Abstract:The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released large amount of radionuclides into the marine environment. Compared with the fission products, data on the distributions of Pu in the marine environment of the western North Pacific after the accident is limited. To better understand the Pu contamination in the marine environment after the accident, for the first time, we determined Pu isotope ratio ( 240 Pu/ 239 Pu) in addition to 239+240 Pu activity in seawater collected in the near coastal … Show more
“…The 239+240 Pu activity concentrations of the zone of >400 km from the FDNPP in this study (1.21–2.19 mBq/m 3 ) was typically in the range of the background data of the Northwest Pacific (Fig. 6 ) 18 , 19 , 24 , 46 , indicating negligible Pu contamination from the accident. Figure 6 Comparison of 239+240 Pu activities in this study with the historical 239+240 Pu data in surface seawater of the Western North Pacific.…”
Section: Resultssupporting
confidence: 49%
“…After the FDNPP accident, 239+240 Pu activity concentrations and 240 Pu/ 239 Pu atom ratios in seawater of Northwest Pacific were investigated to study if there was significant impact for Pu isotopes in seawater before and after the FDNPP accident. The seawater zone of <30 km, 30–200 km and >200 km off FDNNP were investigated respectively 19 , 24 , 38 – 40 . Their results suggested no significant Pu contamination from the accident in these areas.…”
Section: Resultsmentioning
confidence: 99%
“…The total seawater volume is ~1.37 × 10 18 m 3 15 , therefore, the resulting concentration of 239+240 Pu in seawater is extremely low (~mBq/m 3 or ~fg/L level). Moreover, the decreasing trend of 239+240 Pu activity concentration with an apparent half-residence time of 5–21 y in surface seawater of the world’s oceans since 1970 is still unchanged 16 – 19 . The 239+240 Pu activity concentrations in the surface seawater of the North Pacific decreased more than ten-fold from the early 1970 s (8.1–35 mBq/m 3 ) to the year 2000 (0.3–2.7 mBq/m 3 ) 16 .…”
In order to assess the impact of the Fukushima derived Pu isotopes on seawater, a new analytical method to rapidly determine Pu isotopes in seawater by SF-ICP-MS including Fe(OH)2 primary co-precipitation, CaF2/LaF3 secondary co-precipitation and TEVA+UTEVA+DGA extraction chromatographic separation was established. High concentration efficiency (~100%) and high U decontamination factor (~107) were achieved. The plutonium chemical recoveries were 74–88% with the mean of 83 ± 5%. The precisions for both 240Pu/239Pu atom ratios and 239+240Pu activity concentrations were less than 5% when 15 L of seawater samples with the typical 239+240Pu activity of the Northwest Pacific were measured. It just needs 12 hours to determine plutonium using this new method. The limit of detection (LOD) for 239Pu and 240Pu were both 0.08 fg/mL, corresponding to 0.01 mBq/m3 for 239Pu and 0.05 mBq/m3 for 240Pu when a 15 L volume of seawater was measured. This method was applied to determine the seawater samples collected 446–1316 km off the FDNPP accident site in the Northwest Pacific in July of 2013. The obtained 239+240Pu activity concentrations of 1.21–2.19 mBq/m3 and the 240Pu/239Pu atom ratios of 0.198–0.322 suggested that there was no significant Pu contamination from the accident to the Northwest Pacific.
