Association of plutonium with sediments from the Ob and Yenisey Rivers and Estuaries (original) (raw)
Related papers
Earth and Planetary Science Letters, 2006
Plutonium (Pu) isotope ratios can be used to differentiate between sources of Pu contamination such as nuclear weapon production, weapon fallout as well as accidental and routine releases from nuclear installations. To obtain information on the contamination level, speciation and sources of Pu in the Ob and Yenisey river systems (Siberia, Russia) and the adjacent Kara Sea, water was size fractionated onboard ship and the concentrations and atom ratios of 240 Pu and 239 Pu in obtained water fractions (i.e. particles, colloids and low molecular mass species) were determined by accelerator mass spectrometry (AMS). Results show a clear difference in speciation between high 240 Pu/ 239 Pu atom ratio Pu derived from global weapon fallout and low 240 Pu/ 239 Pu atom ratio Pu, presumably originating from weapons grade Pu. In particular, the 240 Pu/ 239 Pu atom ratios (mean 0.18 ± 0.06) for particles (N 0.45 μm) could not be distinguished from global fallout Pu (0.17-0.19), whereas for low molecular mass (LMM; b 8 kDa) species the Pu ratio was much lower than for global fallout Pu in both rivers. The difference was especially well pronounced in the Ob (mean 240 Pu/ 239 Pu atom ratio 0.052 ± 0.023), where the difference was statistically significant (paired t-test, P = 0.02, n = 4). The low 240 Pu/ 239 Pu atom ratios in filtered (b 0.45 μm) water and especially in the LMM fractions were observed at stations along the whole length of the two sampling transects, extending from the lower parts of the Ob and Yenisey Rivers and into the northern Kara Sea. This provides evidence of long-range transport of Pu from low burn-up or non-civil sources into the Arctic Ocean. Pu appears to be predominantly in a dissolved form (b 0.45 μm) throughout the investigated area. The colloidal fraction (8 kDa-0.45 μm) ranged within 24-78% in the river systems and 8-53% in the Kara Sea. Concentrations of 239,240 Pu in filtered (b 0.45 μm) water were very low, ranging from 2.6 to 40.6 mBq m − 3 in the rivers, somewhat higher than in the open Kara Sea (2.4-7.7 mBq m − 3 ) in agreement with previously reported values.
Plutonium Contamination in Soils and Sediments at Mayak Pa, Russia
Health Physics, 2005
The Mayak Production Association (Mayak PA) was established in the late 1940's to produce plutonium for the Soviet Nuclear Weapons Programme. In total, seven reactors and two reprocessing plants have been in operation. Today, the area comprises both military and civilian reactors as well as reprocessing and metallurgical plants. Authorized and accidental releases of radioactive waste have caused severe contamination to the surrounding areas. In the present study, ␣-spectrometry and inductively coupled plasma-mass spectrometry (ICP-MS) have been used to determine plutonium activities and isotope ratios in soil and sediment samples collected from reservoirs of the Techa River at the Mayak area and downstream Techa River. The objective of the study was to determine the total inventory of plutonium in the reservoirs and to identify the different sources contributing to the plutonium contamination. Results based on ␣-spectrometry and ICP-MS measurements show the presence of different sources and confirmed recent reports of civilian reprocessing at Mayak. Determination of activity levels and isotope ratios in soil and sediment samples from the Techa River support the hypothesis that most of the plutonium, like other radionuclides in the Techa River, originated from the very early waste discharges to the Techa River between 1949 and 1951. Analysis of reservoir sediment samples suggest that about 75% of the plutonium isotopes could have been released to Reservoir 10 during the early weapons production operation of the plant, and that the majority of plutonium in Reservoir 10 originates from discharges from power production or reprocessing. Enhanced 240 Pu/ 239 Pu atom ratios in river sediment upper layers (0-2 cm) between 50 and 250 km downstream from the plant indicate a contribution from other, non-fallout sources.
