International Journal of Phytoremediation, 16:1221–1227, 2014 C Taylor & Francis Group, LLC Copyright ISSN: 1522-6514 print / 1549-7879 online DOI: 10.1080/15226514.2013.821452
ARSENIC UPTAKE BY LEMNA MINOR IN HYDROPONIC SYSTEM Chandrima Goswami,1 Arunabha Majumder,2 Amal Kanti Misra,3 and Kaushik Bandyopadhyay1 1
Department of Construction Engineering, Jadavpur University, Kolkata, India School of Water Resource Engineering, Jadavpur University, Kolkata, India 3 Department of Civil Engineering, Jadavpur University, Kolkata, India 2
Arsenic is hazardous and causes several ill effects on human beings. Phytoremediation is the use of aquatic plants for the removal of toxic pollutants from external media. In the present research work, the removal efficiency as well as the arsenic uptake capacity of duckweed Lemna minor has been studied. Arsenic concentration in water samples and plant biomass were determined by AAS. The relative growth factor of Lemna minor was determined. The duckweed had potential to remove as well as uptake arsenic from the aqueous medium. Maximum removal of more than 70% arsenic was achieved at initial concentration of 0.5 mg/l arsenic on 15th day of experimental period of 22 days. Removal percentage was found to decrease with the increase in initial concentration. From BCF value, Lemna minor was found to be a hyperaccumulator of arsenic at initial concentration of 0.5 mg/L, such that accumulation decreased with increase in initial arsenic concentration. KEY WORDS arsenic, phytoremediation, bio concentration factor, relative growth factor, Lemna minor
INTRODUCTION Arsenic is a toxic metalloid that is found in soil, mineral, rocks, natural water (Alvarado et al. 2008) as well as organisms. Anthropogenic activities like mining, use of pesticides, burning of fossil fuels, industrial uses (Muntean et al. 2009) are also responsible for the arsenic pollution in the environment. It has several health hazards on human beings, and the major adverse effect being carcinogenesis (Huang et al. 2004; Wang et al. 2002). There are different conventional methods for the removal of arsenic from water. Bioremediation utilizes the living organisms for the clean-up of contaminated sites, may it be water, soil or sediment (Khataee 2012). Phytoremediation is a kind of bioremediation that involves the use of plants, both terrestrial and aquatic, for the removal of toxic elements from the environment (Soltan and Rashed 2003). It is an eco-friendly and cost-effective method of treatment of pollutants (Bennicelli et al. 2004). It can remove and uptake a wide range of pollutants including metals, organics, etc (Alvarado et al. 2008).
Address correspondence to Chandrima Goswami, Department of Construction Engineering, Jadavpur University, Kolkata-98, India. E-mail: [email protected] 1221
1222
C. GOSWAMI ET AL. Table 1 Scientific names, Common names of plants and their Arsenic accumulation capacity.
Scientific Names of Plants
Common Name
Pteris vittata Pteris cretica
Brake fern Moonlight fern
Callitriche lusitanica Callitriche brutia Lemna minor A. caroliniana Callitriche stagnalis Ceratophyllum demersum
Pedunculate water starwort Lesser duckweed Carolina mosquitofern Pondwater starwort Hornwort
Lemna gibba Egeria densa
Swollen duckweed —
Arsenic (Mg/kg)
References
— —
Baldwin and Butcher 2007 Baldwin and Butcher 2007; Huang et al. 2004 Favas et al. 2012 Favas et al. 2012 Favas et al. 2012 Favas et al. 2012 Favas et al. 2012 Favas et al. 2012; Reay 1972 Favas et al. 2012 Favas et al. 2012; Robinson et al. 2005
2346 523 430 397 4215
1021.7
1000
Arsenic removal efficiency of different macrophytes have been tested by authors (Anderson and Walsh 2007). Arsenic hyperaccumulation by different plants largely depends on the type of plant (Favas et al. 2012) and have been reported by authors. Table 1 includes a few of the arsenic accumulators and their level of accumulation as found by different authors. The aim of the present research work included the evaluation of the effect of arsenic on relative growth of duckweed Lemna minor and also whether the uptake of arsenic in the whole biomass of the duckweed occurred. The experiment was carried out in the terrace of Jadavpur University, Salt Lake Campus, Kolkata in February 2011. EXPERIMENTAL Hydroponic System Arsenic solution preparation: The experiments were conducted in the, Robinson 2005 laboratory with commonly