Disparity in Sr and Cs Uptake in Alpine Plants
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by RERO DOC Digital Library Plant Soil (2012) 355:29–39 DOI 10.1007/s11104-011-1110-6 REGULAR ARTICLE Disparity in 90Sr and 137Cs uptake in Alpine plants: phylogenetic effect and Ca and K availability Thomas Guillaume & Fabienne Chawla & Philipp Steinmann & Jean-Michel Gobat & Pascal Froidevaux Received: 8 September 2011 /Accepted: 15 December 2011 /Published online: 4 February 2012 # Springer Science+Business Media B.V. 2012 Abstract on 6 undisturbed and geochemically different soils in Background and aims Uptake of 90Sr and 137Cs in the Alpine valley of Piora, Switzerland. plants varies widely between soil types and between Results Results show that a strong correlation exists plant species. It is now recognized that the radionu- between the log TF and the log of exchangeable Ca or clide uptake in plants is more influenced by site- K of the soils. specific and plant-specific parameters rather than the Conclusions Cs uptake by Phleum rhaeticum (Poales) bulk radionuclide concentration in soil. We hypothe- and Alchemilla xanthochlora (Rosales) is more sensi- sized that the stress which Alpine plants experience tive to the amount of exchangeable K in the soil than because of the short growing season may enhance the the corresponding uptake by other orders. Moreover, phylogenetic effect on the 137Cs and 90Sr transfer the 90Sr results indicate a phylogenetic effect between factors as well as the dependency of the uptake by Non-Eudicot and Eudicots: the order Poales (Phleum plant to the concentrations of exchangeable Ca and K rhaeticum) concentrating much less 90Sr than Eudicots of soils. do. Methods We carried out a field study on the 90Sr and 137Cs uptake by 11 species of Alpine plants growing Keywords 90Sr . 137Cs . Plant . Phylogenetic effect . Uptake . Soil Electronic supplementary material The online version of this article (doi:10.1007/s11104-011-1110-6) contains supplementary material, which is available to authorized users. Introduction : : * T. Guillaume F. Chawla P. Froidevaux ( ) The radionuclides 137Cs and 90Sr have been widely Institute for Radiation Physics, University Hospital Center, University of Lausanne, dispersed in the environment as a consequence of the Lausanne, Switzerland atmospheric nuclear bomb tests (NBT) of the 1950’s e-mail: [email protected] and 1960’s. Moreover, the accident of the Chernobyl : nuclear power plant increased the 137Cs soil inventory T. Guillaume J.-M. Gobat 90 Institute of Biology, Laboratory Soil & Vegetation, in most European countries. Because Sr is easily University of Neuchâtel, transferred from soil to plant and along the food chain, Neuchâtel, Switzerland it can still be determined above the detection limit in milk teeth of children and in human vertebrae today P. Steinmann Federal Office of Public Health, Radiation Protection, (Froidevaux et al. 2006; Froidevaux et al. 2010). A Bern, Switzerland commonly used parameter to express the extent of the 30 Plant Soil (2012) 355:29–39 transfer of radionuclides from soil to plants is the In addition, Willey and Fawcett (2006) showed that transfer factor (TF), which is the ratio of the mass plant species take up Sr differently and that the uptake activity concentration of the plant to that of the soil. is linked through plant phylogeny. Combining both One prerequisite for the use of the soil-to-plant trans- the phylogenetic approach and the K concentration fer factor concept is the presence of a statistically in the soil solution, Waegeneers et al. (2001) found significant relationship between the content of a given that the genotypic effects in the phytoavailability of radionuclide in the soil and plant (Bunzl et al. 2000). 137Cs are increased at a low K content in the soil. However, TFs found in the literature are highly vari- There exist few studies conducted in Alpine eco- able, even for the same plant species, which introduces systems, regardless of the fact that radionuclide con- considerable uncertainty in modeling (Frissel 1992; tamination of the soil is persistent in this environment Staunton et al. 2003; Vandenhove and Van Hees and that the plant uptake is higher than in lowlands 2007). It is now recognized that the radionuclide up- (Bunzl et al. 2000; Ciuffo et al. 2003; Ciuffo et al. take in plants is more influenced by site-specific and 2002; Pourcelot et al. 2003; Pourcelot et al. 2007). The plant-specific parameters rather than by the bulk ra- scarcity of field studies may lead to a bias in the data dionuclide concentration in soil (Bunzl et al. 2000; found in the literature because equilibrium between Ciuffo et al. 2002). These specific parameters are: 1) the soil, as well as the rhizosphere, and the deposited the radionuclide bioavailability in the soil solution