INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 6, Copyright 2010 All rights reserved Integrated Publishing Association

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1 INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 6, 2011 Copyright 2010 All rights reserved Integrated Publishing Association Research article ISSN Cadmium and Chromium removal by aquatic plant Satya Narain 1, Ojha.C.S.P 2, Mishra.S.K. 1, Chaube.U.C 1, Sharma.P.K 2 1 Department of WRD&M, Indian Institute of Technology Roorkee, (U.K.) Roorkee , India 2 Department of Civil Engineering, Indian Institute of Technology Roorkee, (U.K.) Roorkee , India narainsatya@rediffmail.com ABSTRACT Natural water bodies like ponds are used for the cultivation of aquatic plants, which are often contaminated with organic and variety of toxic metals likes Cd, Fe, Cu, Cr, Mn and Pb, etc., generated by industrial as well as municipal effluents. Generally, it seen that the concentration of metals Cr, Pb, Cd and Fe in water often exceeds than recommended permissible limits of WHO (1995). Thus, it is necessary to maintain the quality of these ponds within permissible limits. Phytoaccumulation is an alternative technique of heavy metals remediation. In this paper, using free floating plant (Water hyacinth) which was obtained from an aquatic system, the removal of heavy metal, such as Chromium and Cadmium were investigated. It has been observed that plants were able to remove Cr and Cd from the municipal contaminated water. The average removal efficiency for the plant species, i.e., water hyacinth was 80.26%, for Cr and 71.28%, for Cd. Average removal rates of Cr and Cd were 0.10µg/day and 0.12µg/day Keywords: Phytoremediation, Heavy metals, Water hyacinth, Cadmium, Chromium 1. Introduction Water pollution is one of the most serious environmental problems due to overpopulation, urbanization, industrialization and illiteracy. Heavy metals are polluting the air, soil, and water (Srivastava and Purnima 1998). However, heavy metals play important role as micronutrients in organisms. These heavy metal ions Cu 2 +, Zn 2+, Mn 2+, Fe 2 +, Ni 2 +, and Co + are essential micronutrients for plants, and Fe 2+ is required in the highest concentration (Kunze et al. 2001). The non essential metals such as Cd 2 +, Hg 2 +, and Pb 2+ are toxic for plants. Each plant species has different tolerance level for the different contaminants. Tilstone and Macnair 1997 defined heavy metal tolerance as the ability of plants to survive in their environment that is toxic to other plants. From last few years, a great interest has been shown for research on aquatic macrophytes as good candidates for pollutant removal or even as bio indicators for heavy metals in aquatic ecosystems (Aoi and Hayashi 1996; Maine et al. 1999). Water hyacinth (Eichhornia crassipes (Mart.) Solms.) is just one of the great members of aquatic plant species successfully used for wastewater treatment. It is important to emphasize that E. crassipes has a huge potential for removal of the vast range of pollutants from wastewater (Chua 1998; Maine et al. 2001; Mangabeira et al. 2004). Aquatic plants (Peterson and Teal 1996), microorganisms (Perkins and Hunter 2000), and algae have the ability to remove organic and inorganic matter, nutrients, pathogens, heavy metals and other pollutants from wastewater (Redding et al. 1997; House et al. 1999) in a completely natural way. But this macrophyte is Received on January, 2011 Published on April

