Heavy Metal Hyper-accumulation in Plants and Metal Distribution in Soil on Tannery and Dying
Industries Polluted Area in Bangladesh
Mohammed Mahabubur Rahman 1*, L Haoliang2
, Y Chongling2, Sirajul Hoque 3
(1 Department of Botany, Dhaka Imperial
College, 28 Mirpur Road, Dhaka 1205, Bangladesh; 2 School of
Life Sciences, Xiamen University, 361005, P.R.China, 3 Dr. Sirajul Hoque in Department of Soil water and Environment University
of Dhaka )
(*
author for correspondence. Email: t_mahabub@yahoo.com Phone and Fax number: 88028016202)
Abstract
The unplanned discharge of all
the by-products, garbage, pollutants and effluents from tannery, and dying
industries are caused serious pollution problems in environment. A study was
conducted to investigate the indigenous plant species which are well adopted to the
polluted environment as effected by industrial effluents which can accumulate
higher concentration of heavy metals of dying and tannery
industries around Dhaka city in Bangladesh. The pollutants in both contaminated
soils were also compared. The results showed that concentrations of Lead（Pb）and Cadmium
(Cd）were ranged from 219.183-2.673
ppm and 1.343-0.316
ppm, respectively, in seven plants samples Enhydra
fluctuans Lour, Ipomoea aquatica Forsk,
Colocasia esculenta L., Spilanthes acmella L.,
Polygonum hydropiper L., Cyperus rotundus L., Echinochloa colonum L. Exceptionally high value of 219.18
ppm was found in Ipomoea aquatica.
The Lead concentration in other plants species ranged between 26.07 and 36.61
ppm. Our results indicated that Ipomoea aquatica may be acted as a Pb
hyper-accumulator.
The concentration of nutrients and heavy metals of
N, K, S, P, Pb and Cd ranged from, 388.90-10032.00, 992.90-2642.10,
2797.00-9762.00,
18.60-932.50,
8.52-32.88
and 0.28-1.85
ppm in soil, respectively among the industrial
sites. Polluted soil contained considerable higher amount of heavy metal in
tannery than dying. There are no significant differences (P>0.05) of pollutants distribution between two sites.
Keywords:
Dying; Hyper-accumulator; Ipomoea aquatica Forsk.;
Metal Pollution, Tannery
1. Introduction
The Industrial wastes and effluents are
increased sharply in recent years in Bangladesh, and discharging of all
by products, wastage and effluents on soil, canals, rivers and water course
along the road sides caused serious environmental pollution. They pollute
productive soils, natural water systems as well as ground water (Kashem and Singh;
1998). The industrial by product, wastes, effluents contain high level of heavy
metals such as As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn (Larsen et al., 1975;
Arora et al., 1985). High amount of
Lead and Cadmium is very dangerous for human body, children, and plant also.
Heavy metal tolerance is a relatively rare trait found only in a few highly
adapted plant species. These plants are capable of growing especially at sites
with normally or artificially elevated levels of heavy metals. Some plant
species are not only tolerant to Zn, Cd and Ni but they are also able to
accumulate these metals in the shoots. Significant progress in phytoremediation
has been made with metals and radionuclides. This process involves rising of plants hydrophobically
and transplanting them in to metal polluted waters where plants absorb and
concentrate the metals in their roots and shoots. Most researchers believe that
plants for phytoremediation should accumulate metals only in the roots several
aquatic species have the ability to remove heavy metals from water, viz., water hyacinth (Eichhornia crassipes (Mast.) Solms)
pennywort (Hydrocotyle umbellata L.)
and duckweed
(Lemna minor L.).
The roots of Indian masters are effective in the removal of Cd, Cr, Cu, Ni, Pb
and Zn and sunflower removes Pb, U, 137Cs and 90Sr from hydrophobically
solutions. Hyperaccumulators accumulate appreciable quantities of metals in
their tissue regardless of the concentration of metal in the soil, as long as
the metal in question is present. The phytoextraction process involves the use
of plants to facilitate the removal of the metal contaminants from a soil
matrix. Several researchers have screened fast growing
high-biomass-accumulating plants, including agronomic crops for their ability
to tolerate and accumulate metals in their shoots. About 400 plants that
hyperaccumulate metals are reported （Majeti
and Helena, 2003）Some
species can hyperaccumulate a particular metal. While some others can
hyperaccumulate more than one metal. Plants that hyper-accumulate metals have
tremendous potential for application in remediation of metals in the
environment.
