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Distribution of 152Eu and 154Eu in the ‘alluvial soil–rhizosphere–plant roots’ system
Journal of Environmental Radioactivity 106 (2012) 58e64
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Distribution of roots’ system
152
Eu and
154
Eu in the ‘alluvial soilerhizosphereeplant
Marya Kropatcheva*, Alexei Chuguevsky, Mikhail Melgunov Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Science, 3 Prosp. Akademika Koptyuga, 630090 Novosibirsk, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 March 2011 Received in revised form 27 September 2011 Accepted 31 October 2011 Available online 6 December 2011
Accumulation of 152Eu and 154Eu isotopes in bulk soil and rhizosphere soil in the near-field zone of influence of the Krasnoyarsk Mining and Chemical Combine was studied. An uneven distribution of specific activity of Eu isotopes was observed, with the gross specific activities of the isotopes in the bulk soil exceeding those of the rhizosphere. In the most contaminated locations the fine and the coarse granulometric fractions are enriched with the isotopes. A laboratory experiment indicated potential removal of soluble Eu isotopes by river flood waters may amount to 3% of the total Eu in both bulk and rhizosphere soils. The root system of plants growing in the contaminated territory accumulates 152Eu and 154 Eu, although the isotopes were not discovered in aboveground parts of plants. Root-hairs were found to be the most contaminated. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: Eu isotopes Alluvial soil Rhizosphere Plant roots
1. Introduction The study of contamination of the Yenisei’s floodplain by technogenic radionuclides and their distribution in the main components of biogeocoenosis has been ongoing since the beginning of 90s. The main source of these radionuclides was the Krasnoyarsk Mining and Chemical Combine (MCC) having three reactors e two direct-flow units worked until 1992 and one closed-cycle unit worked until 2010, and the highest level of contamination is observed in immediate proximity to MCC, within the distance of about 25 km downstream, in the so-called near zone of influence of the MCC. Significant traces of radioactive contamination of the Yenisei’s floodplain were observed up to the Kara Sea (Nosov et al., 1993; Kuznetsov et al., 1994; Nosov, 1997). According to estimations by Vakulovsky et al. (2006), in 1975 the content of 137Cs produced by the MCC in the Yenisei’s floodplain (1900 km) amounted nearly to 540 Ci. So, as the decrease in the content of 137 Cs in undisturbed floodplain soils is only because of radioactive decay (Vakulovsky et al., 2006; Tertyshnik, 2007), by today it has lowered by half. At the time of shutting down the direct-flow reactors, the density of radioactive contamination of floodplain
* Corresponding author. Tel.: þ7 383 333 36 09; fax: þ7 383 333 27 92. E-mail address: [email protected] (M. Kropatcheva). 0265-931X/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvrad.2011.10.021
soils by 137Cs near MCC amounted to 70e90 Ci km2 (Nosov et al., 1993; Linnik et al., 2004). After shutting down the reactors the specific activity of short-lived radionuclides in the MCC’s disposal waters was below 4 Bq l1 and the specific activity of long-lived ones was not more than hundredth parts of Bq l1; these numbers were 100e1000 times lower than before 1992 (Nosov et al., 1993; Nosov, 1997). Nonetheless, the disposal of radionuclides lasted until 2010 was confirmed by the presence of many isotopes in aquatic plants, including the isotopes of plutonium and short-lived isotopes (Sukhorukov et al., 2004; Chuguevsky et al., 2006). An alluvial soil of islands located in the MCC’s near zone of influence accumulated considerable amount of Eu isotopes which was observed up to a pebble bed. In 1991 within some locations of the Atamanovskiy island the density of the soil contamination with 152Eu amounted to 2600 kBq m2, and the number was not lowered during following four years (Nosov, 1996, 1997). A significant part of 152Eu is associated with organic compounds or alumosilicates and Fe-Mn-hydroxides (Sukhorukov et al., 2000, 2004; Bondareva et al., 2005; Bondareva and Bolsunovskii, 2008). In case of transition of 152 Eu from a contaminated soil into a non-contaminated one an effective coefficient of diffusion varies within (2e4)$ 108 sm2 s1 (Nosov, 1997). In the MCC’s near zone of influence in locations of radionuclides accumulation the density of pollution with Eu amounts to 188 kBq m2; at longer distances the
M. Kropatcheva et al. / Journal of Environmental Radioactivity 106 (2012) 58e64
density lowered to 30e50 kBq m2 (Linnik et al., 2004, 2005a, b, 2006). In biomass of all water plants the activity of 152Eu is low despite the fact that 152Eu is the dominant isotope in upper layers of both soil and bottom sediments (Bolsunovsky et al., 2002); in the near zone of influence the migration ability of 152 Eu in bottom sediments exceeds the ability of 241Am, 60Co and 137 Cs (Bondareva and Bolsunovskii, 2008). Our study specially is devoted to the rhizosphere of the Yenisei’s floodplain because in previous studies the rhizosphere was not subject of research. The concept of the rhizosphere was introduced by Lorenz Hiltner in 1904; at present “rhizosphere” means microbiosphere existing at a border between a bulk soil and plant’s roots because its physical, chemical and biological properties significantly differ from ones of a bulk soil (Hartmann et al., 2008). In field studies the rhizosphere is that part of a soil which remains on plant’s roots after shaking the roots; all the rest is the bulk soil (Séguin et al., 2004). Though being a minor part of a pedosphere the rhizosphere is a very important part playing prime role in pedosphere’s geochemistry (Wang et al., 2001, 2002). In a life-sustaining activity plants exude via roots various substances including organic acids, sugars, ammine-acids, Oþ and OSPþ 3 (Marschner et al., 1996; Ehlken and Kirchner, 2002), thus forming microenvironment whose properties may very differ ones of a bulk soil (Lorenz et al., 1994; Courchesne and Gobran, 1997). Qualitative and quantitative compositions of the root’s excretions make impact on various
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parameters of a soil, including its rO, soil type, temperature, accessibility of nutrients, structure of microbial community and others (Gahoonia, 1993; Tagliavini et al., 1995; Gobran and Clegg, 1996; Hodge et al., 1996). Forming soluble organicemetallic complex by exuding via roots organic substances increase solubility of metals (Mench et al., 1988; Treeby et al., 1989; Jones and Brassington, 1998; Naidu and Harter, 1998). Releasing Oþ or OSP 3 roots effectively affect a degree of rO in an adjacent soil thus increasing accessibility of potassium and phosphorus that in turn makes impact on feeding plant roots with potassium (Jungk and Claassen, 1986; Mitsios and Rowell, 1987). The impact of root’s activity on geochemistry of radionuclides, in particular on behavior of radiocaesium, is complex: because plant roots are extracting potassium from clay minerals the latter undergo changes (Tributh et al., 1987; Hinsinger and Jaillard, 1993; Courchesne and Gobran, 1997), which in turn make impact on binding of radionuclides by minerals (Guivarch et al., 1999; Delvaux et al., 2000). The above-cited data argue that a plant rhizosphere plays the important role in technogenic radionuclides behavior; however, the researchers were conducted mainly for radiocaesium. The authors found only one paper dedicated to lanthanides (Wang et al., 2002). Since in previous studies dedicated to the radioactive contamination of the Yenisei’s floodplain the rhizosphere was not a subject for investigation our study may reduce the gap.