available duckweed Lemna minor, with different initial concentrations of arsenic, i.e., 0.5, 1.0, and 2.0 mg/L that were prepared from the arsenic stock solution of 100 mg/L, prepared by dissolving 0.132 g of arsenic trioxide in 1000 ml of distilled water. A control set-up was installed to monitor the growth of duckweed Lemna minor in Mkandawire and Dudel (2005) the absence of arsenic. All reagents used were of analytical grade. For each concentration of arsenic, duplicate set-ups were installed. Initial concentrations obtained were 0.45 mg/L, 0.9 mg/L, and 1.86 mg/L for 0.5, 1.0, and 2.0 mg/L, respectively. Sample Collection Duckweed Lemna minor was collected from the nearby local freshwater pond near Salt Lake, Kolkata and were acclimatized with the same pond water, in the laboratory for 7 days. Fresh fronds were used for arsenic removal from hydroponic environment. Experiment was carried on for a period of 22 days in plastic tubs containing 20 L of working solution of arsenic. pH was noted regularly. Water sample was collected at regular interval of days and further arsenic content was analyzed. After the experimental period, duckweeds were harvested and their fresh weight was measured.
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Sample Preparation and Analysis For arsenic analysis, after 22 days of exposure, harvested duckweeds were rinsed with tap water and then with distilled water, air-dried and further dried at a modified (Khang 2012) temperature of 110◦ C for 2 h. Then the sample was homogenized and digested. The samples were then filtered and diluted by addition of distilled water and made up to 100ml. Further arsenic accumulation in the sample was analyzed by Atomic Absorption Spectrophotometer. Microsoft Excel 2007 software one way anova was used for analysis of data. Statistical significance of data means was determined at 5% alpha. RESULTS AND DISCUSSION Effect of Arsenic on Lemna minor In the present study, the three initial concentrations of arsenic considered for removal by Lemna minor include 0.5, 1.0, and 2.0 mg/l. Biomass of Lemna minor was not found to be much affected at lower arsenic test concentration, such that after completion of experimental period of 15 days and more, chlorosis or yellowing of fronds were noticed. Whereas at higher concentrations of 1.0 and 2.0 mg/L, there was yellowing and shrinkage of fronds with biomass reduction. Mkandawire et al. (2004a) found Lemna gibba tolerated arsenic toxicity within a concentration range of 0.01–0.5 mg/L, after which sudden toxicity was noticed. Percentage Removal of Arsenic Figure 1 represents the percentage removal of arsenic by duckweed Lemna minor. It was found that a maximum removal of more than 70% of arsenic was achieved at initial concentration of 0.5 mg/l of arsenic on the 15th day of the experimental study. Similar results were also obtained by Alvarado et al. 2008, who studied the removal of arsenic at
Figure 1 Percentage removal of arsenic by Lemna minor.
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C. GOSWAMI ET AL.
0.15 mg/l of initial concentration. Over an experimental period of 22 days, the maximum percentage removal was obtained on the 14th day of the experimental period (Alvarado et al. 2008). This was also in agreement with the maximum arsenic concentration in the Lemna minor tissue at that time (Alvarado et al. 2008). In the present study, at concentrations of 1.0 and 2.0 mg/l, the arsenic removal percentage was found to decrease gradually. Duman et al. (2010) found that the accumulation of As III and As V by Lemna minor increased with increasing arsenic concentration in the aqueous solutions, which was in contrary to the present findings. Relative Growth Factor The relative growth factor of Lemna minor after exposure to three different initial arsenic concentrations have been plotted in Figure 2. There was decrease in growth of Lemna minor as found from the results. Negative growth rate of Lemna minor exposed to arsenic concentration of 0.15 mg/l was found by Alvarado et al. 2008. p-value (0.00036) specifies that the different initial concentrations of arsenic do have statistically significant effect on relative growth factor of Lemna minor (p < 0.05). Significant inhibition of growth rate of Lemna gibba related to frond number was found (Mkandawire et al. 2004b) in case of initial concentration range of 0.02–0.05 mg/L arsenic (III).
