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1.
Small ; 17(33): e2101616, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34270865

RESUMO

Phase controllable synthesis of 2D materials is of significance for tuning related electrical, optical, and magnetic properties. Herein, the phase-controllable synthesis of tetragonal and hexagonal FeTe nanoplates has been realized by a rational control of the Fe/Te ratio in a chemical vapor deposition system. Using density functional theory calculations, it has been revealed that with the change of the Fe/Te ratio, the formation energy of active clusters changes, causing the phase-controllable synthesis of FeTe nanoplates. The thickness of the obtained FeTe nanoplates can be tuned down to the 2D limit (2.8 nm for tetragonal and 1.4 nm for hexagonal FeTe). X-ray diffraction pattern, transmission electron microscopy, and high resolution scanning transmission electron microscope analyses exhibit the high crystallinity of the as-grown FeTe nanoplates. The two kinds of FeTe nanoflakes show metallic behavior and good electrical conductivity, featuring 8.44 × 104 S m-1 for 9.8 nm-thick tetragonal FeTe and 5.45 × 104 S m-1 for 7.6 nm-thick hexagonal FeTe. The study provides an efficient and convenient route for tailoring the phases of FeTe nanoplates, which benefits to study phase-sensitive properties, and may pave the way for the synthesis of other multiphase 2D nanosheets with controllable phases.

2.
Mar Pollut Bull ; 199: 115972, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38154170

RESUMO

To investigate the spatial distribution and source of plutonium isotopes in the Beibu Gulf, surface sediments were collected and analyzed using sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). The activities of 239+240Pu in surface sediments ranged from 0.012 to 0.451 mBq/g (mean: 0.171 ± 0.138 mBq/g, n = 36), indicating a decreasing trend in a counterclockwise direction from the southern bay mouth. The counterclockwise decreasing trend in the south of the bay mouth is similar to the current in the Beibu Gulf. The 240Pu/239Pu atom ratios in surface sediments ranged from 0.156 to 0.283 (mean: 0.236 ± 0.031, n = 36), slightly higher than that of the global fallout value of 0.18. This suggests that the Pu in the Beibu Gulf was a combination of global fallout and Pacific Proving Ground (PPG). The average contribution of the plutonium (Pu) derived from the PPG in the sediment was estimated to be 52 % ± 24 %.


Assuntos
Plutônio , Monitoramento de Radiação , Cinza Radioativa , Poluentes Radioativos da Água , Sedimentos Geológicos/química , Plutônio/análise , Poluentes Radioativos da Água/análise , China , Cinza Radioativa/análise
3.
Mar Pollut Bull ; 193: 115222, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37406399

RESUMO

The 239+240Pu activities and 240Pu/239Pu atom ratios of surface sediments from the Eastern Guangdong coast (EGDC) were determined by sector field ICP-MS in order to examine the sources of plutonium (Pu) and quantify their contributions. The 239+240Pu activities in the EGDC ranged from 0.113 to 0.451 Bq kg-1, with an average of 0.225 ± 0.090 Bq kg-1 (n = 17). Consistently high 240Pu/239Pu atom ratios, ranging from 0.218 to 0.274 (average = 0.254 ± 0.014, n = 17), indicate a non-global fallout Pu source in the EGDC. The horizontal distribution of the 240Pu/239Pu atom ratios in the EGDC sediment suggests the non-global fallout Pu is sourced from close-in fallout from the Pacific Proving Grounds (PPG). Using a simple two end-member mixing model, we calculated the relative proportions of Pu from the PPG and global fallout in the EGDC to be 57 ± 9 % and 43 ± 9 %, respectively. Moreover, from the well-defined relationship between 239+240Pu activity and total organic carbon content in sediments and a two end-member mixing model using δ13C, we further calculated the Terr-global fallout (riverine input) and Mar-global fallout (direct atmospheric deposition) to be 11 ± 2 % and 32 ± 6 %, respectively. Finally, from the activity levels and atom ratios of Pu isotopes in the EGDC, we established a baseline for future use in environmental risk assessment related to nuclear power plant operations.


