Assessment of internal radiation exposure to Antarctic biota due to selected natural radionuclides in terrestrial and marine environment.

The present article introduces data on natural radioactivity (40K, 230,232Th, 234,238U) in the Antarctic marine and terrestrial environment. Various biota samples were analysed due to internal exposure to 40K, 230,232Th, 234,238U. Activity concentration of 40K was the highest in both marine and terrestrial samples. Mean values of 40K activity concentration are 1340 Bq/kg and 370 Bq/kg for the marine and terrestrial samples respectively. 234U/238U ratios analysis revealed that sea waters and sea spray are the main source of the uranium in the terrestrial samples. Average 230,232Th, 234,238U activity concentrations in the Antarctic biota do not exceed 6 Bq/kg. Weighted internal dose rates are relatively low; they range from approximately 0.1 to 0.6 µGy/h. Statistically significant differences in radionuclide accumulation were discovered between the mosses and lichens. It may point to various mechanisms of the nutrient absorption from the environment by these organisms.

Anthropogenic radionuclides in Antarctic biota - dosimetrical considerations.

The article presents results of the research on artificial radionuclides (137Cs, 90Sr, 241Am) in the Antarctic environment. Samples of 12 species from the marine environment: Pygoscelis adeliae, Pygoscelis papua, Macronectes giganteus, Pagodroma nivea, Catharacta antarctica, Leptonychotes weddellii, Mirounga leonina, Harpagifer antarcticus, Chaenocephalus aceratus, Nacella concinna, Himantothallus grandifolius, Iridaea cordata (bones, feathers, soft tissues, eggs' shells of birds, bones, skin, fur of mammals, fish, mollusks' soft tissues and shells, algae) and samples of 4 species from the terrestrial environment: Sanionia uncinata, Usnea antarctica, Usnea aurantiaco-atra, Deschampsia antarctica (mosses, lichens, grass) were investigated. Differences in the accumulation of 137Cs between marine and terrestrial ecosystem were shown, which are mostly due to conservatism of mosses and lichens and active removal of cesium by animal body. Furthermore discrepancy between mosses and lichens in the radioceasium accumulation was statistically proven with the additional use of Neutron Activation Analysis. Moreover, the internal weighted dose rates assessment was prepared using the ERICA Tool. The dose rates were relatively low, not exceeding several dozen nGy/h. Nonetheless, one species - Pagodroma nivea, was significantly outstanding due to the highest weighted dose rate it is burdened with.

Low-temperature immobilization of water in Antarctic Turgidosculum complicatulum and in Prasiola crispa. Part I. Turgidosculum complicatulum.

The studies of low-temperature immobilization of bound water in Antarctic lichenized fungus Turgidosculum complicatulum were performed using 1H NMR and DSC over a wide range of thallus hydration. 1H NMR free induction decays were decomposed into a solid component well described by the Gaussian function and two exponentially decaying components coming from a tightly bound water and from a loosely bound water fraction. 1H NMR spectra revealed one averaged mobile proton signal component. 1H NMR measurements recorded in time and in frequency domain suggest the non-cooperative bound water immobilization in T. complicatulum thallus. The threshold of the hydration level estimated by 1H NMR analysis at which the cooperative bound water freezing was detected was Δm/m0 ≈ 0.39, whereas for DSC analysis was equal to Δm/m0 = 0.375. Main ice melting estimated from DSC measurements for zero hydration level of the sample starts at tm = -(19.29 ± 1.19)°C. However, DSC melting peak shows a composed form being a superposition of the main narrow peak (presumably melting of mycobiont areas) and a broad low-temperature shoulder (presumably melting of isolated photobiont cells). DSC traces recorded after two-hour incubation of T. complicatulum thallus at -20 °C suggest much lower threshold level of hydration at which the ice formation occurs (Δm/m0 = 0.0842). Presumably it is a result of diffusion induced migration of separated water molecules to ice microcrystallites already present in thallus, but still beyond the calorimeter resolution.

Extreme dehydration observed in Antarctic Turgidosculum complicatulum and in Prasiola crispa.

Gaseous phase hydration effect of extremely dehydrated thallus of the Antarctic lichenized fungus Turgidosculum complicatulum and of green alga Prasiola crispa was observed using hydration kinetics, sorption isotherm, 1H-NMR spectroscopy and relaxometry. Three bound water fractions were distinguished: (1) very tightly bound water, (2) tightly bound water and (3) a loosely bound water fraction detected at higher levels of hydration. Sorption isotherm was sigmoidal in form and well fitted using Dent model. The relative mass of water saturating primary water binding sites was ΔM/m 0 = 0.055 for T. complicatulum and ΔM/m 0 = 0.131 for P. crispa. 1H-NMR free induction decays (FIDs) for T. complicatulum and for P. crispa were superpositions of a solid signal component, and one averaged liquid signal component for P. crispa thallus ([Formula: see text] ≈ 80 µs) or two liquid signal components coming from a tightly bound ([Formula: see text]≈ 71 µs) and from a loosely bound water fraction ([Formula: see text]≈ 278 µs) for T. complicatulum. 1H-NMR spectra recorded for T. complicatulum and for P. crispa thalli revealed one averaged mobile proton signal component L. The total liquid signal component expressed in units of solid (L 1 + L 2)/S suggests the presence of water soluble fraction in T. complicatulum thallus.

A method of water-soluble solid fraction saturation concentration evaluation in dry thalli of Antarctic lichenized fungi, in vivo.

BACKGROUND: At initial steps of rehydration from cryptobiosis of anhydrobiotic organisms or at rehydration of dry tissues the liquid 1H NMR signal increased anomaly. The surplus in liquid signal may appear if some solid constituents dissolved, or if they were decomposed by enzymatic action. METHODS: Hydration kinetics, sorption isotherm, 1H NMR spectra and high power relaxometry were applied to monitor gaseous phase rehydration of Antarctic lichen Cetraria aculeata. Tightly and loosely bound water signal were distinguished, and the upper hydration limit for dissolution of water soluble solid fraction was not observed. A simple theoretical model was proposed. RESULTS: The hydration courses showed a very tightly bound water fraction, a tightly bound water, and a loosely bound water fraction. Sigmoidal in form sorption isotherm was fitted well by multilayer sorption model. 1H NMR showed one Gaussian signal component from solid matrix of thallus and one or two Lorentzian line components from tightly bound, and from loosely bound water. The hydration dependency of liquid signal was fitted by rational function. CONCLUSIONS: Although in dehydrated C.aculeata the level of carbohydrates and polyols was low, the lichenase action during rehydration process increased it; the averaged saturation concentration cs =(57.3±12.0)%, which resembled that for sucrose. GENERAL SIGNIFICANCE: The proposed method of water soluble solid fraction saturation concentration, cs , calculation from 1H NMR data may be applied for other organisms experiencing extreme dehydration or for dry tissues. We recalculated the published elsewhere data for horse chestnut (Aesculus hippocastanum) bast [water-soluble solid fraction recognized as sucrose, cs =(74.5±5.1)%]; and for Usnea antarctica, where cs =0.81±0.04.