Heavy metals in water, sediments and wetland plants ... - Springer Link

Environ Monit Assess (2009) 158:433–457 DOI 10.1007/s10661-008-0595-9

Heavy metals in water, sediments and wetland plants in an aquatic ecosystem of tropical industrial region, India Prabhat Kumar Rai

Received: 21 May 2008 / Accepted: 29 September 2008 / Published online: 8 November 2008 © Springer Science + Business Media B.V. 2008

Abstract Concentrations of heavy metals (Cu, Cr, Fe, Pb, Zn, Hg, Ni, and Cd) and macronutrients (Mn) were measured in industrial effluents, water, bottom sediments, and wetland plants from a reservoir, Govind Ballabh (G.B.) Pant Sagar, in Singrauli Industrial region, India. The discharge point of a thermal power plant, a coal mine, and chlor-alkali effluent into the G.B. Pant Sagar were selected as sampling sites with one reference site in order to compare the findings. The concentrations of heavy metals in filtered water, sieved sediment samples (0.4–63 μm), and wetland plants were determined with particleinduced X-ray emission. The collected plants were Aponogeton natans, L. Engl. & Krause, Cyperus rotundus, L., Hydrilla verticillata, (L.f.) Royle, Ipomoea aquatica, Forssk., Marsilea quadrifolia, L., Potamogeton pectinatus, L., Eichhornia crassipes, (Mart.) Solms Monogr., Lemna minor, L., Spirodela polyrhiza (L.) Schleid. Linnaea, Azolla pinnata, R.Br., Vallisneria spiralis, L., and Polygonum amphibium, L. In general, metal concen-

P. K. Rai (B) Forest Ecology Biodiversity and Environmental Sciences, School of Earth Sciences and Natural Resource Management, Mizoram University, Tanhril, Aizawl 796001, India e-mail: [email protected]

tration showed a significant positive correlation between industrial effluent, lake water, and lake sediment ( p < 0.01). Likewise, significant positive correlation was recorded with metals concentration in plants and lake ambient, which further indicated the potential of aforesaid set of wetland macrophytes for pollution monitoring. Keywords Wetland plants · Phytoremediation · Heavy metals · Coalmines · Chlor-alkali industry

Introduction Energy production technologies and environmental pollution are intimately linked with each other (Nriagu 1979, 1996; Rai et al. 2007; Rai 2008b). Energy-intensive industries are the industries that are specifically established for power or electricity production, e.g., thermal power plants and coal mines. Energy-intensive industries and chloralkali industries for the manufacture of agrochemicals deteriorate the water quality of lakes and reservoirs due to discharge of different pollutants, especially a range of deleterious heavy metals like Hg, Cd, Cu, Pb, and Cr (Rai and Tripathi 2008a; Rai 2008c, d). Thermal power plants rely in developing countries on coal combustion originating from coal mines, which is one of the most important anthropogenic emission sources of trace elements

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and an important source of a number of metals (Wagner and Boman 2003). Likewise, chlor-alkali industries are also prevalent in agriculture-based economy like India in order to fulfill the demand of agrochemicals, which also discharge deleterious heavy metals, particularly Hg (Rai and Tripathi 2008b; Rai 2008c). Occurrence of toxic heavy metals in lakes, reservoir, and river water affects the lives of local people that depend upon these water sources for their daily requirements (Rai et al. 2002). Consumption of such aquatic food stuff enriched with toxic metals may cause serious health hazards through food-chain magnification (Khan et al. 2000; Rai and Tripathi 2008b). Ion exchange, reverse osmosis, electrolysis, precipitation, and adsorption are a number of methods available to remove toxic metals from water. However, they are expensive, relatively inefficient, and in most cases, they generate a great amount of waste that is difficult to dispose of (Rai and Tripathi 2007). Furthermore, from the economic point of view, the need of an alternative cost-effective technology is recommended as the cleanup of hazardous wastes by conventional technologies is projected to cost at least $400 billion in the USA alone, based on estimates obtained from various institutions (Salt et al. 1995). Methods using living aquatic plants to remove metals from water can be a viable alternative process. Rai (2008b) extensively reviewed the utility of macrophytes in heavy metals removal from polluted aquatic ecosystems. A number of previous laboratory experiments proved that wetland plants can accumulate heavy metals in their tissues (Rai et al. 1995, 2007; Rai 2007a, b, 2008a, c; Rai and Tripathi 2008a). However, very few studies on concentration potential of aquatic macrophytes have been carried out under field conditions (Cymerman and Kempers 2001; Cardwell et al. 2002; Deng et al. 2004). Therefore, the present paper aimed:

1. To analyze the heavy metal concentrations and correlations in effluent, reservoir water and bed sediments 2. To determine the potential for metal accumulation of different naturally growing

Environ Monit Assess (2009) 158:433–457

wetland plants collected from metal contaminated sites.

Study area and sampling sites Study area The Singrauli region (24◦ 15 E to 82◦ 40.9 N) straddles the border between the states of Madhya Pradesh (MP) and Uttar Pradesh (UP) in northern India. The region is one of India’s most important energy centers from 1970s. Eleven open-cast mining sites, occupying nearly 200 km2 , fuel six thermal power stations that generate 6,800 MW or about 10% of India’s installed generation capacity (Rai and Tripathi 2008a). A chlor-alkali industry, Kannoria chemicals, thermal power plants, and coal mines are responsible for discharge of various metals, especially Hg, into G.B. Pant Sagar. G.B. Pant Sagar is one of Asia’s largest man-made reservoir developed at Rihand dam, and the area of submergence is 46,600 ha (Rai et al. 2007). G.B. Pant Sagar is of great importance to the people of the area, not only to the Singrauli but also to the entire eastern Uttar Pradesh. The water of the reservoir is used for drinking, irrigation, fish farming, bathing, generation of 300 MW hydroelectricity, and industrial purposes. Singrauli region lies in the close vicinity of G.B. Pant Sagar, the industries of the area regularly discharge their effluents into the reservoir. Coal fly ash and ash slurry released from thermal power plants and coal mines pose a serious threat to aquatic ecosystem due to presence of various pollutants particularly heavy metals. Sampling sites Figure 1 represents the location of sampling sites in the surrounding of G.B. Pant Sagar. Belwadah Belwadah is a rural area located near the bank of G.B. Pant Sagar and receives the industrial effluents of Anpara thermal power plant. It is located at a distance of about 20 km from Anpara.


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Fig. 1 Study area and location of different sampling sites

Dongia nala Industrial effluent from Kannoria Chemicals mixed with domestic effluent is finally discharged into Dongia nala, a portion of G.B. Pant Sagar. Ash pond (Bina coal mine) Ash pond of G.B. Pant Sagar receives the effluent of Bina coal mine. It may be contaminated by particulate matters, oil and grease, unburned explosives, and other chemicals. If the coal seems contain high amount of pyrites, the mine water may be acidic and thus pollutes the nearby stream after being discharged. Rihand dam (reference site) Rihand dam is situated near the Pipri location of Singrauli region. Rihand dam connects the Rihand River and G.B. Pant Sagar. In close vicinity of this dam, there is no industrial establishment. All environmental parameters were similar to polluted sites except

the presence of point source of pollution. Spot testing also revealed very low metal concentration at Rihand dam among ten spots investigated. Therefore, it was selected as the reference site in order to compare the data recorded from polluted sites. Sampling location was 3 km away from Rihand dam.

