. Dating recent sediment archives (  150 years) constitutes a
prerequisite for environmental and climatic reconstructions. Radiocaesium
( 137 Cs) emitted during thermonuclear bomb testing ( ∼  1950–1980) and nuclear accidents and the decrease in excess lead-210
( 210 Pb xs ) with depth are often combined to establish sediment core
chronology. Although these methods have been widely used during the last
several decades, there is a lack of structured and comprehensive worldwide
synthesis of fallout radionuclide analyses used for dating sediment cores in
environmental and Earth sciences. The current literature overview was based
on the compilation of 573 articles published between 1977 and 2020,
reporting the collection of 1351 individual dating sediment cores (the
dataset can be accessed at https://doi.org/10.1594/PANGAEA.931493 ; Foucher et al.,
2021). This review was conducted in order to map the locations where
 137 Cs fallout events were detected. These included the thermonuclear
bomb testing peak in 1963, the Chernobyl accident in 1986, the Fukushima
accident in 2011, and 24 additional events identified at 112 sites that led
to local or regional radioactive releases (e.g., Sellafield accidents,
Chinese nuclear tests). When 210 Pb xs records were used along with
 137 Cs data, detailed information on the 210 Pb xs age–depth
models were also synthesized. With the current growing number of studies analyzing sediment cores and the
increasing interest in the deployment of sediment fingerprinting techniques
including radionuclides as potential discriminant properties, this
spatialized synthesis provides a unique worldwide compilation for
characterizing fallout radionuclide sources and levels at the global scale.
This synthesis provides in particular a reference of 137 Cs peak
attribution for improving the sediment core dating, and it outlines the main
questions that deserve attention in future research as well as the regions
where additional 137 Cs fallout investigations should be conducted in
priority.

/pdf/a-worldwide-meta-analysis-1977-2020-of-sediment-core-dating-1d4fdfjttc.pdf

A worldwide meta-analysis (1977–2020) of sediment core dating using fallout radionuclides including 137 Cs and 210 Pb xs

Vertical distribution of Pu in forest soil in Qinghai-Tibet Plateau.

The 240Pu/239Pu atom ratio in Chinese soils.

The U-series and Pu isotope signatures in the environment have emerged as important tools for promoting geochemical studies. To enhance the understanding of U and Pu sources and behaviours in river systems, this study examined 234U, 235U, 236U, 238U and 239Pu, 240Pu isotopes in surface sediments collected from the Yangtze River catchment and estuary in China, for the first time. The 234U, 235U, 238U and 236U concentrations were measured in the range of 8.29–20.6 Bq/kg, 0.352–0.789 Bq/kg, 7.39–16.4 Bq/kg and (3.05–21.1) × 107 atoms/g. Additionally, the 236U/238U, 234U/238U and 235U/238U atom ratios were in the range of (1.43–6.85) × 10−8, (6.08–7.01) × 10−5 and (7.49–8.08) × 10−3 respectively. For all samples, the 239+240Pu activity concentrations ranged from 0.01 to 3.40 Bq/kg. In the Yangtze River catchment, 240Pu/239Pu atom ratios presented typical global fallout values (0.168–0.201); while in the Yangtze River estuary, higher values of 0.216–0.264 located between global fallout and PPG (Pacific Proving Grounds) close-in fallout values. From west to east, the 234U, 235U, 236U and 238U activities generally exhibited decreasing trend from the upstream parts of the river to the estuary. The values of 236U concentrations and 236U/238U, 240Pu/239Pu, 236U/239Pu atom ratios located in the range of global fallout level in environmental samples from other regions, therefore, it may be concluded that 236U in surface sediments of the Yangtze River catchment and estuary are mainly derived from global fallout.

Uranium and plutonium isotopes and their environmental implications in surface sediments from the Yangtze River catchment and estuary

/pdf/spatial-distribution-and-migration-of-239-240pu-in-chinese-2kv2a1nw.pdf

Spatial distribution and migration of 239+240Pu in Chinese soils.

Concentration and transport pathways of plutonium in the marine environment play an important role to assess the radioactivity as well as the ecological influence. In order to obtain the results of plutonium concentration from main sources along the coast of Guangxi, surface soil samples and sediment core were analyzed by ICP-MS. The results indicated that the concentration of 239+240Pu in the surface soils and sediments are in the range of 0.136–0.272 and 0.088–0.469 Bq/kg, respectively. The ratios of 240Pu/239Pu are in the range of 0.171–0.198, which coincides with the value of contribution of the global fallout. The sedimentation rate of Sanniang Bay (sample no. SN2) were measured by excess 210Pb, 137Cs and 239+240Pu, respectively.

Distribution and sources of plutonium along the coast of Guangxi, China

To determine the 237Np concentration originating from global fallout in the environment, samples were collected from Guangxi, south of China, and measured by accelerator mass spectrometry (AMS) at CIRCE. Serials standard samples and environment samples were prepared and measured using 242Pu as a tracer. The result indicates that the detection limit of 237Np as low as 10–15 g can be obtained. The concentration of 237Np in the environmental samples is less than 49.09 pg/kg (i.e. 1.280 mBq/kg), and the most probable value of 237Np is approximately 20 pg/kg (i.e. 0.53 mBq/kg).

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822219000675

Accelerator Mass Spectrometry Analysis of 237NP in Environmental Samples

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Distribution and sources of plutonium along the coast of Guangxi, China

Accelerator Mass Spectrometry Analysis of 237NP in Environmental Samples