Uncertainties and recommendations

An assessment of the impacts of changes in climate and UV-B radiation on Arctic terrestrial ecosystems, made within the Arctic Climate Impacts Assessment (ACIA), highlighted the profound implications of projected warming in particular for future ecosystem services, biodiversity and feedbacks to climate. However, although our current understanding of ecological processes and changes driven by climate and UV-B is strong in some geographical areas and in some disciplines, it is weak in others. Even though recently the strength of our predictions has increased dramatically with increased research effort in the Arctic and the introduction of new technologies, our current understanding is still constrained by various uncertainties. The assessment is based on a range of approaches that each have uncertainties, and on data sets that are often far from complete. Uncertainties arise from methodologies and conceptual frameworks, from unpredictable surprises, from lack of validation of models, and from the use of particular scenarios, rather than predictions, of future greenhouse gas emissions and climates. Recommendations to reduce the uncertainties are wide-ranging and relate to all disciplines within the assessment. However, a repeated theme is the critical importance of achieving an adequate spatial and long-term coverage of experiments, observations and monitoring of environmental changes and their impacts throughout the sparsely populated and remote region that is the Arctic.     

Toxicities and tolerances of Cd, Cu, Pb and Zn in a primary producer (Isochrysis galbana) and in a primary consumer (Perna viridis)

Studies on toxicities and tolerances of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) in the brown alga Isochrysis galbana and in the green-lipped mussel Perna viridis were conducted by short-term bioassays using endpoints growth production and mortality, respectively. The 5-day EC(50) and 24-h LC(50) of these heavy metals were determined in the brown alga and mussel, respectively. The EC(50) values calculated for the alga were 0.74 mg/l for Cd, 0.91 mg/l for Cu, 1.40 mg/l for Pb and 0.60 mg/l for Zn. The LC(50) values for the mussels were 1.53 mg/l for Cd, 0.25 mg/l for Cu, 4.12 mg/l for Pb and 3.20 mg/l for Zn. These LC(50) values were within the concentration ranges as reported by other authors who used P. viridis as the test organism. Based on these EC(50) and LC(50) values, the alga was most sensitive to Zn, followed by Cd, Cu and Pb while the mussel was most sensitive to Cu, followed by Cd, Zn and Pb. Differences in the trophic levels, metal handling strategies, biology and ecology of the primary producer (brown alga) and the primary consumer (mussel) are believed to be the plausible causes for the different toxicities and tolerances of the metals studied.     

Concentration measurements of 7Be at ground level air at Palermo, Italy-comparison with solar activity over a period of 21 years

Air activity concentrations of (7)Be in Palermo determined for the period January 1995-December 2002 by gamma-ray spectrometric analysis of particulate samples collected on paper filter by a high-volume sampler (approximately 900 m(3) h(-1)) are reported. The temporal behaviour of (7)Be concentration presents the same characteristics already observed in the measurements carried out over the previous 13-year (1982-1994) investigated period. The mean value of 5.06 mBq m(-3) obtained from the analysis of the 4636 particulate samples collected from 1982 to 2002 can be considered a representative value of (7)Be air concentration at ground level in our geographical zone. The comparison of long-term variation in the (7)Be concentrations with the cyclic solar activity-extended to the whole period of 21 years-confirms the inverse correlation between the two quantities.     

238Pu, 239,240Pu, 241Am, 90Sr and 137Cs in soils around nuclear research centre Rez, near Prague

Forty-four soil samples were taken around the nuclear research centre Rez, near Prague. The mean activity concentrations of 238Pu, 239,240Pu, 241Am, 90Sr and 137Cs in uncultivated soil were 0.010, 0.26, 0.12, 2.7 and 23 Bq.kg(-1), respectively. Contents of radionuclides in cultivated soil were lower and in forest soil higher than in uncultivated soil. The mean activity ratios of 238Pu/239,240Pu, 241Am/239,240Pu, 90Sr/239,240Pu and 239,240Pu/137Cs in uncultivated soil were 0.041, 0.47, 10.9 and 0.013, respectively. The mean activity ratios in cultivated and forest soils were close to the values given above. It follows from the results that the source of 239,240Pu, 90Sr and 137Cs in the studied area is deposition from atmospheric nuclear tests, in the case of 137Cs also deposition from Chernobyl accident. The contribution of the research centre effluents was not proved for these radionuclides. Increased activity ratio of 241Am/239,240Pu indicates the presence of 241Am in the soils studied emanating from sources other than nuclear tests. Uniform distribution of the 241Am/239,240Pu activity ratio around the nuclear research centre and the absence of an area with evidently higher activity ratio, including at sites lying in the main wind direction, suggest that the additional activity of 241Am does not originate from the nuclear research centre. The additional source might be the deposition following the Chernobyl accident.     