Plutonium isotope ratios in the Yenisey and Ob estuaries
Applied Radiation and Isotopes, 2004
Over the past 50 years, nuclear weapons' tests and releases from the nuclear industry have introduced anthropogenic plutonium into the environment. In the Arctic environment, the main source of plutonium is from the atmospheric weapons testing, but previous studies of plutonium in the Kara Sea have shown that, at certain sites, other releases can give rise to enhanced local concentrations. The present paper presents results from determination of plutonium concentrations and isotope ratios in the sediment samples collected during various expeditions to the Kara Sea, the Ob and Yenisey estuaries and their river systems. The data indicated a clear influence from a low 240 Pu: 239 Pu source in surface sediments collected from the Yenisey estuary, whereas plutonium in Ob estuary sediments is dominated by global fallout. The results also show an increase in plutonium concentration (from 0.003 to 11 Bq/kg) and a decrease in 240 Pu: 239 Pu isotope ratio (from 0.16 to 0.05) going upstream from the Yenisey estuary towards the nuclear installation at Krashnoyarsk. r
Applied Radiation and Isotopes, 1995
The major sources of plutonium isotopes in the environment are from nuclear weapons testing via global and close-in (debris) fallout, nuclear fuel reprocessing and fabrication plant effluents. Measurements of differences in the Pu isotopic ratios (239pu/z4°pu, 23sPu/239.~4°Pu and 24~pu/239.2~Pu) have yielded information not only on the time horizons for sedimentary deposits but also on the sources of Pu. We have measured 23sPu, 239.24°pu and ~37Cs concentrations in the surlicial sediments of the Ob and Yenisey Rivers (Russia) and the Kara Sea. The downcore variations of 23sPu and 239.24°Pu concentrations have also been measured in some sediment cores. A comparison of the sediment core inventories of 239' 24°Pu along with the 23spu/239'24°pu activity ratios with those expected from global fallout at the study sites allows us to estimate the relative amounts of reactor-derived 23sPu and 239.2~Pu from the dumped reactor sites in the study area. In surficial sediment samples, the 239.24°Pu concentrations vary between 9.4 and 627 mBq kg -~, with a mean of 250 mBq kg ~.
Activity concentration of plutonium isotopes in bottom sediments and water in Crimean salt lakes
Journal of Radioanalytical and Nuclear Chemistry, 2020
The 238,239+240 Pu activity concentrations in sediments and in water in the Crimean salt lakes were studied. Activity ratio of 238 Pu/ 239+240 Pu in depth profiles of sediments was used to estimate the contribution of two main sources of man-made plutonium to the Pu sediment inventory. The most part of the plutonium was of global origin. Concentration factor of the plutonium isotopes in sediments, radiocapacity factor of the lake, the type of biogeochemical behavior of plutonium in these reservoirs and the sediment inventory of 238,239+240 Pu in the lakes were evaluated.
Marine Pollution Bulletin, 2000
We have measured the concentrations of 239Y240 Pu, 238 Pu, 210 Pb, and 137 Cs in biological samples (5 isopods, 10 bivalves, 2 amphipods, 2 mussell, 1 ®sh fat, 6 ®sh liver and 2 worm tubes) from the Ob and Yenisey Rivers and Kara Sea and sediment samples from the Pechora Sea of the Russian Arctic. Mean concentrations of 137 Cs and 239Y240 Pu in bivalves on which measurable concentrations were found are slightly higher than the values reported for the east, west and Gulf coasts of US. The mean concentrations of 137 Cs and 239Y240 Pu in 27 sur®cial sediment samples from the Pechora Sea are lower than the corresponding values from the Ob and Yenisey Rivers and Kara Sea. The 238 Pu/ 239Y240 Pu activity ratios on 16 of these sediment samples varied between 0.015 and 0.056. The best-®t line between the concentrations of 238 Pu and 239Y240 Pu yielded a mean 238 Pu/ 239Y240 Pu activity ratio of 0.035, suggesting that most of this Pu is derived from global fallout and that there is virtually no detectable input of Pu from either the European nuclear euents, close-in fallout from the nuclear test sites or from the dumped nuclear reactors in the Kara Sea or adjoining marine systems. Ó
Man-made plutonium radioisotopes in the salt lakes of the Crimean peninsula
Journal of Oceanology and Limnology, 2018
Investigations of 239+240 Pu and 238 Pu in the surface layer (0-5 cm) of bottom sediment in the Crimean 10 salt lakes from 4 geographical groups were carried out for the fi rst time. The 239+240 Pu varied widely between regional geographical groups of lakes as well as within groups too and ranged from 11±4 to 451±43 mBq 239+240 Pu/kg. The highest levels of 239+240 Pu-419±27, 443±24 and 451±43 mBq/kg were observed in the Yevpatoriya (Lake Kyzyl-Yar), the Tarkhankut (Dzharylhach) and the Kerch group (Tobechik), respectively. The lowest values of 239+240 Pu were identifi ed in three lakes of the Perekop group and were 20±12, 24±6 and 48±6 mBq/kg. In all lakes 238 Pu was an order of magnitude lower than 239+240 Pu and varied from 4.8±2.6 to 30.7±5.5 mBq/kg. The 238 Pu activity was decay-corrected to 1986. The characteristic ratio of the 238 Pu/ 239+240 Pu activities in the sediment and percentage of the Chernobyl-derived Pu was calculated. The largest percentages of the Chernobyl-derived Pu were observed in the Evpatoriya group (Lake Sasyk-Sivash)-16.2%±8.26%, the Tarkhankut group (Dzharylhach)-8.4%±2.10% and the Kerch group (Aktash)-10.5%±5.56%. The study of the depth distribution of plutonium in the Lake Kyzyl-Yar bottom sediment core (0-25 cm) was fulfi lled. It was shown that 239+240 Pu was high enough in all studied layers of bottom sediment, but the highest activity ratio 238 Pu/ 239+240 Pu (0.062±0.020) was found in the deepest layer of 15-20.5 cm and the percentage of Chernobyl-derived Pu was estimated at 6.8%±2.85% in this layer.
