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Sorption of selected radionuclides from liquid radioactive waste by sorbents of biological origin : the alkaline earth alginates

Fuks Leon, Oszczak-Nowińska Agata

Nukleonika

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2021

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Vol. 66, No. 4

153--158

EN

The sorption of 241Am3+, 85Sr2+ and 137Cs+ by calcium, strontium and barium alginates has been studied under different operation conditions. The most prominent adsorption was found in the pH range of 5–6 for all systems, even if the observed dependence on the acidity of the solution was small. The most favourable time for the adsorption process was found to be about 2 h for calcium alginate and 4 h for the other two sorbents.

2

Short review: the mechanisms of radiocaesium uptake by Arabidopsis roots

Hampton C., Broadley M., White P.

Nukleonika

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2005

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Vol. 50,suppl.1

3-8

EN

Both theoretical models and pharmacological dissection suggest that Cs+ influx to arabidopsis root cells occurs through voltage-insensitive cation channels (VICCs), encoded by members of the AtCNGC and AtGLR gene families, and 'high-affinity' K+/H+ symporters (KUPs), encoded by members of the AtKUP/AtHAK gene family. When arabidopsis have sufficient K, it is observed that VICCs mediate most Cs+ influx to root cells. However, KUPs contribute more to Cs+ influx in roots of K-starved plants. This phenomenon has been attributed to an increased expression of AtHAK5 in roots of K-starved plants. Curiously, although arabidopsis mutants lacking some AtCNGCs show reduced Cs accumulation, mutants lacking other AtCNGCs accumulate more Cs in their shoot than wildtype plants. It is hypothesised, therefore, that the expression of genes encoding diverse K+-transporters might be altered to compensate for the absence of AtCNGCs that contribute significantly to cellular K homeostasis. Increased Cs+ influx and accumulation could then be explained if the lack of an AtCNGC caused a physiological K-deficiency that increased the expression of AtKUPs. Such observations imply that the consequences of a simple genetic manipulation, such as the mis-expression of a AtCNGC gene, on Cs+ influx and accumulation might not be predicted a priori. Finally, since AtCGNCs, AtGLRs and AtKUPs have contrasting Cs+:K+ selectivities, and their relative expression is determined by diverse environmental variables, both the Cs:K ratio in plant tissues and the absolute rates of Cs+ influx and accumulation will depend critically on environmental conditions. This will impact on strategies for phytoremediation and/or the development of 'safer' crops for radiocaesium-contaminated land.

3

Cationic interactions in caesium uptake by king oyster mushroom (Pleurotus eryngii )

Bystrzejewska-Piotrowska G., Manjón J., Pianka D., Bazała M., Urban P.

Nukleonika

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2005

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Vol. 50,suppl.1

9-13

EN

In order to explain influence of common cations (K+, Na+ and Ca2+) on uptake and transport of caesium in macromycetes, a culture of a model mushroom species, king oyster mushroom (Pleurotus eryngii) was set up. Fructification in a growing chamber with stabilised temperature (18°C) and humidity (80%) was preceded by mycelial colonization of the sterilized barley seed medium packed into autoclavable plastic containers. Aliquots of test solutions, containing 0.1 mM caesium chloride carrier traced with 137CsCl and the selected ions, were dosed into the interphase between the container wall and the spawn block. This allowed to study influence of the added ions on the uptake of caesium in a way unaffected by the used growing medium, e.g. soil, as it was in the previous studies. The experiments demonstrated that the major amount of radiocaesium was biologically bound and accumulated in the fruitbodies to a higher extent (56 69%) than in the mycelium. Addition of 10 mM Na+ decreased the transfer factor for caesium (cap/soil) while addition of Ca2+ caused an increase of this value. The effect of potassium addition depended on its concentration in the solution. Also the Cs/K ratio in caps was significantly influenced by addition of 10 and 100 mM Na+. However, the Cs/K ratio in stipes was affected by Ca2+. Discrimination factors, calculated from specific activities (137Cs/40K cap d.w.)/(137Cs/40K stipe d.w.), were also changed after addition of the studied cations. Since the activities of caesium measured in the fruitbodies of single fungal species strongly depend on the content of co-supplied ions, further proofs should be achieved before using mushrooms as bioindicators of the soil caesium contamination.

4

Accumulation of 137Cs in bottom sediments of the Curonian Lagoon

Lujaniene G., Vilimaite-Šilobritiene B., Jokšas K.

