Characteristic of Pu from urban wetland and lacustrine sediments in Suzhou Industrial Park, China

doi:10.1016/j.jenvrad.2019.106134

Journal of Environmental Radioactivity

Volume 213, March 2020, 106134

https://doi.org/10.1016/j.jenvrad.2019.106134 Get rights and content

Highlights

•
^239+240Pu activity concentrations in the wetland surface soils of SIP range from 0.035 to 0.426 mBq/g.
•
²⁴⁰Pu/²³⁹Pu atom ratios were 0.171–0.226 in the wetlands of SIP.
•
²⁴⁰Pu/²³⁹Pu atom ratios were 0.168–0.200 in the sediment core from the Yangcheng Lake.
•
Pu has significant positive correlations with Cu, Sn and Pb but negative correlation with As.

Abstract

In this study, plutonium activity concentrations in the urban wetlands and lacustrine sediment of Suzhou Industrial Park (SIP) are studied for the first time. Results show ^239+240Pu activity concentrations in the wetland surface soils of SIP range from 0.035 to 0.426 mBq/g and the ²⁴⁰Pu/²³⁹Pu atom ratio ranges from 0.171 $\pm$ 0.024 to 0.226 $\pm$ 0.049. Judging from the atom ratio of ²⁴⁰Pu/²³⁹Pu, the main source of Pu in the wetland is global fallout. The correlations of Pu between organic matter and heavy metals are also studied. The correlation coefficients show Pu has significant positive correlations with Cu, Sn and Pb but negative correlation with As. Unlike distributions of Pu in other places, Pu in SIP has weak correlation with organic matter content. A sediment core from Lake Yangcheng is also analyzed to investigate the historical record of Pu deposition. The atom ratios of each layer in the sediment core indicate the area is mainly influenced by global fallout. Using Pu as a discrete-time maker, the deposition rate in Lake Yangcheng is 0.396 $\pm$ 0.019 cm/yr. The calculated inventory of ^239+240Pu is 58.5 Bq/m², which is in the range of inventories of the corresponding latitudes according to UNSCEAR.

Introduction

Pu is an artificial radionuclide associated with nuclear industry including nuclear weapon and energy industry. Common anthropogenic Pu are in the form of ²³⁹Pu (T_1/2 = 2.411 × 10⁴ yr), ²⁴⁰Pu (T_1/2 = 6563 yr), ²⁴¹Pu (T_1/2 = 14.4 yr), ²⁴²Pu (T_1/2 = 3.73 × 10⁵ yr) and ²⁴⁴Pu (T_1/2 = 8.08 × 10⁷ yr). Anthropogenic Pu in the environment mostly comes from the series of nuclear weapon tests from the mid-1940s to the 1980s. The atmospheric nuclear weapon tests conducted by countries such as the former Soviet Union, the United States and China have emitted about 1.1 × 10¹⁶Bq of ^239+240Pu into the environment, and Pu was spread globally due to atmospheric dispersion (Harley, 1980).

The ²⁴⁰Pu/²³⁹Pu atom ratio differs for different sources such as nuclear test, military weapons or industrial sources. Therefore, the atom ratio is often used to identify the sources of radioactive pollutants in the environment (Krey et al., 1976; Warneke et al., 2002). Specifically, ²⁴⁰Pu/²³⁹Pu atom ratio of weapon-grade Pu ranges from 0.01–0.07 (Lindahl et al., 2017), while nuclear reactor-grade Pu exhibits higher atom ratios, ranging from 0.24–0.8 (Warneke et al., 2002; Ketterer and Szechenyi, 2008). Atom ratio values of the Pacific proving ground (PPG) Pu are usually 0.306–0.36, which are higher than the average value of ²⁴⁰Pu/²³⁹Pu atom ratios 0.178 $\pm$ 0.019 (0–30°N) and 0.180 $\pm$ 0.014 (30–71°N) from the global fallout (Krey et al., 1976; Kelley et al., 1999).

As ²³⁹Pu and ²⁴⁰Pu have a high radiotoxicity and long-term persistence in the environment, risk assessment for Pu in the environment is indispensable. More and more researchers are trying to determine the characteristics of distribution, sources and fate of Pu in different layers of the earth, including atmosphere, water and sediments (Hirose and Povinec, 2015; Zhang et al., 2018).

