C. Testa

Soil concentration, vertical distribution and inventory of plutonium, 241Am, 90Sr and 137Cs in the Marche Region of Central Italy.

Soil concentrations of 239+240Pu, 238Pu, 241Am, 90Sr, and 137Cs are investigated in the Marche Region of Central Italy. Mean values in uncultivated soils (0.721 +/- 0.456, 0.023 +/- 0.014, 0.241 +/- 0.165, 5.40 +/- 3.32, and 62.3 +/- 33.9 Bq kg(-1), respectively) are 3.5-8 times higher than the corresponding values in cultivated soils (0.147 +/- 0.054, 0.005 +/- 0.002, 0.047 +/- 0.021, 1.53 +/- 0.44, and 7.70 +/- 2.07 Bq kg(-1)). Radionuclide inventories and ratios are consistent with values reported by the United Nations Scientific Committee on the Effect of Atomic Radiation for this latitude (40-50 degrees N). This suggests that radiocontamination in this region is mainly due to atmospheric deposition of nuclear weapon test fallout. The vertical distribution of these radionuclides is also studied. The results show that, with the exception of 90Sr (68%), more than 90% of these radionuclides are contained in the first 20 cm of soil and that mobility follows the order 90Sr > 241Am > 239+240Pu, 238Pu > 137Cs.

Radiation protection and radioactive scales in oil and gas production.

Low specific-activity scales consisting of alkaline earth metal carbonates and sulfates are often present in some gaseous and liquid hydrocarbon plants. These scales contain a certain concentration of radium, uranium, and thorium which can cause a risk of gamma irradiation and internal radiocontamination when they must be mechanically removed. The gamma dose rates and the 238U, 232Th, 226Ra concentrations were determined in sludges, scales, and waters of some gas and oil hydrocarbon plants located in Italy, Congo, and Tunisia. 238U and 232Th concentrations were were low. The isotopes 238U and 234U resulted in radioactive equilibrium, while 232Th and 228Th were not always equilibrium. A rough correlation was found between the gamma dose rate and the 226Ra concentration. Some considerations and conclusions about radiation protection problems are pointed out.

Plutonium concentration in sediment cores collected in the Mediterranean Sea

As is well known, the determination of plutonium isotopes in the marine environment is of great importance to calculate the contamination due to the nuclear industry and to better understand sedimentation processes. In the last 20 years sea sediment cores have been collected in different areas of the Mediterranean Sea by four Italian research teams. The sampling depth ranged from 50 to 2800 m and the core lengths were 10–30 cm. The radioanalytical procedures were based on plutonium separation by anion exchange resins or by extraction chromatography with Microthene-TOPO; plutonium electroplating was performed before α-spectrometry. The final chemical yields were determined by spiking with 236Pu or 242Pu. In some cases 238Pu could be detected. As far as the vertical profiles are concerned, no significant subsurface maxima resulted for the cores collected at greatest depth; on the contrary interesting peaks were found for cores collected at 50–100 m depth.

Vertical profiles of 239,240Pu and 241Am in two sphagnum mosses of Italian peat

Abstract During the last two years the Urbino University and the Padua ICTIMA CNR collaborated on a special radioecological program having the aim to study the Pu and Am retention behaviour in Sphagnum peat in the Alps region (northern Italy). 239,240 Pu, 238 Pu and 241 Am were separated and determined by extraction chromatography, electroplating and alpha spectrometry; 242 Pu and 243 Am were used as the yield tracers. The paper summarizes the results dealing with the vertical profiles of the radionuclides in Sphagnum compactum and S. nemoreum . Several 1–2 cm high sections were obtained and dated by 210 Pb determination. Typical concentration peaks for Pu and Am were found at a depth corresponding to the early 1960s which is the period characterized by the maximum nuclear weapon tests.

Speciation of natural and antropogenic radionuclides in different sea sediment samples

A sequential extraction method consisting of six operationally-defined fractions was used to determine the geochemical partitioning of natural (U, Th,) and antropogenic (Pu, Am, 137Cs) radionuclides in three sediment samples of different origin (Venice Lagoon, Adriatic Sea; Gaeta Gulf, Thyrrhenian Sea; IAEA-367, Enewetak Atoll, Central Pacific Ocean). Fe, Mn, Al, Ti, Ca, Sr, Pb, Ba, K were also determined in the different fractions to get more information about the chemical association of the single radionuclides. The experimental results were compared to those described in the literature for an IAEA-135 Sea Sediment collected in the Irish Sea in front of the Sellafield Plant (UK).

