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, TW_2, TW_3, TW_4, 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

 

3.7 Lead

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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