Materials and methods Physico-chemical characteristics For the analysis of physico-chemical characteristics of effluent, water samples from different sampling points were collected (in triplicate) at monthly intervals every second week of each month from January 2005 to December 2005. Triplicates (2 L) were collected at a time in plastic

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bottles from various effluent generation points. Samples were stored with ice and brought to the laboratory for the analysis of the different physico-chemical characteristics (APHA 2000). Heavy metal analysis in water, sediments, and wetland plants A total of nine metals (Cu, Cr, Fe, Mn, Ni, Pb, Zn, Hg, and Cd) were investigated during the present study. Samples for heavy metals analysis were collected quarterly (in triplicate) during the month of March, June, September, and December. Composite samples of water and sediments were first sieved in a 63-μm nylon sieve with the use of Milli-Q water followed by nucleopore polycarbonate filter papers (0.4–60 μm). Filtered water samples from all sampling sites were wet digested in HNO3 /HClO4 (3:1, v/v) mixtures at 80◦ C and “oven dried” sieved sediments (top 15-cm sediment around the plant roots were collected) from all sites were wet digested in HNO3 /HClO4 (3:1, v/v) mixtures at 80◦ C. The concentrations of heavy metals in filtered water, sediment samples, and wetland plants were determined with particleinduced X-ray emission (PIXE). Detection limit of metals ranged from 0.01 mg L−1 to 2.5 mg L−1 . Specimens of the aquatic wetland plants (at least three replicates) were collected from all sampling sites in different seasons of the year depending on their growth stages (Table 1). All the samples were thoroughly washed with tap water. Shoots and roots were separated of Eichhornia crassipes, Polygonum amphibium, and Cyperus rotundus to

assess the accumulation efficiency of two types of organs separately. An elemental analysis of plant material requires the breakdown or oxidation of the organic matrix; to achieve this, plants were oven dried at 80◦ C for 24 h before analysis. This treatment removes the surface mineral encrustations and thus gives a measure of accurate element concentration. The dried plant parts were weighed and ground into water for metal concentration analysis. PIXE has been proven an analytical tool capable of detecting elemental concentrations down to parts per million (Murozono et al. 1999) and useful for the study of wastewater and plant tissue analysis (Mireles et al. 2004). Samples were irradiated 3 to 10 min in a vacuum chamber by 3 MeV protons. A LEGe detector was used to measure the concentrations of heavy metals in the samples. For PIXE spectrum analysis, a least-square fitting computer program based on the pattern analysis method (Murozono et al. 1999) was used. Statistical analysis SPSS 10 statistical package was used for statistical analysis. Statistical comparisons of means were examined with one-way analysis of variance. Correlation coefficients were calculated between metals in effluent and water and effluents and sediments. Pearson correlation coefficients were calculated to examine the relationships between the concentrations of elements in water and in aquatic macrophytes and between sediment and aquatic macrophytes.

Table 1 Macrophytes recorded at different sampling sites Rihand dam

Belwadah

Dongia Nala

Ash pond

Aponogeton natans, L. Engl. & Krause Ceratophyllum demersum, L.

Eichhornia crassipes, (Mart.) Solms Monogr. Lemna minor, L.

Azolla piñata, R.Br.

Azolla pinnata, R.Br.

Eichhornia crassipes, (Mart.) Solms Monogr. Lemna minor, L.

Lemna minor, L.

Cyperus rotundus, L. Hydrilla verticillata, (L.f.) Royle Ipomoea aquatica, Forssk. Marsilea quadrifolia, L. Potamogeton pectinatus, L. Potamogeton crispus, L.

Vallisneria spiralis, L. Polygonum amphibium, L.

Spirodela polyrhiza (L.) Schleid. Linnaea Vallisneria spiralis, L.


Results Physico-chemical characteristics and heavy metals analysis of effluents discharged from various industries The physico-chemical characteristics and heavy metal concentration of effluents from all the industries before being mixed with the reservoir water are shown in Tables 2 and 3, while the metal concentration in water and sediments in the reservoir are shown in Tables 4 and 5, respectively. In effluents, values recorded for most of the metals were well above the permissible limit prescribed by Central Pollution Control Board (CPCB) and Environmental Protection Agency (EPA) (Table 3). Furthermore, the aforesaid table revealed that Anpara effluent was most polluted in context of all metals except Hg. Heavy metals in reservoir water and sediments Copper In water, Cu concentrations were recorded maximum (27 ± 1.4 mg L−1 ) at Belwadah site followed by Ash pond (6.8 ± 1.1 mg L−1 ) and Dongia nala (1.2 ± 0.2 mg L−1 ). Cu concentrations were recorded minimum (0.01 ± 0.0 mg L−1 ) at Rihand dam (reference site) during September. In sediment, Cu concentration was maximum (28 ± 2.7 mg kg−1 ) at Ash pond site followed by Belwadah (20 ± 2.1 mg kg−1 ) and Dongia nala (3.6 ± 1.1 mg kg−1 ), while it was minimum (0.6 ± 0.1 mg kg−1 ) at Rihand dam. Regarding seasonal variation, it is evident from Tables 4 and 5 that metals content in reservoir water and sediments were high during the whole year, particularly during pre-summer and summer season, i.e., March and June. However, comparatively low value for all metals were recorded during rainy season, i.e., September, which may be due to the result of dilution due to addition of rain water and subsequent outflow of reservoir water. Chromium In water, Cr concentrations were recorded maximum (34 ± 4.1 mg L−1 ) at Belwadah site followed by Dongia nala (0.8 ± 0.2 mg L−1 ) and Ash pond (0.2 ± 0.01 mg L−1 ). Cr concentrations were observed below detection limit (BDL) at Rihand dam during September. In sedi-

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ment, Cr concentrations were recorded maximum (30 ± 2.3 mg kg−1 ) at Belwadah site followed by Ash pond (8.5 ± 1.2 mg kg−1 ) and Dongia nala (1.4 ± 0.9 mg kg−1 ), while it was minimum (0.3 ± 0.1 mg kg−1 ) at Rihand dam during the month of September. Seasonal variations followed almost the same trend of monthly variation as Cu. Metals content in reservoir water and sediments were particularly high during pre-summer and summer season, i.e., March and June. Comparatively low values for all metals were found during rainy season, i.e., September. Iron In water, Fe concentrations were recorded maximum (41.3 ± 1.7 mg L−1 ) at Ash pond site followed by Belwadah (41 ± 2.9 mg L−1 ) and Dongia nala (5.1 ± 0.4 mg L−1 ). Fe concentration was minimum (0.9 ± 0.1 mg L−1 ) at Rihand dam during the month of September. In sediment, Fe concentration was maximum (85 ± 4.1 mg kg−1 ) at Ash pond site followed by Belwadah (69 ± 5.0 mg kg−1 ) and Dongia nala (12 ± 1.2 mg kg−1 ), while it was minimum (1.2 ± 0.2 mg kg−1 ) at the reference site during the month of September. Seasonal variations followed almost the same trend of monthly variation as for Cu and Cr. Manganese In water, Mn concentrations were recorded maximum (22 ± 1.9 mg L−1 ) during June at Belwadah site followed by Dongia nala (3.1 ± 0.9 mg L−1 ) and Rihand dam (1.5 ± 0.2 mg L−1 ). Mn concentration was minimum (0.02 ± 0.00 mg L−1 ) at Ash pond site during September. In sediment, Mn concentration was maximum (133 ± 6.2 mg kg−1 ) at Ash pond site followed by Belwadah (110 ± 7.1 mg kg−1 ) and Dongia nala (12 ± 1.4 mg kg−1 ), while it was minimum (1.6 ± 0.2 mg kg−1 ) at Rihand dam during the month of June. Seasonal variations followed almost the same trend. Nickel In water, Ni concentrations were recorded maximum (36 ± 3.1 mg L−1 ) at Belwadah site followed by Ash pond (3.7 ± 0.7 mg L−1 ) and Dongia nala (1.3 ± 0.2 mg L−1 ), while Ni concentrations were found minimum (0.01 ± 0.0 mg L−1 ) at Rihand dam during September. In

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Table 2 Physico-chemical characteristics of effluents discharged into G.B. Pant Sagar Physico-chemical parameters Temperature (◦ C) Lowest value Highest value TSS (mg L−1 ) Lowest value Highest value TDS (mg L−1 ) Lowest value Highest value pH Lowest value Highest value Electrical conductivity (micro mho cm−1 ) Lowest value Highest value BOD Lowest value Highest value Total acidity (mg L−1 ) Lowest value Highest value Alkalinity (mg L−1 ) Lowest value Highest value Chloride (mg L−1 ) Lowest value Highest value Hardness (mg L−1 CaCO3 ) Lowest value Highest value Nitrate (mg L−1 ) Lowest value Highest value Phosphate (mg L−1 ) Lowest value Highest value

