alexa Estimation of Toxicity and Genotoxicity of Water, Bottom Sediments and Submerged Macrophyte Elodea canadensis of the Yenisei River in the Presence or Absence of Americium-241
ISSN: 2161-0525
Journal of Environmental & Analytical Toxicology

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  • Research Article   
  • J Environ Anal Toxicol 2016, Vol 6(4): 389
  • DOI: 10.4172/2161-0525.1000389

Estimation of Toxicity and Genotoxicity of Water, Bottom Sediments and Submerged Macrophyte Elodea canadensis of the Yenisei River in the Presence or Absence of Americium-241

Vasyunina Ye A1, Bondareva LG2,3*, Rakitsky VN3 and Federova Ye N3
1Institute of Cytology and Genetics, SB RAS, Novosibirsk, Russia
2Siberian Federal University, Krasnoyarsk, Russia
3FF Erisman Federal Research Center of Hygiene, Moscow Region, Mytishchi, Russia
*Corresponding Author: Bondareva LG, Siberian Federal University, Krasnoyarsk, Russia, Tel: +74955861144, Fax: +74955829294, Email: [email protected]

Received Date: Jul 15, 2016 / Accepted Date: Jul 26, 2016 / Published Date: Jul 29, 2016

Abstract

Toxicity and genotoxicity of one of the most widely spread species of aqueous plants of the Yenisei River – Elodea canadensis and bottom sediments of the Yenisei River containing 241Am have been evaluated for the first time. It is shown that the suspensions and extracts of plants or bottom sediments which do not contain 241Am, inherently decrease the survival of bacterial cells of specific strains as compared to the control samples. Cell death of E. coli in the aqueous plants accumulating 241Am was observed to be even higher, which is consistent with the toxicity of the control samples of aqueous solutions of 241Am salts. Non-radioactive suspensions of the control samples of the plants and bottom sediments also slightly influenced the survival of the S. typhimurium TA98 cells, whereas their survival abruptly decreased in the presence of 241Am. The samples of the bottom sediments without 241Am hardly influenced the «frequency of His reversions» of the indicator S. typhimurium. In the suspensions of the 241Am-containing bottom sediments a dose-dependent effect was observed both in the «frequency of reversions» and in the quantity of the detected His revertants in the S. typhimurium TA98 strain.

Keywords: Radiation; Toxicity and genotoxicity; Bottom sediments; Plants; River Yenisei

Introduction

It is known that the radiation factor can play a dominant role in the negative impact of the environment on human health [1-8]. The entrance of long-lived radionuclides into a human organism usually results in a partial radionuclide deposition [9], and their effect on people can have the character of low dose chronicle inner irradiation. Under ionizing radiation the destruction of water molecules occurs in a human organism, giving rise to the formation of reactive oxygen intermediates (ROI) including hydroxyl- and superoxide-radicals [1- 7]. Under the action of ROI oxidation of lipids, proteins, nucleic acids and other components of the human cells and blood occurs, which can result in various diseases connected with somatic, genetic, immune and other disturbances.

The oxidation damages of DNA are the most significant sources of mutations and they are considered to play a crucial role in the processes of aging, development of cancer diseases and a number of other pathological changes. For example, large-scale nuclear tests performed at the test site «Novaya Zemlya» in 1955-1962 resulted in the continuous prolonged effect of incorporated radionuclides (137Cs and 90Sr) on population of Tundra Nenets living in the Yamalo-Nenets Autonomous Okrug [8,10]. For the population of indigenous people an abrupt increase has been detected in a number of cancerous diseases, secondary immunodeficiency states, allergies, complications of pregnancy and birth defects, ophthalmologic diseases, as well as growth of the number of children with mental retardation, Down syndrome, optic atrophy, limb reduction, anencephaly and thoracopathy. Recently, the biological health state of the Tundra Nenet population of the Yamalo-Nenets Autonomous Okrug has been estimated based on the analysis data for auto-antibodies and lipoproteids of blood donors [11,12]. It has been found that the characteristics of lipoproteins in ∼90% of donors under study deviate towards various pathologies (3- 8% for the control population according to epidemiological studies). Moreover, ∼41% Caucasians and ∼56% Tundra Nenets are shown to have high auto-antibody titers against DNA and cardiolipin which are comparable with those for patients with various autoimmune diseases. Thus, it is obvious that the prolonged influence of technogenic radioactive isotopes can have harmful effects on human health. Taking this into account, the clarification of the danger level of technogenic pollution of the environment and its effect on population health is an urgent task of the global ecology and medicine.

