Dating of Black Sea sediments from Romanian coast using natural 210Pb and fallout 137Cs

The sediment samples collected near the shore from Romania were used for the determination of levels of natural ²¹⁰Pb, ²²⁶Ra and fallout ¹³⁷Cs radionuclides. The sediment samples were dried and ground to a fine powder. Airtight sealed samples were counted by gamma-spectrometer with 110 cm³ well-type HPGe detector for one week each. By using the isotopic analysis results, sediment accumulation rate was determined. A sedimentation rate of 0.20±0.01 cm^.y^-1 was determined using ²¹⁰Pb method and 0.15±0.03 cm^.y^-1 using ¹³⁷Cs isotope. Fallout peak from Chernobyl reactor accident, as well as the peaks due to nuclear tests, act as time markers.     

<Superscript>210</Superscript>Pb and <Superscript>137</Superscript>Cs dating of sediments from Zigetang Lake,Tibetan Plateau

Zigetang Lake located in the central Tibetan Plateau was selected for the purpose of understanding of recent sedimentation rates. Based on ¹³⁷Cs dating marker, the sediment rate was 0.077 cm·yr⁻¹. The sedimentation rate was calculated to be 0.071 cm·yr⁻¹ and 0.029 g·cm⁻²·yr⁻¹ on the basis of ²¹⁰Pb CIC model. ²¹⁰Pb CRS model was also used for understanding of recent sedimentation change. The sediment accumulation rates for the CRS model ranged from 0.022 to 0.038 g·cm⁻²·yr⁻¹ with an irregular high value of 0.12 g·cm⁻²·yr⁻¹ around 1932 at Zigetang Lake core in the past eighty years.     

Natural radionuclides and 137Cs activity concentration in the bottom sediment cores from Kuwait Bay

Summary The activity concentration of natural radionuclides and ¹³⁷Cs in the bottom sediments cores from Kuwait Bay have been determined by γ-ray spectrometry. Particular attention was devoted to the exact determination of two uranium isotopes: ²³⁵U and ²³⁸U in order to find any presence of depleted uranium dispersed during the 1991 Gulf War. The calculated ²³⁸U/²³⁵U activity ratios for all the surface (15 cm) as well as the core profile (up to 70 cm in depth) samples were within the limit of one standard deviation close to the value of 21.5 for natural uranium. Simultaneous instrumental determination of the unsupported ²¹⁰Pb and ²²⁶Ra in a few sediment core profiles was used for quantification of sediment accumulation rates. The calculated sedimentation rates (for the constant atmospheric ²¹⁰Pb flux rate - CRS model) ranged from 0.2 to 0.6 cm ^. y^-1 and were close to the data calculated by the Weibull distribution of ¹³⁷Cs in undisturbed sediment cores.     

Radiochronology of sediments from the Mediterranean Sea using natural210Pb and fallout137Cs

The²¹⁰Pb and¹³⁷Cs profiles of sediment cores from two locations in southern Spain, three locations in southern Turkey and two locations in northern Cyprus were determined by direct -ray spectroscopy. Sedimentation rates were derived for all locations using the²¹⁰Pb data. The rates range from 1.39±0.12 cm · y^–1 (0.50±0.04 g · cm^–2 · y^–1) to 0.08±0.01 cm · y^–1 (0.039±0.003 g · cm^–2 · y^–1). Except for one core, the¹³⁷Cs profiles were also used to compute sedimentation rates. The results are in good agreement with those of²¹⁰Pb values. The results of the Constant Initial Concenration and Constant Rate of Supply dating models are in good agreement with each other. The flux of unsupported²¹⁰Pb varies between 0.11±0.03 to 0.74±0.01 pCi · cm^–2. The average depositional flux was found to be considerably lower for cores from the Eastern Mediterranean.     

Vertical distribution of the natural and artificial radionuclides in various soil profiles to investigate soil erosion

Vertical distributions of ¹³⁷Cs and ²¹⁰Pb in soil profiles were examined to study their availability in soil erosion at Gökova region where there exists intensive agricultural activities on sloppy fields. Since the mobility of these radionuclides depend on soil characteristics, soil samples were analyzed also for their physical and chemical properties. From ¹³⁷Cs inventories measured, erosion rates for cultivated and disturbed (no cultivation) soils were calculated to range from 79.1 to 6.5 t^.ha^-1.y^-1 and from 79.9 to 3.5 t^.ha^-1.y^-1, respectively. The ²¹⁰Pb technique is found to be not suitable for erosion determination for this area, presumably due to the coal-fired power plants operating in the region.     

