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1.
Further studies on the transport in sea water and accumulation in marine sediment of the radionuclides, released from a nuclear power plant, on Urazoko Bay, Fukui Prefecture were reported.The partition of radionuclides among the particle size fractions of a sediment sample indicated that the accumulation of60Co,137Cs and54Mn in the sediment were dominated substantially by the sorption on the particle surface in sea water, and the patterns of their sorption were considerably similar to each other.In regard to the60Co contamination of marine sediments in an area of about 13 km2 around the nuclear power plant, 60% of the60Co contamination were retained in Urazoko Bay, which occupies only 7% of the bottom surface of the region.It is clear that a part of60Co accumulated in the sediment of Urazoko Bay gradually moved to the outerward. 相似文献
2.
The concentrations of90Sr and137Cs, derived from the radioactive fallout, in the surface layers of the adjacent seas of Japan and the North Pacific were determined radiochemically during 1969 to 1973. The90Sr and137Cs concentrations in sea water decreased markedly with increase of the depth and below the depth of 1,000 m, the concentrations were approximately uniform. The distribution of90Sr in the surface water of the North Pacific in spring of 1970 was approximately uniform, except two regions; rather large low-concentration region between 160°E and 170°W and relatively higher contamination area around 32°N and 146°W. 相似文献
3.
Marked fluctuation of concentrations of90Sr and137Cs was observed in the bottom waters at the entrance of Wakasa Bay during 1987–1992, and the cause was investigated. The concentrations of90Sr and137Cs in the bottom waters were significantly low when the upper level of the Japan Sea Proper Water (JSPW) was high and covered the sampling depth, but high when the upper level of the JSPW was low. The cause of the fluctuation observed in the bottom waters is, therefore, suggested to be the vertical fluctuation of the upper level of the JSPW on the shelf slope, which has been little described before. 相似文献
4.
Arrigo A. Cigna 《Ocean Science Journal》2006,41(4):261-290
The concentrations of man made radionuclides in surface seawater since early ′60s are here reported as measured in Italy and
Japan. Most of the data refers to90Sr and137Cs, but occasionally the concentrations of89Sr and134Cs in some Italian samples are also given. The main sources of man made radionuclides were the global fallout produced by
the nuclear weapon tests and the Chernobyl accident. The respective contributions to the contamination of surface seawater
around both countries are discussed. 相似文献
5.
239, 240Pu,137Cs and90Sr concentrations were determined in sea waters from the central and western North Pacific in 1980 and 1982. The results are
consistent with those reported earlier for North Pacific waters. The profiles of90Sr and137Cs show a monotonic decrease with depth, whilst239, 240Pu shows a distinct subsurface maximum at a depth between 400 and 1,000 m.
The calculated inventories of these nuclides significantly exceed the global mean fallout inputs for these latitudes. This
may be due to local fallout input to the ocean at times of large-scale nuclear weapon tests in the equatorial North Pacific.
The existence of measurable amounts of137Cs and239, 240Pu in deep waters suggests that these nuclides are transported by sinking particulate matter from the surface to the deep
ocean. 相似文献
6.
90Sr and137Cs concentrations and their vertical distributions were determined in deep waters in the western Northwest Pacific, including the adjacent seas of Japan, from 1976 to 1979.The profiles of the radionuclides show distribution patterns with two parts with an exponential variation of radioisotope content with depth in both parts.Generally speaking, the inventories of90Sr and137Cs in the open waters of the northwestern Pacific correspond fairly well to the fallout inputs, but in some circumstances there seems to be considerable removal of radionuclides from the water column or they are diluted with water of lower radioactivity from other regions.The possibility of radioisotope remobilization from the bottom sediment or particulate matter is also discussed. 相似文献
7.
8.