Regional studies on ^239+240Pu activity concentration in the surface soils and its vertical distribution covers many part of China. However, ^239+240Pu activities and inventories of the research areas are quite distinct from each other. The ^239+240Pu activities in the surface soil range from 0.023 $\pm$ 0.003 mBq/g (Gansu, Lanzhou, northwestern China) to 1.30 $\pm$ 0.05 mBq/g (Wuling, Chongqing, southwestern China) and the distinct ^239+240Pu activities in China might be caused by the differences of soil particle sizes, organic matter, regional climatic factors and other factors (Zheng et al., 2009; Bu et al., 2014). In the vertical distribution of ^239+240Pu, most Pu depositions (more than 80%) concentrate on the top 10 cm layer of soils (Dong et al., 2010; Bu et al., 2014). However, some soil core analyses show opposite results and the most Pu inventories are in the deeper layers (Zheng et al., 2009; Zhang and Hou, 2019) largely due to soil erosion and downward percolation of fine particles. Studies also show that the inventories of ^239+240Pu in the estuary sediments are much larger than in soils, which might be caused by scavenging of Pu from the seawater and the higher sedimental deposition rates in the estuaries areas (Hao et al., 2018; Liu et al., 2011; Zhang et al., 2018).

The ²⁴⁰Pu/²³⁹Pu atom ratios have also been investigated in different regions and the results show that China has been affected by different sources of Pu and the global fallout is the main source of Pu in mainland (Huang et al., 2019). Studies have shown that the mainland of China, such as the northwest has been affected not only by the global fallout but also the Lop Nor nuclear tests conducted in the 1980s (Bu et al., 2015). Also, some results indicate that China coast including the marginal seas, such as the East China Sea, the Yellow Sea and the South China Sea, has been influenced by both the global fallout and the PPG (Pacific Proving Ground) close-in fallout (Dong et al., 2010; Liu et al., 2011, 2013; Wu et al., 2014; Zhang et al., 2018). It has been demonstrated that Pu derived from the PPG can be transported over long distances to the western Pacific Ocean and to its adjacent marginal seas (Liu et al., 2011; Wu et al., 2014). However, information on the distribution and characteristics of Pu deposition in the wetlands and lakes in the eastern China are very limited. Since China operates nuclear power plants (NPPs) along the east coast, investigating the historical deposition and migration mechanisms of Pu in urban wetlands and lakes is vitally important to understand and evaluate possible future pollution with radionuclides.

In this study, the spatial distributions of ^239+240Pu activity of the urban wetlands in Suzhou Industrial Park (SIP) were measured for the first time and the sources of Pu in this area were investigated to see whether other sources such as Chinese nuclear tests or the Fukushima NPP accident have affected this area. In addition, a sediment core taken from Lake Yangcheng was also analyzed to investigate the historical information of Pu deposited in the lake.

Section snippets

Sample collection and preparation

The locations of the sampling sites are shown in Fig. 1. As seen in Fig. 1, the sample sites are distributed in Suzhou Industrial Park (SIP), Suzhou, eastern China. Suzhou (119°55′–121°20′ E, 30°47′–32°02′ N) is located in the middle of Yangtze River Delta and adjacent to Yangtze River and Lake Taihu. The city is under the impact of subtropical monsoon marine climate, having ~1100 mm annual precipitation.

Surface soil samples were collected in the wetlands of SIP in June 2012 (Fig. 1). The urban

^239+240Pu activity concentration and its distribution in surface soils in Suzhou

The ^239+240Pu activities and ²⁴⁰Pu/²³⁹Pu atom ratios in surface soil samples collected in SIP are presented in Table 1. The results show the activity concentration of ^239+240Pu in the surface soil ranges from 0.035 to 0.426 mBq/g with the average value of 0.156 $\pm$ 0.08 mBq/g (arithmetic average) and 0.126 $\pm$ 0.013 mBq/kg (geometric average). The activity concentration values are close to the values (0.088 $\pm$ 0.031–0.469 $\pm$ 0.057 mBq/g) in Guangxi that Guan et al. (2018) reported. The maximum value of the