“…The 239+240 Pu activity concentrations of the zone of >400 km from the FDNPP in this study (1.21–2.19 mBq/m 3 ) was typically in the range of the background data of the Northwest Pacific (Fig. 6 ) 18 , 19 , 24 , 46 , indicating negligible Pu contamination from the accident. Figure 6 Comparison of 239+240 Pu activities in this study with the historical 239+240 Pu data in surface seawater of the Western North Pacific.…”
Section: Resultssupporting
confidence: 49%
“…After the FDNPP accident, 239+240 Pu activity concentrations and 240 Pu/ 239 Pu atom ratios in seawater of Northwest Pacific were investigated to study if there was significant impact for Pu isotopes in seawater before and after the FDNPP accident. The seawater zone of <30 km, 30–200 km and >200 km off FDNNP were investigated respectively 19 , 24 , 38 – 40 . Their results suggested no significant Pu contamination from the accident in these areas.…”
Section: Resultsmentioning
confidence: 99%
“…The total seawater volume is ~1.37 × 10 18 m 3 15 , therefore, the resulting concentration of 239+240 Pu in seawater is extremely low (~mBq/m 3 or ~fg/L level). Moreover, the decreasing trend of 239+240 Pu activity concentration with an apparent half-residence time of 5–21 y in surface seawater of the world’s oceans since 1970 is still unchanged 16 – 19 . The 239+240 Pu activity concentrations in the surface seawater of the North Pacific decreased more than ten-fold from the early 1970 s (8.1–35 mBq/m 3 ) to the year 2000 (0.3–2.7 mBq/m 3 ) 16 .…”
In order to assess the impact of the Fukushima derived Pu isotopes on seawater, a new analytical method to rapidly determine Pu isotopes in seawater by SF-ICP-MS including Fe(OH)2 primary co-precipitation, CaF2/LaF3 secondary co-precipitation and TEVA+UTEVA+DGA extraction chromatographic separation was established. High concentration efficiency (~100%) and high U decontamination factor (~107) were achieved. The plutonium chemical recoveries were 74–88% with the mean of 83 ± 5%. The precisions for both 240Pu/239Pu atom ratios and 239+240Pu activity concentrations were less than 5% when 15 L of seawater samples with the typical 239+240Pu activity of the Northwest Pacific were measured. It just needs 12 hours to determine plutonium using this new method. The limit of detection (LOD) for 239Pu and 240Pu were both 0.08 fg/mL, corresponding to 0.01 mBq/m3 for 239Pu and 0.05 mBq/m3 for 240Pu when a 15 L volume of seawater was measured. This method was applied to determine the seawater samples collected 446–1316 km off the FDNPP accident site in the Northwest Pacific in July of 2013. The obtained 239+240Pu activity concentrations of 1.21–2.19 mBq/m3 and the 240Pu/239Pu atom ratios of 0.198–0.322 suggested that there was no significant Pu contamination from the accident to the Northwest Pacific.
“…The contribution of Chernobyl-derived Pu was confirmed to be negligible in the North Pacific Ocean 34 . The atomic ratios of 241 Pu/ 239 Pu and 240 Pu/ 239 Pu in seawater and marine sediments suggested that the Pu signal from the immediate impact and atmospheric deposition from the FNA was minor in the Pacific Ocean 12,16,18,[35][36][37]…”
Section: Resultsmentioning
confidence: 99%
“…However, the vertical structure of the 239+240 Pu inventory remains unclear. Furthermore, it was suggested that the 2011 Fukushima Nuclear Accident (FNA) exerted no immediate Pu impact on the northwestern Pacific Ocean 12,[15][16][17][18][19] . Overall, the limited available Pu data usually cover a local area, and therefore cannot yield unbiased interpretation for the Pacific Ocean as a whole.…”
This study examined plutonium (Pu) sources and distribution in the Pacific Ocean based on extensive field datasets over the past 50 years. The basin wide 240Pu/239Pu atom ratios in surface and deep seawater ranged from 0.192 to 0.279 averaging 0.235 ± 0.019, a value consistently higher than that of global fallout at ~ 0.180. The distribution of 240Pu/239Pu atom ratios exhibited a decreasing trend along the North Equatorial Current-Kuroshio to their extension areas. The activity levels of 239+240Pu in Pacific Ocean surface seawater ranged widely from 0.2 to 43.5 mBq m− 3, and increased with latitude. We determined the Pu sourced from the Pacific Proving Grounds (PPG) and global nuclear fallout in the Pacific Ocean based on the Pu isotopic composition. Using a mixing model, we found that the PPG made the dominant Pu contribution (average = 69.6 ± 14.4%) to Pacific Ocean surface seawater. The depth range of maximal 239+240Pu activity in the Pacific Ocean was well defined, averaging 608 ± 137 m. The vertical distribution of the 239+240Pu inventory showed most of Pu retained in the upper 3000 m, namely, the contributions of 239+240Pu inventories at 0-1000 m and 0-3000 m depths accounted for 43.5 ± 9.0% and 75.1 ± 12.0% of the total, respectively. We identified the transport pathway of Pu-PPG in the Pacific Ocean and demonstrated that Pu isotopes hold great promise as tracers of ocean circulation. Finally, via this extensive compilation of Pu isotopic compositions in the Pacific Ocean water, we established a Pu baseline in the region.
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