Fig. 1. Sampling location. Potekhin island (background) M-0 (8 km upstream from the disposal site), Atamanovskaya spit M-1 (6 km downstream from the disposal site), Atamanovskiy island M-2 (7 km downstream from the disposal site), Berezovyi island M-3 (15 km downstream from the disposal site), Balchugovskaya channel M-4 (18 km downstream from the disposal site).
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2. Materials and methods
Table 1 Granulometric fractions, mass %.
2.1. Sampling location The area for selecting sampling sites includes the right bank of the Yenisei river in the near zone of influence of the MCC and the islands located within the zone (Fig. 1). In the area the contaminated disposal waters don’t distance themselves from the right bank down to the inflow of the Kan river into the Yenisei river. Sampling sites were selected in identical conditions: at heads of islands and in locations flooded during high water periods. The background site was located at the head of the Potekhin island (M-0) upstream from the contamination source. Samples were took at the Atamanovskaya spit (M-1), the Atamanovskiy (M-2) and Berezovyi (M-3) islands, and the Balchugovskaya channel (M-4). As in the Balchugovskaya channel the flowing condition exists only during high water periods, the site was selected at the right bank in the bay. Four species of the most common floodplain macrophytes of the genus Carex L. (Carex campylorhina, Carex vulpina, Carex versicaria and Carex gracilis) were selected as the main plant objects. As within the area the selected plants are growing out of any order and their proportion is equal, they were not separated into species. At each site, in order to provide a content of radionuclides in plants enough for laboratory analysis, locations with the maximum activity were selected with the help of an SRP-68-01 dosimeter. At locations of 2.25 m2 all aboveground plant parts were cut and 2 cubes of a soil were retrieved. The cube’s edge is 40 cm, the distance between cubes varies from 60 to 70 cm. Each of fresh cubes was manually separated into plant roots with a rhizosphere material and a bulk soil. As it is mentioned above, a soil remaining on roots after shaking them was considered as a rhizosphere material whereas a separated soil as a bulk (Séguin et al., 2004). The rhizosphere material was dried out together with the roots and then separated from them. The plant’s roots were cleared out with water and dried out for the second time. As the result of the procedure, samples of a soil and a rhizosphere material were of a large size. However, in spite of very scrupulous separation some amount of root-hairs remained in the bulk soil and rhizosphere materials; these root-hairs were analyzed separately from large roots. Quartz and feldspars (plagioclase and potassium feldspar) predominate in mineral composition of the samples. A considerable part consists of pelitic minerals such as Mg-Fe-chlorites and illite. Excluding organic components, the gross mineral compositions of the samples in all locations have no difference. 2.2. Methods To provide the better separation of mineral particles, large roots were washed down. The roots and aboveground part of plants were dried out and ashed according to the standard procedures (Bock, 1979; Obukhov and Plekhanova, 1991). Granulometric contents of a bulk soil and a rhizosphere were determined only for the samples from the Atamanovskaya spit (M1) and the Balchugovskaya channel (M-4) having the most difference in conditions. Fractions of 0.01e0.05 mm and <0.01 mm sizes were obtained by levigation, those of 0.05e0.16 mm, 0.16e0.25 mm, 0.025e0.5 mm and >0.5 mm sizes were obtained by scattering through standard sieves (Kovrigo et al., 2000). As at the beginning of the levigation, a small amount of root-hairs rose to surface, they were analyzed separately. Medium fractions sized 0.05e0.16 mm and 0.16e0.25 mm (75e90 mass % in total) prevail in samples. All other fractions amount to not more than 8 mass % (Table 1). For all samples, determination of 152Eu and 154Eu with gammaray lines of high-energy range (Eg from 100 to 2000 keV) with the
<0.01 mm 0.01e0.05 mm 0.05e0.16 mm 0.16e0.25 mm 0.5e0.25 mm >0.5 mm
Atamanovskaya spit (M-1)
Balchugovskaya channel (M-4)
Soil
Rhizosphere
Soil
Rhizosphere
1.7 2.3 50.7 39.6 4.0 1.7
1.3 1.8 51.7 39.8 3.8 1.6
5.3 7.2 72.4 13.1 1.5 0.5
6.9 4.5 69.3 9.6 8.5 1.3
usage of semiconductor g-spectrometry on the basis of a coaxial HPGe and Ge(Li) semiconductor detector was performed. To increase effectiveness, the registration of analytical measuring signals was done in Marinelly vessels (250 cm2). Masses of tested items varied from 160 to 360 g. Measuring time depended on the level of radioisotopes’ activity and varied from 2 to 24 h. In case of a standard lead-tungsten protection the limits of detecting 152Eu and 154Eu are between 5 and 10 Bq kg1. For measuring lower values, the same detector was put in the low background chamber; in these conditions the limits are between 0.5 and 1 Bq kg1. For a standard spatial source with the activity of 152Eu around 5000 Bq kg1 the repeatability of the analysis, according to the 2s criterion, doesn’t exceed 6%. For the specific activities higher than 100e150 Bq kg1 the total method error doesn’t exceed 15%; it doesn’t exceed: 20% for the activities at 40e100 Bq kg1, 25e30% for the activities at 10e40 Bq kg1, and 30% for the activities at <10 Bq kg1. 3. Results and discussion 3.1. Gross isotope content in bulk soil and rhizosphere Distribution of the Eu isotopes in the bulk soils of the selected sites is extremely uneven (Fig. 2) and specific activities of 152Eu exceed those of 154Eu by several times, that comply with previous data by other researchers (Nosov et al., 1993; Bolsunovsky, 2004; Sukhorukov et al., 2004; Linnik et al., 2004, 2005a, b, 2006; Chuguevsky et al., 2006; Vakulovsky et al., 2006; Bondareva and Bolsunovskii, 2008). The highest dispersion of values of the specific activities in the bulk soil and the rhizosphere is observed at the Atamanovskaya spit (M-1); however, partial overlapping of dispersion ranges doesn’t allow to state significant difference between values of the specific activities. The dispersion is high enough at the Berezovyi island (M3) too. At the Atamanovskiy island (M-2) the specific activities of 154 Eu in the bulk soil and the rhizosphere vary enough to state their significant differences. At the Balchugovskaya channel (M-4) the dispersion of specific activities of both Eu isotopes in the soil and in the rhizosphere is considerably small, that allows to state that the difference between the activities takes place. The distribution of both Eu isotopes in the bulk soil and the rhizosphere from the floodplain sites is similar to each other. The maximum activities in a bulk soil are observed at the Atamanovskaya spit (M-1), they amount to 805 Bq kg1; the maximum specific activities in rhizosphere are also observed in the M-1 point. The amount of the Eu isotopes decreases according to the increase in distance from the contamination source. The specific activities of the Eu isotopes in the bulk soil and the rhizosphere at the Atamanovskiy island (M-2) are almost equal to those of the Berezovyi island (M-3). At the Balchugovskaya channel (M-4) an increase of specific activities of the Eu isotopes is observed; the amount of the Eu isotopes in the bulk soil is practically the same as at the Atamanovskaya spit (M-1), however, it doesn’t exceed the latter. In the rhizosphere, the amount of 152Eu is also higher than amounts in the