With these views in mind, the present work aim was to find out
indigenous plant species which can accumulate higher concentration of heavy
metals and for future cultivate for remediate the pollutants.
2. Methodology
2.1
Collection and Preparation of soil
Study sites are located at two main
polluted areas of Dhaka districts, namely Tannery polluted area of
Hazaribagh and Dye polluted area of Bamoil, Demra. Hazaribagh is at
the western periphery of the city and Bamil Demra is 15 Km away from the city.
Five
soil samples were collected from Hazaribagh tannery area. Five water samples
were also collected from the watercourse of same
area. The
collection of samples was carried out at an interval of 0.25 Km, and no plant species were found to grow on
the bank of watercourse. Consequently, it was not possible to collect plant
species from this area. Soil samples were denoted symbols as TS1, TS2,
TS3, TS4, TS5 while for water samples TW1,
TW2, TW3, TW4, TW5 symbols are
used.
Dye polluted area of Bamoil, Demra is
highly polluted with dye stuffs. There are 5-10 textile dying factories present
in this area. All the byproducts containing pollutants are discharged into a
canal.
Five
soil samples were collected from the bank of canal with an interval of 0.25km
corresponding water samples were also collected from Dye polluted area of Bamoil,
Demra.
Plant
samples were found to grow on the both sides of the canal. Soil samples were
donated symbols as DS1 , DS2 , DS3 , DS4 ,
DS5 while water samples
were DW1, DW2, DW3, DW4, DW5.
Plant samples were marked as P1(Enhydra
fluctuans Lour), P2 (Ipomoea aquatica Forsk), P3 (Colocasia esculenta L.), P4 (Spilanthes acmella L.), P5(Polygonum hydropiper L.), P6(Cyperus rotundus L.), P7 (Echinochloa colonum L.) for laboratory analysis plant samples were
taxonomically identified by prior to drying and grinding. All the samples
were collected at the middle of the May 2005.
2.2 Processing of soils
Soil
samples were dried in air and grind with a motor and pestle. Then soil samples
were sieved with 1 mm sieve
and before grain dying plants debris and other undesirable materials were
removed by hand, then preserved in plastic bottles for chemical
analysis.
2.3 Processing of Plant Samples
Plant
species were dried at 80℃
for 24
h before
grinding. Ground plant samples were preserved for chemical analysis.
2.4
Chemical Analysis
Electrical
conductivity (EC) of the water samples and EC of the soil samples were
determined from saturation extract by conductivity meter. Measurement of pH of
the water and soil samples were done (soil and water ratio 1:25) were done with
help of a glass electrode pH meter. Plant, water and soil samples were digested
for the determination of total Nitrogen (N2) following Kjeldahl’s
method as described by Jackson
(1973). For the determination of Sulfur (S), Potassium (K), Phosphorus (P),
Chromium (Cr), Lead (Pb) and Cadmium (Cd). Plant samples were digested with
Nitric Acid (HNO3) – Perchloric Acid (HClO4) mixture
(2:1) in a closed system. Phosphorus contents of samples were determined by
Vanadomolybdate yellow color method as described by Jackson. Sulfur contents of the samples were
determined by the method of Hunt (1981).Potassium contents of the samples were
determined by Flame photometer. Lead and cadmium were
determined by atomic absorption spectrophotometer.
2.5 Statistical Analysis
The results were statistically evaluated by
T-test in SPSS 13.0 (SPSS Inc., Chicago,USA.) and Microsoft Excel software.