Assuntos
Plutônio , Monitoramento de Radiação , Cinza Radioativa , Poluentes Radioativos da Água , Plutônio/análise , Poluentes Radioativos da Água/análise , Cinza Radioativa/análise , Sedimentos Geológicos
4.
Chemosphere ; 263: 127896, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32854005

RESUMO

Particle-reactive radionuclides are useful for tracing sediment dynamics in marginal seas. We collected a suite of surface sediment samples in May 2014 from the Bohai Sea (BS) and Northern Yellow Sea (NYS) to observe the spatial distribution of Plutonium (Pu) isotopes and 210Pb activities. 239+240Pu activities ranged from 0.001 to 0.288 and 0.040-0.269 Bq kg-1 in BS and NYS surface sediments, respectively. 210Pbex shows a significant correlation with 239+240Pu (r = 0.84, p < 0.01) that suggested these two nuclides were scavenged to the same grade. 240Pu/239Pu atom ratios in BS (0.173-0.256) and NYS (0.196-0.275) were slightly higher than the global fallout value of 0.18 and lower than the Pacific Proving Ground (PPG) value of 0.36, indicating that some fraction of Pu originating from the PPG was capable of being transported to the BS and NYS. Mass balance results showed that 41% of 239+240Pu (8.9 × 109 Bq yr-1) and 18% of 210Pb (2.4 × 1012 Bq yr-1) in the NYS originated in the oceanic input. In the BS, 63% of 210Pb originated from atmospheric deposition and 84% of 239+240Pu originated from riverine input. Using Pu and 210Pb as tracers, we estimate that (1.8-2.6) × 108 t yr-1 and (3.6-3.8) × 108 t yr-1 of sedimentary particles could be transported from the BS to the NYS and from the NYS to the Southern Yellow Sea, respectively. Furthermore, the 226Ra/238U activity ratio distribution suggested that sedimentary particles derived from the Yellow River could be transported to the middle of the BS and coastal areas of the NYS.


Assuntos
Radioisótopos de Chumbo/análise , Plutônio/análise , Monitoramento de Radiação , Poluentes Radioativos da Água/análise , Sedimentos Geológicos , Oceanos e Mares , Rios
5.
Appl Radiat Isot ; 176: 109873, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34315033

RESUMO

Plutonium isotopes in the coral were determined with chemical separation method using AG 1-X8 and AG-MP-1M anion exchange resins and sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) in order to elucidate the activity concentration and source of Pu around Weizhou land in Beibu Gulf, China. Furthermore, the activity concentrations of other radionuclides (238U, 226Ra, 232Th, 137Cs, 40K and 210Pb) were measured by a HPGe spectrometer. The activity concentration of 240+239Pu in the coral is determined to be in the range of 8.95-27.84 mBq/kg. The 240Pu/239Pu atom ratios in the samples range from 0.173 to 0.225, indicating that the main source of plutonium in this area is global fallout while the contribution of PPG is about 30%. Further, the activity concentrations of 238U, 232Th, 40K and 226Ra are determined to be in the range of 18.72-64.63, 1.37-20.8, 29.78-72.52 and 3.48-61.97 Bq/kg, respectively.


Assuntos
Antozoários/química , Plutônio/análise , Radioisótopos/análise , Poluentes Radioativos do Solo/análise , Poluentes Radioativos da Água/análise , Animais , China , Cinza Radioativa/análise
6.
J Environ Radioact ; 240: 106737, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34543861