Figure 2 Relative Growth Factor of Lemna minor at different initial concentrations.
Arsenic Accumulation and Bio Concentration Factor From the results of Favas et al. (2012), it was found that there are different submerged, floating and emergent species studied to have high arsenic accumulation capacities. Table 1 includes some of the aquatic plants and their arsenic accumulation capacities on a dry weight basis. The high arsenic accumulation was found in Callitriche stagnalis (4215 mg/kg DW) (Robinson et al. 2006), followed by Callitriche lusitanica (2346 mg/kg DW), a submerged species. It was found that a maximum of 654.4 mg/kg of arsenic was accumulated by
ARSENIC UPTAKE BY LEMNA MINOR
1225
Figure 3 Arsenic accumulation in Lemna minor biomass. Each value is mean with standard error of three replicates.
Lemna minor at initial concentration of 0.5 mg/l (Fig. 3). With further increase in initial concentration of arsenic, the accumulation decreased to 622 and 524 mg/kg at initial concentrations of 1.0 and 2.0 mg/L respectively. Mkandawire and Dudel (2005) found increase in arsenic concentration in Lemna gibba biomass with increase in arsenic concentration in the external medium. Thus a strong positive correlation of arsenic concentration in Lemna gibba (dry weight) was found with arsenic concentration in the external medium by Mkandawire and Dudel (2005). In the present investigation, arsenic accumulation in Lemna minor (dry weight) had a strong negative correlation (–0.995) with different initial arsenic concentrations in the external medium. Anderson and Walsh (2007) exposed marsh fern Thelypteris palustris to arsenic and found that at a concentration of 0.5 mg/L arsenic, the fern accumulated good amount of arsenic after 2 days of exposure period. Bio Concentration Factor (BCF) has been plotted in Figure 4. BCF values of arsenic by Lemna minor have been included in Table 2. BCF of arsenic by Lemna minor at 0.5 mg/l was 1454.22 in the present investigation. Bio Concentration Factor of Lemna minor was found to be 6100 (Favas et al. 2012) when concentration of water was 4.97 μg/L. High BCF for arsenic by Lemna gibba has also been noted by Mkandawire et al. (2004a). Thus at lower concentration studied, the Lemna minor acts as hyperaccumulator of arsenic. But with further increase in concentration, the BCF decreases to 690.56 and 281.81 for 1.0 and 2.0 mg/l of initial arsenic concentrations respectively. Physiological nature of plants Table 2 Accumulation of arsenic by Lemna minor as well as the BCF values As (mg/L) 0.5 1.0 2.0
As acc in plant (mg/g)
BCF
0.654 0.622 0.524
1454.2 690.56 281.80
1226
C. GOSWAMI ET AL.
Figure 4 Bio Concentration Factor at different initial concentrations of arsenic.
have been reported to get damaged when exposed to high concentrations of arsenic (Wan et al. 2013) and hence their accumulation capacity diminishes. The percentage of arsenic removal capacity of Lemna gibba was studied by Sasmaz and Obek (2009) and it was found that the plant accumulated arsenic particularly in the first two days, after which there was variation in accumulation. They suggested Lemna gibba to be an efficient accumulator, from their results. CONCLUSION Arsenic is threatful to aquatic lives as well as human beings. Hence phytoremediation by duckweed Lemna minor has been considered in the present study owing to their easy availability and the ease of application of the treatment procedure. It can be concluded that the duckweed Lemna minor effectively remediates arsenic contaminated water. Bio concentration factor (1454.2) at 0.5 mg/L initial arsenic concentration indicated hyperaccumulation of arsenic in the biomass. Thus Lemna minor can suitably be used for the remediation of arsenic from aqueous medium at low concentration. FUNDING The authors are thankful to the Department of Environment, Government of West Bengal for their financial assistance. REFERENCES Alvarado S, Guedez M, Lue-Meru MP, Nelson G, Alvaro A, Jesus AC, Gyulu Z. 2008. Arsenic removal from waters by bioremediation with the aquatic plants Water Hyacinth (Eichhornia crassipes) and Lesser Duckweed (Lemna minor). Bioresour Technol 99(17):8436–8440. Anderson L, Walsh MM. 2007. Arsenic uptake by common marsh fern Thelypteris palustris and its potential for phytoremediation. Sci Total Environ 379:263–265.
