Determination and Assessment of Transuranic Isotopes (Pu, Np, Am) Activities and Isotopes Ratios in Antarctic Marine Sediments

• Main Authors: Xibin Han (11682241), Xiaoxiao Han (2855810), Zhihong Li (176839), Zhiyong Liu (160339), Yongcong Zhang (11682244), Liangming Hu (2527819)
• Format: Other Non-Article Part of Journal/Newspaper
• Language: unknown
• Published: 2021
• Subjects: Pharmacology; Biotechnology; Ecology; Inorganic Chemistry; Computational Biology; Environmental Sciences not elsewhere classified; Astronomical and Space Sciences not elsewhere classified; Biological Sciences not elsewhere classified; Chemical Sciences not elsewhere classified; new characteristic index; eight heavy metals; pu atom ratio; pu activity ratio; nuclear weapons tests; 241 </ sup; 240 </ sup; 237 </ sup; 179 ± 0; 037 ± 0; study marine sediments; pu activity ratios; pu /< sup; 239 </ sup; np /< sup; antarctic marine sediments; /< sup; marine sediments; n </; nuclear testing; marine particles; isotopes ratios; transuranic isotopes; sediment properties; sampling depth; positively correlated; organic matter; much higher; important influence; global fallout; enrichment efficiency; dominant source; different fractionations; current source; considerable amount; cold climate; certain region; 926 mbq; 58 ); 293 bq; 277 bq; 221 (<; 20th century; 010 (<; Antarctic; Antarc*; Antarctica
• Online Access: https://doi.org/10.1021/acsearthspacechem.1c00314.s001

Due to the nuclear testing in the 20th century, a considerable amount of anthropogenic transuranic isotopes ( 237 Np, 239, 240 Pu, and 241 Am) was produced, spread, and deposited in the natural environment including Antarctica. Here, activities of 239+240 Pu, 237 Np, and 241 Am in Antarctic marine sediments are determined by ICP-SF-MS, ranging from 0.008 to 0.293 Bq/kg for 239+240 Pu, from 0.057 to 0.926 mBq/kg for 237 Np, and from 0.027 to 0.277 Bq/kg for 241 Am. The dominant source of 237 Np, 239, 240 Pu, and 241 Am in the study marine sediments is global fallout. 240 Pu/ 239 Pu atom ratio is measured to be 0.179 ± 0.010 ( n = 17) on average, which is consistent with the global fallout of the nuclear weapons tests. Average 237 Np/ 239 Pu atom ratio for global fallout is suggested as 0.221 ( n = 58), which may be used as a new characteristic index to indicate the current source of Np in a certain region. Due to the different fractionations of Pu and Am by seawater and the enrichment efficiency of marine particles, 241 Am/ 239+240 Pu activity ratios in these samples (mean, 2.037 ± 0.040; n = 17) are much higher than global fallout. In addition, 237 Np/ 239 Pu atom ratio and 241 Am/ 239+240 Pu activity ratio are found to be positively correlated with the sampling depth. Furthermore, the correlation between organic matter and eight heavy metals with transuranic activities is revealed. The cold climate, latitude, and sediment properties have an important influence on the distributions of Np, Pu, and Am in these marine sediments of Antarctic.