The sites of nuclear energy use and sites of radionuclide accidental releases from research, manufacturing or storage facilities have left a complex legacy of contaminated land [13]. The River Yenisei is one of the largest in the world where the Mining and Chemical Combine of the State Company ROSATOM operates in the town of Zheleznogorsk in the Krasnoyarsk Region including the reactor facility and radiochemical production. The multi-year operation of the Combine has resulted in radioactive contaminations including transuranium elements of the Yenisei River flood plain [14-18]. Among transuranium elements the most significant radionuclides are plutonium, americium and neptunium isotopes [17,18]. So far, hardly has any attention been paid to the behavior of transuranium radionuclides in the Yenisei River ecosystem. The evidence on the scale of the transuranium radioactive contamination of phototrophic organisms in the River Yenisei is also lacking. At present, the scale of the Yenisei River pollution with the transuranium radionuclides is being estimated on the basis of gammaspectrometry and radiochemical studies. The ways of transuranium radionuclides entering into the biomass of aqueous plants are being determined based on the estimation of the content of transuranium elements in different structures, e.g., leaves, stem, roots of aqueous plants and bottom sediments. According to the results obtained the samples of the plants, bottom sediments and water of the River Yenisei contain radionuclides, including 241Am.

Here, we analyze the toxicity and genotoxicity of highly-dispersed aqueous mixtures and extracts of bottom sediments and plants of the Yenisei River which contain 241Am using special bacterial strains.

Materials and Methods

Samples were taken from the River Yenisei. These included an 241Am-containing aqueous plant Elodea canadensis and bottom sediments with and without radioactive contaminants. In the control experiments, the 241Am3+ salt dissolved in nitric acid (2 M) was used. The initial specific activity of 241Am was increased by evaporating water; the solution was neutralized with alkali (NaOH) and, if necessary, treated with catalase in order to remove hydrogen peroxide present in the initial solution. As a control of the 241Am reagent use was made both of dry biomass of aqueous plant Elodea canadensis which had accumulated the 241Am activity under the laboratory conditions [19] and extracts of the plant biomass obtained by physico-chemical fractionation methods [18].

Preparation of suspensions and extracts of the bottom sediments and Elodea canadensis. Aqueous suspensions of the samples were obtained by keeping a dry thoroughly-mashed mass of the control and test plants or bottom sediments (0.2-1.0 g), containing 241Am or without it, dissolved in 10 ml of distilled water at room temperature during 16-18 h, with stirring. Then, the mixtures were boiled for 20 min for additional extraction. Unfiltered aqueous suspensions of the plants and bottom sediments were used in the experiments described below.

To successively extract the necessary components and 241Am from the plants, e.g., to obtain Extract-1, 35 ml of ammonium acetate was added to 40 mg of the dry mass of the radioactive or control plants, and then, the extraction was performed during 24 h (37°C) with constant stirring. The extract was filtered and the pH of the solutions was brought to 6.7-6.8 (Fraction 1). 30 ml of the solution with the specific activity of 241Am=0.525 Bq/ml was obtained. At this fractionation stage, ∼35% of the total radioactivity in the dried sample was extracted from that in the initial dry sample.

To obtain Extract-2, 13 ml of 0.1 M H2SO4 was added to the plant mass which remained after obtaining Extract-1 and then, incubated on a shaker for 20 min at 37°C. The extract was filtered and neutralized with a concentrated solution of KOH to pH 7.0. 13 ml of the solution with the activity of 241Am=1.275 Bq/ml (e.g., ∼34% of radioactivity of the total initial activity in the dry sample) was obtained.

