The Bioaccumulation and Translocation Potential of Some Aquatic Plants

Snežana Branković1, Radmila Glišić1, Marina Topuzović1, Vera Đekić2, Marija Marin3

 

1 University of Kragujevac, Faculty of Science, Department of Biology and Ecology, Radoja Domanovića 12, 34 000 Kragujevac, Republic of Serbia; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

2 Agriculture Research Institute Serbia, Small Grains Research Center, Save Kovačevića 31, 34000 Kragujevac, Republic of Serbia

3 University of Belgrade, Faculty of Biology, Institute of Zoology, Studentski trg 16, 11 000 Belgrade, Republic of Serbi

 

Abstract

The aim of this study was to determine the bioaccumulation and translocation potential for Pb, Cd, Hg and As of macrophytes Typha angustifolia L., Iris pseudacorus L. and Polygonum amphibium L. sampled on the Gruža Reservoir. The concentrations of Hg and As were higher than prescribed maximum water concentrations; the concentrations of Hg and As were higher than target, maximum permitted and remediation values in sediment. T. angustifolia is suitable for the phytoextraction of Hg and As from water and Pb, Cd and As from sediment as well as I. pseudacorus for the phytoextraction of As from water and sediment.

Keywords: bioaccumulation, translocation, elements, macrophytes.

Introduction

 

Water macrophytes are more suitable for the treatment of contaminated waters than land plants, because of their faster growth, higher biomass production and better ability to accumulate pollutants due to direct contact with contaminated water. They are also good indicators of water quality as they react to changes in water quality by changes in the structure of aquatic vegetation. Their ability to hyperaccumulate pollutants, especially heavy metals and metalloids, makes them interesting candidates for research, especially for the treatment of different types of contaminated water (Sood et al., 2012). The macrophytes have the ability to accumulate different elements in a way in which their accumulation corresponds to growing concentrations of the pollutants in water, or to absorb elements independently of the physiological needs of the plant in concentrations that are many times higher than their concentrations in the aquatic environment.

The aqueous macrophytes have several characteristics that are important for the accumulation of metals, such as: their biomass, leaves and epiphytes of macrophytes, which provide an expanded zone for precipitation of certain substances, absorption of metal ions and accumulation and sequestration of pollutants, while rooted species can absorb metals through their roots and rhizomes, but also through leaves. Also, most of the macrophytes are stationary and, as such, are the first line of protection against the various pollutants.

Since they are able to absorb the mineral elements, nutrients or various pollutants from the aquatic environment through the entire plant surface or particular organs, and to accumulate them in large quantities, the aqueous macrophytes contribute to the circulation of nutrients, water control and sediment stability. Also, they play a significant role in biofiltration, bioaccumulation and bioindications, because of their ability accumulate large quantities of different elements and materials. Thanks to their sedentary nature, rooted, submerged and flotant macrophytes, as well as emerged species, have a special role in the bioaccumulation of various substances in shallow littoral waters of lakes, rivers and canals, etc. (Simić et al., 1994).

 

Material and Methods

The multipurpose Gruža Reservoir was created by the partitioning of the middle course of the Gruža River (by formation of the dam during the period from 1979 to 1985) (Ostojić and Čomić, 2005). It is located 20 km southeast of the City of Kragujevac, on 238-269 m above sea level, 32 km from the mouth of the Gruža River in the West Morava River (Figure 1).

 

fig01
Figure 1: The investigated area.

 

Samples of water, sediment (2 liters each), as well as plants (Typha angustifolia L., Iris pseudacorus L., Polygonum amphibium L.) were taken at specified sites of the Gruža Reservoir (Figure 2, 3, 4). In the case of species T. angustifolia L. and I. pseudacorus L. the root, stem and leaf were sampled, while in species P. amphibium the stem and leaf were sampled. The identification of plant material was carried out in the laboratory of the Department of Biology and Ecology, Faculty of Science in Kragujevac, using standard identification keys: Javorka & Csapody (Javorka and Csapody, 1979), Flora of the Republic of Serbia (Josifović, 1970-1980) and Flora Europaea (Tutin, 1964-1980).