radionuclide is time-dependant and is often not (Sanchez et al. 2002), 2) the capacity of plant species reached in laboratory experiments (Waegeneers et al. to absorb bioavailable radionuclides; 3) the availabil- 2009). Additionally, 137Cs and 90Sr concentration in ity of competing ions in the soil solution (Ehlken and soil solution are generally not measurable due to their Kirchner 2002), e. g. K as a chemical analogue to very low concentrations. While TF is a questionable 137Cs and Ca as an analogue to 90Sr (Absalom et al. parameter in soil to plant transfer, it is a readily avail- 2001; Camps et al. 2004; Delvaux et al. 2000; Roca- able quantity that is often tabulated in studies dealing Jove and Vallejo-Calzada 2000; Sanchez et al. 2002; with soil to plant transfer of radionuclide. On the other Smolders et al. 1997). For instance, Smolders et al. hand, the effect of exchangeable Ca and K on TFs is (1997) in a laboratory (pot trial) study described a also questionable, particularly for 137Cs for which RIP negative correlation between the log- CR (plant to soil seems to be a better parameter. Nevertheless, CEC is solution concentration ratio) of 137Cs and the log of probably the simplest parameter that accompanies the the K concentration in the soil solution in 30 different soil classification in the general literature while RIP soils covering a wide range of textures. These authors necessitates a complex determination that has been concluded that 94% of the TF variability can be carried out only on a few soils samples (Sanchez et explained by the K concentration in the soil solution al. 2002). Thus there is an interest to link the ex- 137 and by the Cs distribution coefficient in soil, KD. changeable K and Ca in the soil to the soil to plant Furthermore, several soil parameters have been 137Cs and 90Sr TF. This relationship should involve reported to play an important role in 90Sr and 137Cs various plant species with different uptake potential. transfer to plants: cation exchange capacity (CEC) of This may help to classify plant species and soils soil and associated pH, soil organic matter content according to their capability to transfer radionuclide (SOM), radiocesium interception parameter (RIP).In to the food chain. addition, heterogeneous distribution of radionuclide in The aim of this study was to investigate the rela- soil affects the plant uptake (Bundt et al. 2000; tionship between the 90Sr and the 137Cs TFs for dif- Centofanti and Frossard 2006). ferent species of plants and the exchangeable Ca and Broadley et al. (1999) proposed a method to assess K in the soils. In addition to the effect of competing taxonomic variation in plant uptake of cesium, with ions, we hoped to show any possible phylogenetic Cariophyllidae having the highest Cs concentration in effects on the TFs. We assumed that Alpine plants shoot among superorders. Furthermore, Willey et al. may show enhanced phylogenetic effects on bioaccu- (2005) used a database of 273 plant taxa to show that mulation due to the stress created by the short growth there exists a phylogenetic effect in the 137Cs concen- period at an altitude of 2000 m a.s.l. Because a short tration in plants, with Caryophyllales and Poales pre- growth season means a fast biomass increase rate, it senting the highest and the lowest uptake, respectively. results in a higher requirement in minerals. This might Plant Soil (2012) 355:29–39 31 influence the uptake of 137Cs and 90Sr. To reach these in the soil profile. Plant samples were carefully objectives we chose an Alpine area with different soil washed several times with tap water to remove adher- types. We collected plants from different taxa that ing soil particles; afterwards they were air-dried and were present on the same soil and similar plant species crushed. Plant samples were ashed at 600°C for 48 h. present on different types of soils. Ashes were dissolved in 8 M HNO3 in a pressurized microwave apparatus (MLS ultraCLAVE; Milestone Inc., Monroe, CT) and filtered before measurement. Materials and methods Ca, as well as stable Cs and Sr, were measured on an aliquot using the same techniques as used for the soil Sampling sites samples. The study was conducted in an Alpine valley in Swit- Radionuclide analysis zerland (Val Piora, Ticino; ca 2000 m a.s.l.). This 2 23 km valley is used in the summer for pasturing 137Cs activity was measured on air-dried samples of and is covered with snow from October to May. Six soil and plants in a volume of 250 or 500 ml using sites were selected: three of them, referred hereafter as γ-spectrometry as described in Saidou et al. (2008). sites 1, 4 and 6, are alpine pastures with increasing The total concentration of K in the soil and plant cattle pressure; site 2 is a fen, site 3 is a non-pastured sample was calculated from the activity of 40K.