To obtain Extract-3, 12 ml of 30% H2O2 and 2 drops of 13 M HNO<sub>3</sub> were added to the plant mass which remained after obtaining the second extract. With the mixture heated on the stove, the plant biomass dissolved completely. The liquid was evaporated to the state of wet salts. Then, the residue was dissolved in 20 ml of water and evaporated again. Then, 12 ml of 30% H2O2 and 2 drops of 13 M HNO<sub>3</sub> were again added to the mixture, followed by complete evaporation of the liquid until the solution was dry. To remove H2O2 and the acid the dry residue was twice boiled off with 20 ml of water (each time 20 ml of water was added to the mixture and the mixture was completely boiled off). At the last stage the dry residue was dissolved in 12 ml of water. The obtained solution was neutralized with KOH and treated with catalase to decompose the residues of hydrogen peroxide. As a result, 12 ml of the solution with the specific activity of 241Am=0.94 Bq/ml (e.g., ∼25% of the initial radioactivity in the dry sample) was obtained.

Research Methods

Estimation of the effect of the plant extracts on the survival of bacterial cells:The toxicity of the 241Am-containing samples was estimated as related to the decrease of the number of living cells of the E. coli strains (PQ37, and BH910 (mutT; fpg::KnR; uvrA::TcR) after their cultivation during 2-24 h in a rich nutrient solution, to which the analyzed samples of the thoroughly mashed plants or their aqueous extracts were added. The viability of the cells (3 repeats) incubated with the control and radioactive samples of the plants was estimated based on the number of cells capable of further colony formation on a solid medium 24 hours after inoculation [20].

With the S. typhimurium TA98 and TA102 strains being used for the same purpose, the cell suspensions with the analyzed samples were kept without aeration for several days at room temperature. The number of viable cells was estimated at specific time intervals based on their ability to form colonies on a histidine-containing solid medium using the earlier described method [21].

Estimation of genotoxicity of the studied samples using the SOS-chromotest: Genotoxicity of the plant samples under study was estimated by means of the SOS-chromotest based on their ability to damage DNA and induce a SOS-response. For this purpose a special strain of E. coli was used, being deficient in a number of genes: E. coli PQ37 (F-, thr, leu, his-4, pyrD, thi, galE, galK or galT, srl300::Tn10, rpoB, rpsL, urvA, rfa, trp::Muc,- sfiA::Mud(Ap, lac), cts, lacβU169, PhoC), which had been provided by Quillardet (France). The analysis was performed using a standard technique [22] with some modifications described in [23].

The samples of night culture (0.1 ml) of the strain used were diluted with 5 ml of the LA medium and incubated at 37°C, with their shaking on a shaker during 2-3 h until 2 × 108 bacteria/ml were obtained. Then, 1 ml of the culture was diluted with 9 ml of the fresh LA medium. 10-50 μl of the test solution of the extract of the control or analyzed samples containing 241Am was added to 600 μl of the bacterial cell suspension, to be incubated for 2 h at 37°C. Then, 30 μl was taken each time for the analysis of the activity of β-galactosidase or alkaline phosphatase.

Estimation of the β-galactosidase activity: 270 μl of the buffer B (0,2 M Na-phosphate buffer, pH 7.75, 0.1 M KCl, 10 mM MgSO4, 0.3 mM dithiothreitol and 0.1% SDS) was added to 30 μl of the suspension and the mixture was incubated at 37°C (10-15 min) for cytolysis. β-galactosidase reaction was initiated by adding ortho-nitrophenyl-β- galactoside (60 μl, 4 mg/ml) in accordance to the technique described earlier [22]. After 30 min 0.2 ml of 1 M Na2CO3 was added to the mixture and optical density (A420) was measured to be compared with the control. The analysis was carried out under optimal conditions, A420=0.1-0.4. The samples containing the LA medium substituted for the bacterial culture were used as a negative control. H2O2 (0.2-0.5 μmole per sample) rather than the extract was used as a positive control.