Radiocaesium soil-to-plant transfer in tropical environments

In this work, soil-to-plant transfer factors of radiocaesium are predicted based on soil properties such as pH, organic matter content, exchangeable K+ and clay content valid for the tropical environments in Bangladesh, China and Japan, and using a previously published model. Due to insufficient data of soil properties in the selected regions, the average values of pH, organic matter content, exchangeable K+ and clay content were taken as the input model parameters within the ranges given for Asia. Nevertheless, a complete set of soil properties of Japanese soils was used to compare the measured and calculated TF values of radiocaesium for radish. The calculated TF values for radiocaesium are comparable with the measured values especially for leafy parts of a plant. However, calculated values for rice, an important crop in Asia are found to overestimate the measured values due to an overestimate of calculated CECs in soils in the selected regions. The empirical parameters used in the model need to be re-evaluated for the specific part of a plant and/or for a variety of different plants. Alternatively, a general conversion factor for each part of a plant and/or for a variety of different plants for a specific region is suggested for tropical environments.     

Characterization of an underground site in Northern Italy in view of low radioactivity measurements

A low background station for the measurement of low level radioactivity is under development in Northern Italy. The rock cover is about 300 m water equivalent. We report and discuss measurements of radon concentration in air and of gamma, muon and neutron fluxes performed in the neighborhood of the station site. We present and apply a simple analytical model capable to disentangle the contribution to the measured gamma activities due to 222Rn in air from the one due to 238U and its daughters in the rocks.     

Soil-plant transfer of plutonium and americium in contaminated regions of Belarus after the Chernobyl catastrophe

Experimental data are presented for the soil to plant transfer of plutonium and americium into the main species of grass vegetation of Belarusian grasslands contaminated as a result of the Chernobyl catastrophe of 1986. The content of radionuclides in pore soil solutions and the total reserve of biologically available forms of plutonium and americium in rooting layers of different soil varieties have been established. The distribution coefficients of (239,240)Pu and 241Am between the solid phase and pore waters of soils have been evaluated. The migration ability and biological availability of radionuclides in soils with different structures of the absorbing complex have been analyzed for various landscape conditions. The dependence of soil to plant transfer of plutonium and americium on the content and composition of organic matter, and other characteristics of the soil complex has been studied. On the basis of these data, predictions of the contamination levels of the main grass species of natural and agricultural ecosystems by 241Am are presented.     

Estimation of internal radiation dose to the adult Asian population from the dietary intakes of two long-lived radionuclides

Daily dietary intakes of two naturally occurring long-lived radionuclides, 232Th and 238U, were estimated for the adult population living in a number of Asian countries, using highly sensitive analytical methods such as instrumental and radiochemical neutron activation analysis (INAA and RNAA), and inductively coupled plasma mass spectrometry (ICP-MS). The Asian countries that participated in the study were Bangladesh (BGD), China (CPR), India (IND), Japan (JPN), Pakistan (PAK), Philippines (PHI), Republic of Korea (ROK) and Vietnam (VIE). Altogether, these countries represent more than 50% of the world population. The median daily intakes of 232Th ranged between 0.6 and 14.4 mBq, the lowest being for Philippines and the highest for Bangladesh, and daily intakes of 238U ranged between 6.7 and 62.5 mBq, lowest and the highest being for India and China, respectively. The Asian median intakes were obtained as 4.2 mBq for 232Th and 12.7 mBq for 238U. Although the Asian intakes were lower than intakes of 12.3 mBq (3.0 ug) 232Th and 23.6 mBq (1.9 ug) 238U proposed by the International Commission on Radiological Protection (ICRP) for the ICRP Reference Man, they were comparable to the global intake values of 4.6 mBq 232Th and 15.6 mBq 238U proposed by the United Nation Scientific Commission on Effects of Radiation (UNSCEAR). The annual committed effective doses to Asian population from the dietary intake of 232Th and 238U were calculated to be 0.34 and 0.20 microSv, respectively, which are three orders of magnitude lower than the global average annual radiation dose of 2400 microSv to man from the natural radiation sources as proposed by UNSCEAR.     

Radiocesium accumulation in mosses from highlands of Serbia and Montenegro: chemical and physiological aspects

The aim of this work was (i) to determine the activity levels of 137Cs in mosses from highland ecosystems of Serbia and Montenegro, (ii) to find out if radiocesium is associated with essential biomacromolecules, and (iii) to investigate 137Cs distribution among intracellular compartments. It was found that biomolecules of mosses do not bind significant amounts of radiocesium (2.3-3.3% of the absorbed 137Cs), a behavior that was independent of the moss species. Cellular fractionation of mosses showed that membranes are the primary 137Cs-binding sites at the cellular level. They contained 26.1-43.1% of the initial radiocesium activity. It seems that 137Cs-binding molecules in different mosses are of similar chemical nature, and their distribution between various cellular compartments is not species specific.     

137Cs contamination in tea and yerba mate in South America

Gamma-ray spectra from more than 50 samples of food products available in stores of Buenos Aires city were measured using a germanium detector. Activity concentrations of 137Cs up to 10 Bq/kg were found in tea and yerba mate manufactured in Apóstoles, Argentina. Further measurements of tea leaves, yerba mate leaves and soils, all coming from a cultivated area in that region, also show the presence of 137Cs contamination. The results suggest that the area was fertilized with a product that originated in a region affected by the fallout from the Chernobyl nuclear plant accident.