Conclusions

In this study, we analyzed ^239+240Pu activities and ²⁴⁰Pu/²³⁹Pu atom ratios in surface soil samples and lacustrine sediment samples in Suzhou. The results indicate that the activity concentration of ^239+240Pu from surface soil (0–4 cm) range from 0.035 to 0.426 mBq/g, with a mean of 0.156 $\pm$ 0.08 mBq/g. The ²⁴⁰Pu/²³⁹Pu atom ratio in surface soil samples ranged from 0.176 to 0.226, with a weighted mean of 0.194. The mean ratio was similar to the typical global fallout value. Using the Pearson

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was supported by grants from the National Natural Science Foundation of China (41773004), the Jiangsu Provincial Key Laboratory of Radiation Medicine and Protection, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

References (39)

W.T. Bu et al.
Vertical distribution and migration of global fallout Pu in forest soils in southwestern China
J. Environ. Radioact.
(2014)
W. Dong et al.
Characterization of plutonium in deep-sea sediments of the Sulu and South China seas
J. Environ. Radioact.
(2010)
Y.J. Guan et al.
Distribution and sources of plutonium along the coast of Guangxi, China
Nucl. Instrum. Methods Phys. Res. B
(2018)
Y.P. Hao et al.
Sources of plutonium isotopes and ¹³⁷Cs in coastal seawaters of Liaodong Bay and Bohai Strait, China and its environmental implications
Mar. Pollut. Bull.
(2018)
Y.N. Huang et al.
The ²⁴⁰Pu/²³⁹Pu atom ratio in Chinese soils
Sci. Total Environ.
(2019)
J.M. Kelley et al.
Global distribution of Pu isotopes and ²³⁷Np
Sci. Total Environ.
(1999)
M.E. Ketterer et al.
Determination of plutonium and other transuranic elements by inductively coupled plasma mass spectrometry: a historical perspective and new frontiers in the environmental sciences
Spectrochim. Acta, Part B
(2008)
H.Q. Liao et al.
Determination of plutonium isotopes in freshwater lake sediments by sector-field ICP-MS after separation using ion-exchange chromatography
Appl. Radiat. Isot.
(2008)
Y.Y. Ni et al.
The transfer of fallout plutonium from paddy soil to rice: a field study in Japan
J. Environ. Radioact.
(2019)
S.G. Tims et al.
Plutonium AMS measurements in Yangtze River estuary sediment
Nucl. Instrum. Methods B
(2010)

T. Warneke et al.

A new ground-level fallout record of uranium and plutonium isotopes for northern temperate latitudes

Earth Planet. Sci. Lett.

(2002)

Y. Xu et al.

Association of Plutonium isotopes with natural soil particles of different size and comparison with ¹³⁷Cs

Sci. Total Environ.

(2017)

W.C. Zhang et al.

Level, distribution and sources of plutonium in the coastal areas of China

Chemosphere

(2019)

K.X. Zhang et al.

Vertical distributions and source identification of the radionuclides ²³⁹Pu and ²⁴⁰Pu in the sediments of the Liao River estuary, China

J. Environ. Radioact.

(2018)

J. Zheng et al.

Inductively coupled plasma-sector field mass spectrometry with a high-efficiency sample introduction system for the determination of Pu isotopes in settling particles at femtogram levels

Talanta

(2006)

J. Zheng et al.

Global fallout Pu recorded in lacustrine sediments in Lake Hongfeng, SW China

Environ. Pollut.

(2008)

J. Zheng et al.

Characterization of Pu concentration and its isotopic composition in soils of Gansu in northwestern China

J. Environ. Radioact.

(2009)

W.T. Bu et al.

A method of measurement of ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu in high U content marine sediments by sector field ICP-MS and its application to Fukushima sediment samples

Environ. Sci. Technol.

(2014)

W.T. Bu et al.

Pu isotopes in soils collected downwind from Lop Nor: regional fallout vs. global fallout

Sci. Rep.