Analysis of alkaline phosphatase: The analysis of alkaline phosphatase was carried out using the earlier described technique [22]. Controls and conditions for the analysis of alkaline phosphatase were similar to those for β- galactosidase, except for the 1 M tris- HCl buffer being used with pH 8.0, containing 0.1% SDS and p- nitrophenylphosphate as a substrate (60 μl, 4 mg/ml). The reaction was ceased by adding 200 μl of 1.5 M NaOH and the optical density (A420) was measured.

Analysis of mutagenic activity of the extracts using indicator-strains Salmonella typhimurium (Ames test): In the Ames test, histidine-dependent strains S. typhimurium TA98 and TA102 were used which carried mutation in histidine operon [21], both being provided by Ames. The analysis of mutagenic activity of the samples studied was carried out using a standard technique without metabolic activation.

The sample extracts were obtained by keeping a dry thoroughly mashed mass of the control and test plants or bottom sediments (0.2-1.0 g), containing 241Am or without it. The unfiltered aqueous suspensions of the plants and bottom sediments obtained were used in the experiments described below.

The night culture of the strains TA98 or TA102 was obtained using a standard technique of incubation (16 h at 37°C) in the ampicillinecontaining LB medium. The Ames test was performed according to [21] using the double-layer agar technique. The bottom layer with 2% of agar, minimal medium, 20% of glucose and 50 μg/ml ampicilline also contained 50 tetracycline in the case of the TA102 strain. To obtain the upper layer, 0.2 ml of the 0.5 mM solution of histidine/biotin (for the TA 102 strain biotin is not necessary) was added to 2 ml of the 0,7% melted agar (0.5% NaCl), and, then, after cooling the mixtures down to 45°C, 100 μl of the night culture, containing the analyzed aqueous suspensions or without them, was added to these mixtures. The cells of the TA98 and TA102 strains incubated without the analyzed samples or with the aqueous suspensions of non-radioactive samples were used as negative controls. The mutagenesis: 4-nitroquinoline-1-oxide and H2O2 were used as positive controls.

The number of the surviving cells was estimated by the number of colonies grown in the presence of histidine taking into account the corresponding dilution before inoculation. The reversion frequency was estimated by the ratio of all the revertants detected in the test to the total number of the surviving cells. The average data on the three independent experiments (9 dishes in each independent experiment) are also presented.

Results And Discussion

At the initial stage we investigated the influence of the control samples of neutral aqueous solutions of 241Am nitrate on the cell growth of E. coli PQ37 in a rich nutrient medium. The increase of radioactive 241Am content in the control samples was shown to result in an intense dose-dependent decrease in the survival rate of the bacterial cells in the exponential growth phase as compared to the control samples without radioactivity. The amount of the viable cells was 1.2 × 109 as compared to the control without 241Am. In the case of their cultivation with 241Am the decrease was characterized as follows 2.6 × 108 at 0.045 Bq/ml, 1.8 × 108 at 0.090 Bq/ml and 1.0 × 106 at 0.225 Bq/ml, depending on the radionuclide content in the stationary phase. The increase in the incubation time of the E. coli PQ37 cells in the presence of 241Am (0.225 Bq/ml) resulted in the decreased amount of the surviving cells: after two hours the amount of the surviving cells was 2.5%, after six hours - 1.6%, and after 24 hours -0.75%.

When analyzing the Elodea canadensis samples, the «portion» of the surviving E. coli PQ37 cells was calculated as the ratio of the number of viable cells after 24 hour pre-incubation in the medium containing various amounts of the suspensions of the thoroughly mashed plants to the number of viable cells grown in the medium without them.

In these experiments an intense decrease of the amount of the viable cells was observed in the stationary phase (24 hours) in the presence of plants containing 241Am and non-radioactive plants. For example, when adding into the system 14 mg of the dry plant biomass of the control sample the amount of the viable cells decreased by ∼23 times, e.g., from 5.5 × 109 to 2.0 × 108. When using 241Am (3 Bq) with a lower amount of the biomass introduced, the cell survival decreased as follows: the biomass containing 8 mg/sample –83 times (6.6 107); 10 mg/sample –138 times (4.0 × 107). The increase of the cell death percentage in the case of 241Am-containing plants was in agreement with the decrease of their survival after adding the control samples of 241Am.

