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• Pu tracer is successfully applied to evaluate soil erosion in the Loess Plateau. • Both of natural grassland and artificial forest rehabilitation were effective. • Artificial forest is superior for reducing soil erosion in the short-term. • Natural grass rehabilitation is better for inhibiting soil erosion in the long-term. Soil erosion is a critical threat to the agriculture and ecosystem in the Chinese Loess Plateau area. Ecological rehabilitation has been applied in large area for reduction of the soil erosion. Six soil depth profiles were collected from Nanxiaohegou watershed in the Loess Plateau in northwest China and analyzed for the activity concentrations of plutonium isotopes. The measured 240Pu/239Pu atomic ratios in all these samples (0.186±0.017) showed that the global fallout was the dominant source of plutonium in this region. An exponential decline of 239,240Pu activity concentrations with depth was observed in most of soil profiles. The total inventory of 239,240Pu in the reference site was calculated to be 110 Bq/m2, agreeing well with the reported total fallout value in this latitude. The soil erosion rates were estimated by comparison with the reference site to be 538–941 t/km2/yr in the most of sites. While an excessive inventory of 239,240Pu (186 Bq/m2) compared to the reference site was observed in one site in the base area, indicating a significant accumulation of soil occurred in this area. The soil erosion depths were estimated to be 2.4–4.6 cm in most of sites during 1963–2016, which can be classified as minor erosion. Compared with the erosion rates in the Nanxiaohegou watershed in 1963–2012 which was estimated by other methods, it is suggested that the natural grass is better for long-term ecological restoration, especially in slope area. [ABSTRACT FROM AUTHOR]

In order to measure trace plutonium and its isotopes ratio ( 240 Pu/ 239 Pu) in environmental samples with a high uranium, an analytical method was developed using radiochemical separation for separation of plutonium from matrix and interfering elements including most of uranium and ICP-MS for measurement of plutonium isotopes. A novel measurement method was established for extensively removing the isobaric interference from uranium ( 238 U 1 H and 238 UH 2 + ) and tailing of 238 U, but significantly improving the measurement sensitivity of plutonium isotopes by employing NH 3 /He as collision/reaction cell gases and MS/MS system in the triple quadrupole ICP-MS instrument. The results show that removal efficiency of uranium interference was improved by more than 15 times, and the sensitivity of plutonium isotopes was increased by a factor of more than 3 compared to the conventional ICP-MS. The mechanism on the effective suppress of 238 U interference for 239 Pu measurement using NH 3 -He reaction gases was explored to be the formation of UNH + and UNH 2 + in the reactions of UH + and U + with NH 3 , while no reaction between NH 3 and Pu + . The detection limits of this method were estimated to be 0.55 fg mL -1 for 239 Pu, 0.09 fg mL −1 for 240 Pu. The analytical precision and accuracy of the method for Pu isotopes concentration and 240 Pu/ 239 Pu atomic ratio were evaluated by analysis of sediment reference materials (IAEA-385 and IAEA-412) with different levels of plutonium and uranium. The developed method were successfully applied to determine 239 Pu and 240 Pu concentrations and 240 Pu/ 239 Pu atomic ratios in soil samples collected in coastal areas of eastern China. [ABSTRACT FROM AUTHOR]

Transuranium elements such as Np, Pu and Am, are considered to be the most important radioactive elements in view of their biological toxicity and environmental impact. Concentrations of 237Np, Pu isotopes and 241Am in two sediment cores collected from Peter the Great Bay of Japan Sea were determined using radiochemical separation combined with inductively coupled plasma mass spectrometry (ICP-MS) measurement. The 239,240Pu and 241Am concentrations in all sediment samples range from 0.01 Bq/kg to 2.02 Bq/kg and from 0.01 Bq/kg to 1.11 Bq/kg, respectively, which are comparable to reported values in the investigated area. The average atomic ratios of 240Pu/239Pu (0.20 ± 0.02 and 0.21 ± 0.01) and 241Am/239+240Pu activity ratios (3.32 ± 2.76 and 0.45 ± 0.17) in the two sediment cores indicated that the sources of Pu and Am in this area are global fallout and the Pacific Proving Grounds through the movement of prevailing ocean currents, and no measurable release of Np, Pu and Am from the local K-431 nuclear submarine incident was observed. The extremely low 237Np/239Pu atomic ratios ((2.0–2.5) × 10−4) in this area are mainly attributed to the discrepancy of their different chemical behaviors in the ocean due to the relatively higher solubility of 237Np compared to particle active plutonium isotopes. It was estimated using two end members model that 23% ± 6% of transuranium radionuclides originated from the Pacific Proving Grounds tests, and the rest (ca. 77%) from global fallout. [Display omitted] • Distribution of transuranium radionuclides in the sediment cores were investigated. • The contribution of transuranium from PPG was estimated to be 23 ± 6 %. • No measurable release of transuranium from K-431 incident was observed. • 237Np/239Pu atomic ratio might be unsuitable for the source identification. [ABSTRACT FROM AUTHOR]

Rapid bioassay method for plutonium in urine samples are employed to assess the possible internal dose resulting from exposure to plutonium in the event of a radiological and nuclear emergency. In this work, a rapid method for the determination of plutonium isotopes (239Pu and 240Pu) in large volume of urine samples was developed using tandem quadrupole ICP-MS combined with a high-efficiency sample introduction system (APEX-Ω). The mixture gases of NH 3 and He was employed to effectively eliminate the tailing of 238U and the uranium hydride ions (238U1H+and 238U1H 2 +) and significantly improve the measurement sensitivity of plutonium. The method was validated by analyzing urine samples spiked with known amounts of 239Pu and 240Pu ranging from 1 to 60 fg. The detection limits for the method were estimated to be 0.83 fg for 239Pu, 0.14 fg for 240Pu in 1 L of urine. [Display omitted] • Tandem quadrupole ICP-MS was utilized to measure Pu isotopes in large volume of urine samples. • The interference of 238U (0.23 cps) would be much less a concern at 4.0 mL min−1 NH 3 and 3.0 mL min−1 He. • The detection limits of 239Pu (0.83 fg/L) and 240Pu (0.14 fg/L) are suitable for Pu routine analysis of urine. [ABSTRACT FROM AUTHOR]

To accurately determine ultra-trace Pu isotopes in small environmental samples, we explored ICP-MS/MS in NH 3 –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 NH 3 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. [Display omitted] • The overall interference of uranium was reduced to <2.4 × 10−7 by mass-shift mode. • Ion focusing effect of Pu by He gas and KED resulted in excellent Pu sensitivity. • Single AG1- × 4 column is sufficient for accurate measurement of Pu in small samples. • Low detection limits of 0.4 μBq for both 239Pu and 240Pu and 0.15 mBq for 241Pu. • Measured results of ultra-trace Pu isotopes succeed in sediment dating application. [ABSTRACT FROM AUTHOR]