# Ludwigia natans: a potential aquatic macrophyte for cadmium bioaccumulation and Phytoremediation

· Articles
Authors

D. Marbaniang* & S.S. Chaturvedi
Department of Environmental Studies
North-Eastern Hill University, Shillong-793022
sschaturvedinehu@gmail.com
*Corresponding author: D. Marbaniang; email:baphi66@gmail.com

Abstract

Aquatic macrophytes have tremendous potential for remediation of the heavy metal cadmium. A Laboratory experiment was conducted to evaluate the Cd bioaccumulation capacity of Ludwigia natans. The macrophyte was grown in the laboratory containing nutrient solution and working Cd standard solutions of different concentrations (1, 10, 50, and 100 mgL-1) and harvested at regular time interval of 5 and 10 days. The Cd accumulation by L. natans showed an increase with time and the maximum accumulation was on the 10th day at 50mgL-1 for both the roots and shoots. Cd accumulation in the plant parts was higher in the shoots as compared to the roots. The maximum bioconcentration factor values (7666) which indicate that the plant was a Cd hyperaccumulator and translocation factor values (2.8) which is >1 which points towards the suitability of L. natans for removing Cd from Cd-contaminated water.

Keywords Ludwigia natans, Cadmium, Accumulation, Bioconcentration Factor (BCF), Translocation Factor (TF)

Introduction

Heavy metals pollution in the aquatic environment has become a major cause of concern for many countries especially in India where it is too expensive for remediation process. However, with the rich diversity of aquatic macrophytes and their potential to hyperaccumulate many heavy metals and they can be used as an alternative way of remediating heavy metals from the aquatic system (Rai, 2008). Cadmium (Cd) is one of the potent and highly toxic metals among the other metals found in the earth’s crust and can easily contaminate the food chain (He et al., 2005). It is ranked seventh in the ASTDR (2011) priority list of hazardous substances. There are several sources of Cd in the environment which includes both from the natural and man-made sources. Notably, natural emissions and man-made industrial effluents emitted by ore processing industries and plants have immensely polluted water.

A variety of techniques which includes chemical, physical and biological technology have been used to remediate heavy metal contamination from soil or water. Toxic metals from industrial effluents have been remove by various other techniques such as precipitation, reduction, artificial membranes, and ion exchange, but however these techniques generate a huge amount of waste e.g., sludge, metal rich waste, etc which is difficult to dispose of and therefore, dangerous to the environment and they are also generally expensive, relatively inefficient (Rebhun and Galil, 1990). Phytoaccumulation, one of the biological indicators which indicate the degree of absorption of heavy metals in plants has lately gained its applicability because its cost-effectiveness, long-term and ecological aspect (Weiss et al., 2006). Aquatic macrophytes have received great attention and have shown to be one of the candidates in the aquatic system for pollutant uptake and biological indicators of heavy metal (Maine et al., 2001). An ideal hyperaccumulator plant would have shoots with a high capacity to accumulate heavy metals/metalloids, have a high biomass and rapid growth, and bioconcentration factor (BCF) and translocation factor (TF) values higher than 1 (Garbisu and Alkorta, 2001). Works on duckweed (Zayed et al., 1998; Wang et al., 2002), water hyacinth (Zhu et al., 1999; Wang et al., 2002), S. mucronatus, R. rotundifolia and M. intermedium (Marbaniang and Chaturvedi, 2014) were reported for Cd remediation.

The objective of the present study was to assess the uptake of Cd and phytoremediation potential of L. natans for Cd under laboratory conditions. The experiments were performed in a contained environmental set up inorder to eliminate all external environmental factors.

Materials and Methods

L. natans was collected from M/S Gills and Bills, Shillong, India and they transferred to the laboratory. Plants were washed several times with tap and distilled water in order to remove any adhering soils and plants of similar size, shape and height were selected and kept separately in a 40L capacity tank which contained half strength Hoagland’s solution of pH = 7 (Hoagland and Arnon, 1950) and kept for 15 days prior to experimentation for. After 15 days the acclimatized plants were transferred and maintained in 5% Hoagland’s solution containing working Cd standard solutions of different concentrations 1.0, 10.0, 50.0 and 100.0 mgL-1and then they were exposed to Cd concentrations at a time interval of 5 and 10 days. Cd of analytical grade, were supplied as CdCl2 (Himedia) were used as the source of Cd. Experiments were carried out under controlled temperature (24±10C) and light (3500 Lux) conditions. After each time interval the plants were collected and washed with deionised water to remove any metal adhering to its surface. The washed plant samples were carefully dried the adherent water using absorbent paper and then they are separated to roots and shoots. Samples were dried for 48h in an oven at 70±50C. The dried oven plant root and shoot was then chopped and finally powdered using a mortar and pestle to ensure homogeneity for facilitating organic matter digestion. One control plant groups were also set up where no Cd was added into the medium was not added.