A relatively small difference in the influence of the experimental (+ 241Am) and control (- 241Am) plant samples could be attributed to the fact that the bacteria cells are partially adsorbed on the plant surface, resulting in their accelerated inactivation. Besides, some compounds (for example, salts of heavy metals) could be extracted from the plants, which are toxic to the bacterial strain used. For this reason, the effect of 241Am or its complexes with the plant components could partially have been disguised. Taking this into account, the plant extracts with the plant biomass removed were used for further toxicity analysis.

As is known, free radicals and strong oxidizers – e.g., the products of water radiolysis which appear in the presence of radioactive substances can greatly influence the cell sustainability [1-7]. Thus, to estimate the toxicity of the plant extracts a strain of E. coli BH910 (mutT, fpg::CnR, uvrA::TcR) was used which had mutations in the genes responsible for the repair process of the DNA oxidative damage [24]. This strain is highly sensitive to ionizing radiation and substances leading to the formation of reactive oxygen intermediates, in particular, hydroxyl radical. Moreover, the toxicity of the extracts analyzed in the case of this strain could be indicative of their genotoxicity (due to the DNA damage by free radicals and ROI).

It is worth noting that a great amount of the radionuclide is not extracted from the solid mass while using water or finely ground plant suspensions in the plant extraction. This can be due to the fact that 241Am is rather tightly bound with the intracellar structures of the biomass [19]. For a more complete extraction of all forms of 241Am from the plants the technique of sequential chemical fractionation of plant mass was used which resulted in obtaining three radioactivitycontaining sub-fractions [18]. The first exchange fraction was obtained using ammonium acetate corresponding to the readily extracted («easily soluble») 241Am. The adsorptive part of 241Am was extracted from the residue using the solution of sulfuric acid (fraction 2). And, finally, the tightly bound 241Am was extracted from the plant residue formed when being decomposed with H2O2 and HNO3 (Fraction 3). In the experiments with the strain of E. coli BH910 all the three fractions were used corresponding to the plant extracts containing 241Am and without it.

The cells of the strain of E. coli BH910 were grown for 2, 4, 8 and 24 h in the LB- rich medium at 37°C, and then, their survival rate was analyzed taking into account the formation of colonies on the solid medium. An almost similar decrease of the bacteria growth rate was observed during 2-8 hours in the presence of Extracts 1 and 2, both containing 241Am and without it. However, in the stationary phase, after 24 hours the number of the surviving cells in the presence of the control extracts was higher as compared to the radioactive plants, especially in the case of Fraction 1. A more pronounced decrease in the cell growth rate was observed in the presence of Fraction 3 obtained from the plant containing 241Am after 2 hours of cultivation, and then, the evidence of the survival rate became comparable.

Different effects of Extracts 1-3 from the plants containing 241Am or without it on the bacteria culture in the logarithmic and stationary growth phases are indicative of the fact that the extracts are different in the total content of non-radioactive components + radionuclides. They also differ in their toxicity as related to the bacterial cells. It is worth noting that, in general, the toxicity of the plant extracts containing 241Am is considerably higher than that of the control plants, which is, in principle, rather natural. It cannot be excluded that some difference in the effects of Extracts 1-3 is due to the fact that some of them could contain not only toxic plant compounds but a more toxic mixture formed with 241Am. As a result, in this case we note the effect of synergism in the radionuclide reaction with other components formed in the dissolved biomass.

To study the toxicity of the plants and bottom sediments and plants containing 241Am, using the strains of S. typhimurium TA98 and TA102, aqueous suspensions of the extracts of these samples were employed. It was found that keeping bacterial cells TA98 with the control preparation of 241Am nitrate (0.240 Bq/ml) without aeration resulted in a considerable cell death as early as on the third day, while in the control sample (H2O) the number of the cells had considerably increased by that time (Table 1). Similar results were also obtained for the strain TA102.