RESUMO

The 240Pu/239Pu atom ratios were determined by inductively coupled plasma mass spectrometry for seawater samples from the Okinawa Trough in the western North Pacific Ocean margin to identify their Pu sources and to elucidate the temporal variability in atom ratios in the water columns in the western North Pacific Ocean and its marginal seas. The 239Pu, 240Pu and 239+240Pu water column inventories were 12.2 ± 0.5, 10.5 ± 0.5 and 22.7 ± 0.7 Bq m-2, respectively. The observed 240Pu/239Pu ratios were clearly greater than the mean global fallout ratio of ∼0.18 with a mean value of 0.236 ± 0.014. The observed greater atom ratios confirmed the presence of close-in fallout Pu from nuclear testing at the Pacific Proving Grounds (PPG). The relative percentage of the PPG-derived Pu to global fallout Pu was estimated as 41 ± 10%. The 239+240Pu water column inventory originating from the PPG close-in fallout was also calculated as 9.2 ± 0.4 Bq m-2. The temporal variability in the mean 240Pu/239Pu atom ratios in the water columns in the western North Pacific Ocean and its marginal seas was obtained through comparison of the present study values and the previously reported values, and it had no significant temporal variation with a mean value of 0.237 ± 0.004 during the observation period of 1984-2015. The 239Pu and 240Pu derived from the two different sources of global fallout and the close-in fallout at the PPG were homogenized in the water masses in the studied areas.


Assuntos
Plutônio , Monitoramento de Radiação , Poluentes Radioativos da Água , Oceanos e Mares , Oceano Pacífico , Plutônio/análise , Água , Poluentes Radioativos da Água/análise
7.
Mar Pollut Bull ; 158: 111390, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32753176

RESUMO

Radionuclides from 1950s weapons testing at the Montebello Islands, Western Australia, may impact sea turtle embryos incubating within eggs laid in contaminated sands or be taken up into adult body tissues where they can contribute to radiation dose over a turtles' 60+ year lifespan. We measured plutonium in all local samples including turtle skin, bones, hatchlings, eggshells, sea sediments, diet items and beach sands. The amount of Pu in developing embryos/hatchling samples was orders of magnitude lower than that in the surrounding sands. These contaminated sands caused most dose to eggs (external dose from 137Cs, 152Eu), while most of the dose to adults was from internalised radionuclides (98%). While current dose rates are relatively low, local dose rates were high for about ten years following the 1950s detonations and may have resulted in lethality or health impacts to a generation of turtles that likely carry biomarkers today.


Assuntos
Plutônio/análise , Tartarugas , Poluentes Radioativos da Água/análise , Animais , Sedimentos Geológicos , Ilhas , Austrália Ocidental
8.
Mar Pollut Bull ; 150: 110599, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31733905

RESUMO

This study reviews the current understanding of the inventory and sources of plutonium (Pu) in the marine environment adjacent to China. The 239+240Pu inventory in the China Seas was found to have large spatial variations. The quantity in sediments decreases away from the shore, generally tracing the sedimentation rate distribution. High 239+240Pu inventories indicated that Pu in the water column was easily scavenged since Pu has a high particle affinity. Indeed, substantially higher 240Pu/239Pu atom ratios were observed in the sediment and seawater of the China Seas than are found in global fallout. We thus clarified that Pu sources in the China Seas were from both global fallout and the Pacific Proving Grounds (PPG) in the Pacific Marshall Islands. Plutonium from the latter source is transported into the China Seas through the North Equatorial Current (NEC) and Kuroshio. Using a two end-member mixing model, we revealed that the contribution of Pu from the PPG accounts for over 40% of the Pu in the East China Sea (ECS) and South China Sea (SCS), and less than 20% of the Pu in the Yellow Sea (YS). The distributions and isotopic composition of Pu in the China Seas indicate strong scavenging of Pu in the ECS and high Pu accumulation in the SCS. This information on the inventory and isotopic composition of Pu helps to establish a background for the future study of Pu in the China Seas.