Deep Sea Research Part II: Topical Studies in Oceanography, 1997
Sediment cores collected during R.V. Polar Sea AOS94 expedition from the Chukchi Shelf to the North Pole were analyzed for several decay-series natural radionuclides and Pu isotopes to study sedimentation rates and pathways of radionuclides in the western Arctic Ocean. The measured sedimentation rates vary by more than three orders of magnitude along the transect, from 2~°Pbbased rates of 200-700 cm kyr-~ over the Chukchi Shelf and 89 cm kyr-1 at the Chukchi Slope to 23°Th-based rates of 0.024).3 cm kyr-1 at various settings in the deep basin. 23°Thex profiles in the central western Arctic Basin are characterized by a cyclic pattern and a pronounced sub-surface maximum superimposed on an overall decrease with depth. Sediment inventories of excess 21°pb and 23°Th in the deep basin as a whole cannot account for their in situ production and 21°pb fall-out. The opposite is true at the slope and shallower waters. We contend that, as with other ocean basins, boundary scavenging also exists in the Arctic Ocean. The broad continental shelves and the slope region may have the potential of removing all or most of the particle-reactive radionuclides unaccounted for in the deep basin. The Pu isotope data are consistent with the notion of boundary scavenging. Sediment inventories and concentrations of Pu decrease rapidly offshore. Isotopic composition of Pu suggests mixing of fall-out Pu, which decreases with increasing latitudes, and fuels reprocessing Pu derived from the Russian and Atlantic sides of the Arctic Ocean. Although fuel reprocessing Pu has impinged on the Chukchi Slope, its existence over the Chukchi Shelf is not evident and probably overshadowed by fall-out Pu.
Distributions of 239,240 Pu, 238 Pu and 137 Cs activity concentrations in the cores of sediments in the shallow lake, flooded and upland forest soils taken in the vicinity of Vilnius city were analyzed. The radiochemical, a-spectrometric and mass spectrometric methods were used for the plutonium evaluation and c-spectrometry was used for the radiocesium evaluation. The only peak of enhanced radionuclide activity concentrations was determined for the lake bottom sediments, whereas vertical profiles of the radionuclide activity concentrations in flooded and upland forest soil cores were distinguished by two peaks. The obtained values of the activity concentration ratio 238 Pu/ 239,240 Pu and the isotopic ratio 240 Pu/ 239 Pu indicated that the global fallout was a source of plutonium in the investigated environment. Chernobyl-derived radiocesium was detected solely in the surface layers (2–11 cm) of the studied sample cores. The contribution of the Chernobyl deposits amounted to about 2.26, 6.11 and 20.9 % of the total radiocesium inventory in the bottom sediments, the upland soil and flooded soil, respectively.
transport into the Arctic Ocean from underwater nuclear tests in Chernaya Bay, Novaya Zemlya
Continental Shelf Research, 2000
Radionuclide measurements have been conducted on sediment, seawater and biota samples collected in Chernaya Bay, on the southern coast of Novaya Zemlya, the site of two underwater nuclear tests conducted in the 1950s. Pu levels in sediments from the central region of Chernaya Bay exceed concentrations of 15,000 Bq/kg, and are among the highest ever reported for the marine environment. It is estimated that approximately 11 TBq of Pu from the tests has been retained in the sediments of Chernaya Bay. Plutonium from Chernaya Bay is distinguished by Pu/Pu atom ratios of 0.03 that are much lower than ratios of 0.18 typical of global fallout. High levels of Cs (Bq/kg) and Co (Bq/kg) were also measured in surface sediments in the central regions of Chernaya Bay near the presumed epicentre of the explosions. Applications of a biodi!usion model to excess Pb sediment depth pro"les indicate that the distribution of Pu is governed mainly by sediment mixing in this low sedimentation rate ( (0.1 cm/yr) regime and, as a result, most of the Pu has been retained in the upper 20 cm of the sediment column. Elevated levels of Pu measured in Macoma (104 Bq/kg), Fucus (15 Bq/kg) and polychaete (1292 Bq/kg) from Chernaya Bay, indicate that Pu levels in the benthos are comparatively high and that signi"cant uptake has occurred in the food chain. Although levels of Pu in bottom water from Chernaya Bay are high (4.2 Bq/m), restricted exchange over the fjord sill limits the present rates of Pu transport from