The identified plant material was washed in distilled water, dried at room temperature, and then in a dryer (Binder / Ed15053) for 24 hours at a temperature of 105°C. After that, it was prepared for chemical analysis according to the standard procedure used for water and aquatic plants (APHA, 1995).

The chemical analyses of water, sediment and plant material were made according to standard methods in the Institute of Public Health in Kragujevac, and the determination of concentration of the tested elements (Pb, Cd, Hg, As) was performed by inductively coupled plasma-atomic emission spectrometry (ICP-OES and CAP 6500) directly from the parent solution. Each sample was read in three repetitions, and the contents of the elements in the plant material, sediment and water were expressed in mg/kg of dry matter and mg/l.

 

fig02
Figure 2: Typha angustifolia L.

 

fig03
Figure 3: Iris pseudacorus L.

 

fig04
Figure 4: Polygonum amphibium L.

 

Determination was performed on: mean values, standard deviations, bioaccumulation and translocation factors, as well as the factor of enrichment. The Bioaccumulation Factor (BF) is an index of the ability of a plant to accumulate a certain metal in relation to its concentration in the substrate (Ghosh and Singh, 2006). It is calculated as the ratio of the metal concentration in the root and its concentration in water and sediment. The Translocation Factor (TF) is used to estimate the relative translocation of metals from underground plant organs (roots) to above-ground organs (stems, leaves, etc.). It is calculated as the ratio of metal concentration in the above-ground organ and its concentration in the root (Gupta et al., 2008). The Enrichment Factor (EF) is calculated as the ratio of metal concentration in the above-ground plant organs and its concentration in water and sediment (Branquinho et al., 2007). Also, the relationship between the content of metal in the leaf and the stem was determined.

 

Results and Discussion

The mean values of the concentration of the examined elements in water and sediment are presented (Table 1). The results obtained for analyzed water show that the concentration of Hg was 20 times higher, and the concentration of As was five times higher than the prescribed maximally allowed concentration of these elements in water, in accordance with the Regulation of the Republic of Serbia (Official Gazette RS, 23/94). The concentrations of Pb and Cd in water were below the detection limit.

The concentration of elements in the sediment had the following declining order: As> Hg> Pb> Cd. The Cd concentration exceeded the target value, and concentrations of Hg and As were higher than the target, maximally allowable and remediation values for these elements in sediment according to the Regulation of the Republic of Serbia (Official Gazette RS 50/12).

 

tab01

 

In the scope of the researched plant species, a difference in concentration of the investigated metals was present among their different organs. The concentrations of the investigated elements in T. angustifolia were in the range from 6.07 mg Cd kg-1 to 16016.67 mg As kg-1 in the root of this species (Table 2), while in the stem and leaf the concentrations of Pb and Cd were below the detection limit. The smallest Cd content (0.48 mg kg-1) was found in the leaf of species I. pseudacorus, while the root contained the highest content of As (12616.67 mg kg-1). No content of Hg was detected in the root of this species. The leaf of species P. amphibium contained the least Cd content (0.12 mg kg-1), and the stem the most As content (7515 mg kg-1), while the concentration of Pb in the leaf was below the detection limit.

The root of species the T. angustifolia had the highest concentration of Pb, Cd and As, while the P. amphibium stem contained the highest content of Hg. For species T. angustifolia, the concentrations of the examined elements in relation to the organ have fallen as follows: root> leaf> stem. In the species I. pseudacorus this order was: root> stem> leaf (except Hg), and in the species P. amphibium: stem> sheet.

Numerous studies have shown that there are variations in relation to the degree of accumulation of elements by different plants. The phytoremediation potential of aquatic plants depends on the level of tolerance and toxicity of the plant genera or species used in a particular study. Second, in a particular plant genus and/or species, there is a difference in the potential of bioaccumulation and translocation for the same element. The phytoremediation potential of plants is regulated by environmental factors such as: chemical speciation of the elements, as well as their initial concentrations, temperature, pH, redox potential, salinity and interactions of different elements with one another (Mishra et al., 2009). Aquatic macrophytes have the ability to concentrate pollutants (especially heavy metals) in their roots, stems and leaves. However, the accumulation of heavy metals is much higher in the roots of these plants, as indicated by the results of this research.