(2015)

Cited by (14)

Vertical distribution of plutonium isotopes from the floodplain and lacustrine sediments in Poyang Lake, China
2023, Journal of Environmental Radioactivity
Anthropogenic radionuclides deposited in sediments have been used for environmental radiation risk valuation as well as source identification. In this study, we investigated the vertical distribution of plutonium (Pu) isotopes and ²⁴⁰Pu/²³⁹Pu atom ratios in both floodplain and lacustrine sediments in Poyang Lake. The ^239+240Pu activity concentrations in floodplain sediment cores were found to range from 0.002 to 0.085 Bq kg⁻¹, with a maximum value at the subsurface layer. The activity in lacustrine sediment cores was from 0.062 to 0.351 Bq kg⁻¹ with a mean of 0.138 ± 0.053 Bq kg⁻¹. The inventory of 43.15 Bq m⁻² in lacustrine sediment core is comparable to the average value of global fallout expected at the same latitude. The average ²⁴⁰Pu/²³⁹Pu atomic ratios (0.183 ± 0.032) for sediment cores indicated that the global fallout is the major source of Pu in the studied region. The results are of great significance to the further understanding of sources, records, and environmental impacts of regional nuclear activities in the environment.
Spatial distribution and migration of <sup>239+240</sup>Pu in Chinese soils
2022, Science of the Total Environment
Citation Excerpt :
In this work, we study the surface and vertical distribution of 239+240Pu in soil samples collected in China and aim to: (1) systematically investigate the surface and vertical distribution characterization of 239+240Pu in Chinese soil samples based on all the publicly available surface and core sample data in China; (2) summarize the mean 240Pu/239Pu atom ratio and source identification based on statistical analysis; and (3) provide the migration parameters of 239+240Pu for the CDE model in Chinese soil cores, which can be served as an important reference for harmful heavy metal migration and soil risk assessment research. This study evaluates 239+240Pu surface soil data from 647 samples sites (see more information in Tables S1 and S2; see sample locations in Fig. 1) in China collected from published papers (Sha et al., 1991; Kelley et al., 1999; Jin et al., 2003; Huh and Su, 2004; Zheng et al., 2009; Dong et al., 2010a; Dong et al., 2010b; Dong, 2010; Liu et al., 2013; Bu and Guo, 2013; Wang et al., 2013; Xu et al., 2013; Bu et al., 2014; Bu et al., 2015; Xing, 2015; Yu et al., 2017; Xu et al., 2017; Bu et al., 2017; Guan et al., 2018; Xing et al., 2018; Zhang et al., 2018; Ni et al., 2018; Cao et al., 2019; Zhang et al., 2019; Zhang and Hou, 2019; Wu, 2019; Zhuang et al., 2019; Ni et al., 2020; Wang et al., 2020; Guan et al., 2020; Zhao et al., 2020; Guan et al., 2021; Dang et al., 2021; Zhang et al., 2021). The definition of the surface layer soil depth is not the same across different articles (see more information in Tables S1 and S2).
The migration of radionuclides is a critical threat to the soil and groundwater environment. This study investigates highly radiological toxic ^239+240Pu in 647 surface soils and 66 soil cores in China. First, the spatial distributions of ^239+240Pu activities and ²⁴⁰Pu/²³⁹Pu ratios are presented in Chinese surface soils. Second, four different types of vertical distribution of ^239+240Pu, namely 45.4%, 40.9%, 9.1% and 4.5% of Chinese soil cores proportions are integrated using statistical analysis. Furthermore, different soil types are accompanied by different ^239+240Pu vertical distributions, which relate closely to the ^239+240Pu migration. Finally, based on the Convection Dispersion Equation (CDE) model, the present work find that the apparent convection velocities of ^239+240Pu are ranging from 0.00032 ± 0.00031 cm a⁻¹ to 0.473 ± 0.083 cm a⁻¹. As shown by the four typical vertical activity distribution of ^239+240Pu in soil cores, the deepened activity maximum value position of ^239+240Pu implies a fast migration rate or apparent convection velocity. This study, for the first time, suggests a significant linear correlation (R² = 0.847) between the depth of ^239+240Pu maximum value (cm) and the apparent convection velocity (v, cm a⁻¹). We hypothesize that v usually does not exceed 0.5 cm a⁻¹ in the CDE model. A significant linear correlation is also identified between apparent dispersion coefficient (D, cm² a⁻¹) and v² in Chinese soil cores from the CDE model. It will provide an important reference for harmful heavy metal migration research in the future.
Rapid determination of plutonium isotopes in small samples using single anion exchange separation and ICP-MS/MS measurement in NH<inf>3</inf>–He mode for sediment dating
2022, Talanta
Citation Excerpt :
These values were at least one order of magnitude lower than those (from 0.012 ± 0.012 mBq/g to 1.698 ± 0.210 mBq/g) obtained in the sediments from the Lake Yangcheng [30], which is < 100 km far from the Lake Ge. However, the 240Pu/239Pu atomic ratios in the sediment core of the Lake Ge ranging from 0.137 ± 0.033 to 0.220 ± 0.047 with an average of 0.171 ± 0.016, generally fell in the range of the global fallout values [31] and also agreed well with the results (the 240Pu/239Pu atomic ratios with an average of 0.174) measured in the Lake Yangcheng [30]. This indicated that Pu in the Lake Ge should also be mainly from the global fallout.
To accurately determine ultra-trace Pu isotopes in small environmental samples, we explored ICP-MS/MS in NH₃–He mode, and investigated mechanism of ²³⁸U interference removal and measurement sensitivity improvement for plutonium isotopes. The interference of uranium and uranium hydrides was effectively eliminated using 0.4 mL/min NH₃ as reaction gas by shifting them to U(NH_m)_n⁺ and UH(NH_m)_n⁺. The overall interference of uranium was reduced to <2.4 × 10⁻⁷, while remaining excellent ²³⁹Pu sensitivity (13,900 Mcps/(mg/L)) mainly due to ion focusing effect of Pu by helium gas. On this basis, the purification of plutonium using a single AG1- × 4 column was proved to be sufficient for accurate determination of plutonium isotopes by the developed detection method, and the detection limits for the method were estimated to be 0.16 fg (0.4 μBq) for ²³⁹Pu, 0.046 fg (0.4 μBq) for ²⁴⁰Pu and 0.039 fg (0.15 mBq) for ²⁴¹Pu. The method was validated by analyzing plutonium isotopes in certificated reference materials and reported environmental samples of only 1–2 g. The analytical results of ultra-trace Pu isotopes in small amounts (∼1 g) of lake sediments obtained by the developed method were successfully applied to sediment dating.
