Lichens as monitors of radiocesium and radiostrontium in Austria

doi:10.1016/S0265-931X(98)00069-1

Journal of Environmental Radioactivity

Volume 45, Issue 1, October 1999, Pages 13-27

Dedicated to Prof. Dr. H.C. Eberhard Schnepf, Heidelberg, on the occasion of the 65thbirthday.

https://doi.org/10.1016/S0265-931X(98)00069-1 Get rights and content

Abstract

Many areas of Austria were contaminated to various degrees with radionuclides, following the reactor accident in Chernobyl. In Styria, a province of Austria, the ¹³⁷Cs activity in lichens rose to over 50 kBq kg^-1 from an initial value of 0.4 kBq kg^-1 dry weight before Chernobyl. The ¹³⁷Cs contamination of Pseudevernia furfuracea exceeded the natural radioactivity of ⁴⁰K up to 430 fold. The ecological half-life of ¹³⁷Cs in Pseudevernia furfuracea which grows on spruce was found to be approximately 3 years, whereas 3.8 additional years were needed to reach a fourth of the initial ^{137Cs activity. The half-life of 134}Cs was found to be 1.3 and that of ⁹⁰Sr was between 1.2 and 1.6 years. The corresponding values for the terricolous lichen Cetraria islandica were 2.5 year for ¹³⁷Cs and 1.2 for ⁹⁰Sr. The ¹³⁷Cs levels were found to vary even within short distances. Two reasons, other than the uneven distribution of the radioactive precipitation, are given here for this observation. Pseudevernia, which grew on dead trunks, was contaminated about three times as much at the top end of the trunk as in the lower sections of the tree. This was due to the fact that the rainfall was rather vertical shortly after the Chernobyl accident, so that the upper lichens adsorbed the main part of the radionuclides. Secondly, on a mountain slope, the ¹³⁷Cs level was shown to increase with altitude. This was because it rained slightly more in the higher regions shortly after the Chernobyl accident and because of the shorter vegetation period. A good indication of the high levels of contamination through various γ-ray emitting radionuclides following the reactor accident is also given here by the levels reached by those radionuclides in a soil sample from Graz, capital of Styria. In this sample the activity of all gamma emitting radionuclides was 1654 kBq m^-2. 137Cs showed 2.8% of the overall radioactivity, the corresponding value for 134Cs was 1.1%.

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Cited by (34)