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Baldwin PR, Butcher DJ. 2007. Phytoremediation of arsenic by two hyperaccumulators in a hydroponic environment. Microchem J 85:297–300. Bennicelli R, Stepniewska Z, Banach A, Szajnocha K, Ostrowski J. 2004. The ability of Azolla caroliniana to remove heavy metals (Hg(II), Cr (III), Cr (VI), from municipal waste water. Chemosphere 55:141–146. Duman F, Ozturk F, Aydin Z. 2010. Biological responses of duckweed (Lemna minor L.) exposed to the inorganic arsenic species As(III) and As(V): effects of concentration and duration of exposure. Ecotoxicol 19(5):983–993. Favas PJC, Pratas J, Prasad MNV. 2012. Temporal variation in the arsenic and metal accumulation in the maritime pine tree grown on contaminated soil. Int J Environ Sci Technol (In press). Huang JW, Poynton CY, Kochian LV, Elless MP. 2004. Phytofiltration of arsenic from drinking water using arsenic hyperaccumulating ferns. Environ Sci Technol 38:3412–3417. Khang HV, Hatayama M, Inoue C. 2012. Arsenic accumlation by aquatic macrophyte coontail (Ceratophyllum demersum L.) exposed to arsenite and the effect of iron on the uptake of arsenite and arsenate. Environ Exp Bot 83:47–52. Khataee AR. 2012. Phytoremediation potential of duckweed (Lemna minor L.) in degradation of C.I Acid Blue 92: artificial neural network modelling. Ecotoxicol Environ Safety 80:291–298. Mkandawire M, Lyubun YV, Kosterin PV, Dudel EG. 2004a. Toxicity of arsenic species to Lemna gibba L. and the influence of phosphate on arsenic bioavailability. Environ Toxicol 19(1):26–34. Mkandawire M, Taubert B, Dudel EG. 2004b. Capacity of Lemna gibba L.(duckweed) for Uranium and Arsenic phytoremediation in mine tailing waters. Int J Phytorem 6(4):347–362. Mkandawire M, Dudel EG. 2005. Accumulation of arsenic in Lemna gibba L. (duckweed) in tailing waters of two abandoned uranium mining sites in Saxony, Germany. Sci Total Environ 336(1–3):81–89. Muntean C, Negrea A, Ciopec M, Lupa L, Negrea P, Rosu D. 2009. Studies regarding the arsenic removal from water. Chem Bull Politechnica 54(68):18–20. Reay PF. 1972. The accumulation of arsenic from arsenic-rich natural waters by aquatic plants. J Applied Ecol 9(2):557–565. Robinson B, Kim N, Marchetti M, Moni C, Schroeter L, Dijssel C, Milne G, Clothier B. 2006. Arsenic hyperaccumulation by aquatic macrophytes in the Taupo Volcanic Zone, New Zealand. Environ Exp Bot 58:206–215. Soltan ME, Rashed MN. 2003. Laboratory study on the survival of water hyacinth under several conditions of heavy metal concentrations. Adv Environ Res 7:321–334. Sasmaz A, Obek E. 2009. The accumulation of arsenic, uranium, and boron in Lemna gibba L. exposed to secondary effluents. Ecol Eng 35(10):1564–1567. Wang JP, Qi L, Moore MR, Ng JC. 2002. A review of animal models for the study of arsenic carcinogenesis. Toxicol Lett 133(1):17–31. Wan XM, Lei M, Liu YR, Huang ZC, Chen TB, Gao D. 2013. A comparison of arsenic accumulation and tolerance among four populations of Pteris vittata from habitats with a gradient of arsenic concentration. Sci Total Environ 442:143–151.