Sample Am241Bq/ml Number of colonies per dish × 105*
DAYS
0 3 4 9 30
Control (H2O) 0 77±4 166±15 157±16 108±11 10±2
Control (H2O+241Am) 0.24 80±20 3±1 0 (<105) 0(<105) 0(<105)
Bottom sediments-241Am(control) 0 87±1 144±7 182±4 119±6 4±1
Bottom sediments with 241Am 0.36 69±3 3±1 0 (<105) 0(<105) 0 (<105)
1.08 13±3 0(<105) 0(<105) 0(<105) 0(<105)
Plants - 241Am(control) 0 76±4 127±3 n.d.** 116±5 5±1
Plants (with 241Am) 1.60 76±4 78±3 n.d. 50±3 0(<105)

*Average data from 3 independent experiments, the initial number of the cells is the same in all the cases; **n.d. - not determined

Table 1: Time dependence of the effect of bottom sediment and plant suspensions containing 241Am and without it on the survival rate of the bacteria S. typhimurium TA98.

The samples of the control aqueous suspensions of bottom sediments and plants without radioactivity considerably decreased the survival rate of the cells TA98 (as in the case of the control with H2O) only on the 30th day. In the case of the bottom sediments containing from 0.360 to 1.100 Bq/ml of 241Am the number of living cells decreased by ≈105 -107 times as early as on the third-fourth day (Table 1).

The plant suspensions containing from 0.360 to 1.100 Bq/ml of 241Am decreased the cell survival approximately two times on the tenth incubation day (Table 1). Higher toxicity of the bottom sediments containing 241Am as compared with the radioactive plant samples could be due to a great number of elements, including heavy metals which were extracted together with 241Am, thus increasing the negative effect on the TA98 cells.

Genotoxicity of the samples under study in SOS-chromotest

The genotoxicity of the samples studied in the SOS-chromotest is estimated on the basis of their ability to damage DNA and induce a SOS-response [23]. Using the indicator strain of E. coli PQ37 (sfiA::lacZ) allows one to estimate the expression of one of the SOS-inducible genes (sfiA) based on the b-galactosidase activity. The effect of the substances tested on the survival of the bacterial cells or on the protein synthesis is determined based on the level of the constitutive expression of alkaline phosphatase. The DNA-damaging activity (genotixicity) is determined using the value of the factor of induction (FI). The factor of induction is an indicator of the relative activity of b-galactosidase which correlates with the induction of the gene lacZ expression in the indicator strain E. coli in response to the DNA damage caused by the substances under study.

In the present study the FI value increased with the increase of the 241Am salt content in the control samples. The minimum activity of 241Am inducing a reliable SOS response amounted to 5-6 Bq per sample (for comparison, the minimum inducing dose of alpha and gamma radiation is equal to 2.5 Gy [25]. Similar FI values were obtained when using H2O2 (0.2 μmole per sample) as a genotoxic substance.

The genotoxicity of the plant samples was analyzed using samples containing small amounts of 241Am. A relatively low genotoxicity level of these plant extracts was detected. Nevertheless, the observed FI values are comparable with the values for the control solutions containing the same amount of 241Am.

Analysis of mutagenic activity in the Ames test (Salmonella/Ames assay)

The test on the induction of mutations in S. typhimurium is a bacterial test-system for evaluating reverse mutations from histidine auxotrophy to prototrophy under the action of different substances inducing the mutations, for instance, the substitution of the base pairs or a shift of the reading frame in the genome of these bacteria [22]. The presence of the mutagenic effect in the compounds under study is estimated based on the reverse mutations (reversions) to histidine prototrophy induced by these substances. The criteria of the positive result are either a statistically valid dose-dependent increase in the number of revertants, or a reproducible and statistically valid response, at least, for one concentration of the reagent. Thus, an area is normally revealed where the number of the revertants increases when increasing the dose of the mutagen under study.