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The Chernobyl accident exposed large areas of northern Europe to radiocaesium (¹³⁷Cs). We investigated temporal and spatial variation in concentrations of radiocaesium among five functional groups of alpine plants at two mountain areas in central Norway over a 31-year period from 1991 to 2022. Average concentrations of radiocaesium were initially high in lichens and bryophytes at around 4600–6400 Bq/kg dry weight during 1991–1994 but then decreased dramatically over three decades to current concentrations of <200 Bq/kg for all plant groups in 2019–2022. The effective half-life of radiocaesium was estimated to be 4–6 years in lichens and mosses, 7–13 years in herbaceous plants, and 22–30 years in woody plants, which were less than the physical half-life of 30.2 years. Concentrations of radiocaesium were greater at the nutrient-poor site than at the nutrient-rich site, probably due to greater deposition levels at higher elevations and the geographical pattern of the deposition. Functional groups of plants differed with higher concentrations among non-vascular than vascular plants. Common heather Calluna vulgaris was unusual among woody plants with high concentration of radiocaesium, especially in the new shoots. Our new estimates of concentrations and dynamics of radiocaesium for alpine plants in natural environments will be useful for modelling herbivore exposure and evaluating potential impacts on wildlife and human health.
Current radioactive fallout contamination along a trans-European gradient assessed using terricolous lichens
2022, Chemosphere
Citation Excerpt :
Studies carried out after the Chernobyl and Fukushima Dai-ichi nuclear power plant accidents demonstrated that lichens have the capacity to accumulate high concentrations of radionuclides (Nimis et al.2002). They are also more effective in contaminant absorption than vascular plants, and are able to absorb higher amounts of 137Cs than vascular plants growing in the same contaminated habitats (Anderson et al., 2022; Dalvand et al., 2016; Galhardi et al., 2017; Heinrich et al., 1999; Hofmann et al., 1993; Ohmura et al., 2015; Sawidis et al., 2010). Lichens have a high ratio of surface area to biomass, and a slow growth rate (Nimis et al.2002).
Lichens are considered to be good indicators of contamination of the terrestrial environment. In this study, we investigated the level of ¹³⁷Cs and ⁴⁰K accumulated by Cladonia arbuscula and Stereocaulon alpinum along a longitudinal gradient from northern Norway, across Sweden to southern Poland. Additionally, we compared isotope contents between the selected lichen species, and investigated the correlation of the ¹³⁷Cs content accumulated by C. arbuscula with ¹³⁷Cs fallout after the Chernobyl disaster. The activity of ¹³⁷Cs varied from 3.58 Bq kg⁻¹ to 559 Bq kg⁻¹ for S. alpinum, and from 1.18 Bq kg⁻¹ to 130 Bq kg⁻¹ for C. arbuscula. The activity of ⁴⁰K ranged from 114 Bq kg⁻¹ to 341 Bq kg⁻¹ for S. alpinum and from 27.2 Bq kg⁻¹ to 314 Bq kg⁻¹ for C. arbuscula. The ¹³⁷Cs content did not differ between C. arbuscula and S. alpinum; however, the difference between species was significant for ⁴⁰K accumulation. The activity of ¹³⁷Cs in C. arbuscula was significantly correlated with deposition from 1986. Based on our findings we created a spatial map of ¹³⁷Cs activity in lichens measured 30 years after the event that was the primary source of this isotope. We showed that C. arbuscula can be used to assess contamination and create interpolation maps of radionuclide deposition, even if the primary deposition took place many years ago.
A review on the use of lichens as a biomonitoring tool for environmental radioactivity
2022, Journal of Environmental Radioactivity
Citation Excerpt :
Several factors can describe a local climate such as average annual or daily temperature, humidity, rainfall, solar irradiation, duration of the seasons, etc. There is a loose relationship of climate with latitudes (and altitude to some extent), i.e., the harsher and colder climates are empirically related to high latitudes (and altitudes; see Odland et al., 2018; Asplund and Wardle, 2017; Boddy, 2016; Heinrich et al., 1999; Taylor et al., 1985). Since lichens are present in almost all climates, some species and growth forms will prevail under specific climatic conditions.
Lichens have been widely used as a biomonitoring tool to record the distribution and concentration of airborne radioactivity and pollutants such as metals. There are limitations, however: although pollutants can be preserved in lichen tissues for long periods of time, not all radioactive and inert elements behave similarly. The chemical species of elements at the source, once captured, and the mode of storage within lichens play a role in this biomonitoring tool.
Lichens are a symbiotic association of an algal or cyanobacterial partner (photobiont) with a fungal host (mycobiont). Lichens grow independently of the host substrates, including rocks, soils, trees and human-made structures. Lacking a root system, lichen nutrient or contaminant uptake is mostly through direct atmospheric inputs, mainly as wet and dry deposition. As lichens grow in a large variety of environments and are resilient in harsh climates, they are adapted to capture and retain nutrients from airborne sources.
The context of this review partially relates to future deployment of small modular reactors (SMRs) and mining in remote areas of Canada. SMRs have been identified as a future source of energy (electricity and heat) for remote off-grid mines, potentially replacing diesel fuel generation facilities. For licensing purposes, SMR deployment and mine development requires capabilities to monitor background contaminants (natural radioactivity and metals) before, during and after deployment, including for decommissioning and removal. Key aspects reviewed herein include: (1) how lichens have been used in the past to monitor radioactivity; (2) radiocontaminants capture and storage in lichens; (3) longevity of radiocontaminant storage in lichen tissues; and (4) limitations of lichens use for monitoring radiocontaminants and selected metals.