Concentrations and inventories of137Cs and239,240Pu were determined in sea waters and sediments columns from the western North Pacific from 1980 to 1986.The239,240Pu/137Cs activity ratio in the water column shows a tendency to increase from the surface (10–3) to bottom waters (10–1), but the ratio in sediment is within a rather narrow range (10–2 to 10–1), indicating more effective removal of plutonium from the water column than137Cs. In regions south of 40N, the radionuclide inventories in the water column significantly exceed the estimated global fallout (stratospheric fallout due to the atmospheric nuclear explosion), especially in the case of239,240Pu. These excess inventories imply that local or close-in fallout derived from nuclear explosions in the equatorial North Pacific are well-preserved and retained in the regions, despite about 20 years since the atmospheric nuclear explosion moratorium. Data suggesting lateral transport of137Cs in surface water from north of 40N to southern regions is shown. Some data on90Sr contents are also shown. 相似文献
9.
D. Knapinska-Skiba R. Bojanowski Z. Radecki G. E. Millward 《Estuarine, Coastal and Shelf Science》2001,53(6):779
The activity concentrations of dissolved137Cs have been determined in the water column and137Cs and134Cs in the sediments and the sediment porewaters of the southern Baltic Sea. The mean activity concentration of dissolved137Cs in the Gdansk Deep declined from 109 Bq m−3in June 1986 to 61 Bq m−3in 1999. In sediments, the activity concentrations of137Cs (33-231 Bq kg−1) were highest in muds and the activity concentrations of134Cs were about 6% of the total Cs activity. The Chernobyl contribution to137Cs activity was between 43% and 77%. The porewater activity concentrations of137Cs in muddy sediments were in the range 71 to 3900 Bq m−3and were higher than those in the overlying seawater. The diffusive flux of dissolved137Cs from the muddy sediments was estimated in the range 5 to 480 Bq m−2year−1. The flux of137Cs from sediment porewaters of the southern Baltic Sea was about 45% of the total, including fluxes of137Cs from wet and dry atmospheric deposition and the fluvial inputs. The results were used to elucidate the rate of recovery of the sediments and the waters of the southern Baltic from Chernobyl-derived137Cs. 相似文献
10.
An analysis of the variations in the concentrations of 137Cs and 90Sr radionuclides in the Baltic Sea surface waters after the accident at the Chernobyl nuclear power plant was performed. An instability of the 137Cs concentration values during the short-term observations was found, when these values were differed 2-to 3-fold. The concentrations of 90Sr appeared to be more stable; meanwhile, their deviations sometimes exceeded the ranges of the experimental errors. By the variations in the monthly average values of the radionuclide concentrations in the surface waters of the Baltic Sea in 1989–1995, no trend of the water self-purification was observed. The theoretical results obtained confirmed the potential of the formation and propagation of patches with increased concentrations of 137Cs in the southeastern part of the Baltic Sea. The most reliable factor that controlled the process of self-purification of the Baltic Sea water appeared to be the mean annual value of the concentration of radionuclides. Pronounced divergences were obtained between the measured and calculated mean annual concentrations of 137Cs and 90Sr radionuclides in the surface waters of the Baltic Sea in 1989–2001. These divergences are explained by the potential influence of the waters from the Gulf of Bothnia and by other additional supplies of radionuclides to the marine environment, which were not included into the mathematical models. 相似文献
11.
D.S. Swan M.S. Baxter I.G. McKinley W. Jack 《Estuarine, Coastal and Shelf Science》1982,15(5):515-536
Analysis of 210Pb, 226Ra, 137Cs and 134Cs in short sediment cores provide first estimates of deposition rates in some Clyde sea lochs. The radio-caesium nuclides originate mainly in the liquid effluent released at distance from the Clyde by the Windscale nuclear fuel reprocessing plant and their concentrations in Clyde sediments provide information on (a) enrichment factors onto particulate matter, (b) surficial mixing coefficients and (c) sedimentation rates. A radiocaesium residence time in coastal waters of ca. 103 years reflects the importance of scavenging by the high nearshore particulate flux. 210Pb levels in sediments are controlled, in the unsupported fraction, by a major input sorbed on catchment particulates and, in the supported component, by 226Ra activities occasionally perturbed by unusually high surface values probably of planktonic origin. In one loch, detectable levels of 134Cs and 60Co are attributed to their discharge by nuclear submarines. 相似文献
12.
