cr-Sc and Sc-Fe having correlation
coefficients of 0.652, 0.6164 and 0.8063 in Fig. 12 indicate
that they are closely associated with each other and variation
in concentration of one can influence the concentration of
others.
Fig. 12 Showing the relationship of (a) Cr with Fe; (b) Cr with Sc; (c) Sc
with Fe of Bakchor bore log
V.
CONCLUSIONS
In the present study, concentrations of various trace
elements were assessed in subsurface soil and sediment in
various depth of Singair Upazila. The drilling cores are
mainly composed of silty clay, very fine silty sand, fine to
very fine sand, fine to medium sand and fine sand with mica
layers at different depths. Instrumental Neutron Activation
0
40
80
120
160
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
Cr (mg/kg)
i
0
1
2
3
4
5
6
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
Sc (mg/kg)
j
0
2000
4000
6000
8000
10000
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
Fe (mg/kg)
k
0
3000
6000
9000
12000
15000
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
Co (mg/kg)
l
y = 287.94x + 18692
R
2
= 0.652
0
10000
20000
30000
40000
50000
60000
0 20 40 60 80 100 120
Cr (mg/kg)
Fe (m g/kg)
(a)
a(
y = 0.0686x + 7.2827
R
2
= 0.6164
0
3
6
9
12
15
18
0 20 40 60 80 100 120
Cr (mg/kg)
Sc (m g/K g)
(b)
y = 3663.8x - 5364.5
R
2
= 0.8063
0
10000
20000
30000
40000
50000
60000
0 5 10 15 20
Sc (mg/kg)
Fe (m g/kg )
(c)
0
200
400
600
800
1000
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
Mn (mg/kg)
e
0
3000
6000
9000
12000
15000
18000
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
Na (mg/kg)
f
0
5
10
15
20
25
30
35
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
Th (mg/kg)
h
0
6000
12000
18000
24000
30000
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19. 5 21 22.5 24 25.5 27
Depth (ft)
K (mg/kg)
g
0
10
20
30
40
50
60
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
La (mg/kg)
b
0
1
2
3
4
5
6
7
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
U (mg/kg)
a
0
5
10
15
20
25
30
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
Br (mg/kg)
c
0.00
0.20
0.40
0.60
0.80
1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 25.5 27
Depth (ft)
Sb (mg/kg)
d

International Journal of Environmental Protection Feb. 2013, Vol. 3 Iss. 2, PP. 5-13
- 13 -
Analysis method has been used for analysis wherein the
average concentrations of U, La, Br, As, Sb, Mn, k, Th, Cr,
Sc, Fe and Co are almost same for the soil samples from two
villages except (mean concentration of Na is 2972.32 mg/kg
but the median concentration is 13.21 mg/kg) of Bakchor
soil samples which is higher than Panishain soil samples.
The mean, median and standard deviation of trace metals
concentration from the two study sites soil samples
demonstrate same distribution characteristics of soil.
Pearson correlation coefficients among most trace elements
are almost same. This phenomenon is a result of almost
same parent materials between two study soils.
However, distribution of arsenic in soil and sediments
depend not only on the texture but also on the concentration
of metal (Fe, Mn) oxides and some other factors. The
concentrations of arsenic are also plotted as a function of
different selected parameters. Arsenic exhibited significant
correlation with iron and manganese. Analytical results of
selected borehole sediment samples of contaminated areas
(Bakchor and Panishain villages) show that the vertical
distribution of arsenic and iron has not followed any regular
or particular pattern but is rather randomly distributed over
all layers and the correlation coefficient [R
2
=0.6568 (n=16),
R
2
=0.4668 (n=18)] between total arsenic and iron in the core
sediment are significant. Furthermore a highly significant
correlation was observed between Fe-Mn, Cr-Fe, Cr-Sc and
Sc-Fe which indicate that they are closely associated with
each other and variation in concentration of one can
influence the concentration of others.
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