Bryophytes and lichens as fallout originated radionuclide indicators in the Svalbard archipelago (High Arctic)
2020, Polar Science
Arctic environment is very sensitive to anthropogenic pollutants, especially in terms of radionuclide contamination which persists in polar regions due to very slow biological turnover rate. The main aim of the study was to determine concentrations of ¹³⁷Cs in selected cryptogamic species (bryophytes and lichens) in different areas of Svalbard archipelago in the period of 1985–2017 and thus recognize the level of ¹³⁷Cs contamination in Svalbard as well as to indicate the best fallout originated radionuclide bioindicators in the Arctic region. The ¹³⁷Cs activity was measured in 31 samples of cryptogams (Cetraria islandica (L.) Ach., Cetrariella delisei (Bory ex Schaer.) Kärnefelt & A. Thell, Flavocetraria nivalis (L.) Kärnefelt & A. Thell, Ptilidium ciliare (L.) Hampe, Racomitrium lanuginosum (Hedw.) Brid., Sanionia uncinata (Hedw.) Loeske, and Sphaerophorus globosus (Huds.) Vain.) collected between 1985 and 2017 at six different locations in Svalbard: Adventdalen, Bellsund, Kaffiøyra, Ny-Ålesund, Petuniabukta, and Sørkapp Land. Analyses showed that species R. lanuginosum and C. delisei can be recommended as the best bioindicators of changes in radioactivity level in the Arctic region.
Distribution of radionuclides in moss-lichen cover and needles on the same grounds of landscape-climatic zones of Siberia
2019, Journal of Environmental Radioactivity
The radiation status of the landscape and climatic zones of Siberia at the turn of the 20th and 21st centuries is characterized using bioindicators/biomonitors: lichens, mosses, and needles, according to the results obtained at the sites of their joint growth. The maximal activity of ¹³⁷Cs in these components is observed in the forest-tundra landscaped zone, polluted during the period of nuclear tests from the nuclear test site “Novaya Zemlya” and also due to slow migration of these elements to the soil under the arctic conditions. In the southern territories the specific activity of radiocesium in the moss-lichen cover and needles of conifers corresponds to the regional background, in the forest-tundra zone it sometimes exceeds it, but in general does not pose a threat to human health.
Determined differences in the contents of radioactive elements in lichens and mosses that grow together on sites in different landscape zones of Siberia statistically not significant within one or two standard deviations, and recorded only in the range of 3ϭ at the level of significance 0.05. Specificity of radionuclide distribution in lichens, mosses and needles (differences for epigeals and epiphytic lichens; different species selected at one site, annual and perennial needles, etc.) made it possible to identify the causes of variations in their activities in different zones, along with landscape features of these zones. In the needles of conifers potassium concentration exceeds the content in lichens, at lower levels of thorium and ¹³⁷Cs.
The contents of uranium and thorium in the studied components in all landscape-climatic zones correspond to the natural ones, except for the single local territories, because of the possible anthropogenic influence.
Thirty years after chernobyl: Long-term determination of <sup>137</sup>Cs effective half-life in the lichen Stereocaulon vesuvianum
2017, Journal of Environmental Radioactivity
Citation Excerpt :
This affected the local appearance of 137Cs in food, feed, mushrooms and wildlife, hence the health risk due to 137Cs and other nuclides to human consumers (Barnett et al., 1999; Battiston et al., 1989; Falandysz et al., 2015; Smith et al., 1993; Zarubina, 2014). Several studies carried out before and after the Chernobyl accident, and more recently after the Fukushima Dai-ichi Nuclear Power plant accident on 11 March 2011, have demonstrated that lichens have the capacity to retain high concentrations of radionuclides (Dalvand et al., 2016; Eckl et al., 1984; Heinrich et al., 1999; Hofmann et al., 1993; Machart et al., 2007; Ohmura et al., 2015; Sawidis and Heinrich, 1992; Sawidis et al. 2010; Stocki et al., 2016), and more sensitive as radiocontamination bio-monitors than other plants (Galhardi et al., 2017). Since lichens have no roots, they absorb much of their raw materials directly from air and moisture around them.
It has been widely shown that nuclear fallout includes substances, which accumulate in organisms such as crustaceans, fish, mushrooms and lichens, helping to evaluate the activity concentration of contaminants accumulated on a long time. In this context, radiocaesium deposited in soil following the Chernobyl accident on 26 April 1986 is known to have remained persistently available for plant uptake in many areas of Europe. Studies on the lichen Stereocaulon vesuvianum show the plant's high capacity to retain radionuclides from the substrate and the air. After the Chernobyl accident, starting from September 1986, at the Radioactivity Laboratory (LaRa) of the University of Naples Federico II, four monitoring campaigns to evaluate the activity concentration of four isotopes of the two elements caesium and ruthenium (¹³⁴Cs, ¹³⁷Cs, ¹⁰³Ru and ¹⁰⁶Ru) were carried out until 1999. This study allowed the effective half-life of ¹³⁴Cs and ¹³⁷Cs to be estimated.
Twenty-eight years after the accident, in December 2014, a further sampling was carried out; only ¹³⁷Cs was revealed beyond the detection limits, measuring activity concentrations ranging from 20 to 40 Bq/kg, while the other radionuclides were no longer observed due to their shorter half-life. The last sampling allowed more precise determination of the effective half-life of ¹³⁷Cs (6.2 ± 0.1 year), due to the larger dataset on a large time period.

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