Vertical and spatial distribution of plutonium and radio-cesium in lake sediment of China
2022, Nuclear Analysis
Anthropogenic radionuclides of plutonium and ¹³⁷Cs in the environment were usually applied for tracing the environmental impact of nuclear activities as well as establishing the chronology of recent lake sediment. In this study, the vertical distribution and spatial differentiation of plutonium and ¹³⁷Cs in lake sediments of China were systematically contrastive analyzed to elucidate the regional influence by the local fallout from Chinese nuclear tests. The results demonstrated that the inventory of ¹³⁷Cs and ^239,240Pu, and their isotopic composition in lake sediments in northwestern China were obviously different from other regions, indicating that a portion of radionuclides in lakes in northwest China were originated from the Chinese Lop Nor Nuclear Test site (CNTs), and radionuclides in lakes of other regions may be completely originated from global fallout. Usually, the anthropogenic radionuclides recorded in lake sediments showed a single peak corresponding to the maximum deposition of 1964. However, two or three accumulation peaks of radionuclides were also observed in a few lakes. For the application of radionuclides on the dating of recent sediment, the accumulative peak of ^239,240Pu and ¹³⁷Cs signed to the period of 1963–1964 is the only practicable time marker for lake sediments in other regions of China. Isotopic information, such as ²⁴⁰Pu/²³⁹Pu ratio and ^239,240Pu/¹³⁷Cs activity ratio, may be useful for accurate sediment chronology, as well as used as a fingerprint to identify the source of the associated radioactive substance in the environment.
Distribution of plutonium isotopes in soils between two nuclear test sites: Semipalatinsk and Lop Nor
2022, Journal of Environmental Radioactivity
Plutonium (Pu) has attracted attention as an environmental tracer due to its radiotoxicity and the possibility of sources linked with nuclear accidents in recent years. Plutonium isotopes (^239,240Pu) were detected at trace levels in soils collected from the Xinjiang region located between the Semipalatinsk nuclear test site and China's Lop Nor nuclear test site. Little is known regarding the spatial variation of ^239,240Pu in soils from this region. This study reports the use of Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICP-MS) methods to distinguish between Pu isotopes derived from global fallout and nuclear weapon tests. We found that the ^239,240Pu activity concentrations ranged from 0.035 to 1.338 mBq/g; the ²⁴⁰Pu/²³⁹Pu atomic ratios were 0.157–0.223 with a weighted average of 0.180 ± 0.002, corresponding with the expected average global fallout ratio of 0.180 ± 0.014. This indicated that global fallout is the major source of Pu in the study region. The ^239,240Pu inventories in these soils ranged from 23.67 to 222.7 Bq/m², corresponding with those from other areas in China and other countries within the latitude range. Our Pu isotope data was supplemented with other published Pu data for soils collected in the vicinity of the Semipalatinsk nuclear test site and Lop Nor nuclear test site. Results indicate that ^239,240Pu inventories and ²⁴⁰Pu/²³⁹Pu atomic ratios in soils exhibit large variations with distance from the Semipalatinsk nuclear test site. High deposition and accumulation of Pu, and low ²⁴⁰Pu/²³⁹Pu ratios were observed in close-in fallout and downwind regions of the Semipalatinsk nuclear test site and China's Lop Nor nuclear test site.
Distribution and source identification of Pu in the tidal flat wetlands of northern Jiangsu Province and radial sand ridge of southern Yellow Sea-An explanation of “land-sea interaction”
2021, Catena
Citation Excerpt :
These samples maybe received PPG close-in fallout Pu from the currents from the south of the ECS. Compared with the previous study results, most of the 240Pu/239Pu atom ratios in our study were consistent with the ratios in the soils of China (0.19) (e.g. Dong et al., 2010; Lindahl et al., 2011; Bu et al., 2014, 2015, 2018; Xing, 2015; Xu et al., 2017; Zhang et al., 2018; Xing et al., 2018; Huang, 2019; Guan et al., 2018, 2020), which indicated that the Pu in our samples was from the global fallout. While the 240Pu/239Pu atom ratios in our study samples were lower compared with the ratios in the samples of China Seas, both seawater and sediment, except for samples in the northern Yellow Sea (~0.18) (Xu et al., 2018) and the Liaodong Bay (0.173–0.241) (Zhuang et al., 2019).
²³⁹Pu, ²⁴⁰Pu in the surface sediments from tidal flat wetlands in northern Jiangsu Province and radial sand ridge in southern Yellow Sea were analyzed by SF-ICP-MS. Tidal flat wetlands and radial sand ridge are the special sediment deposits in coastal area, which are the ideal places to study “land-sea interaction”. The ²⁴⁰Pu/²³⁹Pu atom ratios in our research samples show that the Pu in most samples is from global fallout, only the Pu in a few samples near Yangtze River Estuary and channel of radial sand ridge is affected by the close-in Pu fallout from Pacific Proving Grounds (PPG), and the contribution of Pu from PPG is 41.5–50%. In composition, since the study samples are mainly sand, the ^239+240Pu activities in our samples are lower than those in river sediments of China. The transport of Pu is a very important scientific issue, and researches have shown that Pu is “transported” into the coastal areas and seas from the land- based “source”. In addition, the Pu distribution in coastal areas and seas is affected by the input of rivers and ocean currents, which is a manifestation of the “land-sea interaction”.

