Self-attenuation corrections for Pb-210 in gamma-ray spectrometry using well and coaxial HPGe detectors.

Semi-empirical methods for 210Pb self-attenuation corrections were applied to sediment samples in vial and cylindrical geometries, and were validated against Monte Carlo modelling. Full Monte Carlo modelling (GESPECOR code) of the Cutshall transmission method was successfully applied for the determination of mass attenuation coefficients and efficiency transfer factors for coaxial detectors, and compared with the values derived from the matrix chemical composition. Simplified approaches were recommended when dealing with large numbers of samples.

Temporal variability of beryllium-7 fallout in southwest UK.

Cosmogenic beryllium-7 has been widely employed as a sediment tracing tool and continued development of its use as a soil erosion tracer requires knowledge of fallout temporal dynamics. Data regarding beryllium-7 fallout in the UK are scarce and here the authors provide a record of beryllium-7 fallout in southwest England spanning a two-year period. A monthly fallout record was developed for Plymouth, UK using regular rainfall sampling to determine beryllium-7 rainfall activity concentration (Bq L(-1)) and deposition flux (Bq m(-2)). Data showed a general tendency for higher activity during the spring/summer months and lower activity in the autumn/winter months. Comparison with data for other UK sites (Chilton and Aberporth) for the same period found significant differences in (7)Be activity in rainwater and lower variability in Plymouth than Chilton and Aberporth. Total deposition was largely controlled by rainfall in Plymouth although regression coefficients suggested greater importance of other atmospheric controls at the Chilton and Aberporth sites. Use of a deposition proportion to rainfall proportion ratio identified periods when deposition was influenced by varying (7)Be activity in rainfall. Broad ranges in ratios were found for Chilton and Aberporth and this has implications for sediment tracer studies requiring estimates of (7)Be deposition flux across months or seasons.

Assessment of measurement result uncertainty in determination of (210)Pb with the focus on matrix composition effect in gamma-ray spectrometry.

Reference materials were used to assess measurement result uncertainty in determination of (210)Pb by gamma-ray spectrometry, liquid scintillation counting, or indirectly by alpha-particle spectrometry, using its daughter (210)Po in radioactive equilibrium. Combined standard uncertainties of (210)Pb massic activities obtained by liquid scintillation counting are in the range 2-12%, depending on matrices and massic activity values. They are in the range 1-3% for the measurement of its daughter (210)Po using alpha-particle spectrometry. Three approaches (direct computation of counting efficiency and efficiency transfer approaches based on the computation and, respectively, experimental determination of the efficiency transfer factors) were applied for the evaluation of (210)Pb using gamma-ray spectrometry. Combined standard uncertainties of gamma-ray spectrometry results were found in the range 2-17%. The effect of matrix composition on self-attenuation was investigated and a detailed assessment of uncertainty components was performed.

Comparative assessment of erosion and deposition rates on cultivated land in the Transylvanian Plain of Romania using ¹³7Cs and ²¹°Pbex.

Soil erosion and sedimentation are natural landscape forming processes. However, they can be accelerated by human activities and therefore increase negative impacts on agricultural production as well as disturbing watershed management. Romania currently faces major environmental challenges and pressure on soil and water resources due to unsustainable farming practices and inappropriate tillage practices. The present work represents the first attempt to test the combined use of radionuclide approaches (i.e. (137)Cs and (210)Pb(ex)) to quantify soil erosion changes in cultivated Transylvanian fields (Romania) at different temporal scales. Fourteen soil cores were collected along two transects in a cultivated field and two reference sites were selected to establish the mean reference inventories for both (137)Cs and (210)Pb(ex). A value of 5460 ± 880 Bq m(-2) (n = 10; CV = 16%) was determined for the (137)Cs mean reference inventory for both sites, given as areal activity ± standard deviation, at 2σ confidence interval. As regarding (210)Pb(ex) reference inventory, its value (9640 Bq m(-2)) is only given by the areal activity of one soil core from the second site. The high erosion rates obtained with the (210)Pb(ex) approach are an effect of the up and down ploughing practices which took place at the time of the local agricultural cooperative starting in the late 1950s. The middle-term redistribution rates provided by the (137)Cs technique highlighted preponderant deposition processes in the field investigated, reflecting the changes in the cultivation system with ploughing across the slope at the beginning of 1990s.

Indicators of the Fukushima radioactive release in NW Romania.

As a result of the Fukushima nuclear release, (131)I was found in different environmental media (rainwater, sheep and cow milk, herbage, sheep meat and thyroid tissue) in north-west Romania. On April 4, 2011 a maximum value of 1.40 ± 0.21 Bq/L in (131)I activity was found in rainwater obtained from the Arad region. The obtained value corresponded with the maximum of (131)I concentration in air, as measured by Toma et al. (2011) for the Pitesti area. One day later, sheep milk from the Cluj area was found to contain a maximum activity of 9.22 ± 0.95 Bq/L. A value of 0.85 ± 0.07 µSv was calculated as the total monthly effective dose received by the population as a result of the ingestion of sheep milk and sheep meat contaminated with (131)I. Only rainwater samples contained (134)Cs and (137)Cs at levels close to minimum detectable activity. Since the determined values could be influenced by Chernobyl (137)Cs, the (137)Cs concentrations are subject to uncertainty. The radioiodine transfer coefficients (Fm) and the concentration ratio (CR) from herbage to sheep milk, as well as sheep meat, from the Cluj-Apahida area are also presented.