The210Pb and137Cs profiles in sediment cores from Bay of Quinte,Lake Ontario

²¹⁰Pb,²²⁶Ra and¹³⁷Cs profiles have been measured for sediment cores from three locations in Bay of Quinte, Lake Ontario, Canada. Compaction of the sediment with depth of burial is taken into account in calculating recent sedimentation rates and age profiles at these locations from the excess²¹⁰Pb profiles. The rates are 1.803+0.592 cm·y^–1 (0.254±0.083 g·cm^–2·y^–1), 0.101±0.017 cm·y^–1 (0.036+0.006 g·cm^–2·y^–1), and 0.795±0.218 cm·y^–1 (0.076±0.021 g·cm^–2·y^–1). The corresponding fluxes of excess²¹⁰Pb to sediment/water interface are determined to be 1.652, 0.253, and 1.123 pCi·cm^–2·y^–1, respectively. The anomalies observed in the radionuclide concentration profiles are attributed to physical mixing. It is postulated that the significantly higher flux of²¹⁰Pb observed at one of the locations is due to inputs from Trent River which joins the Bay near this location.     

Sedimentation rate in the Sungai Linggi estuary using excess 210Pb and 137Cs

The purpose of this study was to estimate the sedimentation rate in the Sungai Linggi estuary using the constant initial concentration of unsupported or excess ²¹⁰Pb model and verified with ¹³⁷Cs method. Five sediment cores were collected on 25 January 2011 using gravity corer with the inner tube of 50 cm length and 7.5 cm diameter. The total ²¹⁰Pb activities in the sediment cores profile at all sampling stations were varied and upper than those obtained for supported ²¹⁰Pb i.e. ²²⁶Ra, indicated disequilibrium among ²¹⁰Pb and its grandparents in the ²³⁸U decay series. Meanwhile, the lower ¹³⁷Cs activities were observed at all sampling stations due to no significant sources of ¹³⁷Cs releases were transferred into Malaysian marine. The estimation of sedimentation rate indicated the agreement of ²¹⁰Pb and ¹³⁷Cs method with a general presence of deep mixing in the Sungai Linggi estuary. Therefore, the apparent sedimentation rates calculated from ²¹⁰Pb profiles generally reflect the true value with the range from 0.70 to 1.97 cmyr^?1. High sedimentation rate was observed at some sampling stations which are located in river channel, estuary and closer to mainland. This suggested that land-use development, agriculture activities, channelization etc. introduced a large amount of sediment loaded into those areas.     

137Cs and 210Pb radionuclides in open and closed water ecosystems

The aim of this study was to determine the level of radionuclide concentration in sediment cores in two different water ecosystems; one closed and one open. Based on this data the changes in these ecosystems were interpreted. Two sediment cores from the Dobczyce reservoir and the Smreczynski Staw Lake were collected and divided into 1 cm thick sub-samples. The samples were air dried and homogenized. The ¹³⁷Cs and ²¹⁰Pb (²¹⁰Pb_sup, ²¹⁰Pb_total, ²¹⁰Pb_uns) concentrations were measured using gamma and alpha spectrometry. Results showed that the ¹³⁷Cs concentration in the Dobczyce reservoir is lower than in the Smreczynski Staw Lake. Total ²¹⁰Pb concentration in the Dobczyce reservoir was around 70 Bq kg^?1 and in the Smreczynski Staw Lake was about 500 or 1,200 Bq kg^?1 with the decreasing tendency in the sediment core. Sediments are very important constituents of water ecosystems. In spite of the young age of the Dobczyce reservoir, the ¹³⁷Cs and ²¹⁰Pb radionuclides were very useful in understanding of the processes which have taken place in these ecosystems. The estimated sedimentation rate indicated such processes as regular sedimentation, mixing of sediments or floods. In the Smreczynski Staw Lake the changes have reflected the changes which took place in the Tatra Mountains.     