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Fig. 2. Specific activities of Eu isotopes in a bulk soil and a rhizosphere.
M-2 point and M-3 point, but it is lower than the amount of 152Eu at the Atamanovskaya spit (M-1). As to the 154Eu isotope, in the rhizosphere from the Balchugovskaya channel (M-4) further decrease in its specific activities is observed. The increase of specific activities at the Balchugovskaya channel (M-4) is due to favorable conditions for sedimentation at that part of the channel (Linnik et al., 2004, 2005a); larger amount of fine fractions in samples from the M-4 point compare to those from the M-1 point (11e12% versus 3e4% accordingly) confirms the reason. The significant difference between specific activities in the bulk soil and the rhizosphere from the Balchugovskaya channel (M-4) mainly caused by the rhizosphere’s organic matter: the amount of total organic carbon in the sample form the M-4 point is 0.6% in the bulk soil and about 3% in the rhizosphere. Several researchers (Kornilovich et al., 1997; Benes et al., 2003; Wang et al., 2011) showed up that presence of humin substances significantly decreases a sorption of Eu due to forming humate complexes. 3.2. Eu isotope content in granulometric fractions Percentage of the specific activities in granulometric fractions of the bulk soil and the rhizosphere sampled at the Atamanovskaya spit (M-1) and the Balchugovskaya channel (M-4) is generally the same for both isotopes (Fig. 3). An average value weighted by fractions correlates well with the specific activities of gross samples; predominance in the soil is typical. Fractions predominating by mass (0.16e0.25 mm and 0.05e0.16 mm) contain the lowest amount of the Eu isotopes. In the rhizosphere of the M-4 point, the percentage of specific activities of these fractions increases, mostly due to the decrease in the activity in the 0.01e0.05 mm fractions. The highest Eu isotope activity is observed in the finest fractions of the bulk soil; it is 2e3.6 times lower in the rhizosphere. This fine fractions enrichment by the Eu isotopes can be attributed to increase in the surface area, which favors sorption. One-half of the fine fractions fall on the clay minerals represented by chloriteeillite association. As it is shown by Gritchenko et al. (2001), Linnik et al. (2004) in such association the main sorbent for technogenic radionuclides is illite, our data confirm that. Similar to the fine fractions, the coarse fractions (0.25e0.5 mm and >0.5 mm) are notably enriched with the Eu isotopes. The specific activities of coarse fraction may amount to values typical for the specific activities of fine fraction. For example, the specific activities of 154Eu of the bulk soil from the M-1 point amounts to 663 Bq kg1 in the 0.25e0.5 mm fractions and to 511 Bq kg1 in the >0.5 mm fractions; the specific activities of 152Eu in the rhizosphere of the M-4 point amount to 3218 Bq kg1 in 0.25e0.5 mm fractions.
The percentage of specific activity of the Eu isotopes in the coarse fractions from the Atamanovskaya spit (M-1) amounts to 31e40%, those of the Balchugovskaya channel (M-4) amounts 17e29%. Most probably, the enrichment of coarse fractions is determined by high percent of organic matter in these fractions, hence, by sorbing the Eu isotopes by humus (Benes et al., 2003); the statement needs, however, further arguments. 3.3. Laboratory experiment for isotope removal In parallel with the granulometric fractionation, a laboratory experiment for evaluating Eu isotope removal from the alluvial soils under the influence of high waters was conducted. A sample of a bulk soil or a rhizosphere was put into a vessel with distilled water for 3 days; the content of the vessel was regularly stirred. The liquid phase was reduced by decantation, then evaporated to the volume of 50 ml and analyzed. The experiment showed up a removal of a notable amount of Eu isotopes; in some cases the amount was up to 2.9% of the specific activities in an original sample. From the samples from the Atamanovskaya spit (M-1), 1.2e1.3% of their content in the bulk soil and 2.5e2.7% in the rhizosphere were removed; note, that the correlation with the gross specific activities was not observed. Since in the rhizosphere of the M-1 point there is more acidic condition caused by living activity of plants and microbial activity, significant amount of the Eu isotopes are moved into mobile forms providing their migration. In the Balchugovskaya channel (M-4) the picture is completely opposite, the removal correlates with gross content: 2.8e2.9% of total amount was removed from the soil and 1.4e1.5% from the rhizosphere. This corresponds to the data of the model by Legin et al. (2001) showing that Eu isotopes associated with humus compounds of floodplain soils practically do not form soluble forms in flooding conditions. 3.4. Root system of plants Eu isotopes are observed in root system of the studied plants, although their presence is not recorded in aboveground parts. It is known that the content of stable europium in plants depends, to a significant extent, on its content in the substrate, and the accumulation occurs primarily in root system of plants (Ivanov, 1997). In case of the Eu isotopes, a similar situation is observed. At the Atamanovskaya spit (M-1) the maximum specific activities of europium isotopes in large roots, amounting to 136 Bq kg1 (152Eu) and 32 Bq kg1 (154Eu), are discovered. At the bigger distances from the spit, the isotope activities decrease by 3 times and increase again at
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Fig. 3. Distribution of
152
Eu and
154
Eu in granulometric fractions of a bulk soil and a rhizosphere at the Atamanovskaya spit (M-1) and the Balchugovskaya channel (M-4).