Anpara

Kannoria

Bina

27 ± 1.2 41 ± 1.4

25 ± 1.1 39 ± 1.4

26 ± 1.4 36 ± 1.3

995 ± 22.8 2750 ± 144

98 ± 2.8 329 ± 3.1

199 ± 2.2 570 ± 4.1

510 ± 17.4 850 ± 26.2

390 ± 20.4 725 ± 34

760 ± 8.9 1430 ± 101

7.53 ± 0.3 8.55 ± 0.2

2.9 ± 0.12 4.3 ± 0.2

5.8 ± 0.11 7.5 ± 2.0

210 ± 4.8 630 ± 9.3

810 ± 41 1990 ± 105

193 ± 5.2 550 ± 3.9

138 ± 4.8 175 ± 7.3

74 ± 6.9 98 ± 7.6

129 ± 7.9 158 ± 8.3

21 ± 1.2 40 ± 1.4

121 ± 11.7 489 ± 14.0

19.9 ± 1.9 37.9 ± 2.6

110 ± 8.1 330 ± 4.3

63 ± 8.0 117 ± 1.9

87.5 ± 1.6 290 ± 1.4

370 ± 11.1 593 ± 10.3

990 ± 33 2500 ± 99.3

269 ± 6.4 430 ± 9.2

354 ± 21.6 633 ± 23.7

690 ± 3.9 980 ± 47

290 ± 7.1 489 ± 12.3

43 ± 9.6 159 ± 11.3

37.8 ± 1.8 68.4 ± 1.3

149 ± 1.9 391 ± 18.7

3.3 ± 0.3 9.2 ± 0.7

2.2 ± 0.3 7.3 ± 0.7

4.1 ± 0.7 10.4 ± 0.9

Table 3 Metals concentration in effluent before being discharged into G.B. Pant Sagar (all values in mg L−1 ) Metals examined

Anpara

Kannoria

Bina

Standard (CPCB 1998)

Standard (USEPA 2002)

Cu Cr Fe Mn Ni Pb Zn Hg Cd

39 ± 3.1 44 ± 4.6 94 ± 9.5 98 ± 11.0 54 ± 8.9 19.8 ± 3.4 38 ± 8.4 6.5 ± 1.4 6.0 ± 1.0

5.9 ± 1.0 7.9 ± 1.1 16.5 ± 1.4 18.9 ± 1.6 3.7 ± 0.8 5.9 ± 0.7 4.9 ± 0.5 9.8 ± 2.5 3.1 ± 0.3

17.5 ± 1.4 3.9 ± 0.7 18 ± 1.3 15 ± 1.7 8.6 ± 1.4 3.0 ± 0.4 12.0 ± 1.0 0.4 ± 0.01 3.0 ± 0.7

3.0 0.10 3.0 5.0 3.0 0.10 5.0 0.01 2.0

5.0 2.0 100 5.0 5.0 0.10 5.0 0.01 1.0

CPCB Central Pollution Control Board, Government of India, New Delhi (1998), EPA Environmental Protection Agency (USA)

Belwadah March June Sept. Dec. Dongia Nala March June Sept. Dec. Ash Pond March June Sept. Dec. Rihand dam March June Sept. Dec.

Month

0.7 ± 0.2 0.8 ± 0.2 0.3 ± .01 0.5 ± .09 0.18 ± .01 0.2 ± .01 .09 ± .01 0.1 ± .04 .02 ± .021 .03 ± .031

0.9 ± 0.1 1.2 ± 0.2 0.6 ± 0.1 0.8 ± 0.2

5.4 ± 1.3 6.8 ± 1.1 4.3 ± 1.2 4.9 ± 0.9

0.01 ± .01 0.02 ± .02 0.01 ± 0.0 0.1 ± 0.03 – 0.01 ± .01

29 ± 2.7 34 ± 4.1 19 ± 1.6 32 ± 1.8

Cr

22 ± 2.1 27 ± 1.4 16 ± 1.4 24 ± 1.8

Cu

1.1 ± 0.2 1.2 ± 0.4 0.9 ± 0.1 1.1 ± 0.2

41.3 ± 1.7 38 ± 3.1 27.5 ± 1.4 34 ± 2.7

4.6 ± .06 5.1 ± 0.4 1.2 ± 0.1 3.9 ± 0.9

33 ± 2.4 41 ± 2.9 22 ± 2.2 37 ± 2.7

Fe

1.3 ± 0.4 1.5 ± 0.2 1.1 ± 0.2 1.4 ± 0.3

0.2 ± .01 0.4 ± .09 .02 ± 0.0 0.3 ± .04

2.9 ± 0.7 3.1 ± 0.9 1.8 ± 0.2 2.6 ± 0.1

18 ± 1.4 22 ± 1.9 11 ± 1.1 19 ± 1.0

Mn

Table 4 Metal concentrations in G.B. Pant Sagar water (all values in mg L−1 )

.07 ± .01 .09 ± .01 .01 ± 0.0 .08 ± .01

3.2 ± 0.6 3.7 ± .7 1.9 ± 0.4 2.1 ± 0.9

0.9 ± 0.1 1.3 ± 0.2 0.4 ± .09 0.6 ± .07

26 ± 1.9 36 ± 3.1 16 ± 1.2 29 ± 1.8

Ni

.06 ± .01 .08 ± .01 .02 ± 0.0 .09 ± .01

0.9 ± 0.1 1.1 ± 0.2 0.3 ± .09 0.4 ± 0.1

0.7 ± 0.1 1.1 ± 0.2 0.3 ± .01 0.4 ± .09

13 ± 0.9 17 ± 1.7 8 ± 0.79 15 ± 1.2

Pb

1.0 ± 0.2 1.2 ± 0.3 0.8 ± 0.1 0.9 ± 0.1

4.2 ± 0.90 5.1 ± 0.8 2.9 ± 0.30 3.2 ± 0.4

3.0 ± 0.1 3.2 ± 0.3 1.9 ± .09 1.7 ± 0.1

13 ± .01 21 ± 1.1 11 ± 0.9 14 ± 1.1

Zn

– – – –

.17 ± .01 .19 ± .01 .01 ± 0.0 0.1 ± .01

3.9 ± 0.3 4.1 ± 0.4 2.7 ± 0.1 2.9 ± 0.1

1.8 ± 0.1 2.0 ± 0.3 1.1 ± 0.3 1.7 ± 0.3

Hg

0.01 ± 0.0 0.02 ± 0.0 .01 ± 0.00 0.01 ± 0.01

1.0 ± 0.3 1.2 ± 0.2 0.6 ± 0.01 0.8 ± 0.1

0.7 ± .09 0.9 ± 0.1 0.3 ± .05 0.5 ± .03

4.1 ± 0.6 4.5 ± 0.9 2.9 ± 0.4 3.7 ± 0.8

Cd

Environ Monit Assess (2009) 158:433–457 439

Cu

Belwadah March 20 ± 2.1 June 17 ± 1.9 Sept. 14 ± 1.7 Dec. 18 ± 1.3 Dongia Nala March 3.6 ± 1.1 June 2.4 ± 0.5 Sept. 1.9 ± 0.6 Dec. 2.5 ± 0.9 Ash Pond March 28 ± 2.7 June 26 ± 2.3 Sept. 17 ± 2.0 Dec. 21 ± 2.1 Rihand dam (reference site) March 0.6 ± 0.1 June 0.4 ± 0.09 Sept. 0.6 ± 0.1 Dec. 0.5 ± 0.1

Month 69 ± 5.0 48 ± 4.9 40 ± 3.7 65 ± 6.2 12 ± 1.2 8.0 ± 1.0 6.0 ± 0.9 10 ± 1.3 85 ± 4.1 79 ± 4.0 42 ± 3.7 51 ± 3.9 1.9 ± 0.3 2.1 ± 0.4 1.2 ± 0.2 1.9 ± 0.3