For digestion, the plant samples were carried out according to Kara and Zeytunluoglu (2007). Atomic Absorption Spectrophotometer (AAS 3110, Perkin-Elmer) was used to determine the Cd contents in plant root and shoot parts. The bioconcentration factor (BCF) is a useful parameter and it provides the ability index of a plant to accumulate metals with respect to metal concentration in the medium and it was calculated on a dry weight basis (Zayed et al., 1998).

Translocation Factor (TF) is generally the translocation of heavy metal from roots to aerial part and indicates the internal metal transportation of the plant. The translocation factor is determined as a ratio of metal accumulated in the shoot to metal accumulated in the root (Deng et al., 2004).

Wherein, TF>1 indicates that the plant translocate metals effectively from the root to the shoot.

Statistics analyses

ANOVA and multiple linear regressions were performed for all the data to confirm their validity using SPSS 17.0. The data were all presented as mean ± standard error of three replicates. Fisher least significant difference (LSD) test was performed at p < 0.05 to check the significant difference between the means for different uptake at different Cd concentrations.

Results and Discussion

Accumulation of cadmium: Cadmium content in the roots and shoots L. natansshowed increases in metal accumulation in the roots and shoots if metal concentrations and time period are enhanced. At cadmium concentration of 1, 10, 50 and 100mgL-1, the cadmium content (Table 1) in L. natansroots increased to the maximum 2477, 5541, 7343 and 6670 $\mu$gg-1 dry weight and in case of shoots it was 5188, 7540, 8520 and 8040 $\mu$gg-1 dry weight at 10th day of harvesting and accumulation ranges from 836-7343 $\mu$g/g dry weight in roots and 2346-8520 $\mu$gg-1 dry weight in shoots (Figure 1). The maximum accumulation was on the 10th day at 50mg/L in both the roots and shoots and minimum was on the 5th day (1mgL-1) in roots and shoots. In L. natans, the accumulation of cadmium in the root and shoot increased significantly (p<0.05) from 5 to 10 days.

Hadad et al., (2010) reported that submerged plants have a greater surface area as compared to non-submerged plants and their shoots are in constant contact with the water medium which may help them to bioconcentrate more nutrients and metals which corroborates with the present study where it was observed that the considerable amount of cadmium accumulated by L. natanswas in the shoots as compared to the roots. The shoots of this submerged species also receives Cd form the roots but however due to their constant contact with the medium they may have also accumulate Cd directly from the medium to a greater extent which corroborates with the findings of Dunbabin and Bowmer (1992); Sivaci et al., (2004); Peng et al., (2008); Marbaniang and Chaturvedi, (2014).

The multiple regression model with all two predictors produced R² = .628, F(2, 21) = 17.7, p < .001 for L. natans. As can be seen in Table 2 the concentration of cadmium in the medium had significant positive regression weights, indicating with higher cadmium concentration in the medium and time were expected to have higher cadmium uptake in L. natans. Time i.e., number of days contribute to the multiple regression model and it have a significant regression weights, indicating that uptake of cadmium does depend on time period.

Table 1: Accumulation of cadmium (µgg-1 dry wt) in roots and shoots of L. natansat different exposure time

 Metal concentration (mgL-1) Exposure time (days) 5 d 10 d Roots Shoots Roots Shoots 1.0 836±3.3a 2346±12a 2477±6.2a 5188±4.4a 10.0 2926±8.8b 5932±6.2b 5541±7.2b 7540±5.7ab 50.0 5623±12c 6666±8.8c 7343±8.8bc 8520±10b 100.0 5263±8.8d 6053±8.8cd 6670±11c 8040±17.3b Control BDL BDL BDL BDL

Table 2: Summary statistics, correlations and results from the regression analysis

 Variable Mean Std error Correlation with uptake Multiple regression weights B ? Uptake 10871.25 1716.183 Time (in days) 1.50 1032.146 .505* 3918.000** .505 Concentrations (mgL-1) 40.25 13.193 .610** 60.454*** .610

Bioconcentration factor (BCF) value indicates the ability of the plant to accumulate metal in their tissue parts. The BCF values at different cadmium concentrations (1,10, 50 and 100 mgL-1) were evaluated at 5 and 10 day. There was a general decrease in BCF with the increase in cadmium concentration at 5th and 10th day respectively. The BCF values of cadmium of the experimental plants increased with exposure periods. The maximum BCF value (7666) was obtained when treated with 1mgL-1 of cadmium at 10th day of harvesting (Table 3).