Fig. 4. Specific activities of Eu isotopes in large roots and root-hairs.
M. Kropatcheva et al. / Journal of Environmental Radioactivity 106 (2012) 58e64
the Balchugovskaya channel (M-4); the activities do not, however, reach the values in the M-1 point (Fig. 4). In root-hairs presented in all samples of the bulk soil and the rhizosphere the specific activities of the Eu isotopes are higher than in large roots (Fig. 4). Despite the percentage of the root-hairs to the total mass is low (from 0.9% to 1.6%), a significant percent of total specific activity of sample was found out in them. It was noted by other researchers (Kelley et al., 1999; Fellows et al., 2003) that percentage of Eu in root-hairs is higher compare to other roots of the plants. The specific activities of root-hairs in the samples from the Atamanovskaya spit (M-1) amount to 1462 Bq kg1 in the bulk soil and to 588 Bq kg1 in the rhizosphere. In the root-hairs from the Balchugovskaya channel (M-4) the activities are lower: 1019 Bq kg1 and 326 Bq kg1 respectively. We suppose that notable predominance of the Eu isotopes in the root-hairs discovered in the bulk soil, compared to those in the rhizosphere, may be explained by different pH in substrates, that results in different sorption mechanisms, hence, in changing contents of europium’s forms available to plants. For example, in alkali conditions (these are observed in the soil) inner-sphere complexation and/or surface precipitation play a major role whereas in more acidic conditions (these are observed in the rhizosphere) outer-sphere complexation and ion exchange dominate (Benes et al., 2003; Wang et al., 2011). 4. Conclusions Accumulation of the Eu isotopes in the bulk soil and the rhizosphere depends on distance from the contamination source, amount of organic matter in samples and hydrological condition of the Yenisei river. Specific activities of 152Eu and 154Eu in the bulk soil exceed those in the rhizosphere. Variations of specific activities in the rhizosphere are like to those in the bulk soil: in nearly all locations very uneven distribution of specific isotope activities is confirmed. The only exception is the site at the Balchugovskaya channel in which the specific activities of 152Eu and 154Eu in the bulk soil and in the rhizosphere are even at the most degree and notably different; because of notable amount of organic matter in the rhizosphere, the sorption of Eu isotopes in the soil exceed those in the rhizosphere. The examples of the most contaminated sites show up that the fine and the coarse granulometric fractions are enriched with isotopes. The reason of such isotope distribution in the fractions may be some difference in their mineralogical contents; however, there is need for extra research. The laboratory experiment shows that the removal of the Eu isotopes during high water periods may amount to 3% of their content in the sample. Though all roots of plants growing at the contaminated territory accumulate both 152Eu and 154Eu, it is the root-hairs that are the most contaminated parts of the plants. However, the isotopes aren’t observed in aboveground parts of the plants. Acknowledgments The work was partly supported by RFBR Grants 10-05-00370 and 10-05-01021 and the SB RAS Integration project N 1. References 2003. Kinetics of Benes, P., Stamberg, K., Vopálka, D., Siroký, L., Procházková, S, radioeuropium sorption on Gorleben sand from aqueous solutions and ground water. Journal of Radioanalytical and Nuclear Chemistry 256 (3), 465e472. Bock, R., 1979. A Handbook of Decomposition Methods in Analytical Chemistry. Internal. Textbook Comp. Ltd., London.
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Linnik, V.G., Brown, J.E., Dowdall, M., Potapov, V.N., Nosov, A.V., Surkov, V.V., Sokolov, A.V., Wright, S.M., Borghuis, S., 2006. Patterns and inventories of radioactive contamination of island sites of the Yenisey river, Russia. Journal of Environmental Radioactivity 87, 188e208. Lorenz, S.E., Hamon, R.E., McGrath, S.P., 1994. Differences between soil solutions obtained from rhizosphere and non-rhizosphere soils by water displacement and soil centrifugation. European Journal of Soil Science 45, 431e438. Marschner, P., Godbold, D.L., Jentschke, G., 1996. Dynamics of lead accumulation in mycorrhizal and non-mycorrhizal Norway spruce (Picea abies (L.) Karst). Plant and Soil 178, 239e245. Mench, M., Morel, J.L., Guckert, A., Guillet, B., 1988. Metal binding with root exudates of low molecular weight. Journal of Soil Science 39, 521e527. Mitsios, I.K., Rowell, D.L., 1987. Plant uptake of exchangeable and non-exchangeable potassium. I. Measurement and modelling for onion roots in a chalky Boulder clay soil. Journal of Soil Science 38, 53e63. Naidu, R., Harter, R.D., 1998. Effect of different organic ligands on cadmium sorption by and extractability from soils. Soil Science Society of America 62, 644e650. Nosov, A.V., 1996. Analysis of the radiation environment on the Enisei river after decommissioning of straight through reactors at the Krasnoyarsk miningchemical complex. Atomic Energy 81 (3), 670e674. Nosov, A.V., 1997. Investigation of the mechanisms of the migration of radioactive substances in the Enisei flood plain. Russian Meteorology and Hydrology 12, 84e91 (in Russian). Nosov, A.V., Ashanin, M.V., Ivanov, A.B., Martynova, A.M., 1993. Radioactive contamination of the R. Enisey due to discharges from Krasnoyarsk mining and chemical corporation. Atomic Energy 74 (2), 139e144. Obukhov, A.I., Plekhanova, I.O., 1991. Atomic-absorption Analysis in Soil-biological Studies. Moscow State University, Moscow (in Russian). Séguin, V., Gagnon, C., Courchesne, F., 2004. Changes in water extractable metals, pH and organic carbon concentrations at the soil-root interface of forested soils. Plant and Soil 260, 1e17.