Radiometric dating of sediment records in Kuwait’s marine area

Six sediment cores collected from the Northwestern Arabian/Persian Gulf have been radiometrically dated by ²¹⁰Pb. Three cores were collected from stations within the Kuwait Bay, and three others were collected from stations outside the bay. Two models have been used for ²¹⁰Pb dating of sediment cores, i.e. Constant Flux: Constant Sedimentation (CF:CS) Model and the Constant Rate of Supply (CRS) Model. The average rates were found to vary significantly between 0.16 and 1.00 cm y^?1 for stations outside and within the bay respectively. The variability of the sedimentation rate was essentially physiographic characteristics and variable hydrodynamic condition. In this study, ¹³⁷Cs fallout radiotracer was also used to construct a realistic chronology. It was observed that the ¹³⁷Cs in the entire vertical profile has been continuously contributed by fluvial and atmospheric deposition.     

137Cs dating of lake cores from the Nahuel Huapi National Park, Patagonia, Argentina: Historical records and profile measurements

Historical records of short lived (¹⁴⁰Ba, ¹³¹I, ¹⁰³Ru and ⁹⁵Zr+⁹⁵Nb) and long-lived (¹³⁷Cs and ⁹⁰Sr) fission products by fallout measurements performed in Argentina since 1959 were analyzed in order to define the main characteristics of ¹³⁷Cs fallout time evolution in the Nahuel Huapi National Park, Patagonia, Argentina. Sedimentary cores were sampled from Lake Nahuel Huapi and Lake Morenito, which are located within Nahuel Huapi National Park. ¹³⁷Cs specific activity profiles were measured and ²¹⁰Pb dating was performed in each core. The time evolution of ¹³⁷Cs fallout shows different characteristics than records taken in the Northern Hemisphere.¹³⁷Cs specific activity profiles of the cores studied reproduce the fallout time sequence observed in the historical records, and the chronology obtained shows excellent agreement with ²¹⁰Pb dating.     

Natural and artificial radionuclides as a tool for sedimentation studies in the Arctic region

Natural ²¹⁰Pb and artificial ¹³⁷Cs were applied for estimation of sedimentation rates for 14 cores collected in the White Sea, Franz Victoria and Novaya Zemlya troughs. Vertical profiles of ¹³⁷Cs with high resolution (0.5–1 cm) are presented for 18 cores. The agreement between sedimentation rates obtained from ²¹⁰Pb age-dating and ¹³⁷Cs vertical profiles was found. Two maxima of ¹³⁷Cs specific activity were observed in the cores near the North Dvina and Onega mouths, which may be correspond to the Chernobyl accident and global fallouts in early 1960-s.     

Sedimentation rate of the floodplain sediments of the Yamuna river basin (tributary of the river Ganges, India) by using 210Pb and 137Cs techniques

The isotopes ¹³⁷Cs and ²¹⁰Pb were determined in sediment cores originating from the floodplain of the river Yamuna (the largest tributary in the Ganges river system, India). Sampling was done at five locations: Sharanpur (next to the Himalayan foothills), Delhi, Jagmanpur, Hamirpur and Allahabad, where Yamuna meets the Ganges. The rate of sedimentation derived from both techniques, ¹³⁷Cs and ²¹⁰Pb, appears to be quite similar. At the station Sharanpur the highest rate of sedimentation (5.99 cm/y) was noticed, most probably due to deforestation and other human influences in the Himalayan regions, while the lowest rate was observed in Hamirpur (2.48 cm/y). All the five cores studied showed a ¹³⁷Cs peak of 1963, due to radioactive fallout, caused by weapon tests. The three upstream stations (Sharanpur, Delhi and Jagmanpur) showed a ¹³⁷Cs peak due to the Chernobyl event. These measurements reflect that Chernobyl debris have been transferred to the low latitude river system across the Himalayas.     

210Pb fluxes in sediment layers sampled from Northern Patagonia lakes

Unsupported ²¹⁰Pb fluxes were determined from sediment core inventories in lakes located in Northern Patagonia, Argentina. Total ²¹⁰Pb, ²²⁶Ra, associated with supported ²¹⁰Pb, and ¹³⁷Cs specific activity profiles were measured by gamma-ray spectrometry. Unsupported ²¹⁰Pb fluxes showed very low values when compared to other regions, with a 12 fold variation, ranging from 4 to 48 Bq m^–2.y^–1. The linear correlation observed between the ²¹⁰Pb fluxes and¹³⁷Cs cumulative fluxes in sediment cores sampled from water bodies within a zone with similar precipitation demonstrated that both radioisotopes behave in the same manner in these systems concerning the processes occurred from fallout to sediment deposition, and that there are no appreciable local or regional sources of unsupported ²¹⁰Pb. Positive correlation of ²¹⁰Pb fluxes with organic matter contents of the uppermost sediment core layers was also observed.     