Plants which have the ability to accumulate heavy metal in the tissues are generally classified as a good accumulator. Generally it is considered that a plant useful for phytoremediation should have a BCF value greater then 1000 (Zayed et al., 1998). In the present study, the BCF value of L. natans was 7666, which suggest that it maybe be considered as a good accumulator of cadmium. The response of aquatic macrophytes to cadmium concentration varies from species to species in terms of metal accumulation and BCF. The Cd BCF have been reported in different species by Jain et al., (1990); Phetsombat et al., (2006) ; Abhilash et al., (2009); Ha et al., (2011); Das et al., (2014); Marbaniang and Chaturvedi, (2014 ). It has been found that in spite of significant increases of Cd concentration in the plant over the 5th and 10th day range of exposure concentrations, the relationship of Cd BCF to Cd exposure concentration was negatively correlated (Figure 2). The inverse BCF to exposure relationship may be due to the fact that, even though with the passages of time the concentration of Cd also increases, however, the internal accumulation of Cd does not rise as quickly as the external exposure levels. This indicates that the plants may have developed certain mechanism to control a significant degree over Cd accumulation. Thus, the BCF values decreases with the increase of exposure concentration of Cd in the medium.

Translocation Factor (TF) in plants is the ratio of heavy metal accumulation in the shoots parts to the roots. Translocation of heavy metal in plants are generally dependent on plant species, type of heavy metals and various environmental factors like pH, redox potential (Eh), temperature, salinity (Fritioff et al., 2005). Yanqun et al., (2005) reported that a TF value greater than 1, the plants are considered as an accumulator species, whereas TF lesser than 1 is an excluder species. The TF>1 indicated that there is a transport of metal from root to leaf probably through an efficient metal transporter system (Zhao et al., 2002) metals sequestration in the leaf vacuoles and apoplast (Lasat et al., 2000).

Table 3: Bioconcentration Factor (BCF) and Translocation Factor (TF) for cadmium in L. natans

 Cd concentration (mgL-1) Bioconcentration Factor Translocation Factor 5d 10d 5d 10d 1 3183 7666 2.8 2.0 10 885 1308 2.0 1.3 50 245 317 1.1 1.1 100 113 147 1.1 1.5

Conclusion

In the present study, L. natans was found to accumulate Cd in both its root and shoot in a high degree. This plant has great potential for removing Cd from the surrounding water with the values of BCFs >103. The present study indicates that L. natans is suitable for the phytoremediation of Cd contamination from water. Therefore, L. natans could be useful for phytoremediation of Cd from contaminated water. Furthermore, field experiments are needed to carry out their Phytoremediation potentials of these plants for phytoremediation technique.

Acknowledgements

Authors would like to acknowledge UGC Govt. of India for providing financial support under Rajiv Gandhi National Fellowship Programme to carry out the study. The authors also would like to thank the Head, Department of Environmental Studies, North Eastern Hill University, for providing necessary laboratory facilities.

References

Abhilash, P.C., Pandey, V.C., Srivastava, P., Rakesh, P.S., Chandran, S., Singh, N. and Thomas, A.P. 2009. Phytofiltration of cadmium from water by Limnocharis flava (L.) Buchenau grown in free-floating culture system. J. Hazard. Mater., 170(2&3): 791–797.

ATSDR, 2011. CERCLA priority list of hazardous substances, agency for toxic substances and disease control (Online), available URL: http://www.atsdr.cdc.gov/spl/index.html Accessed on 1 Jul 2014.

Das, S., Goswami, S. and Talukdar, A.D. 2014. A Study on Cadmium Phytoremediation Potential of Water Lettuce, Pistia stratiotes L. Bull Environ Contam Toxicol, 92: 169–174.

Demirezen, D. and Aksoy, A. 2004. Accumulation of heavy metals in Typha angustifolia (L.) and Potamogeton pectinatus (L.) living in Sultan Marsh (Kayseri, Turkey). Chemosphere., 56: 685–696.

Deng, H., Ye, Z.H. and Wong, M.H. 2004. Accumulation of lead, zinc, copper and cadmium by 12 wetland plant species thriving in metal-contaminated sites in China. Environ. Pollut., 132: 29-40.