Sukhorukov, F.V., Melgunov, M.C., Kovalev, S.I., 2000. The main traits of distribution of technogenous radionuclides in alluvial soils and bottom sediments of the Yenisei river. Contemporary Problems of Ecology 1, 39e50 (in Russian). Sukhorukov, F.V., Degermendzhy, A.G., Belolipetsky, V.M., et al., 2004. Distribution and Migration of Radionuclides in the Yenisei Plain. Publ. House of SB RAS “Geo”, Novosibirsk (in Russian). Tagliavini, M., Masia, A., Quartieri, M., 1995. Bulk soil pH and rhizosphere pH of peach trees in calcareous and alkaline soils as affected by the form of nitrogen fertilizers. Plant and Soil 176, 263e271. Tertyshnik, E.G., 2007. Radionuclide contamination of the Yenisei river during 1972e2001. Candidate’s Dissertation for the Degree of Candidate in Geographical Sciences, NPO Taifun, Obninsk (in Russian). Treeby, M., Marschner, H., Römheld, V., 1989. Mobilization of iron and other micronutrient cations from a calcareous soil by plant-borne, microbial, and synthetic metal chelators. Plant and Soil 114, 217e226. Tributh, H., Boguslawski, E., Lieres, A., Steffens, D., Mengel, K., 1987. Effect of potassium removal by crops on transformation of illitic clay minerals. Soil Science 143, 404e409. Vakulovsky, S.M., Tertyshnik, E.G., Borodina, T.S., Iskra, A.A., 2006. Man-made radionuclides in the Yenisey river. In: Proceedings of International Conference “Radioactivity after Nuclear Explosions and Accidents”, vol. II. Gidrometeoizdat, St.-Petersburg, pp. 294e299 (in Russian). Wang, Z., Shan, X.-Q., Zhang, S., 2001. Comparison of speciation and bioavailability of rare earth elements between wet rhizosphere soil and air-dried bulk soil. Analytica Chimica Acta 441, 147e156. Wang, Z., Shan, X.-Q., Zhang, S., 2002. Comparison between fractionation and bioavailability of trace elements in rhizosphere and bulk soils. Chemosphere 46, 1163e1171. Wang, Y.Q., Fan, Q.H., Li, P., Zheng, X.B., Xu, J.Z., Jin, Y.R., Wu, W.S., 2011. The sorption of Eu(III) on calcareous soil: effects of pH, ionic strength, temperature, foreign ions and humic acid. Journal of Radioanalytical and Nuclear Chemistry 287 (1), 231e237.
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Distribution of roots’ system
152
Eu and
154
Eu in the ‘alluvial soilerhizosphereeplant
Marya Kropatcheva*, Alexei Chuguevsky, Mikhail Melgunov Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Science, 3 Prosp. Akademika Koptyuga, 630090 Novosibirsk, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 March 2011 Received in revised form 27 September 2011 Accepted 31 October 2011 Available online 6 December 2011
Accumulation of 152Eu and 154Eu isotopes in bulk soil and rhizosphere soil in the near-field zone of influence of the Krasnoyarsk Mining and Chemical Combine was studied. An uneven distribution of specific activity of Eu isotopes was observed, with the gross specific activities of the isotopes in the bulk soil exceeding those of the rhizosphere. In the most contaminated locations the fine and the coarse granulometric fractions are enriched with the isotopes. A laboratory experiment indicated potential removal of soluble Eu isotopes by river flood waters may amount to 3% of the total Eu in both bulk and rhizosphere soils. The root system of plants growing in the contaminated territory accumulates 152Eu and 154 Eu, although the isotopes were not discovered in aboveground parts of plants. Root-hairs were found to be the most contaminated. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: Eu isotopes Alluvial soil Rhizosphere Plant roots
1. Introduction The study of contamination of the Yenisei’s floodplain by technogenic radionuclides and their distribution in the main components of biogeocoenosis has been ongoing since the beginning of 90s. The main source of these radionuclides was the Krasnoyarsk Mining and Chemical Combine (MCC) having three reactors e two direct-flow units worked until 1992 and one closed-cycle unit worked until 2010, and the highest level of contamination is observed in immediate proximity to MCC, within the distance of about 25 km downstream, in the so-called near zone of influence of the MCC. Significant traces of radioactive contamination of the Yenisei’s floodplain were observed up to the Kara Sea (Nosov et al., 1993; Kuznetsov et al., 1994; Nosov, 1997). According to estimations by Vakulovsky et al. (2006), in 1975 the content of 137Cs produced by the MCC in the Yenisei’s floodplain (1900 km) amounted nearly to 540 Ci. So, as the decrease in the content of 137 Cs in undisturbed floodplain soils is only because of radioactive decay (Vakulovsky et al., 2006; Tertyshnik, 2007), by today it has lowered by half. At the time of shutting down the direct-flow reactors, the density of radioactive contamination of floodplain
* Corresponding author. Tel.: þ7 383 333 36 09; fax: þ7 383 333 27 92. E-mail address: [email protected] (M. Kropatcheva). 0265-931X/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvrad.2011.10.021
soils by 137Cs near MCC amounted to 70e90 Ci km2 (Nosov et al., 1993; Linnik et al., 2004). After shutting down the reactors the specific activity of short-lived radionuclides in the MCC’s disposal waters was below 4 Bq l1 and the specific activity of long-lived ones was not more than hundredth parts of Bq l1; these numbers were 100e1000 times lower than before 1992 (Nosov et al., 1993; Nosov, 1997). Nonetheless, the disposal of radionuclides lasted until 2010 was confirmed by the presence of many isotopes in aquatic plants, including the isotopes of plutonium and short-lived isotopes (Sukhorukov et al., 2004; Chuguevsky et al., 2006). An alluvial soil of islands located in the MCC’s near zone of influence accumulated considerable amount of Eu isotopes which was observed up to a pebble bed. In 1991 within some locations of the Atamanovskiy island the density of the soil contamination with 152Eu amounted to 2600 kBq m2, and the number was not lowered during following four years (Nosov, 1996, 1997). A significant part of 152Eu is associated with organic compounds or alumosilicates and Fe-Mn-hydroxides (Sukhorukov et al., 2000, 2004; Bondareva et al., 2005; Bondareva and Bolsunovskii, 2008). In case of transition of 152 Eu from a contaminated soil into a non-contaminated one an effective coefficient of diffusion varies within (2e4)$ 108 sm2 s1 (Nosov, 1997). In the MCC’s near zone of influence in locations of radionuclides accumulation the density of pollution with Eu amounts to 188 kBq m2; at longer distances the
M. Kropatcheva et al. / Journal of Environmental Radioactivity 106 (2012) 58e64