When using a highly sensitive to oxidizers test strain S. typhimurium TA102 the frequency of reversions in the case of the control aqueous solutions containing 241Am was shown to be dose-dependent, which was observed to grow with the increase of radioactivity in the sample. On the contrary, in the TA98 strain the aqueous solutions containing 241Am in the same dose range did not result in any considerable mutagenic effect. However, to study the control water and bottom sediment samples a less sensitive strain S. typhimurium TA98 proved to be more appropriate. The results of mutagenicity analysis of the water and bottom sediment samples either with 241Am or without it are presented in Table 2.

No Sample Activity241Am,mBq/dish Number of revertants per dish Number of surviving cells×105 Frequency of reversions
1. H2O (negative control) 0 31 255±9 1.2 × 10-6
2. H×O, (positive control)** 0 97 267±4 3.6×10-6
3. Control (H2O+241Am) 22.0 27 250±9 1.1×10-6
81.0 30 248±9 1.2×10-6
4. Bottom sediments+241Am 17.0 28 257±10.8 1.1 × 10-6
5. Bottom sediments without Am241(control for no6) 0 30 269±11 1.1× 10-6
6. Bottom sediments+241Am 51.0 79 254±10.3 3.1×10-6
7 Bottom sediments without Am241(control for no 8) 0 32 255±6.1 1.3×10-6
8. Bottom sediments+241Am 102.0 62 233±5.0 2.7×10-6

Table 2: Estimation of the mutagenic activity for the test solution of 241Am nitrate and bottom sediment samples in the Ames test (strain S. typhimuriumTA98)*.

The number of His revertants in the test strain TA98, which appear upon adding the control aqueous solutions containing 241Am (to 0.81 Bq per dish), does not exceed the number of revertants in the control experiments with the bottom sediment samples which do not contain 241Am (Table 2). At the same time, upon adding bottom sediments containing 241Am in the amount of 0.051-0.102 Bq per dish, the number of revertants considerably exceeds that for the control solution of 241Am with the comparable radioactivity.

Thus, we have shown a considerable inhibiting effect of the control water samples containing 241Am on the growth of the bacterial cells. At the same time, the toxic effect of the test water samples containing 241Am is less expressed than the influence of the suspensions and extracts of the plants and bottom sediments. In spite of the fact that the control plants themselves decreased the survival of the cells of E. coli PQ37, the increase of the cell death in E. coli in the case of the plants containing 241Am was higher, being in agreement with the toxicity of the control samples of the 241Am salt aqueous solutions. The most vivid fresult concerning the effect of the samples from the Yenisei on the cell survival was obtained in the case of the bacteria of the S. typhimurium TA98 strain. While the non-radioactive plant and bottom sediment samples slightly influenced the survival of these cells (the effect was observed only on the 30th day), the radioactive suspensions of the plants and bottom sediments greatly decreased the cell survival and their toxic effect was considerably higher than that of the control water samples containing a comparable amount of 241Am (Table 2).

The bottom sediment samples without 241Am slightly influenced the «reversion frequency» of specific strains. For the suspensions of the bottom sediments of the control systems containing 241Am, a dosedependent effect was found both in the «reversion frequency» and in the amount of His revertants (Table 2). Thus, it is evident that the accumulation of 241Am in plants and bottom sediments of the Yenisei river channel results in their transformation to genotoxic components of the ecosystem. Moreover, the bottom sediments containing 241Am, are more toxic than radioactive plant samples due to a considerable number of substances present in the bottom sediments. These assumptions are evidenced by our experimental data on different effects of Extracts 1-3 obtained by sequential extraction of the same 241Am-containing plants on the cell growth.

Acknowledgements

The studies were carried out with the partial financial support of the project of the RFBI 16-05-0205.

References

Citation: Vasyunina Ye А, Bondareva LG, Rakitsky VN, Federova Ye N (2016) Estimation of Toxicity and Genotoxicity of Water, Bottom Sediments and Submerged Macrophyte Elodea canadensis of the Yenisei River in the Presence or Absence of Americium-241. J Environ Anal Toxicol 6: 389. Doi: 10.4172/2161-0525.1000389

Copyright: © 2016 Vasyunina Ye А, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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