Assuntos
Plutônio/análise , Monitoramento de Radiação , Poluentes Radioativos da Água/análise , China , Sedimentos Geológicos , Micronésia , Oceanos e Mares , Ilhas do Pacífico , Cinza Radioativa
9.
Appl Radiat Isot ; 159: 109098, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32250770

RESUMO

Uranium and plutonium are both poisonous radioactive elements, which are very harmful to human health and environment. Therefore, it is of great significance to study the distribution of 238U concentration and 239+240Pu activity in the uranium mine surrounding soils. We have collected some surface soil sediments within 2 km of two uranium mines and a solid waste management center in Guangxi Province. The 238U concentration in these study areas is in the range of 1.44-83.91 mg/g, and the 238U concentration in the A uranium mine surrounding surface soils is higher than that in the B uranium mine and the solid waste management center. While the B uranium mine and the solid waster management center don't pollute the surrounding soils because the 238U concentrations in their surrounding soils are similar to the average 238U concentration in the soil. The 239+240Pu activities in soil samples collected around the two uranium mines and the solid waste management center are close ranged from 0.06 mBq/g to 0.51 mBq/g. Moreover, the 240Pu/239Pu atom ratios in our study samples are ranged from 0.15 to 0.23, which indicate the Pu may come from the global fallout. In addition, we study heavy metals in our collected samples, only heavy metal Tl has weak positive correlations with 238U concentrations and 239+240Pu activities. And there is a weak positive correlation between 238U concentrations and 239+240Pu activities.

10.
Mar Pollut Bull ; 161(Pt B): 111775, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33122149

RESUMO

Concentrations of 129I and 127I in kelps (Saccharina) collected from coastal waters off northern Japan were monitored from 2007 to 2019. During the 2007-2008 test operation of the Rokkasho nuclear fuel reprocessing plant, 129I discharge from the plant increased, and the 129I concentration and 129I/127I atom ratio in the kelps reached maxima of 42 µBq/g-dry and 264 × 10-11, respectively. By 2009, both had decreased by one order of magnitude. After the Fukushima Dai-ichi Nuclear Power Plant accident in 2011, the 129I concentration and 129I/127I atom ratio in the kelps increased to 2.24 µBq/g-dry and 11.6 × 10-11, respectively. After 2012, the ratio in kelps decreased to (2.1-8.9) × 10-11, which is almost the same as the seawater value off Aomori Prefecture before the test operation. The 129I/127I atom ratio in kelps thus represents the ambient seawater ratio during the growth period of the kelps.


Assuntos
Acidente Nuclear de Fukushima , Monitoramento de Radiação , Poluentes Radioativos da Água , Radioisótopos de Césio/análise , Radioisótopos do Iodo/análise , Japão , Poluentes Radioativos da Água/análise
11.
Sci Total Environ ; 691: 572-583, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31325857

RESUMO

Since the 1956 completion of nuclear testing at the Montebello Islands, Western Australia, this remote uninhabited island group has been relatively undisturbed (no major remediations) and currently functions as high-value marine and terrestrial habitat within the Montebello/Barrow Islands Marine Conservation Reserves. The former weapons testing sites, therefore, provide a unique opportunity for assessing the fate and behaviour of Anthropocene radionuclides subjected to natural processes across a range of shallow-marine to island-terrestrial ecological units (ecotopes). We collected soil, sediment and biota samples and analysed their radionuclide content using gamma and alpha spectrometry, photostimulated luminescence autoradiography and accelerator mass spectrometry. We found the activity levels of the fission and neutron-activation products have decreased by ~hundred-fold near the ground zero locations. However, Pu concentrations remain elevated, some of which are high relative to most other Australian and international sites (up to 25,050 Bq kg-1 of 239+240+241Pu). Across ecotopes, Pu ranked from highest to lowest in the following order: island soils > dunes > foredunes > marine sediments > and beach intertidal zone. Low values of Pu and other radionuclides were detected in all local wildlife tested including endangered species. Activity concentrations ranked (highest to lowest) terrestrial arthropods > terrestrial mammal and reptile bones > algae > oyster flesh > whole crab > sea turtle bone > stingray and teleost fish livers > sea cucumber flesh > sea turtle skin > teleost fish muscle. The three detonations (one from within a ship and two from 30 m towers) resulted in differing contaminant forms, with the ship detonation producing the highest activity concentrations and finer more inhalable particulate forms. The three sites are distinct in their 240/239Pu and 241/239Pu atom ratios, including the Pu transported by natural process or within migratory living organisms.