The distribution and inventory of artificial radionuclides,239,240Pu and137Cs were determined in the East China and the Yellow Seas in 1987. Almost all of239,240Pu and 50 to 80% of137Cs in the continental shelf area are retained in the sediment column.239,240Pu sediment inventory in the sea area is larger than the fallout input and tends to increase southwardly. This excess239,240Pu and the lateral distribution are attributable to the supply of239,240Pu by the Yangtze River discharge. On the contrary,137Cs sediment inventory shows a decrease to the south, and the fact can be accounted for by the southward dispersion of fine silt particles discharged from the Yellow River. Total137Cs inventory is smaller than the estimated fallout input, and the fact seems to indicate dispersion of137Cs out of the shelf region. Vertical profiles of239,240Pu and137Cs contents in sediments differ from that of natural210Pb, implying the effect of varied accumulation rates of the artificial radionuclides over the sediment particle mixing by benthic organisms. Apparent maximum sediment particle mixing coefficient (D
B
) calculated from the excess210Pb profiles in stations located between the inner and outer shelves ranged from 1.4 to 8.3 cm2y–1. ThisD
B
value is higher than that in the Okinawa Trough (1.0 cm2y–1), but lower than previously estimatedD
B
value (26 cm2y–1) in the outer shelf mud. 相似文献
13.
The physico-chemical states of artificial radionuclides,90Sr,137Cs and144Ce in seawater were investigated by radiochemical analysis of filtered and unfiltered seawater. The difference of radionuclide concentrations between unfiltered and filtered seawaters was defined as the particulate form radioisotope and its particle ratio was discussed.Practically no particulate90Sr, greater than 0.22 in size, was observed in both coastal and open seawaters, but some of137Cs seemed to be insoluble in some circumstances, especially in coastal waters. A considerable amount of144Ce was found to be particulate.An estimation of the radionuclides in particulate form was made for Kashima-nada seawaters collected in 1970 to 1972, and it was shown that the possible occurrence of particulate radionuclides, greater than 0.22 in size, were 1% or less for90Sr and 6% for137Cs. In the coastal water, 80 % of144Ce were seemed to be in particulate form, but in the open seawater only a few%. The influences of suspended materials to137Cs and144Ce concentration levels in seawater were not negligible and further investigations are desirable. 相似文献
14.
Geochemical tracers, including Ba, Co, Th, 7Be, 137Cs and 210Pb, and magnetic properties were used to characterize terrestrial runoff collected in nearshore time-series sediment traps in Hanalei Bay, Kauai, during flood and dry conditions in summer 2006, and to fingerprint possible runoff sources in the lower watershed. In combination, the tracers indicate that runoff during a flood in August could have come from cultivated taro fields bordering the lower reach of the river. Land-based runoff associated with summer floods may have a greater impact on coral reef communities in Hanalei Bay than in winter because sediment persists for several months. During dry periods, sediment carried by the Hanalei River appears to have been mobilized primarily by undercutting of low 7Be, low 137Cs riverbanks composed of soil weathered from tholeiitic basalt with low Ba and Co concentrations. Following a moderate rainfall event in September, high 7Be sediment carried by the Hanalei River was probably mobilized by overland flow in the upper watershed. Ba-desorption in low-salinity coastal water limited its use to a qualitative runoff tracer in nearshore sediment. 210Pb had limited usefulness as a terrestrial tracer in the nearshore due to a large dissolved oceanic source and scavenging onto resuspended bottom sediment. 210Pb-scavenging does, however, illustrate the role resuspension could play in the accumulation of particle-reactive contaminants in nearshore sediment. Co and 137Cs were not affected by desorption or geochemical scavenging and showed the greatest potential as quantitative sediment provenance indicators in material collected in nearshore sediment traps. 相似文献
15.