Dunbabin, J.S. and Bowmer, K.H. 1992. Potential use of constructed wetlands for treatment of industrial waste waters containing metals. Sci. Total Environ., 3: 151–168

Fritioff, A., Kautsky, L. and Greger, M. 2005. Influence of temperature and salinity on heavy metal uptake by submersed plants. Environ. Pollut., 133: 265-274.

Fritioff, A. and Greger, M. 2007. Fate of cadmium in Elodea Canadensis, Chemosphere., 67: 365–375.

Garbisu, C. and Alkorta, I. 2001. Phytoextraction: a costeffective plant based technology for the removal of metals from the environment. Bioresour Technol, 77: 229–236.

Ha, N.T.H., Sakakibara, M. and Sano, S. 2011. Accumulation of Indium and other heavy metals by Eleocharis acicularis: an option for phytoremediation and phytomining. Bioresour Technol., 102: 2228–2234.

Hadad, H.R., Mufarrege, M.M., Pinciroli, M., Di Luca, G.A. and Maine, M.A. 2010. Morphological response of Typha domingensis to an industrial effluent containing heavy metals in a constructed wetland. Arch Environ Contam Toxicol., 58(3): 666-75.

He, Z.L., Yang, X.E. and Stoffela, P.J. 2005. Trace elements in agroecosystems and impacts on the environment. J Trace Elem Med Biol, 19:125–140.

Hoagland, D.R. and Arnon, D.I. 1950. The water-culture method for growing plants without soil. Calif. Agric. Exp. STN., 347: 1-32.

Kara, Y. and Zeytunluoglu, A. 2007. Bioaccumulation of Toxic Metals (Cd and Cu) by Groenlandia densa (L.) Fourr. Bull. Environ. Contam. Toxicol., 79: 609–612.

Lasat, M.M., Pence, N.S., Garvin, D.F., Ebbs, S.D. and Kochian, L.V. 2000. Molecular physiology of zinc transport in zinc hyperaccumulator Thlaspi caerulescens. J. Exp. Bot., 51: 71-79.

Maine, M.A., Duarte, M.V. and Sune, N.L. 2001. Cadmium uptake by Pistia stratiotes. Water Res., 35(11): 2629-2634.

Marbaniang, D. and Chaturvedi, S.S. 2014. Cadmium uptake and Phytoremediation potential of three Aquatic Macrophytes of Meghalaya, India. Int Res J EnvironSci., 3(6): 1-4.

Peng, K., Luo, C., Lou, L., Li, X. and Shen, Z. 2008. Bioaccumulation of heavy metals by the aquatic plants Potamogeton pectinatus L. and Potamogeton malaianus Miq. and their potential use for contamination indicators and in wastewater treatment. Sci Total Environ., 392: 22–29.

Phetsombat, S., Kruatrachue, M., Pokethitiyook, P. and Upatham, S. 2006. Toxicity and bioaccumulation of cadmium and lead in Salvinia cucullata. J Environ Biol, 27(4): 645-652.

Rai, P.K. (2008). Heavy metal pollution in aquatic ecosystems and its phytoremediation using wetland plants: an ecosustainable approach. Int J Phytoremediation, 10: 133–160.

Rebhun, M. and Galil, N. 1990. Wastewater treatment technologies. In: L. Zirm and J. Mayer (eds). The Management of Hazardous Substances in the Environment, 85–102.

Sivaci, E.R., Sivaci A., Sokmen M. 2004. Biosorption of cadmium by Myriophyllum spicatum L. and Myriophyllum triphyllum orchard. Chemosphere, 56: 1043–1048.

Wang, Q., Cui, Y. and Dong, Y. 2002. Phytoremediation of polluted waters: potentials and prospects of wetland plants. Acta Biotechnol, 22: 199–208.

Weiss, J., Hondzom, M., Biesbor, D. and Semmen, M. 2006. Laboratory study of heavy metal phytoremediation by three wetland macrophytes. Int. J. Phytorem., 8:245-259.

Yanqun, Z., Yuan, L., Jianjun, C., Haiyan, C., Li, Q. and Schvartz, C. 2005. Hyperaccumulation of Pb, Zn and Cd in herbaceous grown on lead-zinc mining area in Yunnan. China, Environ. Int., 31: 755-762.

Zayed, A., Gowthaman, S. and Terry, N. 1998. Phytoaccumulation of trace elements by wetlands. I. Duckweed. J Environ Qual., 27: 339–344.

Zhu, Y.L., Zayed, A.M., Qian, J.H., Souza, M.D. and Terry, N. 1999. Phytoaccumulation of trace elements by wetland plants: II Water hyacinth. J Environ Qual, 28: 339–344.

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