Specific Activities Of 210Pb Research Articles

The Chronology of Modern Sedimentation in the Storefjorden Strait (Svalbard Archipelago)

Periods of formation of different sedimentary lithotypes were determined using the results of the study of modern sedimentation processes in the Storefjorden Strait (West Spitsbergen). The chronology of sedimentation was established from variations in specific activity of 210Pb and 226Ra and verified by 137Cs data. Sedimentation rates have varied considerably over the last century in different parts of the sedimentation basin, ranging from 0.04 to 0.3 cm/yr. Sedimentation in the Storefjorden Strait was closely related to changing climatic conditions. Climatic factors (air temperature, atmospheric precipitation) have a different effect in morphologically different sections of the sedimentation basin. In the south of the strait, lithotypes are determined by an oceanological factor (bottom current). Despite the changes in sedimentation rate, the lithotype in the south of Storefjorden has remained stable for more than 100 years. In the north and in the central part of the strait, cooling in the period from 1970 to 1995 caused a change in the bottom sediment structure.

Investigation of self-attenuation of 210Pb (46 keV) gamma ray in sediment, certified reference material and high-density minerals: Implication to precise measurement of 210Pb

High resolution gamma spectrometry is one of the most widely used techniques in the measurements of environmental level 210Pb in sediment from coastal and freshwater environments and such measurements are needed to establish 210Pb chronology for the past 100–150 years. Precise measurement of 210Pb in sediment and soil requires appropriate self-absorption correction for its low-energy (46.5 keV) gamma radiation due to differences in the matrix between the sample and standard used to calibrate the instrument. Here we report a method that involves precise determination of 210Pb activity in sediment sample by calibrating the HPGe well detector with RGU-1-IAEA Certified Reference Material for well-defined geometries. A comparison of the 210Pb activity obtained from gamma-ray spectrometry with that obtained from alpha spectrometry via 210Po, using 209Po as yield tracer, indicates good agreement. We propose an empirical relation between the absolute efficiencies and packing densities of sample in a well-defined geometry (cylindrical counting vial) by affecting the count rate of 210Pb and its progenitor, 226Ra (via 214Pb and 214Bi). The effects of self-attenuation of 46.5 keV (210Pb), for naturally-occurring high-density minerals (apatite, titanite, monazite, and cerite) are evaluated. Specific activity of 210Pb on apatite measured by alpha and gamma spectrometry are compared. This study is relevant and useful for precise measurements of gamma-emitting environmental radionuclides such as 210Pb, 7Be, 137Cs as well as 226Ra.

Estimating emission source of lead using 210Pb specific activity (210Pb/Pb) and zinc as tracers in Slovenian forest soils

Specific activity of 210Pb (210Pb/Pb) is a good indicator for distinguishing local and remote emission sources of Pb deposited on some forest floors in Slovenia. Another parameter (zinc in soil) gives additional information on possible emission sources and distance of Pb transported from the source. The procedure based on 210Pb activity measurements and non-destructive Pb and Zn determination is rather simple, and not necessary any chemical pre-treatments with strong acids. The soils investigated in this study were collected from several temperate forest sites (Žirovski Vrh, Idrija, Kocevski Rog, Pohorje, Gorisnica, Rakitna, Hotavlje, Otovci, Ptujska gora and Puce) in Slovenia where high level of Pb contamination has been known in some places. Regression analyses of the results suggest an applicability of the proposed procedure for estimating emission sources and atmospheric transportation of Pb.

Deposition of atmospheric 210Pb and total beta activity in Finland

The seasonal and regional variation of the atmospheric 210Pb deposition in Finland was studied. The 210Pb activity concentration in precipitation shows a decreasing trend from southeastern Finland north-westwards. An average deposition of 40 Bq/m2 during a 12 months period was observed. The deposition of 210Pb shows a seasonal variation with minimum in spring and maximum in autumn and winter. The specific activity of 210Pb (activity of 210Pb per unit mass of stable lead) in the atmosphere has returned to the level prior to World War II owing to the reduced lead emissions into the atmosphere.