1.4 ± 0.9 1.2 ± 0.7 0.7 ± 0.1 1.3 ± 0.3 8.5 ± 1.2 7.9 ± 1.0 3.9 ± 0.9 4.1 ± 0.9 0.5 ± 0.1 0.4 ± 0.9 0.3 ± 0.1 0.4 ± 0.08

Fe

30 ± 2.3 19 ± 2.1 16 ± 1.9 27 ± 1.7

Cr

2.1 ± 0.3 1.6 ± 0.2 2.3 ± 0.1 2.0 ± 0.1

133 ± 6.2 127 ± 7.1 90 ± 5.1 96 ± 5.3

12 ± 1.4 9.0 ± 1.5 7.0 ± 1.1 10 ± 1.0

110 ± 7.1 90 ± 6.2 78 ± 6.7 105 ± 7.8

Mn

Table 5 Metal concentrations in G.B. Pant Sagar sediments (all values in mg kg−1 )

0.3 ± 0.09 0.1 ± 0.08 0.4 ± 0.03 0.2 ± 0.01

27 ± 2.9 23 ± 2.6 12 ± 1.3 18 ± 1.7

0.8 ± 0.1 0.7 ± 0.1 0.4 ± 0.1 0.5 ± 0.1

35 ± 3.3 31 ± 3.0 23 ± 2.9 33 ± 2.8

Ni

0.2 ± 0.01 0.18 ± 0.01 0.3 ± 0.01 0.19 ± 0.01

7.5 ± 1.1 6.0 ± 1.0 5.3 ± 0.9 6.8 ± 0.8

3.1 ± 0.9 2.3 ± 0.7 1.2 ± 0.2 1.8 ± 0.3

10.0 ± 1.0 9.0 ± 0.7 6.0 ± 0.9 8.0 ± 0.5

Pb

1.7 ± 0.5 1.5 ± 0.4 1.9 ± 0.3 1.3 ± 0.1

57 ± 2.9 53 ± 2.7 40 ± 1.9 49 ± 2.3

7.9 ± 1.0 7.4 ± 0.9 6.1 ± 1.1 6.8 ± 0.7

55 ± 3.9 51 ± 3.3 47 ± 3.1 49 ± 3.7

Zn

0.05 ± 0.01 0.02 ± 0.0 0.01 ± 0.0 0.03 ± 0.01

3.2 ± 0.4 2.9 ± 0.5 1.0 ± 0.1 2.3 ± 0.3

6.8 ± 0.4 5.2 ± 0.4 4.1 ± 0.2 4.9 ± 0.6

1.2 ± 0.3 1.2 ± 0.2 1.0 ± 0.2 0.8 ± 0.1

Hg

.2 ± 0.09 .1 ± 0.01 .3 ± 0.08 .19 ± .07

4.6 ± 1.0 4.1 ± 0.7 2.7 ± 0.5 3.8 ± 0.9

1.2 ± 0.9 0.8 ± 0.2 0.4 ± 0.1 0.6 ± 0.1

1.4 ± 0.3 1.3 ± 0.2 1.1 ± 0.4 1.2 ± 0.1

Cd

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sediment, Ni concentrations was maximum (35 ± 3.3 mg kg−1 ) at Belwadah site followed by Ash pond (27 ± 2.9 mg kg−1 ) and Dongia nala (0.8 ± 0.1 mg kg−1 ), while it was minimum (0.1 ± 0.08 mg kg−1 ) at Rihand dam during the month of June. Seasonal variations followed almost the same trend of monthly variation as others. Lead In water, Pb concentrations were recorded maximum (17 ± 1.7 mg L−1 ) at Belwadah site followed by Ash pond (1.1 ± 0.2 mg L−1 ) and Dongia nala (1.1 ± 0.2 mg L−1 ). Pb concentration was minimum (0.02 ± 0.0 mg L−1 ) at Rihand dam during September. In sediment, Pb concentration was maximum (10 ± 1.0 mg kg−1 ) at Belwadah site followed by Ash pond (7.5 ± 1.1 mg kg−1 ) and Dongia nala (3.1 ± 0.9 mg kg−1 ), while it was minimum (0.18 ± 0.01 mg kg−1 ) at Rihand dam during the month of June. Seasonal variations followed almost the same trend of monthly variation as others. Zinc In water, Zn concentrations were recorded maximum (21 ± 1.1 mg L−1 ) at Belwadah site during June followed by Ash pond (5.1 ± 0.8 mg L−1 ) and Dongia nala (3.2 ± 0.3 mg L−1 ). Zn concentration was minimum (0.8 ± 0.1 mg L−1 ) at the reference site during September, whereas, in sediment, Zn concentration was maximum (57 ± 2.9 mg kg−1 ) at Ash pond site followed by Belwadah (55 ± 3.9 mg kg−1 ) and Dongia nala (7.9 ± 1.0 mg kg−1 ) while it was minimum (1.3 ± 0.1 mg kg−1 ) at the reference site during the month of December. Mercury In water, Hg concentrations were recorded maximum (4.1 ± 0.4 mg L−1 ) at Dongia nala site followed by Belwadah (2.0 ± 0.3 mg L−1 ) and Ash pond (0.19 ± 0.01 mg L−1 ). Hg concentrations were found BDL at Rihand dam (reference site) during all the seasons. In sediment, Hg concentration was maximum (6.8 ± 0.4 mg kg−1 ) at Dongia nala site followed by Ash pond (1.2 ± 0.4 mg kg−1 ) and Belwadah (1.2 ± 0.3 mg kg−1 ), while it was minimum (0.02 ± 0.0 mg kg−1 ) at Rihand dam during the month of June. Seasonal variations followed almost the same trend of monthly variation as others.

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Cadmium In water, Cd concentrations were recorded maximum (4.5 ± 0.9 mg L−1 ) at Belwadah site followed by Ash pond (1.2 ± 0.2 mg L−1 ) and Dongia nala (0.9 ± 0.1 mg L−1 ). Cd concentration was minimum (0.01 ± 0.00 mg L−1 ) at Rihand dam during September. In sediment, Cd concentration was maximum (4.6 ± 1.0 mg kg−1 ) at Ash pond site (unlike metal concentration in water) followed by Belwadah (1.4 ± 0.3 mg kg−1 ) and Dongia nala (1.2 ± 0.9 mg kg−1 ), while it was minimum (0.1 ± 0.01 mg kg−1 ) at Rihand dam during the month of June. Seasonal variations followed almost the same trend of monthly variation as abovementioned metals. At some sites, metal concentrations in sediment were recorded minimum during the month of June. All the metals analyzed in wastewaters followed the same seasonal trend, i.e., high during the summer season, from March to June, low during the rainy month, starting from September, which may be explained as a rain-dilution effect. The most polluted site was Belwadah, i.e., waters and sediments had the highest concentration of all the relevant metals except Hg, as its maximum is observed at Dongia nala. In contrast, Dongia nala showed, in general, comparatively lower concentrations with the exception of Hg. The reference site was characterized by the presence of low concentrations of metals in waters and in sediments (Tables 4 and 5). Statistical analysis revealed positive and highly significant correlation ( p < 0.01) between heavy metals in effluent and metals in water (range, 0.934–0.985) and metals in effluent and metals in sediment (range, 0.913–0.973), whereas there was positive and significant correlation ( p < 0.01) between metals in lake sediment and metals in lake water (0.733–0.891). Heavy metal accumulation in macrophytes Figure 2a–r represents the metal accumulation in naturally growing wetland plants at different sampling sites. Maximum eight macrophytes were recorded from the reference site near Rihand dam (least polluted site). Minimum three macrophytes were recorded from Belwadah (most polluted site), while Dongia nala and Ash pond recorded five and four macrophytes, respectively (Table 5).