The discharge of radioactive waste, from nuclear fuel reprocessing facilities, into the coastal waters of north-west Europe has resulted in a significant increase in the inventories of a number of artificial radionuclides in the North Atlantic. Radiocaesium, 90Sr and 99Tc, which behave conservatively in seawater, have been used widely as tracers of water movement through the North Sea, Norwegian Coastal Current, Barents Sea, Greenland Sea, Fram Strait, Eurasian Basin, East Greenland Current and Denmark Strait overflow. These studies are summarised in the present paper. It has been estimated that 22% of the 137Cs Sellafield discharge has passed into the Barents Sea, en route to the Nansen Basin, via the Bjomoya-Fugloya Section, with another 13% passing through the Fram Strait. This amounts to 14 PBq 137Cs. Quantifying the influx of other radionuclides has been more problematic. The inflowing Atlantic water now appears to be diluting waters in the Arctic Basin, which were contaminated in the late 1970s and early 1980s as a result of the substantial decrease in the discharge of reprocessing wastes. Sellafield (U.K.) has dominated the supply of 134Cs, 137Cs, 90Sr, 99Tc and Pu, whereas La Hague (France) has contributed a larger proportion of 129I and 125Sb. 相似文献
16.
17.
J. N. Smith K. M. Ellis K. Naes S. Dahle D. Matishov 《Deep Sea Research Part II: Topical Studies in Oceanography》1995,42(6)
Radionuclide measurements have been conducted on sediment cores collected in 1992 in the south-eastern region of the Barents Sea, known as the Pechora Sea. Cesium-137 and 239,24OPu activities in surface sediments are generally less than 30 Bq/kg, with the highest levels being measured in sediments off the southwestern coastline of the island of Novaya Zemlya. High correlations between both 137Cs and 239,24OPu and the concentration of fine (< 63 μm) particles in surface sediments indicate that much of the variance in radionuclide concentrations throughout the Pechora Sea can be explained by particle size fractionation. However, elevated activities of 137Cs (138 Bq/kg), 60Co (92 Bq/kg), 241Am (433 Bq/kg), and especially 239,24OPu (8.47 × 103 Bq/kg) were measured in one surface sediment sample from the fjord of Chernaya Bay on the southern coast of Novaya Zemlya. The source of radioactive contamination is two underwater nuclear tests conducted in Chernaya Bay in 1955 and 1957.The 238Pu/239,240Vu activity ratio of 0.0245 in Chernaya Bay is equivalent to values measured in global fallout. The 240Pu/239Pu atom ratio (0.0304), measured by mass spectrometry, is much lower than values (0.18) typical of global fallout, but is consistent with ratios measured for fallout from the early (1951–1955) series of weapons tests at the Nevada Test Site. The timing of the Chernaya Bay source term, estimated from the 241Am/241Pu ratio, is consistent with the timing of the 1955 and 1957 underwater nuclear tests. Relatively low initial yields of 241Pu (241Pu/239Pu atom RATIO = 0.00 123) in these tests have resulted in relatively low 241Am/239,240Pu activity ratios (0.05) in recent sediments in Chernaya Bay.Radionuclide tracer profiles in cores from the Pechora Sea can be simulated using a two-layer biodiffusion model with rapid, near-homogeneous mixing in the surface mixed layer and reduced mixing in the deep layer. Lead-210 profiles are consistent with a wide range of sedimentation and mixing rates in the deep sediment layer. However, the 137Cs and 239,240Pu results further constrain the model parameters and indicate that the downward transport of radionuclides in the sediments is governed primarily by sediment mixing, with sediment burial playing a secondary role. 相似文献
18.