3. Results
and Discussions
Soil pH values
as affected by industrial effluents are presented in Table 1. It is revealed from the
data that pH values did not show any definite trend in the variation with
distance from the effluent sources. The values ranged from 6.67 to 7.55 in different sites along the watercourse
of the Bamoil, Demra area as affected by the effluents of dyeing
industries. In Rayer Bazar area under the influence of tannery industries, the
pH values ranged between 7.30 and 7.94. Although the pH values of Hazaribagh
area are slightly higher than those of Demra area, the two areas are mere or
less identical. Similar results reported previously by Kashem and Singh
(1998) in
the same area.
The
pH values of water samples varied between 6.81 and 8.17 in Demra area and between 7.17 and 7.30 in Hazaribagh area. Though variation
existing in relation to distance from effluent sources in Demra area, there was
no definite trend in the change of variation.
Table
1
Nutrient elements and Heavy metals concentration (For water parameter).
|
Sample no
|
pH
|
EC
μs/cm
|
Total N
ppm
|
K
ppm
|
S
ppm
|
P
ppm
|
Pb
ppm
|
Cd
ppm
|
|
DW1
|
7.03
|
933
|
11.07
|
119.07
|
218.75
|
2.50
|
0.27
|
0.09
|
|
DW2
|
6.81
|
1788
|
10.96
|
109.96
|
984.35
|
13.12
|
0.22
|
0.03
|
|
DW3
|
8.17
|
1247
|
12.50
|
29.29
|
0992.12
|
6.25
|
0.15
|
0.06
|
|
DW4
|
7.19
|
1000
|
11.04
|
10.54
|
355.93
|
3.12
|
0.39
|
0.03
|
|
DW5
|
8.02
|
1017
|
10.39
|
18.42
|
515.62
|
4.75
|
0.20
|
0.43
|
|
TW1
|
7.17
|
160
|
11.52
|
13.69
|
226.30
|
1.75
|
0.63
|
0.05
|
|
TW2
|
7.18
|
114
|
11.35
|
11.47
|
725.00
|
1.87
|
0.65
|
0.06
|
|
TW3
|
7.17
|
105
|
14.30
|
10.34
|
734.3
|
2.25
|
0.58
|
0.05
|
|
TW4
|
7.30
|
96
|
13.20
|
10.22
|
375.00
|
3.00
|
0.67
|
0.06
|
|
TW5
|
7.25
|
1765
|
11.80
|
9.91
|
361.50
|
2.50
|
0.69
|
0.07
|
3.1
Electrical Conductivity (EC)
Electrical
conductivity is a measure of the dissolved salts present in soil and water. The
values of water EC varied in the range of 5.596 to 10.588 μs/cm in Bamiol,
Demra area
and from 0.956 to 10.588 μs/cm in Hazaribag area. Electrical
conductivity values of saturation extract of soil varied between 1.780 and
4.228 μs/cm in Bamoil, Demra area and between 1.732 μs/cm to
7.330 μs/cm in Hazaribagh area. The EC values varied
irregularly in relation to distance (Table 1) possibly because of the
connection of different drainage systems originating from different sources to
the main channel of watercourse.
3.2
Nutrient contents of the samples
Soil
and water samples were analyzed for N, P, K and S which are essential for plant
growth. Different kinds of plants were found to grow in Bamoli Dema area but
along the watercourse of Hazaribagh area there was no plant growth at all. Total
Nitrogen content of the water samples was more or less similar in both
locations (Table 1). Soils from these areas however showed extreme
variation in the total nitrogen contents of the soils. The nitrogen content
varied between 388.90 and 2296.00 ppm in Bamoil, Demra area. On the other
hand soils total nitrogen contents of soil samples varied between 418.90 and 10163.00
ppm in
Hazaribagh area (Table
2). The
higher contents of total nitrogen in soils are due to the accumulation of
debris of leather under the influence of tannery industry.