Quantification of measurement uncertainty in the sequential determination of 210Pb and 210Po by liquid scintillation counting and alpha-particle spectrometry

Methodologies for the quantification of measurement uncertainties associated with the determination of 210Pb- and 210Po-specific activities by liquid scintillation counting (LSC) and alpha-particle spectrometry are presented, and are demonstrated using the soil reference material IAEA-326. Major contributors to the combined uncertainty associated with the measurement result of 210Pb were the uncertainties of net count rates in the 210Pb energy region of the sample spectrum and in the 210Bi energy region of the blank spectrum. The predominant sources of uncertainty in the measurement of 210Po were the uncertainties of net count rates in the regions of interest of 209Po and 210Po. The relative standard uncertainty of 210Po exponentially increases with the time interval between the sampling date and the separation date of Po, and this effect is strongly dependent on the 210Po/210Pb activity ratio. When the specific activity of 210Pb is much higher than that of 210Po in the sample, the relative standard uncertainty of the 210Po determination increases significantly within a short time interval between the sampling date (or reference date) and the separation date of Po in samples.

Study of Aerosol Deposition at a Wind Exposed Forest Edge Using210Pb and137Cs Soil Inventories

The radionuclide 210Pb derived from gaseous 222Rn present in the atmosphere becomes attached to the same aerosols as the bulk of the main pollutants sulphur and nitrogen. When scavenged from the atmosphere by precipitation, the 210Pb is readily attached to organic matter in the surface horizons of the soil. Inventories of 210Pb in soil can thus be used to measure the spatial variations in wet (or cloud) deposition due to orography averaged over many precipitation events (half-life of 210Pb is 22.3 yr). Similar arguments apply to 137Cs inventories (half-life 30.0 yr), although more care has to be taken in interpreting the results due to possible resuspension and migration of the 137Cs. The method has been applied to quantify the long-term enhancement in aerosol and cloud water (occult) deposition as a consequence of increased aerodynamic roughness at an exposed forest canopy in the Highlands of Scotland. The specific activities of 210Pb and 137Cs in dried soil samples were determined by γ-spectrometry using HpGe detectors, one of which was fitted with a Compton suppression shield. Measurements revealed an average canopy enhancement in deposition of 36 ± 12% relative to the open heathland, in agreement with independent measurements of occult deposition at similar sites and model estimates. Deposition at the exposed edge exceeds that in the open by ≳50%, and thus provides evidence of a pronounced edge effect.

Determination of Lead-210 in an Ice Core from an Arctic Glacier by an Alpha-Ray Measurement

Measurements of 210Pb (half life of 22.3 y) at various depths down to 180m in an ice core from an Arctic glacier, Asgardfonna, in northern Spitsbergen have been made. The activity of 210Pb was obtained by counting α-rays from its daughter nuclide, 210Po (half life of 138d). The specific activity of 210Pb at the surface of the glacier, 110mBq/kg, decreased exponentially with depth to 4.72mBq/kg at about 30m depth. Below 30m, the activities were nearly constant and the average value from 30m to 180m was 4.85±1.33mBq/kg. This result indicates that the atmospheric 210Pb deposit onto the glacier decays as a function of time at a rate controlled by its half life. The α spectrometric method for the determination of 210Pb in an ice sample and the result of the ice core dating are described in this paper.

How reliable is the210Pb dating method? Old and new results from Switzerland

We present a historical overview of applications of210Pb dating in Switzerland with a special emphasis on the work performed at the University of Bern. It is demonstrated that the average specific activity of210Pb in the lower atmosphere is very constant and does not show seasonal variations. We then concentrate on new results from Lobsigensee, a very small lake, and on published and new data from Lake Zurich. Several210Pb profiles from these lakes show obvious disturbances and a disagreement of the resulting sedimentation rate when compared to that for the 23 years defined by137Cs peaks of 1986 (Chernobyl) and 1963 (bomb fallout).

Specific activity of 210Pb and historical changes of lead levels

Specific activity of 210Pb and historical changes of lead levels

Stable lead, 210Pb and 210Po in the liver and kidneys of cattle. II. Animals from an area near an abandoned lead mine

The concentrations of 210Pb, 210Po and stable lead in the livers and kidneys of 35 animals from an area close to an abandoned lead mine were determined. The median liver concentrations were 12·9 pCi 210Pb, 35·8 pCi 210Po and 0·58 mg stable lead/kg wet tissue, and the median kidney concentrations were 19·5 pCi 210Pb, 152·4 pCi 210Po and 1·20 mg stable lead/kg wet tissue. The specific activity of 210Pb was 20·0 nCi/g Pb in both the livers and the kidneys. The median values for the ratios of the concentrations in the kidneys to those in the livers were 1·47 for 210Pb, 4·15 for 210Po and 2·04 for stable lead. The median ratio of 210Po to 210Pb was 2·50 in the livers and 8·18 in the kidneys. Significant correlations were found between the liver and the kidney levels of 210Pb, 210Po and stable lead and between 210Po and 210Pb in the kidneys, 210Po and 210Pb in the livers, and 210Pb and stable lead in the livers. All the data and their relationships were compared with corresponding data from a control group of cattle from an area which was apparently unaffected by pollution from traffic or industry.