442

a)

Eichhornia(shoot) belwadah

250

metal mgKg-1 in biomass

Fig. 2 a–r Metals removal by naturally occurring wetland plants at different sampling sites


200

150

100

50

0 Cu

Cr

Fe

Mn

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Zn

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Cd

Zn

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metals

b)

Eichhornia(root) belwadah 1600


1400 1200 1000 800 600 400 200 0 Cu

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metals

Some macrophytes, e.g., P. amphibium and C. rotundus are of semi-aquatic nature and were recorded along the reservoir bank. Copper Cu accumulation was recorded maximum by E. crassipes growing at Belwadah followed by Vallisneria spiralis at Dongia nala, while the accumulation was observed minimum by Marsilea quadrifolia growing at Rihand dam (reference site). At Belwadah, E. crassipes removed 560 ± 15.0 mg kg−1 Cu through root and 51 ± 5.1 mg kg−1 Cu through shoot, while Lemna minor at Belwadah removed 398 ± 4.6 mg kg−1 Cu.

Spirodela polyrhiza accumulated least amount of Cu (97 ± 4.1 mg kg−1 ) among plants collected from Belwadah. At Dongia nala, after V. spiralis, L. minor ranked second accumulating 440 ± 10.7 mg kg−1 Cu, while E. crassipes showed comparatively less accumulated Cu (root, 315 ± 10.0 mg kg−1 Cu; shoot, 34 ± 3.1 mg kg−1 Cu) in biomass. Azolla pinnata was found to be the lowest (257 ± 8.1 mg kg−1 ) Cu accumulator at Dongia nala. P. amphibium was found to be the most efficient accumulator (root, 413 ± 10.3 mg kg−1 Cu; shoot, 69 ± 5.9 mg kg−1 Cu) of Cu at Ash pond showing better performance

Environ Monit Assess (2009) 158:433–457 Fig. 2 (continued)

443

c)

Lemna minor(belwadah) 2000


1800 1600 1400 1200 1000 800 600 400 200 0 Cu

Cr

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Hg

Cd

Zn

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metals

d)

Spirodela(belwadah) 350

metal (mgkg-1) biomass

300

250

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0 Cu

Cr

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metals

than Cu accumulated (root, 315 ± 10.0 mg kg−1 Cu; shoot, 43± 4.6 mg kg−1 Cu) at Dongia nala. In comparison with P. amphibium and L. minor, A. pinnata accumulated less (284 ± 12.0 mg kg−1 Cu) copper at Ash pond site. L. minor accumulated 410± 10.3 mg kg−1 Cu at Ash pond site; however, it was comparatively less when compared with amount accumulated at Dongia nala and slightly higher when compared with Cu accumulated at Belwadah. At Rihand dam (reference site), significant Cu accumulator were C. rotundus (shoot, 39 ± 3.1 mg kg−1 Cu; root, 203 ±

15.1 mg kg−1 Cu), Potamogeton pectinatus (6 ± 0.9 mg kg−1 Cu), and Potamogeton crispus (5.2 ± 1.1 mg kg−1 Cu). Chromium Cr accumulation was maximum (1,758 ± 33.9 mg kg−1 ) by V. spiralis at Dongia nala and minimum (1.4 ± 0.4 mg kg−1 ) at Rihand dam site by Ceratophyllum demersum. At Belwadah, L. minor recorded maximum (1,700 ± 60.0 mg kg−1 ) Cr accumulation followed by E. crassipes (root, 250 ± 15.0 mg kg−1 ; shoot, 54 ± 5.0 mg kg−1 ). In addition to V. spiralis (1,758 ±

444 Fig. 2 (continued)


e) Polygonum(root) dongia nala

1600

metal (mgKg-1) in biomass

1400 1200 1000 800 600 400 200 0 Cu

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metals

f)

Polygonum (shoot) dongia nala 140


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100

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60

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33.9 mg kg−1 ) at Dongia nala, which accumulated maximum Cr, L. minor (1,750 ± 32.9 mg kg−1 ) Cr, E. crassipes (root, 309 ± 13.1 mg kg−1 ; shoot, 23 ± 2.4 mg kg−1 ), and A. pinnata (281 ± 7.8 mg kg−1 ) were also found to be efficient Cr accumulator. The Cr accumulation in E. crassipes and L. minor was comparatively higher at Dongia nala, as compared with the Cr accumulated by these plants at Belwadah. L. minor showed maximum (560 ± 10.0 mg kg−1 ) Cr accumulation at Ash pond, but it was comparatively lower

when compared with Belwadah and Dongia nala. P. amphibium showed 260 ± 9.3 mg kg−1 Cr in root and 18 ± 3.0 mg kg−1 in shoot, while minimum accumulation (126 ± 3.9 mg kg−1 ) of Cr was shown by A. pinnata at Ash pond site. At Rihand dam, C. rotundus showed significant (root, 510 ± 10 mg kg−1 ; shoot, 30 ± 2.5 mg kg−1 ) Cr accumulation followed by Hydrilla verticillata (4.34 ± 1.0 mg kg−1 ), Aponogeton natans (3.74 ± 0.9 mg kg−1 ), Ipomoea aquatica (3.03 ± 0.8 mg kg−1 ), M. quadrifolia (2.98 ± 0.9 mg kg−1 ),


445

g)

Eichhornia(root) dongia nala

1600


1400 1200 1000 800 600 400 200 0 Cu

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metals

h)

Eichhornia(shoot) belwadah

250


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metals

P. pectinatus (2.6 ± 0.5 mg kg−1 ), and P. crispus (1.7 ± 0.4. mg kg−1 ). Iron P. amphibium showed maximum (root, 1,651 ± 37.0 mg kg−1 ; shoot, 230 ± 15.0 mg kg−1 ) Fe accumulation at Ash pond of G.B. Pant Sagar followed by L. minor (1,403 ± 33.5 mg kg−1 ), which was also collected from Ash pond. Furthermore, P. amphibium accumulated very high Fe content in biomass (root, 1,385 ± 78.1 mg kg−1 ; shoot, 117 ± 7.9 mg kg−1 Fe) at Dongia nala. Likewise, A. pinnata accumulated 880 ± 17.3 mg kg−1

Fe at Ash pond followed by 670 ± 14.1 mg kg−1 Fe at Dongia nala, and E. crassipes accumulated root, 598 ± 13.5 mg kg−1 ; shoot, 117 ± 7.9 mg kg−1 Fe at Dongia nala, while E. crassipes at Belwadah showed 590 ± 20.0 mg kg−1 Fe accumulation with root and 160 ± 7.0 mg kg−1 Fe in shoot. At Rihand dam, P. pectinatus (590 ± 13.7 mg kg−1 Fe), P. crispus (402 ± 12.3 mg kg−1 Fe), C. rotundus (root, 185 ± 8.9 mg kg−1 Fe; shoot, 90 ± 7.4 mg kg−1 Fe), Hydrilla (88 ± 3.8 mg kg−1 Fe), and C. demersum (70 ± 6.1 mg kg−1 Fe) were certain plants, which accumulated Fe in appreciable amount, while Fe



i)

Lemna minor (dongia nala)

2000 1800

metal (mgKg-1)

1600 1400 1200 1000 800 600 400 200 0 Cu

Cr

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Zn

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Zn

Hg

Cd

metals Vallisneria (dongia nala)

j) 2000


1800 1600 1400 1200 1000 800 600 400 200 0 Cu

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Mn

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metals

accumulation was minimum in I. aquatica (10 ± 1.0 mg kg−1 Fe).

was minimum (18 ± 2.1 mg kg−1 ) in I. aquatica of Rihand dam site.