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ARSENIC UPTAKE BY LEMNA MINOR IN HYDROPONIC SYSTEM Chandrima Goswami,1 Arunabha Majumder,2 Amal Kanti Misra,3 and Kaushik Bandyopadhyay1 1
Department of Construction Engineering, Jadavpur University, Kolkata, India School of Water Resource Engineering, Jadavpur University, Kolkata, India 3 Department of Civil Engineering, Jadavpur University, Kolkata, India 2
Arsenic is hazardous and causes several ill effects on human beings. Phytoremediation is the use of aquatic plants for the removal of toxic pollutants from external media. In the present research work, the removal efficiency as well as the arsenic uptake capacity of duckweed Lemna minor has been studied. Arsenic concentration in water samples and plant biomass were determined by AAS. The relative growth factor of Lemna minor was determined. The duckweed had potential to remove as well as uptake arsenic from the aqueous medium. Maximum removal of more than 70% arsenic was achieved at initial concentration of 0.5 mg/l arsenic on 15th day of experimental period of 22 days. Removal percentage was found to decrease with the increase in initial concentration. From BCF value, Lemna minor was found to be a hyperaccumulator of arsenic at initial concentration of 0.5 mg/L, such that accumulation decreased with increase in initial arsenic concentration. KEY WORDS arsenic, phytoremediation, bio concentration factor, relative growth factor, Lemna minor
INTRODUCTION Arsenic is a toxic metalloid that is found in soil, mineral, rocks, natural water (Alvarado et al. 2008) as well as organisms. Anthropogenic activities like mining, use of pesticides, burning of fossil fuels, industrial uses (Muntean et al. 2009) are also responsible for the arsenic pollution in the environment. It has several health hazards on human beings, and the major adverse effect being carcinogenesis (Huang et al. 2004; Wang et al. 2002). There are different conventional methods for the removal of arsenic from water. Bioremediation utilizes the living organisms for the clean-up of contaminated sites, may it be water, soil or sediment (Khataee 2012). Phytoremediation is a kind of bioremediation that involves the use of plants, both terrestrial and aquatic, for the removal of toxic elements from the environment (Soltan and Rashed 2003). It is an eco-friendly and cost-effective method of treatment of pollutants (Bennicelli et al. 2004). It can remove and uptake a wide range of pollutants including metals, organics, etc (Alvarado et al. 2008).
Address correspondence to Chandrima Goswami, Department of Construction Engineering, Jadavpur University, Kolkata-98, India. E-mail: [email protected] 1221
1222
C. GOSWAMI ET AL. Table 1 Scientific names, Common names of plants and their Arsenic accumulation capacity.
Scientific Names of Plants
Common Name
Pteris vittata Pteris cretica
Brake fern Moonlight fern
Callitriche lusitanica Callitriche brutia Lemna minor A. caroliniana Callitriche stagnalis Ceratophyllum demersum
Pedunculate water starwort Lesser duckweed Carolina mosquitofern Pondwater starwort Hornwort
Lemna gibba Egeria densa
Swollen duckweed —
Arsenic (Mg/kg)
References
— —
Baldwin and Butcher 2007 Baldwin and Butcher 2007; Huang et al. 2004 Favas et al. 2012 Favas et al. 2012 Favas et al. 2012 Favas et al. 2012 Favas et al. 2012 Favas et al. 2012; Reay 1972 Favas et al. 2012 Favas et al. 2012; Robinson et al. 2005
2346 523 430 397 4215
1021.7
1000
Arsenic removal efficiency of different macrophytes have been tested by authors (Anderson and Walsh 2007). Arsenic hyperaccumulation by different plants largely depends on the type of plant (Favas et al. 2012) and have been reported by authors. Table 1 includes a few of the arsenic accumulators and their level of accumulation as found by different authors. The aim of the present research work included the evaluation of the effect of arsenic on relative growth of duckweed Lemna minor and also whether the uptake of arsenic in the whole biomass of the duckweed occurred. The experiment was carried out in the terrace of Jadavpur University, Salt Lake Campus, Kolkata in February 2011. EXPERIMENTAL Hydroponic System Arsenic solution preparation: The experiments were conducted in the, Robinson 2005 laboratory with commonly available duckweed Lemna minor, with different initial concentrations