density lowered to 30e50 kBq m2 (Linnik et al., 2004, 2005a, b, 2006). In biomass of all water plants the activity of 152Eu is low despite the fact that 152Eu is the dominant isotope in upper layers of both soil and bottom sediments (Bolsunovsky et al., 2002); in the near zone of influence the migration ability of 152 Eu in bottom sediments exceeds the ability of 241Am, 60Co and 137 Cs (Bondareva and Bolsunovskii, 2008). Our study specially is devoted to the rhizosphere of the Yenisei’s floodplain because in previous studies the rhizosphere was not subject of research. The concept of the rhizosphere was introduced by Lorenz Hiltner in 1904; at present “rhizosphere” means microbiosphere existing at a border between a bulk soil and plant’s roots because its physical, chemical and biological properties significantly differ from ones of a bulk soil (Hartmann et al., 2008). In field studies the rhizosphere is that part of a soil which remains on plant’s roots after shaking the roots; all the rest is the bulk soil (Séguin et al., 2004). Though being a minor part of a pedosphere the rhizosphere is a very important part playing prime role in pedosphere’s geochemistry (Wang et al., 2001, 2002). In a life-sustaining activity plants exude via roots various substances including organic acids, sugars, ammine-acids, Oþ and OSPþ 3 (Marschner et al., 1996; Ehlken and Kirchner, 2002), thus forming microenvironment whose properties may very differ ones of a bulk soil (Lorenz et al., 1994; Courchesne and Gobran, 1997). Qualitative and quantitative compositions of the root’s excretions make impact on various
59
parameters of a soil, including its rO, soil type, temperature, accessibility of nutrients, structure of microbial community and others (Gahoonia, 1993; Tagliavini et al., 1995; Gobran and Clegg, 1996; Hodge et al., 1996). Forming soluble organicemetallic complex by exuding via roots organic substances increase solubility of metals (Mench et al., 1988; Treeby et al., 1989; Jones and Brassington, 1998; Naidu and Harter, 1998). Releasing Oþ or OSP 3 roots effectively affect a degree of rO in an adjacent soil thus increasing accessibility of potassium and phosphorus that in turn makes impact on feeding plant roots with potassium (Jungk and Claassen, 1986; Mitsios and Rowell, 1987). The impact of root’s activity on geochemistry of radionuclides, in particular on behavior of radiocaesium, is complex: because plant roots are extracting potassium from clay minerals the latter undergo changes (Tributh et al., 1987; Hinsinger and Jaillard, 1993; Courchesne and Gobran, 1997), which in turn make impact on binding of radionuclides by minerals (Guivarch et al., 1999; Delvaux et al., 2000). The above-cited data argue that a plant rhizosphere plays the important role in technogenic radionuclides behavior; however, the researchers were conducted mainly for radiocaesium. The authors found only one paper dedicated to lanthanides (Wang et al., 2002). Since in previous studies dedicated to the radioactive contamination of the Yenisei’s floodplain the rhizosphere was not a subject for investigation our study may reduce the gap.
Fig. 1. Sampling location. Potekhin island (background) M-0 (8 km upstream from the disposal site), Atamanovskaya spit M-1 (6 km downstream from the disposal site), Atamanovskiy island M-2 (7 km downstream from the disposal site), Berezovyi island M-3 (15 km downstream from the disposal site), Balchugovskaya channel M-4 (18 km downstream from the disposal site).
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2. Materials and methods
Table 1 Granulometric fractions, mass %.
2.1. Sampling location The area for selecting sampling sites includes the right bank of the Yenisei river in the near zone of influence of the MCC and the islands located within the zone (Fig. 1). In the area the contaminated disposal waters don’t distance themselves from the right bank down to the inflow of the Kan river into the Yenisei river. Sampling sites were selected in identical conditions: at heads of islands and in locations flooded during high water periods. The background site was located at the head of the Potekhin island (M-0) upstream from the contamination source. Samples were took at the Atamanovskaya spit (M-1), the Atamanovskiy (M-2) and Berezovyi (M-3) islands, and the Balchugovskaya channel (M-4). As in the Balchugovskaya channel the flowing condition exists only during high water periods, the site was selected at the right bank in the bay. Four species of the most common floodplain macrophytes of the genus Carex L. (Carex campylorhina, Carex vulpina, Carex versicaria and Carex gracilis) were selected as the main plant objects. As within the area the selected plants are growing out of any order and their proportion is equal, they were not separated into species. At each site, in order to provide a content of radionuclides in plants enough for laboratory analysis, locations with the maximum activity were selected with the help of an SRP-68-01 dosimeter. At locations of 2.25 m2 all aboveground plant parts were cut and 2 cubes of a soil were retrieved. The cube’s edge is 40 cm, the distance between cubes varies from 60 to 70 cm. Each of fresh cubes was manually separated into plant roots with a rhizosphere material and a bulk soil. As it is mentioned above, a soil remaining on roots after shaking them was considered as a rhizosphere material whereas a separated soil as a bulk (Séguin et al., 2004). The rhizosphere material was dried out together with the roots and then separated from them. The plant’s roots were cleared out with water and dried out for the second time. As the result of the procedure, samples of a soil and a rhizosphere material were of a large size. However, in spite of very scrupulous separation some amount of root-hairs remained in the bulk soil and rhizosphere materials; these root-hairs were analyzed separately from large roots. Quartz and feldspars (plagioclase and potassium feldspar) predominate in mineral composition of the samples. A considerable part consists of pelitic minerals such as Mg-Fe-chlorites and illite. Excluding organic components, the gross mineral compositions of the samples in all locations have no difference. 2.2. Methods To provide the better separation of mineral particles, large roots were washed down. The roots and aboveground part of plants were dried out and ashed according to the standard procedures (Bock, 1979; Obukhov and Plekhanova, 1991). Granulometric contents of a bulk soil and a rhizosphere were determined only for the samples from the Atamanovskaya spit (M1) and the Balchugovskaya channel (M-4) having the most difference in conditions. Fractions of 0.01e0.05 mm and <0.01 mm sizes were obtained by levigation, those of 0.05e0.16 mm, 0.16e0.25 mm, 0.025e0.5 mm and >0.5 mm sizes were obtained by scattering through standard sieves (Kovrigo et al., 2000). As at the beginning of the levigation, a small amount of root-hairs rose to surface, they were analyzed separately. Medium fractions sized 0.05e0.16 mm and 0.16e0.25 mm (75e90 mass % in total) prevail in samples. All other fractions amount to not more than 8 mass % (Table 1). For all samples, determination of 152Eu and 154Eu with gammaray lines of high-energy range (Eg from 100 to 2000 keV) with the