Assuntos
Plutônio/análise , Monitoramento de Radiação , Cinza Radioativa/análise , Poluentes Radioativos/análise , Armas Nucleares , Austrália Ocidental
12.
Environ Pollut ; 246: 303-310, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30557804

RESUMO

The marine environment is complex, and it is desirable to have measurements for seawater samples collected at the early stage after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident to determine the impact of Fukushima-derived radionuclides on this environment. Here Pu isotopes in seawater collected 33-163 km from the FDNPP site at the very early stage after the accident were determined (May 2011, within two months after the accident). The distribution and temporal variation of 239Pu and 240Pu were studied. The results indicated that both 239+240Pu activity concentrations (from 0.81 ±â€¯0.16 to 11.18 ±â€¯1.28 mBq/m3) and 240Pu/239Pu atom ratios (from 0.216 ±â€¯0.032 to 0.308 ±â€¯0.036) in these seawater samples were within the corresponding background ranges before the accident, and this suggested that Fukushima-derived Pu isotopes, if any, were in too limited amount to be distinguished from the background level in the seawater. The analysis of Pu isotopic composition indicated that the major sources of Pu in the seawater after the accident were still global fallout and the Pacific Proving Ground close-in fallout. The contribution analysis showed that the contributions of the Pacific Proving Ground close-in fallout in the water column of the study area ranged from 26% to 77% with the average being 48%.


Assuntos
Acidente Nuclear de Fukushima , Plutônio/análise , Monitoramento de Radiação , Radioisótopos/análise , Água do Mar/análise , Poluentes Radioativos da Água/análise , Japão
13.
Environ Pollut ; 250: 578-585, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31026706

RESUMO

Three soil core samples were collected from a forest located about 1.1 km south of the Fukushima Daiichi Nuclear Power Plant (FDNPP) boundary in 2017, and the vertical profiles of 129I from the FDNPP accident were determined by the combination of TMAH (tetramethyl ammonium hydroxide) extraction and ICP-MS/MS analysis. The humus layer above the soil layer was heavily contaminated with 134Cs (1983-5985 Bq g-1) and 137Cs (1947-5902 Bq g-1) (decay-corrected to March 11, 2011). The 129I activity concentrations decreased sharply with the soil depth, from 1894 to 34.1, from 9384 to 78.9, and from 2536 to 51.3 mBq kg-1, for the three sites. Downward migration of 129I was slightly faster than the one of 134Cs. In addition, the cumulative 129I inventories were observed to be 43.4 ±â€¯1.0, 71.7 ±â€¯1.8, and 56.5 ±â€¯1.8 Bq m-2, respectively. Subsequently, the cumulative 131I inventories were estimated to be 1.76 ±â€¯0.06, 2.90 ±â€¯0.11, and 2.28 ±â€¯0.10 GBq m-2 (decay-corrected to March 11, 2011), respectively. Finally, the total atmospheric deposition of 129I on the land of Japan due to the FDNPP accident was estimated to be around 1.09-1.71 kg (7.11-11.2 GBq).


Assuntos
Florestas , Acidente Nuclear de Fukushima , Centrais Nucleares , Radioisótopos/análise , Poluentes Radioativos do Solo/análise , Japão , Monitoramento de Radiação , Solo , Espectrometria de Massas em Tandem
14.
J Environ Radioact ; 181: 78-84, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29107833