of arsenic, i.e., 0.5, 1.0, and 2.0 mg/L that were prepared from the arsenic stock solution of 100 mg/L, prepared by dissolving 0.132 g of arsenic trioxide in 1000 ml of distilled water. A control set-up was installed to monitor the growth of duckweed Lemna minor in Mkandawire and Dudel (2005) the absence of arsenic. All reagents used were of analytical grade. For each concentration of arsenic, duplicate set-ups were installed. Initial concentrations obtained were 0.45 mg/L, 0.9 mg/L, and 1.86 mg/L for 0.5, 1.0, and 2.0 mg/L, respectively. Sample Collection Duckweed Lemna minor was collected from the nearby local freshwater pond near Salt Lake, Kolkata and were acclimatized with the same pond water, in the laboratory for 7 days. Fresh fronds were used for arsenic removal from hydroponic environment. Experiment was carried on for a period of 22 days in plastic tubs containing 20 L of working solution of arsenic. pH was noted regularly. Water sample was collected at regular interval of days and further arsenic content was analyzed. After the experimental period, duckweeds were harvested and their fresh weight was measured.
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Sample Preparation and Analysis For arsenic analysis, after 22 days of exposure, harvested duckweeds were rinsed with tap water and then with distilled water, air-dried and further dried at a modified (Khang 2012) temperature of 110◦ C for 2 h. Then the sample was homogenized and digested. The samples were then filtered and diluted by addition of distilled water and made up to 100ml. Further arsenic accumulation in the sample was analyzed by Atomic Absorption Spectrophotometer. Microsoft Excel 2007 software one way anova was used for analysis of data. Statistical significance of data means was determined at 5% alpha. RESULTS AND DISCUSSION Effect of Arsenic on Lemna minor In the present study, the three initial concentrations of arsenic considered for removal by Lemna minor include 0.5, 1.0, and 2.0 mg/l. Biomass of Lemna minor was not found to be much affected at lower arsenic test concentration, such that after completion of experimental period of 15 days and more, chlorosis or yellowing of fronds were noticed. Whereas at higher concentrations of 1.0 and 2.0 mg/L, there was yellowing and shrinkage of fronds with biomass reduction. Mkandawire et al. (2004a) found Lemna gibba tolerated arsenic toxicity within a concentration range of 0.01–0.5 mg/L, after which sudden toxicity was noticed. Percentage Removal of Arsenic Figure 1 represents the percentage removal of arsenic by duckweed Lemna minor. It was found that a maximum removal of more than 70% of arsenic was achieved at initial concentration of 0.5 mg/l of arsenic on the 15th day of the experimental study. Similar results were also obtained by Alvarado et al. 2008, who studied the removal of arsenic at
Figure 1 Percentage removal of arsenic by Lemna minor.
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C. GOSWAMI ET AL.
0.15 mg/l of initial concentration. Over an experimental period of 22 days, the maximum percentage removal was obtained on the 14th day of the experimental period (Alvarado et al. 2008). This was also in agreement with the maximum arsenic concentration in the Lemna minor tissue at that time (Alvarado et al. 2008). In the present study, at concentrations of 1.0 and 2.0 mg/l, the arsenic removal percentage was found to decrease gradually. Duman et al. (2010) found that the accumulation of As III and As V by Lemna minor increased with increasing arsenic concentration in the aqueous solutions, which was in contrary to the present findings. Relative Growth Factor The relative growth factor of Lemna minor after exposure to three different initial arsenic concentrations have been plotted in Figure 2. There was decrease in growth of Lemna minor as found from the results. Negative growth rate of Lemna minor exposed to arsenic concentration of 0.15 mg/l was found by Alvarado et al. 2008. p-value (0.00036) specifies that the different initial concentrations of arsenic do have statistically significant effect on relative growth factor of Lemna minor (p < 0.05). Significant inhibition of growth rate of Lemna gibba related to frond number was found (Mkandawire et al. 2004b) in case of initial concentration range of 0.02–0.05 mg/L arsenic (III).