Table
2 Nutrient elements and heavy metals concentration (For soil parameter).
|
Sample no
|
pH
|
EC
μs/cm
|
Total N
ppm
|
K
ppm
|
S
ppm
|
P
ppm
|
Pb
ppm
|
Cd
ppm
|
|
DS1
|
7.46
|
705
|
1077.00
|
1790.70
|
7296.00
|
932.50
|
8.52
|
1.22
|
|
DS2
|
7.12
|
485
|
2296.00
|
1899.60
|
6620.00
|
736.80
|
23.53
|
1.85
|
|
DS3
|
7.30
|
705
|
755.00
|
992.90
|
4876.00
|
595.70
|
28.94
|
0.96
|
|
DS4
|
6.67
|
575
|
610.40
|
1853.60
|
4752.00
|
629.75
|
15.83
|
0.28
|
|
DS5
|
7.55
|
297
|
388.90
|
2642.10
|
3363.00
|
550.44
|
15.56
|
0.42
|
|
TS1
|
7.85
|
1222
|
4852.00
|
2369.00
|
4886.00
|
710.80
|
27.86
|
1.08
|
|
TS2
|
7.30
|
289
|
4834.80
|
2747.00
|
6448.00
|
919.00
|
32.88
|
1.38
|
|
TS3
|
7.55
|
1082
|
10163.00
|
1634.00
|
9762.00
|
18.60
|
32.06
|
1.57
|
|
TS4
|
7.94
|
580
|
10032.00
|
1722.00
|
3408.00
|
379.90
|
11.72
|
0.61
|
|
TS5
|
7.48
|
396
|
418.90
|
2184.00
|
2797.00
|
322.30
|
13.43
|
0.78
|
3.3
Total nitrogen
The
contents of total nitrogen in the plant samples varied between 7840.00 and 37270.00
ppm The
uptake of nitrogen by different plant species varied considerably. Ipomoea aquatica Forsk showed the
highest percentage of nitrogen in the above ground portion of the plant and the
lowest value was shown by Echinochloa
colonum L. Nitrogen content of plant species did not show any positive
relationship with the contents of total nitrogen contents of the water and
soil. Nitogen content of the plant species showed considerable variation among
themselves. Total nitrogen distribution in two sites was showed in Fig 1.
3.4 Potassium
Potassium
contents of the water samples were in general decreased with the increase in
distance from the point source in Hazaribagh area and in
Bamoil Demra
area the variation of potassium contents with distance was irregular (Table 1) The total potassium contents in
soils in both locations did not show any definite trend in the variation with
the increase of distance from the point source (Table2). Potassium contents of the plant
species varied considerably and the highest value of 45440.00
ppm was found
in Enhydra fluctuans and the lowest
value of 11890.00 ppm was recorded with Polygonum
hydropiper. More than 3% of plant potassium was found in Enhydra fluctuans, Ipomoea aquatica, Colocasia
esculenta, Spilanthes acmella, and less than 2% of potassium was recorded
with Polygonum hydropiper, Cyperus
rotundus, Echinochloa colonum. This result
indicated that the accumulation of potassium by plant depended on plant species
under investigation.
3.5 Sulfur
Sulfur
contents of the water samples varied from 218.75 ppm at the nearest site to the
point source and then increased in second and third sample sites and with the
further increase in distance the values decreased considerable in Demra area (Table 1). Similar trend in sulfur content
of the water samples was also noticed in Hazaribagh area. Total sulfur content
of the soils decreased gradually with the increase in distance from point
source in Demra area but in Hazaribagh area no such trend was found in case of
soil sulfur. Sulfur contents of the plant samples were in general high compared
values were obtained with Enhydra fluctuans and Echinochloa colonum
respectively. The nutrient contents of the plant species clearly revealed that
accumulation of different plant nutrients varied considerably among plant
species.
3.6 Phosphorus
An
examination of the data presented in table 1, indicated that phosphorus
contents of the water samples were in general higher in the Demra area and
varied between 2.50 and 13.12 ppm. In Hazaribagh area the
Phosphorus contents varied between 1.75 and 3.00 ppm. There was no
definite trend in the change of phosphorus contents with the increase of
distance from point sources. Soil samples collected from the sites
corresponding to the water sampling sites showed variation with out any
definite pattern of variation in both the locations. Colocasia of the plant species was found to contain the highest
percentage of Phosphorus (Table 3). The lowest value of Phosphorus was found in Enhydra fluctuans. Ipomoea aquatica and Spilanthes acmella were found to contain more than 200 ppm of phosphorus.