2 also one of the most dangerous invasive aquatic weed in the world (Wilson et al. 2005). Metals cannot be easily degraded and the cleanup usually requires their removal. However, this energy intensive approach can be prohibitively expensive. Phytoremediation offers a cost effective, nonintrusive and safe alternative to conventional cleanup techniques. Metal uptake by plant has three patterns: a. True exclusion in which metals are restricted from entering the plant, b. Shoot exclusion in which metals are accumulated in the root but translocation to the shoot is restricted, and c. Accumulation where metals are concentrated in the plant parts. Hyper accumulators can tolerate, uptake, and translocate high levels of certain heavy metals that would be toxic to most organisms. They are defined as plants whose leaves may contain >100 mg/kg of Cd, >1000 mg/kg of Ni and Cu, or >10,000 mg/kg of Zn and Mn (dry weight) when grown in metal rich medium (Zavoda et al. 2001). Accumulation and particularly hyper accumulation have attracted considerable interest in recent years. Ebbs et al. (1997) stated that in order to achieve a successful phytoremediation of soil polluted with metals, a strategy of combining a rapid screening of plant species possessing the ability to tolerate and accumulate heavy metals with agronomic practices that enhance shoot biomass production and increase metal bioavailability in the rhizosphere must be adapted. The objectives of this study were (a) To assess the ability of aquatic plant (water hyacinth) to tolerate water contaminated with two heavy metals (Cd and Cr); (b) To determine the heavy metal selectivity for each plant, and (c) To examine the plant ability to hydroponically treat water contaminated with heavy metals. 2. Site selection The Roorkee is located south of Haridwar city (latitude North and longitude East) near the Ganga River. It is observed that the pollution of surface and subsurface water has been increased due to domestic and industrial waste water. In this study, we have selected few places near Roorkee to collect waste water. 2.1 Waste Water and Plant Sampling Figure 1: Map of Tansipur village pond situated in Roorkee (from Google source). 1298

3 The main area of interest is along the north side and the flood plain region located in the Roorkee. The first set of raw waste water sampling has been collected in the last week of March Plants like water hyacinth were collected from the pond of Tansipur village which is situated at south side of the Roorkee city as shown in Figure 1 obtained from Google source. 3. Material and Methods 3.1 Experimental Procedure First of all, water samples were collected in the plastic bottles after washing with deionizeddistilled and rinsed with 10% nitric acid. Afterwards, all samples have been filtered using 0.45 μm cellulose acetate filters and it is acidified to ph of 2 to 5 with nitric acid in the laboratory, so that the metal does not attach to the wall of sampling Bottles. 3.2 Experimental setup Two evaporator pans of 0.5 cm thick iron material were used for the experiment. Each pan is having area of m 2 and 30 cm depth. These two pans were filled with municipal waste water. First pan is used for water hyacinth (plant); and second pan is used as a control (300 l capacity). The control in each pan was used to observe differences in growth rates among each plant due to uptake of contaminants. Temperature (water and ambient air), evapotranspiration (pan with plants) and evaporation (control) were recorded every day during the experimental period. Leaf area of the plants was also measured. The experimental setup is shown in Figure 2. It consists of evaporator pans (tank), temperature, wind speed and soil temperature monitoring system. Figure 2: Experimental setup of evaporator pans containing waste water and aquatic plants. 3.3 Selection of aquatic plants In the present study, we used aquatic plant species as a water hyacinth (Eichornia crassepes) as shown in Figure 2. Water hyacinth is an aquatic vascular plant with rounded, upright and shiny green leaves similar to orchids (U.S. EPA, 1988). The water hyacinth (E. crassipens) is fast growing perennial aquatic macrophyte (Reddy and Sutton, 1984). It is a member of pickerelweed family (Pontederiaceae) and its name Eichhornia was derived from wellknown 19th century Prussian politician J.A.F. Eichhorn (Aquatics, 2005). This tropical plant spread throughout the world in late 19th and early 20th century (Wilson et al. 2005). 1299