 

tab02

 

The bioaccumulation factor calculated for water ranged from 0 for Hg in species I. pseudacorus to 62589.55 for As in species T. angustifolia (Figure 5). The enrichment factor calculated for water ranged from 87.86 at the stem of species T. angustifolia to 29366.94 at the stem of species P. amphibium for metalloid As.

 

fig05
Figure 5: The bioaccumulation and translocation factors of water for investigated plant species.

 

The bioaccumulation factor calculated for sediment ranged from 0 for Hg in species I. pseudacorus to 2.39 for As in species T. angustifolia (Figure 6). The bioaccumulation factor of sediment in species T. angustifolia for Pb, Cd and As was greater than 1, as well as for metalloid As in species I. pseudacorus. The greatest enrichment factor calculated for sediment was determined at the stem of species P. amphibium for As (0.68).

 

fig06
Figure 6: The bioaccumulation and translocation factors of sediment for investigated plant species.

 

In species T. angustifolia, it was shown that the translocation factor of stem and leaf for Pb and Cd, as well as of stem for As is equal to 0 (Figure 7). Also, the translocation factor equal to 0 was found for the stem and leaf for Hg in species I. pseudacorus. The ratio of concentration for Hg in leaf and stem greater than 1 was established for both studied species, as well as the same ratio for As (45.7), in species T. angustifolia.

 

fig07
Figure 7: The translocation factors and ratio of investigated metals in leaf and stem.

 

Plant species that have a greater ability to accumulate and translocate metals from the root to the above-ground organs can be useful in their removal from the soil and applicable in phytoremediation of contaminated soils (Porebska and Ostrowska, 1999). The plant's ability to accumulate metals from water and soil can be estimated by using the bioaccumulation factor, while the ability of plants to translocate them from root to above-ground organs can be determined by the translocation factor. The enrichment factor offers an estimation of the translocation of metals from the root to the above-ground organs. All three biological factors can be applied in the estimation of the plant species' potential application in phytoremediation. According to some authors, TF> 1 expresses the ability of plants to transport nutrients from the root to the above-ground organs, most likely due to efficient metal transport systems (Zhao et al,. 2007). Also, according to Fitz and Wenzel (2002), plants exhibiting TF, and especially BF values greater than one, are suitable for phytoextraction. The obtained results show that the species T. angustifolia is suitable for the phytoextraction of Hg and As from water, and the species I. pseudacorus for the phytoextraction of As from water and sediment. Also, the species T. angustifolia can be used for the phytoextraction of Pb, Cd and As from sediment. All three studied species demonstrated a low capacity to absorb and accumulate the examined elements from sediment, while all of them absorb Hg and As from water to a great extent and accumulate them in stems and leaves.

The results obtained indicate the important role of macrophytic vegetation in aquatic ecosystems, with respect to bioremediation and bioindication, and confirm the assumption that chemical analysis of test-species can provide very important data, which offers a complete picture of the ecological status of an investigated aquatic ecosystem. Aquatic macrophytes can be used in water quality studies of ecosystems and in monitoring of metals and other pollutants. Monitoring of chemical content of plants taken from localities endangered by pollution can contribute to finding an overall and integral solution to protection, sanitation and revitalization problems in the Gruža Reservoir area.

 

Conclusion

The concentration of Hg was 20 times higher and the concentration of As was five times higher than the prescribed maximum permitted concentration of these elements in water, while the concentration of Cd in the sediment exceeded the target value. Also, the concentrations of Hg and As were higher than the target, maximum allowable and remedial values for these elements in the sediment according to the Regulation of the Republic of Serbia. The root of the species T. angustifolia contained the most Pb, Cd and As, while the stem of the species P. amphibium contained the most Hg. The obtained results indicate that all three investigated plant species are suitable for phytoextraction of certain elements: T. angustifolia for phytoextraction of Hg and As from water, I. pseudacorus for phytoextraction of As from water and sediment, T. angustifolia for phytoextraction Pb, Cd and As from the sediment. In addition, the species have a low ability to absorb and accumulate the examined elements from sediments, but to a greater extent they absorb Hg and As from water and accumulate them in stems and leaves.

 

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