I. Serrano

Removal of radionuclides in drinking water by membrane treatment using ultrafiltration, reverse osmosis and electrodialysis reversal

A pilot plant had been built to test the behaviour of ultrafiltration (UF), reverse osmosis (RO), and electrodialysis reversal (EDR) in order to improve the quality of the water supplied to Barcelona metropolitan area from the Llobregat River. This paper presents results from two studies to reduce natural radioactivity. The results from the pilot plant with four different scenarios were used to design the full-scale treatment plant built (SJD WTP). The samples taken at different steps of the treatment were analysed to determine gross alpha, gross beta and uranium activity. The results obtained revealed a significant improvement in the radiological water quality provided by both membrane techniques (RO and EDR showed removal rates higher than 60%). However, UF did not show any significant removal capacity for gross alpha, gross beta or uranium activities. RO was better at reducing the radiological parameters studied and this treatment was selected and applied at the full scale treatment plant. The RO treatment used at the SJD WTP reduced the concentration of both gross alpha and gross beta activities and also produced water of high quality with an average removal of 95% for gross alpha activity and almost 93% for gross beta activity at the treatment plant.

Natural and anthropogenic radionuclides in airborne particulate samples collected in Barcelona (Spain)

Results for naturally occurring (7)Be, (210)Pb, (40)K, (214)Bi, (214)Pb, (212)Pb, (228)Ac and (208)Tl and anthropogenic (137)Cs in airborne particulate matter in the Barcelona area during the period from January 2001 to December 2005 are presented and discussed. The (212)Pb and (208)Tl, (214)Bi and (214)Pb, (7)Be and (210)Pb radionuclide levels showed a significant correlation with each other, with correlation coefficients of 0.99, 0.78 and 0.69, respectively, suggesting similar origin/behaviour of these radionuclides in the air. Caessium-137 and Potassium-40 were transported to the air as resuspended particle from the soil. The (7)Be and (210)Pb concentrations showed similar seasonal variations, with a tendency for maximum concentrations during the summer months. An inverse relationship was observed between the (7)Be, (210)Pb, (40)K and (137)Cs concentrations and weekly rainfall, indicating washout of atmospheric aerosols carrying these radionuclides.

Influence of the Fukushima Dai-ichi nuclear accident on Spanish environmental radioactivity levels

This paper presents measurements of the effect of the atmospheric radioactive release from the Fukushima Dai-ichi nuclear power station at three sites belonging to the Spanish environmental monitoring system. Measured values varied depending on the locations of the sites in Spain and their respective climatic characteristics. (134)Cs, (136)Cs, (137)Cs, (131)I, and (132)Te activity concentrations in filter samples were studied and associated levels of (131)I fallout were estimated from wet and dry deposition. Particulate aerosol activity concentrations ranges, in μBq/m(3), were 1.63-3080 ((131)I), 2.8-690 ((137)Cs), 1.3-620 ((134)Cs) and 3.6-330 ((132)Te), while the associated (131)I fallout was roughly estimated to be less than 20 Bq/m(2), Gaseous (131)I was also detected and the (131)I-gaseous/(131)I-total ratio increased at the three stations from approximately 0.75 at the end of March to 0.85-0.9 during the first few days of April. Finally, the presence of (131)I in some crucial parts of the food chain was also studied. (131)I was detected in samples from goats and cows milk (maximum levels of 1.11 Bq/L) and in broadleaf plants (maximum level 1.42 Bq/kg).

Natural radioactivity in drinking water in Catalonia (Spain)

A survey to study natural radioactivity in drinking water was carried out in Catalonia (northeast Spain). Approximately 800 samples of drinking water were analysed between 1986 and 1993. The samples were categorized according to origin: bottled or public supply. The samples were analysed for gross alpha, gross beta, 234U, 235U, 238U, 226Ra, 228Ra, 230Th, 232Th, 210Pb, and 210Po activity. The activity concentration for gross alpha was found to range from 0.02 to 1.75 Bq/L and for gross beta from 0.04 to 2.9 Bq/L. The gross beta activity content in the majority of the samples is due to 40K. Average concentrations of 234U, 238U, 226Ra, and 210Pb in the waters studied ranged from 10 to 100 mBq/L. Concentrations of 700 mBq/L were obtained for 234U, 960 mBq/L for226 Ra, and 1130 mBq/L for 210Pb. The highest levels of alpha radioactivity are due to the presence of granitic formations in the region. A high degree of radioactive disequilibrium was noted among members of the uranium series present in some samples of water. The 234U238U activity ratio varied between 1 and 4, and the waters with the lowest uranium activity registered the highest level of 234U238U activity ratio.

Distribution of uranium isotopes in surface water of the Llobregat river basin (Northeast Spain).