4 This aquatic plant has been obtained from Tansipur (south side of Roorkee city) stagnant pond, where it was grown hydroponically. The plants were translocated to the system and it was kept for 2 weeks in clean water to acclimatize before adding the contaminants. 3.4 Heavy metal contaminant An attempt is made to remove two heavy metals (i.e., Cd and Cr) from waste water. These metals were present in the waste water in the form of Chromium nitrate [Cr (NO3)3], and Cadmium nitrate [Cd (NO3)2]. The heavy metals were measured in µg/l. 4. Sampling and analysis Water samples of 500 ml were collected from three compartments respectively at 5 days intervals up to 50 days. An elemental analysis of cadmium and chromium was performed by inductively coupled plasma mass spectrometry (ICP MS) using an Elan 6000 instrument (Perkin Elmer Sciex, USA). Plant samples of 5 g each were collected during initial time and after completion of the experiment. Afterwards, an analysis is made for investigating the presence of heavy metals. The plant samples were dried in a convection oven for 24 hr at 45 0 C temperature to ascertain the accumulation of each contaminant and avoid evaporation of Cd. Dry plants were grinded into small pieces and digested with hydrochloric and nitric acids (5 +5 ml per sample) in a closed vessel at a temperature of C. After reaction fume generated and 20ml H 2 O 2 is added to the vessels for complete digestion and removal of color and fume. The sample is allowed to cool for at least 15 minutes and water was added to make sample 100ml. Then the heavy metal elements were determined by the same analytical methods used for water samples previously. 4.1 Results and discussion The ambient air and water temperature were fluctuating during the whole experimental period at temperature of 20 0 C and 30 0 C respectively. Figs. 3 and 4 contain a series of plots to show how effective the water hyacinth plants are in utilizing the heavy metals. To prepare these figures, first of all mass balance of individual heavy metals was performed. At different time steps, the mass balance computations revealed the metal uptake by plants along with the metal present in the water body. Fig. 3 presents one such variation with regard to Chromium. Considering that Fig. 3 does not manifest any role of leaf area index on the metal uptake, a normalized metal uptake for each plant was computed by dividing its metal uptake with the leaf area index. Such a normalized plot is shown in Fig. 4. It can be seen that the considerable improvement in Fig. 4 in compared with Fig 3. The metal uptake by this plant is quite significant and this plant can be effectively used in management of waste water. As per normal practice water hyacinth can be removed and used as a compost product/fodder/miscellaneous usage. However, the focus of the present work is only on quantification of the metal uptake of this plant and not on how the metal accumulated in the plant is subsequently is recycled. In this work, only a part of experimental findings have been presented. Currently, field experiments are on the way to explore its full potential at a larger scale. 1300

5 v a lu e o f C r(p p b ) in p lan t C r uptake by Water hyac inth P oly. (C r uptake by Water hyacinth) y = 0.003x x R 2 = Ava ila ble C r(ppb) in pa n Figure 3: Graph between chromium uptake by water hyacinth plant and available chromium in pan. C d (p p b ) u p ta k e b y W ater H y c i n th C d uptake by Water hyac inth L inear (C d uptake by W ater hy ac inth) y = x R 2 = C a dm ium (ppb) a va ila ble in pa n Figure 4: Graph between cadmium uptake by water hyacinth plant and available Cadmium in pan. 4.2 Chromium The initial concentration of chromium in the control and treated pan was 6.2 µg/l. After treatment, the magnitude of chromium remained 0.5µ/l for water hyacinth. But, the removal rate of metal was high. The average removal efficiency for the plant species, i.e., water hyacinth was 80.26%, for Cr. 4.3 Cadmium The initial cadmium concentration in the control tanks was 8.6 µ g/l, which decreased by the end of the experiment to 1.3µ g/l for water hyacinth, The plant showed different removal patterns of Cd from the water and average removal efficiency for the plant species, i.e., water hyacinth was 71.28%, for Cd is very low in capaired to Cr. 1301