Manganese Maximum Mn accumulation was recorded in A. pinnata (1,014 ± 20.3 mg kg−1 ) of Ash pond site followed by C. rotundus (988 ± 31.1 mg kg−1 in root; 149 ± 14.1 mg kg−1 in shoot) of Rihand dam (reference site), L. minor (990 ± 19.1 mg kg−1 ) of Ash pond site, E. crassipes (root, 880 ± 28.5 mg kg−1 ; shoot, 123 ± 11.3 mg kg−1 Mn) of Belwadah, and V. spiralis (836 ± 17.1 mg kg−1 Mn), while Mn accumulation

Nickel Maximum Ni accumulation was recorded in A. pinnata (1,758 ± 101 mg kg−1 ) collected from Dongia nala followed by L. minor (1, 667 ± 101.3 mg kg−1 ) and V. spiralis (1, 630 ± 110 mg kg−1 ) also growing at Dongia nala, L. minor (1,600 ± 91.3 mg kg−1 ) collected from Belwadah, Azolla (870 ± 48 mg kg−1 ) of Ash pond, and C. rotundus (root, 303 ± 13.0 mg kg−1 ; shoot, 38 ± 4.4 mg kg−1 ) at Rihand dam site, while


447

k)

Azolla (dongia nala)

2000


1800 1600 1400 1200 1000 800 600 400 200 0 Cu

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metals

l)

Azolla (ashpond)

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metals

it was recorded minimum in C. demersum (0.9 ± 0.1 mg kg−1 ) growing at Rihand dam site. Ni accumulation was also significant in E. crassipes (root, 264 ± 7.9 mg kg−1 ; shoot, 87 ± 4.8 mg kg−1 ) at Dongia nala, E. crassipes (root, 260 ± 8.1 mg kg−1 ; shoot, 80 ± 5.9 mg kg−1 ) growing at Belwadah and in P. amphibium (root, 170 ± 36 mg kg−1 ; shoot, 28 ± 3.8 mg kg−1 ) growing at Dongia nala. Lead L. minor accumulated maximum Pb (1, 800 ± 54.0 mg kg−1 ) at Belwadah followed

by C. rotundus (root, 933 ± 21.0 mg kg−1 ; shoot, 23 ± 2.4 mg kg−1 ) at Rihand dam site, L. minor (540 ± 6.9 mg kg−1 ) at Ash pond, A. pinnata (417 ± 7.8 mg kg−1 ) at Dongia nala, P. amphibium (317 ± 3.0 mg kg−1 ; shoot, 38 ± 4.1 mg kg−1 ) at Dongia nala and V. spiralis (319 ± 9.0 mg kg−1 ) again at Dongia nala, while C. demersum accumulated minimum (10.6 ± 1.3 mg kg−1 ) Pb collected from Rihand dam site. E. crassipes (root, 267 ± 9.0 mg kg−1 ; shoot, 37 ± 3.0 mg kg−1 ) and L. minor (267 ± 7.9 mg kg−1 )



m)

Lemna minor (ashpond)

1600


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Zn

Hg

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metals

n)

Polygonum (root) ashpond

1800

metal (mgKg-1) ashpond

1600 1400 1200 1000 800 600 400 200 0 Cu

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metals

showed almost equal accumulation. P. amphibium (root, 191 ± 4.5 mg kg−1 ; shoot, 23 ± 3.4 mg kg−1 ), S. polyrhiza, P. crispus (43 ± 5.0 mg kg−1 ), and A. natans (44 ± 1.0 mg kg−1 ) also showed Pb accumulation up to significant extent. Zinc E. crassipes at Dongia nala recorded maximum Zn accumulation (root, 1,400 ± 74.3 mg kg−1 ; shoot, 197 ± 11.9 mg kg−1 ) followed by E. crassipes (root, 1,200 ± 38.0 mg kg−1 ;

shoot, 190 ± 14.0 mg kg−1 ) at Belwadah, V. spiralis (1,298 ± 53.0 mg kg−1 ) at Dongia nala, L. minor (1,267 ± 49.0 mg kg−1 ) at Dongia nala, A. pinnata (936 ± 53.0 mg kg−1 ) at Ash pond, L. minor (844 ± 21.0 mg kg−1 ) at Ash pond, L. minor (823 ± 21.0 mg kg−1 ) at Belwadah, H. verticillata (691 ± 17.7 mg kg−1 ) at Rihand dam, P. amphibium (root, 590 ± 17.2 mg kg−1 ; shoot, 61 ± 10.0 mg kg−1 ) at Dongia nala, C. rotundus (root, 620 ± 15.5 mg kg−1 ; shoot,


449

o) Polygonum (shoot) ashpond

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p)

Rihand dam site (control)

800 A. natans C. demerrsum Hydrilla


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10 ± 1.0 mg kg−1 ), and C. demersum (432 ± 21.1 mg kg−1 ), while P. pectinatus accumulated minimum (29.1 ± 2.7 mg kg−1 ) Zn at Rihand dam. Mercury E. crassipes accumulated maximum Hg (root, 991 ± 19.0 mg kg−1 ; shoot, 103 ± 9.1 mg kg−1 ) growing at Dongia nala followed by V. spiralis (1,071 ± 17.0 mg kg−1 ) at Dongia nala, C. rotundus (root, 620 ± 15.5 mg kg−1 ; shoot, 10 ± 1.0 mg kg−1 ) at Rihand dam (reference site), P. amphibium (root, 590 ± 16.9 mg kg−1 ;

shoot, 40 ± 6.2 mg kg−1 ) collected from Dongia nala, A. pinnata (505 ± 13.0 mg kg−1 ) also from Dongia nala, E. crassipes (root, 464 ± 18.0 mg kg−1 ; shoot, 39 ± 3.1 mg kg−1 ) at Rihand dam, A. pinnata (370 ± 12.2 mg kg−1 ) of Ash pond site, L. minor (181 ± 12.0 mg kg−1 ) collected from Dongia nala, L. minor (149 ± 13.8 mg kg−1 ) collected from Belwadah, while A. natans accumulated minimum (0.23 ± 0.09 mg kg−1 ) Hg in the biomass collected from Rihand dam site, which was selected as reference site.



q)

Rihand dam (control site) 700


600

Ipomea Marsilea P.Pectinatus P. crispus

500

400

300

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0 Cu

Cr

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Mn

Cadmium E. crassipes collected from Belwadah site accumulated maximum Cd (root, 1,500 ± 47 mg kg−1 ; shoot, 165 ± 10.1 mg kg−1 ) followed by L. minor (1495 ± 199.5 mg kg−1 ) of Belwadah, E. crassipes (root, 1,013 ± 27.2 mg kg−1 ; shoot, 120 ± 7.1 mg kg−1 ) growing at Dongia nala, L. minor (1,015 ± 27.8 mg kg−1 ) collected from Dongia nala, V. spiralis (836 ± 23.3 mg kg−1 ) of Dongia nala, C. rotundus (root, 740 ± 23.0 mg kg−1 ; shoot, 120 ± 7.1 mg kg−1 ) at Rihand dam site, P. amphibium (root, 403 ± 13.9 mg kg−1 ; shoot, 21 ± 1.3 mg kg−1 ) collected from Dongia nala, L. minor (353 ± 16.4 mg kg−1 ) at Ash pond, A. pinnata (313 ± 17.9 mg kg−1 ) at Ash pond, and S. polyrhiza (118 ± 11.0 mg kg−1 ) of Belwadah, while C. demersum collected from

Ni

Pb

Zn

Hg

Cd

metals

r)

Rihand dam (reference site) accumulated minimum (0.34 ± 0.09 mg kg−1 ) Cd in plant biomass.