Nukleonika

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2005

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Vol. 50, nr 1

23-29

EN

Measurements of activity concentrations and speciation of 137Cs in bottom sediments of the Curonian Lagoon were carried out in samples collected in 1999-2003. In addition, the sorption-desorption processes of caesium in disturbed bottom sediments of fresh and sea water systems were investigated in long-term experiments (up to 375 days) in order to better understand the caesium behaviour during the Baltic Sea water flooding events to the Curonian Lagoon. The modified Tessier method was used to study caesium associations with geochemical phases of bottom sediments. The effect of carbonate coatings of bottom sediments on the Cs sorption-desorption process was observed. The comparative analyses of 137Cs solid phase speciation in bottom sediments after 241 and 375 days of the sorption experiment with that of the 137Cs speciation, determined in the same sediment sample before the sorption experiment, indicated that after 375 days of sorption the equilibrium was not reached, however, the Cs distribution in geochemical phases was found to be close to equilibrium. The desorption experiments evidenced the release of caesium into solution from regular exchange complex and transfer from other phases to the frayed edge sites on the layered clay minerals with its further fixation in the crystal lattice. The remobilization of "fixed" caesium was not observed, on the contrary, the redistribution of caesium with its subsequent fixation in clay minerals was observed, and on a time scale its fixation kinetics was comparable with the sorption experiment. This study showed that flooding events of sea water contaminated with caesium can cause a significant accumulation of caesium in the bottom sediments of the Curonian Lagoon and result in the redistribution of 137Cs activity concentration in the bottom sediments from one area to another.

5

Measurement of plutonium isotopes in ground-level air in Northern-Germany - history and recent results

Wershofen H., Arnold D., Steinkopff T.

Nukleonika

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2001

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Vol. 46, nr 4

155-159

EN

The history of plutonium measurements performed on ground-level aerosols is summarised. Recent results are presented, the activity ratios a((239+240)Pu)/a(137Cs) and a(238Pu)/a((239+240)Pu) measured are discussed and potential sources of 238Pu are considered.

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Pierwiastki promieniotwórcze a problem zagrożeń radioekologicznych w miastach regionu sudeckiego

Strzelecki R., Wołkowicz S., Nałęcz T.

Przegląd Geologiczny

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2000

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Vol. 48, nr 12

1139-1150

PL

Sudety stanowiące fragment Masywy Czeskiego są obszarem, gdzie na rozległych terenach występują formacje skalne o podwyższonej promieniotwórczości naturalnej. Ludność zamieszkała na tym obszarze otrzymuje więc znacznie wyższe dawki promieniowania niż w innych regionach Polski. Pracami pomiarowymi objęto 14 miast. Najwyższa wartość mocy dawki promieniowania gamma, znacząco przekraczająca 100 nGy/h, została stwierdzona w miastach zlokalizowanych częściowo lub w całości na granitach karkonoskich (Szklarska Poręba, Jelenia Góra, Karpacz, Kowary). Znacząca niższa wartość, wahająca się od 72 do 62 nGy/h, stwierdzono w miastach zlokalizowanych na skalach osadowych. Mimo to, wartości te są prawie dwukrotnie wyższe od wartości średniej mocy dawki promieniowania gamma obliczanej dla całej Polski. Wielkość dawki promieniowania gamma zależy od zawartości radionuklidów naturalnych, w tym przede wszystkim od zawartości uranu (>4 ppm) i toru (>12 ppm). Wysoka koncentracja uranu w granicie karkonoskim, brak słabo przepuszczalnych utworów w nadkładzie, głębokie zwietrzenie górotworu i obecność licznych stref uskokowych powoduje, że miasta zlokalizowane w granicach jego wychodni są zagrożone wysokim ryzykiem radonowym. Udział skażenia cezem poczarnobyłskim w całkowitej dawce promieniowania gamma jest marginesowy i jedynie w rejonie Lądka Zdroju stwierdzono podwyższoną koncentrację tego radionuklidu, przy czym relatywnie wysoką wartość (88,8 kBq/m2) stwierdzono tylko na jednym punkcie pomiarowym.

EN

The Sudetes, being the fragment of Czech Massif, is an area with numerous exposures of rock formations characterized by increased natural radioacttivity. Autochthons of this region are submitted to significantly higher radiation doses rate than populations in other parts of Poland. Radiation measures were realized in 14 towns and the highest gamma dose rate, more than 100 nGy/h, were noticed in towns located totally or partially on the Karkonosze granites (a. e. Szklarska Poręba, Jelenia Góra Karpacz, Kowary). Distinctly lower doses, from 62 to 72 nGy/h, were measured in towns founded on the sedimentary rocks but they are still almost twice higher than an average dose of gamma radiation, calculated for the whole Poland area. Value of radiation dose depends on a content of natural radionuclides, mainly on an amount of uranium (>4 ppm) and thorium (> 12 ppm). High uranium concentration in the Karkonosze granites, a lack of low permeable sediments within an overburden, deep weathering ofmagmatic massif as well as occurrence of numerous fault zones favour a high radon risk in towns founded on such rock basement. Participation of post-Chernobyl caesium in a gamma dose is quite subordinate and only in the vicinity of Lądek Zdrój was detected its incresed concentration but the relatively high value (88,8 kBq/m2) was noticed in a single measure point.