RESUMO

Activity concentration of plutonium (Pu) and its isotopic compositions are extensively used for measuring transport processes of Pu and identifying its source. We investigated the spatial distribution characteristics of 239+240Pu activity concentrations and 240Pu/239Pu atom ratio in several sediment cores collected from the Liao River coastal zone. Additionally, we calculated the 239+240Pu inventories and based on the 240Pu/239Pu atom ratio to trace Pu source. The activity concentrations of 239+240Pu in surface sediments of the Liao River estuary ranged between 0.103 ± 0.008 and 0.978 ± 0.035 mBq/g, with an average of 0.294 ± 0.024 mBq/g. The 240Pu/239Pu atom ratios, ranging from 0.173 ± 0.047 to 0.215 ± 0.061 (mean: 0.188 ± 0.049 (1σ)), were consistent with global fallout value, which indicates the global atmospheric fallout is the main source of Pu in sediment cores from the both sides of Liao River estuary. As for the tidal flat core LT-2, the mean 240Pu/239Pu atom ratio, slightly higher than that of the global fallout value, was 0.217 ± 0.050. Such pattern of Pu isotopic compositions indicated that Pu on the tidal flat in the Liao River estuary is sourced from a combination of global fallout and close-in fallout from the PPG by ocean currents transporting. And by using a two end-member mixing model, the results indicate the relative contribution of the PPG close-in fallout to core LT-2 is round 27% and 73% can be attributed to global fallout and river input. Therefore, these results clearly indicate that the direct global fallout is the main source of Pu in the Liao River estuary.


Assuntos
Sedimentos Geológicos/química , Plutônio/análise , Monitoramento de Radiação , Poluentes Radioativos da Água/análise , China , Rios/química
15.
Mar Pollut Bull ; 130: 240-248, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29866553

RESUMO

In order to investigate the sources of plutonium in seawaters of Liaodong Bay and Bohai Strait, China, surface seawater samples were collected and analyzed for 239+240Pu and 137Cs by radiochemical separation combined with ICP-MS and γ-spectrometry, respectively. A large variation of 239+240Pu activities was observed, ranging from 1.993 to 29.677 mBq/m3 in the Liaodong Bay and from 0.932 to 10.183 mBq/m3 in the Bohai Strait. 137Cs activities showed little variation between the investigated locations, which was attributed to the different behavior characteristics of 239+240Pu and 137Cs in seawaters. The 240Pu/239Pu atom ratios showed a significant variation between the Liaodong Bay (0.185) and Bohai Strait (0.225), indicating that Pu derived from the Pacific Proving Grounds might have been transported to the Bohai Strait but not yet to the Liaodong Bay, which could further provide valuable reference for evaluating the seawater exchange cycle between the Bohai Sea and Yellow Sea.


Assuntos
Radioisótopos de Césio/análise , Plutônio/análise , Movimentos da Água , Poluentes Radioativos da Água/análise , Baías , China , Água do Mar/análise
16.
Mar Pollut Bull ; 135: 808-818, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30301101

RESUMO

The 240Pu/239Pu atom ratio and 239+240Pu activity of seawater in the East China Sea (ECS) was measured in order to examine the Pu sources and elaborate Pu scavenging process. High 240Pu/239Pu atom ratios (0.187-0.243, average = 0.221 ±â€¯0.017) in the surface water and water column were observed during 2011, implying of non-global fallout Pu sources. The distribution of 240Pu/239Pu atom ratio in the ECS was in agreement with the introduction pathway of the Kuroshio, showing a decreasing trend away from the outer shelf. An even higher 240Pu/239Pu atom ratios (0.243-0.263, average = 0.253 ±â€¯0.007) were observed in the Kuroshio, indicating the non-global fallout Pu signal from the Pacific Proving Grounds (PPG). Using a two end-member mixing model, the Pu source from the PPG contribution was calculated to be 36 ±â€¯9% in the ECS seawater. The 239+240Pu activities of surface seawater were in the range of 2.00-2.95 mBq m-3 in the ECS. The spatial distribution of 239+240Pu activity in the surface seawater showed an increasing trend from the outer shelf to the nearshore. Moreover, 239+240Pu inventory of water column at the station DH23 in the ECS was calculated to be ~0.29 Bq m-2, which was 1-3 orders of magnitude lower than the estimates of sediment cores in the ECS shelf (9-407 Bq m-2). Such differences were determined by the high degree Pu scavenging efficiency in the ECS and high Pu input carried by terrestrial sediments from the Yangtze River. Finally, both 240Pu/239Pu atom ratios and 239+240Pu activities were identical before and after the Fukushima nuclear accident (FNA), suggesting that the impact of the FNA on the ECS was negligible.