6 4.4 Removal efficiency The removal efficiency of each plant for the heavy metal ions is shown in Table 1. The removal efficiency for Cr was % and for Cd was % for water hyacinth. Therefore, the ion selectivity for the two cultivars was Cr>Cd. 4.5 Mass balance A mass balance was performed on the system in order to determine the elements removal pathways. The results are shown in Tables 2 and 3. On the average, about µ g (Water hyacinth) of Cr was removed by plants but in case of Cd about µ g was removed by water hyacinth in total experimental period. The other portion µg and µg may have precipitated as Cr (OH) 2 and Cd (OH) 2. But in control experiment about µg and µg have precipitated as Cr (OH) 2 and Cd (OH) 2 respectively. The result also showed that plant uptake of Cr and Cd was dependent on the initial concentration in water. Element Table 1: Removal efficiencies of Heavy metals Initial concentration (µg/l) Water hyacinth Concentration (µg/l) Final Removal Cr Cd Efficiency (%) Table 2: Mass balance details in complete experimental period Element Details µg available in path Chromium Total Plant uptake Cadmium Precipitation Available in water Total Plant uptake Precipitation Available in water Table 3: Mass balance without Treatment (Control) in complete experimental period Chromium Cadmiumm Without plant(µg) Total (Cr) Precipitation Available in Water Total (Cd) Precipitation Available in Water

7 4.6 Plant tolerance Generally, all the experimental plants showed a slight reduction in the plant growth, branching, leaf size, and root system. Water hyacinth shows promising results in terms of tolerance to the heavy metals concentration in the aqueous solution. A light green color of the water hyacinth leaves grown in the contaminated compartment was apparent. 5. Conclusions The aquatic plant (i.e., water hyacinth) has the ability to remove heavy metals (Cr and Cd) from contaminated waste water. The average removal efficiency for the plant species water hyacinth was 80.26%, for Cr and 71.28%, for Cd. The removal rates of Cd and Cr were constant 0.10 µg/day for Cr and 0.12 µg/day for Cd. About µg (Water hyacinth) of Cr was removed but in case of Cd about µg was removed by water hyacinth in total experimental period. The other portion µg and µg may have precipitated as Cr (OH) 2 and Cd (OH) 2. But in control experiment about µg and µg have precipitated as Cr (OH) 2 and Cd (OH) 2 respectively. 6. References 1. Aoi, T. and Hayashi, T. (1996). Nutrient removal by water lettuce (Pistia stratiotes). Water Sci. Tech. 34(7 8), pp Chua, H. (1998). Bio accumulation of environmental residues of rare earth elements in aquatic flora Eichhornia crassipes (Mart.) Solms. in Guangdong Province of China. The Science of Total Environment 214(1 3),pp Ebbs, S. D. and Kochain, L. V. (1997). Toxicity of zinc and copper to Brassica species: implication for phytoremediation. J. Environ Qual; 26.pp Ebbs, S. D., Lasat, M.M., Brady, D.J., Cornish, J., Gordon. R. and Kochain, L. V. (1997). Phytoextraction of cadmium and zinc from a contaminated soil. J. Environ Qual. 26(5), pp House, C. H., Bergmann, B. A., Stomp, A. M., Frederick, D. J. (1999). Combining constructed wetlands and aquatic and soil filters for reclamation and reuse of water. Ecological Engineering, 12(1 2),pp Kunze, R., Frommer, W. B. and Flugge U.I. (2001). Metabolic engineering in plants: the role of membrane transport. Metab. Eng., (4),pp Maine, M. A., Sune, N. L., Panigatti, M. C. and Pizarro, M. J. (1999). Relationships between water chemistry and macrophyte chemistry in lotic and lentic environment. Arch. Hydrobiol.145 (2), pp Maine, M. A., Duarte, M. V., and Sune, N. L. (2001). Cadmium uptake by floating macrophytes. Water Res., 35(11), pp Mangabeira, P. A. O., Labejof, L., Lamperti, A., de Almeida, A. A. F., Oliveira, A. H., Escaig, F., Severo, M. I. G., da C. Silva, D., Saloes, M., Mielke., M. S., Lucena, E. R., Martinis, M. C., Santana, K. B., Gavrilov, K. L., Galle, P. and Levi Setti, R. (2004). 1303

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