Discussion The present study evidenced that the heavy metals in industrial effluent and reservoir water were above permissible limit prescribed by Bureau of Indian Standards (1983), CPCB (1998), and US EPA (2002). Once discharged in the aquatic environment, metals such as Cd, Cu, Pb, and Zn undergo many physical, chemical, and biological transformations (Rai 2008c). Most heavy metals in aquatic


ecosystems eventually become associated with particulate matter, which settles and accumulate in the bottom sediments. Present study also revealed high concentrations of deleterious metals in bed sediments. The accumulation of pollutants in the bottom sediments of water bodies and the remobilization of these substances from the latter are two of the most important mechanisms in the regulation of pollutant concentrations in an aquatic environment (Linnik and Zubenko 2000). Furthemore, under certain conditions, bottom sediments can be a strong source of secondary water pollution (Denisova et al. 1989; Linnik et al. 1993; Rai 2008c). The heavy metal pollution of aquatic ecosystems is often most obviously reflected in high metal levels in sediments and macrophytes than in elevated concentrations in water. Lentic ecosystems (G.B. Pant Sagar in present case) with low pollutant dispersal efficiency and self-purification capacity (e.g., lakes and reservoirs) accumulate heavy metals in their bottom sediments in considerable quantities. Scavenging of pollutants from water and aquatic sediments is extremely costly and technically challenging, as the concentration and variety of persistent pollutants (like heavy metals) is serious and escalating (Ali et al. 1999; Rai and Tripathi 2007). The current technologies available for pollution abatement are highly expensive and, in most cases, are liabilities to industry. According to Mehrotra and Aowal (1982), pollution control measures consume up to 15% of the outlay in the case of industries such as steel fertilizer, etc. Modern industrial wastewater treatment plants also have recurring expenses for maintenance; the processes employed are delicate and liable to failures in the absence of regular maintenance. The aforesaid factors have prompted the research for low-cost pollution abatement techniques, e.g., use of wetland plants in constructed/natural wetlands (Rai 2008a). However, the efficiency and survival of wetland plants should be monitored in natural conditions, which are under pollution stress, particularly heavy metal pollution. Biological indicators such as aquatic wetland plants are increasingly used, in addition to physical and chemical parameters for determining and monitoring water quality (Tremp and Kohler 1995). In

451

lake ecosystem, phytoplankton and macrophytes inhabiting the littoral zone act either source or sink for pollutants entering the lake and play a great role in biogeochemical cycling of elements (Ali et al. 1999). Freshwater aquatic plants are physiologically adapted to survival in permanent or semi-permanent freshwater ecosystems. The distribution and behavior of aquatic plants are often correlated with water quality (Carbiener et al. 1990; Romero and Onaindia 1995). Water chemistry (physico-chemical parameters) had a great role in influencing phyto-diversity in lake, which acts either as a filter or pollution source for the plankton in open waters (Ali et al. 1999). Enrichment of nutrients also occurs due to disposal of domestic and industrial effluents from surrounding areas, which support the growth of a variety of macrophytes. Though some heavy metals like Mn and Zn are essential nutrients, they also impose potential toxicity if they attain very high concentrations, so plants possess complex biochemistry pathways to control their uptake and translocation. Studies and experiments using radioactive tracers have established that most rooted aquatic plants can take up chemicals primarily from the sediment pore water (Jackson 1998). The concentrations of metals in aquatic plants can be more than 100,000 times greater than in associated water column (Albers and Camardese 1993; Jackson 1998). Aquatic plants thus accumulate metals that they take from the environment and concentrate within the trophic chains causing an accumulative effect (Outridge and Noller 1991; Tremp and Kohler 1995; Rai 2008c). Therefore, certain aquatic plant species can be used as indicators of environmental pollution; otherwise, that might be difficult to detect. Crowder (1991) also studied the phenomenon of biomagnification in relation to aquatic ecosystems. Rai (2008c) also observed the transfer of Hg from abiotic (water and sediments) to biotic (algae, aquatic macrophytes, and fishes) components, belonging to different trophic levels in a tropical lake of India. Extent of accumulation of nine metals was investigated in all the collected plants from different sampling sites. In the present work, principal Cu accumulators were E. crassipes, V. spiralis, L. minor, A. pinnata, P. amphibium, C.

452

rotundus, and P. pectinatus. Also in the literature, Qian et al. (1999) observed phyto-accumulation of Cu by various wetland plants, and accumulation of Cu was recorded maximum in roots of water lettuce (1,038 mg kg−1 ) and smooth cord grass (194 mg kg−1 ). Similarly, floating wetland plants bioaccumulate Cu to higher levels of 300 to 15,000 mg kg−1 in duckweed, L. minor (Jain et al. 1989; Bassi and Sharma 1993; Dirilgen and Inel 1994; Zayed et al. 1998), 6,000–7,000 mg kg−1 in water hyacinth, E. crassipes (Low et al. 1994; Zhu et al. 1999), and 2,500–3,000 mg kg−1 in Vallisneria (Gupta and Chandra 1998). C. demersum accumulated 3.45 ± 0.33 mg kg−1 Cu in the lakes of west Poland (Szymanowska et al. 1999). Deng et al. (2004) also observed accumulation of Cu along with Pb and Cd and showed that metals accumulated by wetland plants were mostly distributed in root tissues, suggesting the existence of an exclusion strategy leading to metal tolerance. However, in laboratory conditions, Miretzky et al. (2004) reported 90.41% Cu removal from L. minor and 91.70% from Spirodela intermedia. Cr accumulation was maximum by V. spiralis at Dongia nala and minimum at Rihand dam site by C. demersum. In literatures, several potent plants have showed the efficiency for Cr removal. Zhu et al. (1999) and Lytle et al. (1996) reported that water hyacinth is a very good accumulator of Cr and simultaneously converts toxic Cr (VI) to relatively non-toxic Cr (III). Qian et al. (1999) reported that smartweed (Polygonum hydropiperoides) acquired the highest concentration of Cr (2,980 mg kg−1 ) in its roots. Contrary to this, Cyperus alternifolius had highest Cr concentration (44 mg kg−1 ) in its shoots. The work of Zayed et al. (1998) and Zhu et al. (1999) observed that E. crassipes accumulated 3,951 mg kg−1 Cr in its biomass and L.minor accumulated 2,870 mg kg−1 Cr. Bacopa was reported to accumulate 3,200 mg kg−1 Cr in their biomass (Sinha et al. 1996). Like in the case of Cu, floating and submerged plant species were more efficient in Cr accumulation as compared to rooted emergent species in accumulating Cr from contaminated waters (Jana 1988; Srivastava et al. 1994; Vajpayee et al. 2001). Fe is one of the vital elements for humans and for other forms of life. Nevertheless, high doses of Fe are known to cause hemorrhagic necrosis,


sloughing of mucosa areas in the stomach, tissue damage to a variety of organs by catalyzing the conversion of H2 O2 to free radical ions that attack cell membranes, proteins and break the DNA double strands, and cause oncogene activation (Gurzau et al. 2003). Past studies have documented the Fe phytoremediation ability of the obnoxious free-floating macrophytes from nutrient-rich wastewaters (Tripathi and Upadhyay 2003; Sooknahand Wilkie 2004; Jayaweera et al. 2007; Jayaweeraa et al. 2008). Polygonum, Vallisneria, Lemna, and E. crassipes were the top accumulators of Fe from all the selected sites of the G.B. Pant Sagar. Jayaweeraa et al. (2008) also reported very high accumulation of Fe in E. crassipes biomass under varying nutrient conditions and showed the highest phytoremediation efficiency of 47% during optimum growth at the sixth week with a highest accumulation of 6707 Fe mg kg−1 dry weight. Furthermore, previous studies showed that hyacinth roots form plaques of Fe (OH)3 by diffusing photosynthetically produced O2 to the rhizosphere to avoid the formation of H2 S and to counteract Fe2+ and Mn2+ toxicity at lower dissolved oxygen levels (Vesk and Allaway 1997; Vesk et al. 1999; Soltan and Rashed 2003). Mn is one of the elements that received very little attention in the literature with respect to its uptake and accumulation by macrophytes. In the present study, Eichhornia from Belwadah (root, 880 ± 28.5 mg kg−1 ; shoot, 123 ± 11.3 mg kg−1 ), Vallisneria from Dongia nala (836 ± 17.1 mg kg−1 ), Azolla from Ash pond (1, 014 ± 20.3 mg kg−1 ), and C.rotundus (root, 988 ± 31.1 mg kg−1 ; shoot, 149 ± 14.1 mg kg−1 ) were the top accumulators of Mn. In the literature, Bur-reed (Sparaganium americanum), bladderwort (Utricularia sp.), and the liverwort (Scapania undulata (L.) Dum.) are the top wetland species reported for Mn accumulation (Caines et al. 1985; Albers and Camardese 1993). These aquatic plants accumulated 1,590, 3,660, and 9,377 mg kg−1 Mn in the shoots, respectively, when exposed to external Mn concentration of 2.75, 2.75, and 50 mg L−1 . Qian et al. (1999) reported that umbrella plant (C. alternifolius) accumulated Mn to the greatest level (198 mg kg−1 ) followed by slightly lower values (187 mg kg−1 )