210Pb and 210Po in liver and kidneys of cattle--I. Animals from an area with little traffic or industry.

The concentrations of 210Pb, 210Po and stable lead were determined in liver and kidneys of 40 animals from a mainly agricultural region with little traffic or industry. Median liver concentrations of 18.0 microCi 210Pb and 33.3 microCi 210Po per kg wet tissue, and median kidney concentrations of 44.0 microCi 210Pb and 178.5 microCi 210Po/kg wet tissue were observed. The specific activity of 210Pb was 161 and 132 nCi 210Pb/g Pb in liver and kidneys, respectively. On the average, the kidneys contained 2.37 more 210Pb, 5.05 more 210Po and 2.89 more Pb than the livers. The ratio 210Po/210Pb was 2.18 in the liver and 3.95 in the kidneys. Correlation analysis revealed significant correlations between 210Po in liver and kidneys, Pb in liver and kidneys, 210Po and 210Pb in kidneys, 210Pb and Pb in liver, 210Pb and Pb in kidneys, 210Po and Pb in liver, as well as 210Po and Pb in kidneys. No significant correlation was observed between the concentrations of either 210Po or 210Pb in liver or kidneys and the age of the animals.

Specific activity of 210-Pb in the environment.

Abstract A review of data on the specific activity of 210Pb (pCi 210Pb/mg stable Pb) in the environment is presented. Experimental results on aerosol, plant, animal and human samples from Finland are reported. Large variations (18-2450 pCi/mg Pb) were observed for aerosol samples taken from various locations and under different meteorological conditions. Results for the biological samples revealed a much narrower range. A considerable decrease of specific activity was observed along the food chain plant—animal—man, thus indicating contamination of the food chain by technological (low-activity) lead. Arctic values of specific activity were observed to be generally higher than “normal” values. Human samples from southern Finland contained about 20pCi 210Pb/mgPb. Possibilities of utilizing specific activity measurements in lead pollution studies and in elucidating the origin of stable lead in the human diet are discussed.

Radiolead ( 210 Pb) and Stable Lead in the Lichen Cladonia alpestris

Lichens of the genus Cladonia, mainly C. alpestris, collected during 1882-1972 were analyzed for stable lead and 210Pb. The specific activity of 210Pb (210Pb/Pb ratio) indicates a constant value of about 2 mCi/kg up to 1940, and then decreased to 0.6 mCi/kg during 1950-1960. As the average annual 210Pb deposition is relatively constant, the decrease in the 210Pb/Pb ratio after 1940 indicates an increased deposition of stable lead after 1940. A single exponential variation of the 210Pb/Pb ratio, in respect to latitude, was found in lichens collected in 1964. Values for 210Pb and stable lead in C. alpestris, collected in central Sweden during 1961-1972, appear to be relatively constant and the average area content of 210Pb and stable lead in lichen carpets was 15 ± 2 nCi/m2 and 25 ± 5 mg/m2 respectively. The pattern of vertical distribution was converted to a model for the translocation of lead in lichens, which included the diffusion principle. The diffusion coefficient for lead in the top layer of the lichen carpet was estimated to be about (0.2 ± 0.1) x 10-6 cm2 x s-1. (Less)

Disequilibrium of the 238U series in basalt

Radioisotope analyses of basalt samples from Hawaii, Japan, and Iwo Jima show that: (1) 234U and 238U are virtually in radioactive equilibrium, (2) 230Th exceeds equilibrium values in all these samples, (3) 210Pb concentrations range from 10–200% of the equilibrium values and average 30% deficient, and (4) 226Ra is probably not in equilibrium with 234U. The source regions of the basalts or magma forming processes are open systems, chemically. The enrichment of some of the uranium-daughter nuclides is insufficient to account for the excess 206Pb in volcanic rocks. The isotopic composition of lead and specific activity of 210Pb in sublimates from Showa-shinzan, Japan are also reported.