Determination of 210Pb activity concentration in ground-level air by gamma-ray spectrometry in Tripoli, Libya

²¹⁰Pb activity concentration at ground-level air of Tripoli was determined by gamma-ray spectrometric analysis of 20 particulate samples collected. Each sample, the air filtered through chlorinated vinyl polychloride Petrianow was 78,000 m³ on average. Activity concentrations of ²¹⁰Pb were ranging from 78-186 mBq^.m^-3. Estimated effective dose to adult from inhaled ²¹⁰Pb was calculated to be 2.7 mSv^.y^-1.     

Distribution of radioisotopes in sediment cores from nearshore off Xinghua Bay mouth,Fujian, China

Two marine sediment cores were collected from nearshore off Xinghua Bay mouth in Fujian, China and the ⁴⁰K, ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra, ²²⁸Th and ²³⁸U in the cores were measured using γ-spectroscopy. For the core ZK6, the activities of ⁴⁰K were vertically homogeneous within measured error in the whole core and ²²⁶Ra, ²²⁸Ra and ²²⁸Th showed large vertical variations with the same tendency. The sedimentation rates were 0.400 cm·y⁻¹ above 50 cm and 0.737 cm·y⁻¹ below depth of 50 cm. The change of sedimentation rates indicates the heterotaxy, which was justified by the absence of ¹³⁷Cs in the zone of 25–50 cm. For core ZK6, the sedimentation rate was 0.179 cm·y⁻¹. Vertical distributions of ⁴⁰K, ²²⁶Ra, ²²⁸Ra, ²²⁸Th and ²³⁸U in the core ZK18 are similar to each other although there were significant large variations with depth. The large variations of radioisotopes with depth in the cores mean that the sediment cores have been disturbed largely due to marine environment change. The mean activities of radioisotopes in the core ZK6 are higher than ZK18 that may be ascribed to different hydrodynamic environments.     

Radioactive nuclides as tracers of environmental processes

Summary Relatively short-lived radioactive nuclides of cosmogenic origin, such as⁷Be (T_1/2=53.3 d),³²P (14.3 d),³³P (25.3 d),³⁵S (87.4 d) as well as²²Na (2.6 y) have come to be recognized as potential tools to trace environmental processes, such as precipitation, washout (precipitation scavenging), resuspension, atmospheric particle deposition and deposition patterns of airborne contaminants, aerosol deposition and aerosol trapping by above ground vegetation (air-to-vegetation transfer). Of the above radionuclides,⁷Be as well as²¹⁰Pb of terrestrial origin and¹³⁷Cs, a fission product radionuclide, are commonly used for determining the atmospheric particle deposition parameters. It was found that the deposition velocity of⁷Be-associated aerosol particles varied from 0.3 to 0.8 cm^. s^-1(average 0.5 cm^. s^-1), the washout ratio for⁷Be varied from 103 to 375 (average 144), the resuspension factor for the⁷Be-associated particles varied from 1.6^. 10^-4to 4.2^. 10^-4m^-1(average 2.3^. 10^-4m^-1) and the air-to-vegetation transfer rate for⁷Be varied from 5258 to 16180 m^3.kg^-1(average 9856 m^3.kg^-1) for grass, gramineae or poaceae the species. For the¹³⁷Cs-associated aerosol particles the deposition velocity varied from 1.3 to 6.3 cm^. s^-1(average 3.4 cm^. s^-1), the washout ratio for¹³⁷Cs varied from 284 to 3810 (average 1295), the resuspension factor for the¹³⁷Cs-associated aerosol particles varied from 0.1^. 10^-4to 1.2^. 10^-4m^-1(average 0.6^. 10^-4m^-1) and the air-to-vegetation transfer rate for¹³⁷Cs varied from 39638 to 345279 m^3.kg^-1(average 181197 m^3.kg^-1) for grass, gramineae or poaceaethe species.     