in shoot tissues of smartweed P. hydropiperoides among 12 plant species observed by them. Lemna from Belwadah (1,600 ± 91.3 mg kg−1 ) and Dongia nala (1,667 ± 101.3 mg kg−1 ) site accumulated exceptionally high amount of Ni in biomass, while from Ash pond, maximum Ni accumulation was recorded in Azolla (870 ± 48.0 mg kg−1 ). Earlier, highest Ni accumulation (9,000 mg kg−1 ) was also reported in water fern (Azolla filiculoides) and Salvinia natans (6,295 mg kg−1 ; Sela et al. 1989; Srivastava et al. 1994). Lemna also reported to accumulate high Ni ranging from 500 to 5500 mg kg−1 dry weight (Jain et al. 1990; Sharma and Guar 1995; Zayed et al. 1998; Rai 2007a). During the course of the present study, Lemna (1,800 ± 54.0 mg kg−1 Pb; 540 ± 6.9 mg kg−1 Pb) from Belwadah and Ash pond, respectively, while Polygonum (root, 317 ± 13.0 mg kg−1 Pb; shoot, 38 ± 4.1 mg kg−1 Pb) from Dongia nala were the highest accumulators of Pb. Cyperus (root, 933 ± 21.0 mg kg−1 Pb; shoot, 23 ± 2.4 mg kg−1 Pb) accumulated exceptionally high amount of Pb in biomass in spite of comparatively low concentration in external medium at the reference site, which means that even very little concentration of Pb bioaccumulated actively. Several floating wetland plant species were reported to accumulate appreciable amounts of Pb such as water hyacinth, which when treated with 8 mg L−1 Pb accumulated 25,800 mg kg−1 Pb (Muramoto and Oki 1983). Likewise, Giant duckweed (Lemna polyrhiza) accumulated 10,000 mg kg−1 Pb on whole plant tissue basis when supplied with 10 mg L−1 Pb in solution culture (Sharma and Guar 1995), and water velvet (Azolla sp.) accumulated 1,200 mg kg−1 Pb after 14 days of exposure to 1 mg L−1 in water (Jain et al. 1990). Rai (2007a) also investigated the efficiency of L. minor in Pb and Ni removal from industrial effluents. Like Pb, in the literature, information on Hg accumulation in natural conditions by wetland plants is highly limited. Lenka et al. (1990) reported that water hyacinth exposed to Hg contaminated effluent containing 0.13 mg L−1 Hg accumulated 946 mg kg−1 Hg. Qian et al. (1999) reported Hg concentrations in both roots (1,217 mg kg−1 ) and shoots (92 mg kg−1 ) of water lettuce (Pistia stratiotes) followed by fuzzy

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water clover (Marsilea drummondii), which accumulated 1,127 mg kg−1 and 60 mg kg−1 in roots and shoots, respectively. Lenka et al. (1992) also reported to bioaccumulate Hg in P. stratiotes to 5,000-fold of its initial concentration in the external medium. In the present investigation, E. crassipes from Belwadah (root, 1,500 ± 18.0 mg kg−1 ; shoot, 39 ± 3.1 mg kg−1 ) and from Dongia nala (root, 991 ± 19.0 mg kg−1 ; shoot, 103 ± 9.1 mg kg−1 ), Vallisneria (1,071 ± 17.0 mg kg−1 ) from Dongia nala, and Azolla from Ash pond (936 ± 53 mg kg−1 ) were the most potent plants for accumulation of Hg. Interestingly, C.rotundus from the reference site accumulated very high Hg (root, 620 ± 15.5 mg kg−1 ; shoot, 10 ± 1.0 mg kg−1 ). Therefore, it may be assumed that whatever little amount of Hg present in the external medium actively bioaccumulated in Cyperus. Furthermore, Rai (2008c) analyzed Hg in water, sediments, plants, and fishes collected from G.B. Pant Sagar at different sampling points, receiving the discharge of chlor-alkali effluent. Hg concentrations increased significantly from lake water and sediments to algae and aquatic macrophytes. Statistical analysis (Pearson correlation) revealed a significant positive correlation between Hg in water and plants (r = 0.88–0.93; p < 0.01 and p < 0.05) and for Hg in sediment and plants (r = 0.50–0.83; p < 0.01 and p < 0.05). However, the increase in Hg concentration in fishes was not significantly correlated with lake ambient, i.e., water (r = 0.31–0.36), sediments (r = 0.29–0.33) and aquatic plants (r = 0.31–0.36; Rai 2008c). E. crassipes and L. minor collected from Belwadah site accumulated high concentrations of Cd in their biomass. Similarly, Vallisneria, Polygonum, and Cyperus were also the leading accumulators of Cd. Previous studies also reported that the floating plants water hyacinth (E. crassipes) and duckweed (L. minor) were very good accumulators of Cd and accumulated exceptionally high 6,000 and 13,000 mg kg−1 Cd, respectively, when supplied with 10 mg L−1 Cd (Zayed et al. 1998; Zhu et al. 1999). These two species were also found to be the top species in Cd accumulation throughout the literature (Muramoto et al. 1989; Huebert and Shay 1993). Qian et al. (1999), in his phytoremediation

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experiment, showed that Water Zinnia (Wedelia trilobata) accumulated the highest Cd concentration (148 mg kg−1 ) in shoot tissues while Smart weed (P. hydropiperoides (root, 1,300 mg kg−1 ; shoot, 90 mg kg−1 ) attained the second highest concentration of Cd in both roots and shoots. Cd and Zn accumulated in E. crassipes (root) at Belwadah showed significant positive correlation with Cd (0.914; p < 0.01) and Zn (0.90; p < 0.01) concentrations in Anpara effluent. Cr, Hg, and Ni concentrations in L. minor at Dongia nala showed significant positive correlation with Cr (0.873; p < 0.01), Hg (0.71; p < 0.05), and Ni (0.73; p < 0.05) concentrations recorded in Kannoria effluent. Similarly, Ni, Zn, and Hg content in A. pinnata collected from Dongia nala showed significant positive correlation with Ni (0.87; p < 0.01), Zn (0.83; p < 0.05), and Hg (0.743; p < 0.05) concentrations recorded in Kannoria effluent. Mn, Pb, Fe, and Cd accumulated in Polygonum (root) of Ash pond showed significant positive correlation with Mn (0.978; p < 0.01), Pb (0.937; p < 0.01), Fe (0.946; p < 0.01), and Cd (0.891; p < 0.01) concentrations recorded in Kannoria effluent. Likewise, aforesaid metals accumulated in plants also showed significant positive correlation with these metals recorded in reservoir water (range, 0.781–0.983; p < 0.01) and sediment (range, 0.508–0.673; p < 0.05). The E. crassipes, P. amphibium, and C. rotundus, where roots and shoots were investigated separately, translocation factor, i.e., ratio of shoot to root metal concentration, was negative. The extent of metal accumulation in roots were comparatively high than shoots. Therefore, rhizofiltration was the key mechanism in the heavy metal removal from lake water and sediment in rooted wetland plants.

Conclusion Aquatic wetland plants are a promising candidate for accumulation of heavy metals from thermal power plant, coal mine, and chlor-alkali effluent. Macrophyte plants are potentially valuable as indicators of heavy metals in river, lake, and ponds, as revealed by a positive and significant correla-


tion between metals in reservoir’s environment and metals in wetland plants. Metal concentration showed a significant positive correlation between industrial effluent and lake water and with effluent and lake sediment. The present work paves the way for the use of wetland plants in constructed and natural wetlands designed for wastewater treatment. Harvesting of wetland plants is recommended at regular intervals to prevent the transfer of heavy metals to higher trophic levels. Acknowledgements The author is thankful to the Council of Scientific and Industrial Research, New Delhi, India for the financial assistance to Prabhat Kumar Rai in the form of Junior Research Fellowship and Senior Research Fellowship. The first author also extends his regard to Professor A.N. Rai, Vice Chancellor Mizoram University for kind cooperation and support.

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