A study is presented on the distribution of (234)U, (238)U, (235)U isotopes in surface water of the Llobregat river basin (Northeast Spain), from 2001 to 2006. Sixty-six superficial water samples were collected at 16 points distributed throughout the Llobregat river basin. Uranium isotopes were measured by alpha spectrometry (PIPS detectors). The test procedure was validated according to the quality requirements of the ISO17025 standard. The activity concentration for the total dissolved uranium ranges from 20 to 261mBqL(-1). The highest concentrations of uranium were detected in an area with formations of sedimentary rock, limestone and lignite. A high degree of radioactive disequilibrium was noted among the uranium isotopes. The (234)U/(238)U activity ratio varied between 1.1 and 1.9 and the waters with the lowest uranium activity registered the highest level of (234)U/(238)U activity ratio. Correlations between uranium activity in the tested water and chemical and physical characteristics of the aquifer were found.

Experimental analysis of the mass efficiency curve for gross alpha activity and morphological study of the residue obtained by the co-precipitation method

Gross alpha activity determination in drinking water is one of the radiological parameters that must be determined in order to decide whether further specific analyses of radionuclides in samples is required. This parameter can be determined by the co-precipitation method using a ZnS(Ag) scintillation detector or a proportional counter. The method consists of collecting all alpha emitters of interest using barium and iron as carriers as they provide more uniform and homogeneous residues than the evaporation method, especially for highly saline waters. In the course of our work, the efficiencies of the gas proportional and ZnS(Ag) detectors for alpha particle detection in water residues were studied in function of sample mass (precipitate) with residues ranging between 16.0 and 35.0mg. In addition, the structure and morphological composition of a residue collected by the co-precipitation method was studied with the aim of verifying whether the residue is a homogeneous mixture. The effect of alpha energy on the efficiency and stability of the calibration samples (mass and efficiency) was studied using (230)Th, natural uranium ((nat)U) and (241)Am radionuclides.

Coincidence summing corrections for volume samples using the PENELOPE/penEasy Monte Carlo code

The coincidence summing correction factors estimated with penEasy, a steering program for the Monte Carlo simulation code PENELOPE, and with penEasy-eXtended, an in-house modified version of penEasy, are presented and discussed for (152)Eu and (134)Cs in volume sources. The geometries and experimental data were obtained from an intercomparison study organized by the International Committee for Radionuclide Metrology (ICRM). A significant improvement in the results calculated with PENELOPE/penEasy was obtained when X-rays are included in the (152)Eu simulations.

Influence of long-range atmospheric transport pathways and climate teleconnection patterns on the variability of surface 210 Pb and 7 Be concentrations in southwestern Europe

The variability of the atmospheric concentration of the 7Be and 210Pb radionuclides is strongly linked to the origin of air masses, the strength of their sources and the processes of wet and dry deposition. It has been shown how these processes and their variability are strongly affected by climate change. Thus, a deeper knowledge of the relationship between the atmospheric radionuclides variability measured close to the ground and these atmospheric processes could help in the analysis of climate scenarios. In the present study, we analyze the atmospheric variability of a 14-year time series of 7Be and 210Pb in a Mediterranean coastal city using a synergy of different indicators and tools such as: the local meteorological conditions, global and regional climate indexes and a lagrangian atmospheric transport model. We particularly focus on the relationships between the main pathways of air masses and sun spots occurrence, the variability of the local relative humidity and temperature conditions, and the main modes of regional climate variability, such as the North Atlantic Oscillation (NAO) and the Western Mediterranean Oscillation (WeMO). The variability of the observed atmospheric concentrations of both 7Be and 210Pb radionuclides was found to be mainly positively associated to the local climate conditions of temperature and to the pathways of air masses arriving at the station. Measured radionuclide concentrations significantly increase when air masses travel at low tropospheric levels from central Europe and the western part of the Iberian Peninsula, while low concentrations are associated with westerly air masses. We found a significant negative correlation between the WeMO index and the atmospheric variability of both radionuclides and no significant association was observed for the NAO index.

Comparison of different sampling methods for the determination of low-level radionuclides in air.

The aim of this work is to check the consistency of results given by different air dust samplers (flow-rates between 2 and 700m(3)/h) and measurement protocols at a single location. The study is focussed on (210)Pb since is the only nuclide that can be easily assessed through all the studied sampler types. Results from high- and mid-volume samplers agreed well to within the associated uncertainties. Gross beta activity from low-volume samplers can be used as a good indicator of the evolution of (210)Pb concentration in air.

Validation of aerosol low-level activities by comparison with a deep underground laboratory.

The activities on air filters of the radionuclides (40)K and (137)Cs were measured in an above ground laboratory and compared with the activities measured in an underground laboratory. The average relative differences were lower than 20% for (137)Cs and (40)K. The temporal series of these radionuclides in the period 2006-2010 are also presented. These results form the baseline of these radionuclides in the studied period, and are particularly interesting because they correspond to the radioactive background in Barcelona before the Fukushima accident.