Assuntos
Plutônio/análise , Poluentes Radioativos da Água/análise , China , Acidente Nuclear de Fukushima , Sedimentos Geológicos , Micronésia , Rios , Água do Mar
17.
Sci Total Environ ; 610-611: 200-211, 2018 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-28803197

RESUMO

In order to examine the sources of plutonium (Pu) and elaborate its scavenging and accumulation processes, 240Pu/239Pu atom ratios and 239+240Pu activities in the water column of the South China Sea (SCS) were determined and compared with our previously reported data for the sediments. Consistently high 240Pu/239Pu atom ratios that ranged from 0.184-0.250 (average=0.228±0.015), indicative of non-global fallout Pu sources were observed both in the surface water and at depth during 2012-2014. The spatial distribution of the 240Pu/239Pu atom ratio in the SCS showed a decreasing trend away from the Luzon Strait, which was very consistent with the introduction pathway of the Kuroshio Current. The Kuroshio had an even heavier Pu isotopic ratio ranging from 0.250-0.263 (average=0.255±0.006), traceable to the non-global fallout Pu signature from the Pacific Proving Grounds (PPG). Using a simple two end-member mixing model, we further revealed that this PPG source contributed 41±17% of the Pu in the SCS water column. The 239+240Pu activities in the SCS surface seawater varied from 1.59 to 2.94mBqm-3, with an average of 2.34±0.38mBqm-3. Such an activity level was ~40% higher than that in the Kuroshio. The distribution of 239+240Pu in the surface seawater further showed a general trend of increase from the Kuroshio to the SCS basin, suggesting significant accumulation of Pu within the SCS. The 239+240Pu inventory of the water column in the SCS basin at the SEATS station with a total depth of ~3840m was estimated to be ~29Bqm-2, which was substantially higher than the sediment core estimates made for the SCS basin (3.75Bqm-2) but much lower than the sediment core estimates made for the shelf of the northern SCS (365.6Bqm-2). Such differences were determined by the lower scavenging efficiency of Pu in the SCS basin compared to the northern SCS shelf.

18.
Anal Chim Acta ; 1008: 66-73, 2018 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-29420945

RESUMO

To reconstruct 131I deposition and identify the source of radioiodine due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, 129I activity and 129I/127I atom ratio should be obtained by preparing and analyzing large numbers of samples economically. In this study, great efforts were made to realize mild TMAH (tetramethyl ammonium hydroxide) extraction of environmental samples at 90 °C to obtain solutions suitable for the following triple-quadrupole inductively coupled plasma-mass spectrometry (ICP-QQQ) MS/MS mode analysis. After releasing iodine from organic matter in the TMAH extraction solution via K2S2O8 oxidation, organic matter was removed effectively by solvent extraction and back-extraction to avoid a serious matrix effect during ICP-QQQ analysis. At the same time, interfering elements, especially, Mo, Cd, and In were also removed effectively, to avoid their undesirable interferences during mass spectrometric analysis. In addition, 0.01% (NH4)2SO3 was selected to introduce I- into ICP-QQQ to ensure there was no memory effect and a stable signal was gotten. Subsequently, ICP-QQQ MS/MS mode was applied to further eliminate polyatomic interferences (127I(H2 and D)+, 97MoO2+, 113InO+, and 113CdO+) and isobaric interference from 129Xe+. Finally, the developed method was successfully applied to measure 129I/127I atom ratios ((2.61-27.0) × 10-7) and 129I activities (3.51-11.4 mBq kg-1) in soil samples. The developed method allows a greater number of ordinary laboratories to participate in the field of radioiodine analysis.