Table
3 Nutrient elements and heavy metals concentration (For plants parameter)
|
Sample no
|
Total N
ppm
|
K
ppm
|
S
ppm
|
P
ppm
|
Pb
ppm
|
Cd
ppm
|
|
P1
|
28040.00
|
45440.00
|
10850.00
|
40.00
|
2.67
|
1.06
|
|
P2
|
37270.00
|
32550.00
|
6380.00
|
230.00
|
219.18
|
0.32
|
|
P3
|
22340.00
|
40430.00
|
7230.00
|
450.00
|
29.67
|
1.04
|
|
P4
|
24490.00
|
41430.00
|
8410.00
|
350.00
|
32.00
|
0.87
|
|
P5
|
10840.00
|
11890.00
|
5310.00
|
100.00
|
30.88
|
0.82
|
|
P6
|
11870.00
|
18390.00
|
6470.00
|
170.00
|
26.07
|
1.34
|
|
P7
|
7840.00
|
14190.00
|
3360.00
|
70.00
|
36.61
|
1.01
|
Lead
contents varied considerably among the water samples collected from the water
courses of the two locations without showing any definite trend in the change.
The values of water samples were in general higher in Hazaribagh area, the
ranges being 0.580 to 0.390 ppm in Demra location. Lead contents of the soil
samples ranged from 8.52 to 28.94 ppm in Demra region and from 11.72 to 32.88
ppm in Hazaribagh region. Relatively higher values of soil Lead were found in
the second and third sites from the point source in both areas. Among the plant
species, lead concentration was the lowest in Enhydra fluctuans and reached 2.67 ppm. Exceptionally high value of
219.18 ppm was found in Ipomoea aquatica.(Table3) The lead concentration in
other plants species ranged between 26.07 and 36.61 ppm.
3.8 Cadmium
Data presented in Table1
revealed
that in both the areas, Cadmium concentration varied between 0.029 and
0.088 ppm in water samples except DW5 (furthest from the point
source in Demra area) which was approximately 10 fold higher than that of other
sites. Concentrations of Cadmium in soil samples in general varied between
0.416 and 1.576 ppm except DS2 (the second site in Demra areas)
where the value was 18.476 ppm. The concentration of Cadmium in Ipomoea aquatica was however 0.316ppm,
collected from DS2 site which was the lowest value among plant
species. The highest value of 1.344 ppm was recorded with Cyperus rotundus although the Cadmium concentrations were lowest in
both soil and water samples. It was revealed from the data that the
accumulation of Cadmium in plant species did not depend on the concentration of
Cadmium in the growth medium, rather genotype of the plant played significant
role in the accumulation of cadmium.
Fig 2 showed that the fluctuation of
the both sites of Cd distribution. But Tannery Cd is very high in the linked point
(1000
m) with the Buriganga
river. This point
also adjacent with the municipal waste waters. May be that is why the Cd
concentration is higher than that of dying site. The nutrient
concentrations in Ipomoea aquatica.
plant was in general in the optimum range but a hyper-accumulator of Lead. The
nutrient concentrations in Ipomoea aquatica
plant was in general in the optimum range but a hyperaccumulator of
lead. The average value of concentration of heavy metal
in dying industry site of Pb and Cd is 18.48 and 0.95 ppm respectively, and the average
concentration of Cd in tannery is 1.15 fold than that in dying site. Pb
concentration in tannery also showed the same. (Table 2 and 3). May be
in this phenomenon the plant species can not grew up in the tannery industry
site.
Fig 1 Total nitrogen distribution in two sites Fig 2
Cadmium distribution in two sites (Soil)
4. Conclusions
Serious environmental pollution may be occurred by the dying and tannery
industries at Dhaka in Bangladesh.
The results of the present study showing that the Ipomoea
aquatica
Forsk is
a hyper-accumulator species. This plant can easily accumulate the heavy metal
from the industrial solid wastes, effluents contaminated sediment. Ipomoea aquatica species can adapt in the contaminated soils and
acted as potential bio-resource for remediate the pollutant area in Bangladesh.
The future study would be focus on the distribution of heavy metals in dominant
species and physiological response on nutrient and heavy metals concentration
in polluted areas.
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