Determination of210Pb in sediments by extraction chromatography

A selective method is described for the determination of210Pb in sediments, based on the separation of the daughter210Bi by extraction chromatography with Microthene 710-tri-n-octylphosphine oxide (TOPO) and on a final source counting with a low background β-counter. The average chemical yield is 92.0%. The detection limit for 2 g samples is 19 Bq kg−1. An IAEA reference sediment sample was analyzed to check the reliability of the method.

Concentration and vertical distribution of plutonium and americium in Italian mosses and lichens

The plutonium and americium concentration and vertical distribution in some Italian mosses and lichens have been determined. The239,240Pu,238Pu and241Am concentration ranges in tree trunk lichens 0.83–1.87, 0.052–0.154 and 0.180–0.770 Bq/kg, respectively. The corresponding values in tree mosses are higher and more scattered ranging from 0.321 to 4.96, from 0.029 to 0.171 and from 0.200 to 1.93 Bq/kg. The mean238Pu/239,240Pu and241Am/239,240Pu ratios are 0.088±0.037 and 0.38±0.13 in lichens and 0.091±0.072 and 0.54±0.16 in tree mosses. The Pu and Am concentrations are relatively low in terrestrial mosses. The239,240Pu,238Pu and241Am vertical distributions in a terrestrial moss core (Neckera Crispa) collected near Urbino (central Italy) show an exponential decrease with the height. On the contrary the241Am vertical distribution in another terrestrial moss core (Sphagnum Compactum) collected in the Alps (northern Italy) shows an interesting peak at 16 cm which corresponds to the deposition of fallout from the nuclear weapon tests in 1960s. The241Am movement upward and downward in the moss core is also studied. The results show once again that both mosses and lichens are very effective accumulators of Pu and Am and that they can be used as good biological indicators of the radionuclide airbome pollution from nuclear facilities and nuclear weapon tests. They can play a very impotant role in cycling naturally or artificially enhanced radionuclides in the atmosphere over long time scales.

Determination of plutonium and americium in moss and lichen samples

A simple, sensitive and selective method is described for the simultaneous determination of plutonium and americium in lichen and moss samples which can be used as the atmospheric radioactivity bioindicators. Plutonium is separated from a HCl leaching solution by a Microthene-TNOA column; americium is separated by a KL-HDEHP column and purified by PMBP-TOPO extraction. A special attention has been paid to the decontamination of plutonium and americium from210Po. Ten lichen and 12 moss samples from tree trunks have been analyzed: starting from 2 g sample, the average yields and the detection limits were 70.2±12.5% and 28 mBq/kg for plutonium and 70.0±15.1% and 34 mBq/kg for americium. The concentrations (mBq/kg) ranged from ≤28 to 4960 for239,240Pu, from ≤28 to 171 for238Pu and from ≤34 to 1930 for241Am, respectively.

NEW RADIOCHEMICAL PROCEDURES FOR ENVIRONMENTAL ACTINIDE MEASUREMENTS AND DATA QUALITY CONTROL

Suitable separation techniques were prepared for actinide,90Sr and226Ra determinations in environmental and industrial samples. Extraction chromatography with tri-n-octylphosphine oxide (TOPO) and di(2-ethylhexyl) phosphoric acid (HDEHP) solutions was used. IN some cases, a powder of Microthene (Microporous polyethylene) supporting solid TOPO was prepared thus obtaining a material showing better storing and column preparation features.Uranium and226Ra were determined in phosphorites, phosphoric acid and phosphogypsum.Uranium, thorium and226Ra were also measured in the low specific activity scales of hydrocarbon production equipment:226Ra was found to concentrate in some parts of the plant so causing a radiation protection problem.Plutonium and90Sr were measured either in some Mediterranean Sea samples or in environmental samples collected in Antarctica. Some interesting sea sediment profiles were also obtained.All the chemical methods were verified by: a) adding some yield tracers (232U,228Th,242Pu); b) analyzing some certified samples supplied by IAEA and NIST; c) participating in some international intercomparison runs; d) using, when possible, both an analytical and a radiometric method and e) following the radioactivity decay or growth (90Y and226Ra).

90Sr, 137Cs, 238Pu, 239+240Pu and 241Am levels in terrestrial and marine ecosystems around the italian base in Antarctica

During the last 14 years the Radioecology Laboratory of Parma University and the General Chemistry Institute of Urbino University collaborated on a radioecological programme having the aim to observe the evolution of antropogenic radioactivity in Antarctica in the period 1987-2001. The artificial radionuclides considered were 90Sr, 137Cs, 239+240Pu,238Pu and 241Am. The contamination seems to be higher in the continental environment rather than in the marine one. Mosses, algae and lichens showed the highest values for all radionuclides analyzed. The results prove that the Antarctic continent is interested by radioactive pollution. As far as 137Cs is concerned, a progressive decrease was observed.