<0.01 mm 0.01e0.05 mm 0.05e0.16 mm 0.16e0.25 mm 0.5e0.25 mm >0.5 mm
Atamanovskaya spit (M-1)
Balchugovskaya channel (M-4)
Soil
Rhizosphere
Soil
Rhizosphere
1.7 2.3 50.7 39.6 4.0 1.7
1.3 1.8 51.7 39.8 3.8 1.6
5.3 7.2 72.4 13.1 1.5 0.5
6.9 4.5 69.3 9.6 8.5 1.3
usage of semiconductor g-spectrometry on the basis of a coaxial HPGe and Ge(Li) semiconductor detector was performed. To increase effectiveness, the registration of analytical measuring signals was done in Marinelly vessels (250 cm2). Masses of tested items varied from 160 to 360 g. Measuring time depended on the level of radioisotopes’ activity and varied from 2 to 24 h. In case of a standard lead-tungsten protection the limits of detecting 152Eu and 154Eu are between 5 and 10 Bq kg1. For measuring lower values, the same detector was put in the low background chamber; in these conditions the limits are between 0.5 and 1 Bq kg1. For a standard spatial source with the activity of 152Eu around 5000 Bq kg1 the repeatability of the analysis, according to the 2s criterion, doesn’t exceed 6%. For the specific activities higher than 100e150 Bq kg1 the total method error doesn’t exceed 15%; it doesn’t exceed: 20% for the activities at 40e100 Bq kg1, 25e30% for the activities at 10e40 Bq kg1, and 30% for the activities at <10 Bq kg1. 3. Results and discussion 3.1. Gross isotope content in bulk soil and rhizosphere Distribution of the Eu isotopes in the bulk soils of the selected sites is extremely uneven (Fig. 2) and specific activities of 152Eu exceed those of 154Eu by several times, that comply with previous data by other researchers (Nosov et al., 1993; Bolsunovsky, 2004; Sukhorukov et al., 2004; Linnik et al., 2004, 2005a, b, 2006; Chuguevsky et al., 2006; Vakulovsky et al., 2006; Bondareva and Bolsunovskii, 2008). The highest dispersion of values of the specific activities in the bulk soil and the rhizosphere is observed at the Atamanovskaya spit (M-1); however, partial overlapping of dispersion ranges doesn’t allow to state significant difference between values of the specific activities. The dispersion is high enough at the Berezovyi island (M3) too. At the Atamanovskiy island (M-2) the specific activities of 154 Eu in the bulk soil and the rhizosphere vary enough to state their significant differences. At the Balchugovskaya channel (M-4) the dispersion of specific activities of both Eu isotopes in the soil and in the rhizosphere is considerably small, that allows to state that the difference between the activities takes place. The distribution of both Eu isotopes in the bulk soil and the rhizosphere from the floodplain sites is similar to each other. The maximum activities in a bulk soil are observed at the Atamanovskaya spit (M-1), they amount to 805 Bq kg1; the maximum specific activities in rhizosphere are also observed in the M-1 point. The amount of the Eu isotopes decreases according to the increase in distance from the contamination source. The specific activities of the Eu isotopes in the bulk soil and the rhizosphere at the Atamanovskiy island (M-2) are almost equal to those of the Berezovyi island (M-3). At the Balchugovskaya channel (M-4) an increase of specific activities of the Eu isotopes is observed; the amount of the Eu isotopes in the bulk soil is practically the same as at the Atamanovskaya spit (M-1), however, it doesn’t exceed the latter. In the rhizosphere, the amount of 152Eu is also higher than amounts in the
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Fig. 2. Specific activities of Eu isotopes in a bulk soil and a rhizosphere.
M-2 point and M-3 point, but it is lower than the amount of 152Eu at the Atamanovskaya spit (M-1). As to the 154Eu isotope, in the rhizosphere from the Balchugovskaya channel (M-4) further decrease in its specific activities is observed. The increase of specific activities at the Balchugovskaya channel (M-4) is due to favorable conditions for sedimentation at that part of the channel (Linnik et al., 2004, 2005a); larger amount of fine fractions in samples from the M-4 point compare to those from the M-1 point (11e12% versus 3e4% accordingly) confirms the reason. The significant difference between specific activities in the bulk soil and the rhizosphere from the Balchugovskaya channel (M-4) mainly caused by the rhizosphere’s organic matter: the amount of total organic carbon in the sample form the M-4 point is 0.6% in the bulk soil and about 3% in the rhizosphere. Several researchers (Kornilovich et al., 1997; Benes et al., 2003; Wang et al., 2011) showed up that presence of humin substances significantly decreases a sorption of Eu due to forming humate complexes. 3.2. Eu isotope content in granulometric fractions Percentage of the specific activities in granulometric fractions of the bulk soil and the rhizosphere sampled at the Atamanovskaya spit (M-1) and the Balchugovskaya channel (M-4) is generally the same for both isotopes (Fig. 3). An average value weighted by fractions correlates well with the specific activities of gross samples; predominance in the soil is typical. Fractions predominating by mass (0.16e0.25 mm and 0.05e0.16 mm) contain the lowest amount of the Eu isotopes. In the rhizosphere of the M-4 point, the percentage of specific activities of these fractions increases, mostly due to the decrease in the activity in the 0.01e0.05 mm fractions. The highest Eu isotope activity is observed in the finest fractions of the bulk soil; it is 2e3.6 times lower in the rhizosphere. This fine fractions enrichment by the Eu isotopes can be attributed to increase in the surface area, which favors sorption. One-half of the fine fractions fall on the clay minerals represented by chloriteeillite association. As it is shown by Gritchenko et al. (2001), Linnik et al. (2004) in such association the main sorbent for technogenic radionuclides is illite, our data confirm that. Similar to the fine fractions, the coarse fractions (0.25e0.5 mm and >0.5 mm) are notably enriched with the Eu isotopes. The specific activities of coarse fraction may amount to values typical for the specific activities of fine fraction. For example, the specific activities of 154Eu of the bulk soil from the M-1 point amounts to 663 Bq kg1 in the 0.25e0.5 mm fractions and to 511 Bq kg1 in the >0.5 mm fractions; the specific activities of 152Eu in the rhizosphere of the M-4 point amount to 3218 Bq kg1 in 0.25e0.5 mm fractions.