Inventories of 239+240Pu, 137Cs, and excess 210Pb in sediment cores from brackish Lake Obuchi, Rokkasho Village, Japan

The aim of this study was to measure the distribution and inventories of ^239+240Pu, ¹³⁷Cs, and excess ²¹⁰Pb (²¹⁰Pb_excess) in sediment core samples from brackish Lake Obuchi, which is in the vicinity of nuclear fuel facilities in Rokkasho Village, Japan. The inventory of the ^239+240Pu activity in the sediment samples from the estuary of a freshwater river, the central point of the lake, and the deepest point in the lake were 0.18, 0.29, and 0.24 kBq·m^–2, respectively. The inventories of ¹³⁷Cs and ²¹⁰Pb_excess in sediments were 0.83–1.2 kBq·m^–2 and 25–30 kBq·m^–2, respectively. The mean ^239+240Pu/¹³⁷Cs and ²¹⁰Pb_excess/¹³⁷Cs activity ratios were 0.23 and 28, respectively. The^239+240Pu/¹³⁷Cs activity ratios were approximately 13–24 times the ratio expected from global fallout. The inventories of ^239+240Pu and ²¹⁰Pb in sediments were higher than the inventory expected from atmospheric fallout, but the ¹³⁷Cs inventory was significantly lower than expected.This revised version was published online in November 2005 with corrections to the Cover Date.     

Marine Sediments and Snow from Ross Sea Region (Antarctica) Dating by 210Pb Method

Abstract

²¹⁰Pb is widely used to determine accumulation rates in order to obtain a time scale in environmental samples. The most accurate method uses the determination of ²¹⁰Pb via its grand-daughter ²¹⁰Po by alpha spectrometry. Unfortunately this method requires a complex wet-chemistry procedure to achieve the separation of ²¹⁰Po from its matrix. In this work a simplified procedure for the chemical separation of ²¹⁰Po is proposed and applied to three marine sediment cores and a 10 m snow core collected in Antarctica. The calculated sedimentation rates for marine sediments range from 0.053 to 0.071 cm y^?1. The mean annual accumulation rate for the snow is 16.6 cm y^?1 w.e. A comparison with literature data in the same region is given.     

Sedimentation and lateral transport of 210Pb over the East China Sea Shelf

²¹⁰Pb is an effective tracer of constraining particle transport and sedimentation in shelf regions. To reveal the spatial pattern of ²¹⁰Pb over the East China Sea (i.e. ECS) Shelf, ²¹⁰Pb in the surface sediments were examined at 11 stations, as well as ²³⁴Th and ²¹⁰Pb in the water column at four stations. Overall, the plume zone of the Yangtze River along the coastline is a source area of ²¹⁰Pb for the outer shelf, exporting 0.46 dpm cm^?2 year^?1 at least, which accounts for about 25 % of ²¹⁰Pb input into this region. In the southern ECS Shelf to the north of the Taiwan Strait, the focusing factor (f) values are higher than unity, indicating a sink area of ²¹⁰Pb. Boundary scavenging of ²¹⁰Pb contributes 0.36 dpm cm^?2 year^?1 to this sink area on the basis of a mass balance model evaluation. Lateral transport of ²¹⁰Pb to this region, quantified by ²³⁴Th and ²¹⁰Pb in the water column, varied from 3.34 to 6.39 dpm cm^?2 year^?1 with an average of 4.83 dpm cm^?2 year^?1, also supporting its sink characteristic. To the southwest of the Cheju Island, the f values were less than unity, revealing a source region of ²¹⁰Pb. The average export flux of ²¹⁰Pb from this region was 1.64 dpm cm^?2 year^?1. Therefore, ²¹⁰Pb sedimentation/settling showed significantly heterogeneous sedimentation of particulate matter over the ECS Shelf.     

210Pb and 137Cs geochronologies in the Cananeia-Iguape Estuary (Săo Paulo, Brazil)

Sediment cores were collected at the Cananeia-Iguape Estuary and thelevels of ²¹⁰Pb, ²²⁶Ra and ¹³⁷Cs were measuredby gamma-ray spectrometry. The total ²¹⁰Pb levels in sedimentsvaried from 13.5 to 122.5 Bq . kg ^—1 , for ²²⁶Raranged from 2.4 to 28 Bq . kg ^—1 and for ¹³⁷Csfrom 0.28 to 6.1 Bq . kg ^—1 . Sedimentation rates were calculatedfrom the slope of the excess ²¹⁰Pb profile in the core. The valuesobtained varied from 5 to 10 mm . y^—1 , depending on thesediment deposition inputs in the local of sampling.