Distribution and inventories of 90Sr, 137Cs, 241Am and Pu isotopes in sediments of the Northwest Pacific Ocean 总被引：1，自引：0，他引：1
《Marine Geology》2005,216(4):249-263
Bottom sediments collected in the Northwest (NW) Pacific Ocean in 1997 were analysed for 90Sr, 137Cs, 239,240Pu and 241Am contents to determine their distribution patterns, inventories and sources. Enhanced inventories of 239,240Pu and 241Am were observed in the latitudinal belts of 10–20°N and 30–40°N, which correspond to major areas of local (tropospheric) and global (stratospheric) fallout (with a contribution from local fallout), respectively. The sediment inventory of 239,240Pu near the Bikini Atoll exceeded its overlying water inventory, however, in the mid-latitudes, more than 70% of 239,240Pu still remains in the water column. 241Am inventories in sediments exceeded that of the water column for the entire NW Pacific Ocean. Higher 137Cs and 90Sr sediment inventories in the latitudinal belt of 30–40°N are due to global fallout, and they account for about 10% and less than 5% of the water column inventories, respectively. The observed activity ratios of 137Cs/90Sr, 238Pu/239,240Pu and 241Am/239,240Pu in sediment were at some stations higher than the global fallout ratios due to contributions from local fallout and due to specific processes in the water column. Two end-member mixing model based on the 240Pu/239Pu atom ratios observed in global and local fallout yielded ∼60% contribution of the local fallout in the bottom sediments near the Bikini Atoll. The upward decrease in the 240Pu/239Pu atom ratios in the sediment column indicates a decrease in the contribution of local fallout to the Pu inventory with time. 241Am and 241Pu dating of sediment layers was utilized to explain a hiatus in sediment accumulation in the deep seafloor. 相似文献
19.
Hideyuki Kawamura Toshimichi Ito Takuya Kobayashi Shigeyoshi Otosaka Naoki Hirose Orihiko Togawa 《Journal of Oceanography》2010,66(5):649-662
A numerical experiment is carried out to reproduce distribution of concentration of 90Sr and 137Cs, estimate their total amount and verify their source in the Japan Sea. Model results are in good agreement with observational
findings in the Japan Sea expeditions between 1997 and 2002 by the Japan Atomic Energy Agency. Vertical profiles of the concentration
of 90Sr and 137Cs show exponential decreases with depth from the sea surface to the sea bottom. From the model and observational results,
it is suggested that the concentration of 90Sr and 137Cs in the surface layer is approximately in the range of 1.0–1.5 Bq/m3 and 2.0–2.5 Bq/m3, respectively. On the other hand, it is found that the concentration in the intermediate and deep layer
is higher than that observed in the northwestern Pacific Ocean, suggesting active winter convection in the Japan Sea. The
total amount of 90Sr and 137Cs in the seawater is evaluated to be 1.34 × 1015 Bq and 2.02 × 1015 Bq, respectively, in the numerical experiment, which demonstrates an estimation by observational data obtained in the Japan
Sea expeditions. The total amount of 90Sr and 137Cs changed during the second half of 20th century corresponding to deposition at the sea surface with the maximums of 4.86
× 1015 Bq for 90Sr and 7.33 × 1015 Bq for 137Cs, respectively, in the mid-1960s. The numerical experiment suggests that the main source of 90Sr and 137Cs has been global fallout, although there have been some potential sources in the Japan Sea. 相似文献
20.
As part of a broad research program on the behavior of critical radionuclides to be discharged into the sea by the first Brazilian nuclear powerplant, the uptake accumulation and loss of 137Cs, 60Co and 125I by locally abundant seaweed species was studiedUptake in static 12 liter aquarium experiments reached apparent steady-state in 2–7 days (60Co and 125I) or 2–3 weeks (137Cs). Elimination followed a reverse pattern, being comparatively fast for 137Cs and slow for 60Co and 125I. Dry weight bioaccumulation factors (BFs) were variable, falling in the 101 range for 137Cs, 103 for 125I and 103–104 for 60Co. Various short-term experiments performed over a 16 month period, showed marked temporal variations of 60Co BFs for all species.The results demonstrated that the studied species may play an important role in the transfer of the critical radionuclides through local food webs and can be employed as useful monitors for routine or accidental radionuclide releases. 相似文献