19.
Environ Int ; 59: 92-102, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23792418

RESUMO

A combination of state-of-the-art isotopic fingerprinting techniques and atmospheric transport modelling using real-time historical meteorological data has been used to demonstrate direct tropospheric transport of radioactive debris from specific nuclear detonations at the Semipalatinsk test site in Kazakhstan to Norway via large areas of Europe. A selection of archived air filters collected at ground level at 9 stations in Norway during the most intensive atmospheric nuclear weapon testing periods (1957-1958 and 1961-1962) has been screened for radioactive particles and analysed with respect to the concentrations and atom ratios of plutonium (Pu) and uranium (U) using accelerator mass spectrometry (AMS). Digital autoradiography screening demonstrated the presence of radioactive particles in the filters. Concentrations of (236)U (0.17-23nBqm(-3)) and (239+240)Pu (1.3-782µBqm(-3)) as well as the atom ratios (240)Pu/(239)Pu (0.0517-0.237) and (236)U/(239)Pu (0.0188-0.7) varied widely indicating several different sources. Filter samples from autumn and winter tended to have lower atom ratios than those sampled in spring and summer, and this likely reflects a tropospheric influence in months with little stratospheric fallout. Very high (236)U, (239+240)Pu and gross beta activity concentrations as well as low (240)Pu/(239)Pu (0.0517-0.077), (241)Pu/(239)Pu (0.00025-0.00062) and (236)U/(239)Pu (0.0188-0.046) atom ratios, characteristic of close-in and tropospheric fallout, were observed in filters collected at all stations in Nov 1962, 7-12days after three low-yield detonations at Semipalatinsk (Kazakhstan). Atmospheric transport modelling (NOAA HYSPLIT_4) using real-time meteorological data confirmed that long range transport of radionuclides, and possibly radioactive particles, from Semipalatinsk to Norway during this period was plausible. The present work shows that direct tropospheric transport of fallout from atmospheric nuclear detonations periodically may have had much larger influence on radionuclide air concentrations and deposition than previously anticipated.


Assuntos
Atmosfera/química , Armas Nucleares , Plutônio/análise , Cinza Radioativa/análise , Urânio/análise , Filtros de Ar , Cazaquistão , Espectrometria de Massas , Noruega , Vento
20.
Sci Total Environ ; 461-462: 734-41, 2013 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-23770554

RESUMO

In the present work, state of the art isotopic fingerprinting techniques are applied to an Arctic ice core in order to quantify deposition of U and Pu, and to identify possible tropospheric transport of debris from former Soviet Union test sites Semipalatinsk (Central Asia) and Novaya Zemlya (Arctic Ocean). An ice core chronology of (236)U, (239)Pu, and (240)Pu concentrations, and atom ratios, measured by accelerator mass spectrometry in a 28.6m deep ice core from the Austfonna glacier at Nordaustlandet, Svalbard is presented. The ice core chronology corresponds to the period 1949 to 1999. The main sources of Pu and (236)U contamination in the Arctic were the atmospheric nuclear detonations in the period 1945 to 1980, as global fallout, and tropospheric fallout from the former Soviet Union test sites Novaya Zemlya and Semipalatinsk. Activity concentrations of (239+240)Pu ranged from 0.008 to 0.254 mBq cm(-2) and (236)U from 0.0039 to 0.053 µBq cm(-2). Concentrations varied in concordance with (137)Cs concentrations in the same ice core. In contrast to previous published results, the concentrations of Pu and (236)U were found to be higher at depths corresponding to the pre-moratorium period (1949 to 1959) than to the post-moratorium period (1961 and 1962). The (240)Pu/(239)Pu ratio ranged from 0.15 to 0.19, and (236)U/(239)Pu ranged from 0.18 to 1.4. The Pu atom ratios ranged within the limits of global fallout in the most intensive period of nuclear atmospheric testing (1952 to 1962). To the best knowledge of the authors the present work is the first publication on biogeochemical cycles with respect to (236)U concentrations and (236)U/(239)Pu atom ratios in the Arctic and in ice cores.


Assuntos
Atmosfera/química , Camada de Gelo/química , Plutônio/análise , Monitoramento de Radiação/métodos , Cinza Radioativa/análise , Urânio/análise , Regiões Árticas , Autorradiografia , História do Século XX , Espectrometria de Massas , Monitoramento de Radiação/história , U.R.S.S.
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