Figure 2 Relative Growth Factor of Lemna minor at different initial concentrations.
Arsenic Accumulation and Bio Concentration Factor From the results of Favas et al. (2012), it was found that there are different submerged, floating and emergent species studied to have high arsenic accumulation capacities. Table 1 includes some of the aquatic plants and their arsenic accumulation capacities on a dry weight basis. The high arsenic accumulation was found in Callitriche stagnalis (4215 mg/kg DW) (Robinson et al. 2006), followed by Callitriche lusitanica (2346 mg/kg DW), a submerged species. It was found that a maximum of 654.4 mg/kg of arsenic was accumulated by
ARSENIC UPTAKE BY LEMNA MINOR
1225
Figure 3 Arsenic accumulation in Lemna minor biomass. Each value is mean with standard error of three replicates.
Lemna minor at initial concentration of 0.5 mg/l (Fig. 3). With further increase in initial concentration of arsenic, the accumulation decreased to 622 and 524 mg/kg at initial concentrations of 1.0 and 2.0 mg/L respectively. Mkandawire and Dudel (2005) found increase in arsenic concentration in Lemna gibba biomass with increase in arsenic concentration in the external medium. Thus a strong positive correlation of arsenic concentration in Lemna gibba (dry weight) was found with arsenic concentration in the external medium by Mkandawire and Dudel (2005). In the present investigation, arsenic accumulation in Lemna minor (dry weight) had a strong negative correlation (–0.995) with different initial arsenic concentrations in the external medium. Anderson and Walsh (2007) exposed marsh fern Thelypteris palustris to arsenic and found that at a concentration of 0.5 mg/L arsenic, the fern accumulated good amount of arsenic after 2 days of exposure period. Bio Concentration Factor (BCF) has been plotted in Figure 4. BCF values of arsenic by Lemna minor have been included in Table 2. BCF of arsenic by Lemna minor at 0.5 mg/l was 1454.22 in the present investigation. Bio Concentration Factor of Lemna minor was found to be 6100 (Favas et al. 2012) when concentration of water was 4.97 μg/L. High BCF for arsenic by Lemna gibba has also been noted by Mkandawire et al. (2004a). Thus at lower concentration studied, the Lemna minor acts as hyperaccumulator of arsenic. But with further increase in concentration, the BCF decreases to 690.56 and 281.81 for 1.0 and 2.0 mg/l of initial arsenic concentrations respectively. Physiological nature of plants Table 2 Accumulation of arsenic by Lemna minor as well as the BCF values As (mg/L) 0.5 1.0 2.0
As acc in plant (mg/g)
BCF
0.654 0.622 0.524
1454.2 690.56 281.80
1226
C. GOSWAMI ET AL.
Figure 4 Bio Concentration Factor at different initial concentrations of arsenic.
have been reported to get damaged when exposed to high concentrations of arsenic (Wan et al. 2013) and hence their accumulation capacity diminishes. The percentage of arsenic removal capacity of Lemna gibba was studied by Sasmaz and Obek (2009) and it was found that the plant accumulated arsenic particularly in the first two days, after which there was variation in accumulation. They suggested Lemna gibba to be an efficient accumulator, from their results. CONCLUSION Arsenic is threatful to aquatic lives as well as human beings. Hence phytoremediation by duckweed Lemna minor has been considered in the present study owing to their easy availability and the ease of application of the treatment procedure. It can be concluded that the duckweed Lemna minor effectively remediates arsenic contaminated water. Bio concentration factor (1454.2) at 0.5 mg/L initial arsenic concentration indicated hyperaccumulation of arsenic in the biomass. Thus Lemna minor can suitably be used for the remediation of arsenic from aqueous medium at low concentration. FUNDING The authors are thankful to the Department of Environment, Government of West Bengal for their financial assistance. REFERENCES Alvarado S, Guedez M, Lue-Meru MP, Nelson G, Alvaro A, Jesus AC, Gyulu Z. 2008. Arsenic removal from waters by bioremediation with the aquatic plants Water Hyacinth (Eichhornia crassipes) and Lesser Duckweed (Lemna minor). Bioresour Technol 99(17):8436–8440. Anderson L, Walsh MM. 2007. Arsenic uptake by common marsh fern Thelypteris palustris and its potential for phytoremediation. Sci Total Environ 379:263–265.