View all citing articles on Scopus

View full text

Characteristic of Pu from urban wetland and lacustrine sediments in Suzhou Industrial Park, China

Highlights

Abstract

Introduction

Section snippets

Sample collection and preparation

239+240Pu activity concentration and its distribution in surface soils in Suzhou

Conclusions

Declaration of competing interest

Acknowledgments

J. Environ. Radioact.

J. Environ. Radioact.

Nucl. Instrum. Methods Phys. Res. B

Mar. Pollut. Bull.

Sci. Total Environ.

Sci. Total Environ.

Spectrochim. Acta, Part B

Appl. Radiat. Isot.

J. Environ. Radioact.

Nucl. Instrum. Methods B

Earth Planet. Sci. Lett.

Sci. Total Environ.

Chemosphere

J. Environ. Radioact.

Talanta

Environ. Pollut.

J. Environ. Radioact.

A method of measurement of 239Pu, 240Pu, 241Pu in high U content marine sediments by sector field ICP-MS and its application to Fukushima sediment samples

Environ. Sci. Technol.

Pu isotopes in soils collected downwind from Lop Nor: regional fallout vs. global fallout

Sci. Rep.

^239+240Pu activity concentration and its distribution in surface soils in Suzhou

A method of measurement of ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu in high U content marine sediments by sector field ICP-MS and its application to Fukushima sediment samples