The percentage of specific activity of the Eu isotopes in the coarse fractions from the Atamanovskaya spit (M-1) amounts to 31e40%, those of the Balchugovskaya channel (M-4) amounts 17e29%. Most probably, the enrichment of coarse fractions is determined by high percent of organic matter in these fractions, hence, by sorbing the Eu isotopes by humus (Benes et al., 2003); the statement needs, however, further arguments. 3.3. Laboratory experiment for isotope removal In parallel with the granulometric fractionation, a laboratory experiment for evaluating Eu isotope removal from the alluvial soils under the influence of high waters was conducted. A sample of a bulk soil or a rhizosphere was put into a vessel with distilled water for 3 days; the content of the vessel was regularly stirred. The liquid phase was reduced by decantation, then evaporated to the volume of 50 ml and analyzed. The experiment showed up a removal of a notable amount of Eu isotopes; in some cases the amount was up to 2.9% of the specific activities in an original sample. From the samples from the Atamanovskaya spit (M-1), 1.2e1.3% of their content in the bulk soil and 2.5e2.7% in the rhizosphere were removed; note, that the correlation with the gross specific activities was not observed. Since in the rhizosphere of the M-1 point there is more acidic condition caused by living activity of plants and microbial activity, significant amount of the Eu isotopes are moved into mobile forms providing their migration. In the Balchugovskaya channel (M-4) the picture is completely opposite, the removal correlates with gross content: 2.8e2.9% of total amount was removed from the soil and 1.4e1.5% from the rhizosphere. This corresponds to the data of the model by Legin et al. (2001) showing that Eu isotopes associated with humus compounds of floodplain soils practically do not form soluble forms in flooding conditions. 3.4. Root system of plants Eu isotopes are observed in root system of the studied plants, although their presence is not recorded in aboveground parts. It is known that the content of stable europium in plants depends, to a significant extent, on its content in the substrate, and the accumulation occurs primarily in root system of plants (Ivanov, 1997). In case of the Eu isotopes, a similar situation is observed. At the Atamanovskaya spit (M-1) the maximum specific activities of europium isotopes in large roots, amounting to 136 Bq kg1 (152Eu) and 32 Bq kg1 (154Eu), are discovered. At the bigger distances from the spit, the isotope activities decrease by 3 times and increase again at
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Fig. 3. Distribution of
152
Eu and
154
Eu in granulometric fractions of a bulk soil and a rhizosphere at the Atamanovskaya spit (M-1) and the Balchugovskaya channel (M-4).
Fig. 4. Specific activities of Eu isotopes in large roots and root-hairs.
M. Kropatcheva et al. / Journal of Environmental Radioactivity 106 (2012) 58e64
the Balchugovskaya channel (M-4); the activities do not, however, reach the values in the M-1 point (Fig. 4). In root-hairs presented in all samples of the bulk soil and the rhizosphere the specific activities of the Eu isotopes are higher than in large roots (Fig. 4). Despite the percentage of the root-hairs to the total mass is low (from 0.9% to 1.6%), a significant percent of total specific activity of sample was found out in them. It was noted by other researchers (Kelley et al., 1999; Fellows et al., 2003) that percentage of Eu in root-hairs is higher compare to other roots of the plants. The specific activities of root-hairs in the samples from the Atamanovskaya spit (M-1) amount to 1462 Bq kg1 in the bulk soil and to 588 Bq kg1 in the rhizosphere. In the root-hairs from the Balchugovskaya channel (M-4) the activities are lower: 1019 Bq kg1 and 326 Bq kg1 respectively. We suppose that notable predominance of the Eu isotopes in the root-hairs discovered in the bulk soil, compared to those in the rhizosphere, may be explained by different pH in substrates, that results in different sorption mechanisms, hence, in changing contents of europium’s forms available to plants. For example, in alkali conditions (these are observed in the soil) inner-sphere complexation and/or surface precipitation play a major role whereas in more acidic conditions (these are observed in the rhizosphere) outer-sphere complexation and ion exchange dominate (Benes et al., 2003; Wang et al., 2011). 4. Conclusions Accumulation of the Eu isotopes in the bulk soil and the rhizosphere depends on distance from the contamination source, amount of organic matter in samples and hydrological condition of the Yenisei river. Specific activities of 152Eu and 154Eu in the bulk soil exceed those in the rhizosphere. Variations of specific activities in the rhizosphere are like to those in the bulk soil: in nearly all locations very uneven distribution of specific isotope activities is confirmed. The only exception is the site at the Balchugovskaya channel in which the specific activities of 152Eu and 154Eu in the bulk soil and in the rhizosphere are even at the most degree and notably different; because of notable amount of organic matter in the rhizosphere, the sorption of Eu isotopes in the soil exceed those in the rhizosphere. The examples of the most contaminated sites show up that the fine and the coarse granulometric fractions are enriched with isotopes. The reason of such isotope distribution in the fractions may be some difference in their mineralogical contents; however, there is need for extra research. The laboratory experiment shows that the removal of the Eu isotopes during high water periods may amount to 3% of their content in the sample. Though all roots of plants growing at the contaminated territory accumulate both 152Eu and 154Eu, it is the root-hairs that are the most contaminated parts of the plants. However, the isotopes aren’t observed in aboveground parts of the plants. Acknowledgments The work was partly supported by RFBR Grants 10-05-00370 and 10-05-01021 and the SB RAS Integration project N 1. References 2003. Kinetics of Benes, P., Stamberg, K., Vopálka, D., Siroký, L., Procházková, S, radioeuropium sorption on Gorleben sand from aqueous solutions and ground water. Journal of Radioanalytical and Nuclear Chemistry 256 (3), 465e472. Bock, R., 1979. A Handbook of Decomposition Methods in Analytical Chemistry. Internal. Textbook Comp. Ltd., London.
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