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Baldwin PR, Butcher DJ. 2007. Phytoremediation of arsenic by two hyperaccumulators in a hydroponic environment. Microchem J 85:297–300. Bennicelli R, Stepniewska Z, Banach A, Szajnocha K, Ostrowski J. 2004. The ability of Azolla caroliniana to remove heavy metals (Hg(II), Cr (III), Cr (VI), from municipal waste water. Chemosphere 55:141–146. Duman F, Ozturk F, Aydin Z. 2010. Biological responses of duckweed (Lemna minor L.) exposed to the inorganic arsenic species As(III) and As(V): effects of concentration and duration of exposure. Ecotoxicol 19(5):983–993. Favas PJC, Pratas J, Prasad MNV. 2012. Temporal variation in the arsenic and metal accumulation in the maritime pine tree grown on contaminated soil. Int J Environ Sci Technol (In press). Huang JW, Poynton CY, Kochian LV, Elless MP. 2004. Phytofiltration of arsenic from drinking water using arsenic hyperaccumulating ferns. Environ Sci Technol 38:3412–3417. Khang HV, Hatayama M, Inoue C. 2012. Arsenic accumlation by aquatic macrophyte coontail (Ceratophyllum demersum L.) exposed to arsenite and the effect of iron on the uptake of arsenite and arsenate. Environ Exp Bot 83:47–52. Khataee AR. 2012. Phytoremediation potential of duckweed (Lemna minor L.) in degradation of C.I Acid Blue 92: artificial neural network modelling. Ecotoxicol Environ Safety 80:291–298. Mkandawire M, Lyubun YV, Kosterin PV, Dudel EG. 2004a. Toxicity of arsenic species to Lemna gibba L. and the influence of phosphate on arsenic bioavailability. Environ Toxicol 19(1):26–34. Mkandawire M, Taubert B, Dudel EG. 2004b. Capacity of Lemna gibba L.(duckweed) for Uranium and Arsenic phytoremediation in mine tailing waters. Int J Phytorem 6(4):347–362. Mkandawire M, Dudel EG. 2005. Accumulation of arsenic in Lemna gibba L. (duckweed) in tailing waters of two abandoned uranium mining sites in Saxony, Germany. Sci Total Environ 336(1–3):81–89. Muntean C, Negrea A, Ciopec M, Lupa L, Negrea P, Rosu D. 2009. Studies regarding the arsenic removal from water. Chem Bull Politechnica 54(68):18–20. Reay PF. 1972. The accumulation of arsenic from arsenic-rich natural waters by aquatic plants. J Applied Ecol 9(2):557–565. Robinson B, Kim N, Marchetti M, Moni C, Schroeter L, Dijssel C, Milne G, Clothier B. 2006. Arsenic hyperaccumulation by aquatic macrophytes in the Taupo Volcanic Zone, New Zealand. Environ Exp Bot 58:206–215. Soltan ME, Rashed MN. 2003. Laboratory study on the survival of water hyacinth under several conditions of heavy metal concentrations. Adv Environ Res 7:321–334. Sasmaz A, Obek E. 2009. The accumulation of arsenic, uranium, and boron in Lemna gibba L. exposed to secondary effluents. Ecol Eng 35(10):1564–1567. Wang JP, Qi L, Moore MR, Ng JC. 2002. A review of animal models for the study of arsenic carcinogenesis. Toxicol Lett 133(1):17–31. Wan XM, Lei M, Liu YR, Huang ZC, Chen TB, Gao D. 2013. A comparison of arsenic accumulation and tolerance among four populations of Pteris vittata from habitats with a gradient of arsenic concentration. Sci Total Environ 442:143–151.
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