239,240 Pu and 236 U records of an ice core from the eastern Tien Shan (Central Asia)

• Published in: Journal of Glaciology
• Main Authors: WANG, CHAOMIN, HOU, SHUGUI, PANG, HONGXI, LIU, YAPING, GÄGGELER, HEINZ WALTER, CHRISTL, MARCUS, SYNAL, HANS-ARNO
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2017
• Subjects: ice core; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/jog.2017.59; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143017000594

ABSTRACT Radioisotopes ( 239 Pu, 240 Pu, 236 U) formed during atmospheric nuclear weapons testing (NWT) can be used for dating and therefore be applied as markers of the beginning of the Anthropocene Epoch. Moreover, 240 Pu/ 239 Pu ratios enable source identification (general fallout, local emission sources). Ice core segments from a 57.6 m ice core to bedrock from eastern Tien Shan, China were selected for 239,240 Pu and 236 U analyses by using compact low-energy accelerator mass spectrometry. The observed 240 Pu/ 239 Pu atom ratios were 0.18 ± 0.02, with one exception, indicating global fallout. No evidence for emissions from the nearby local sources Lop Nor was observed. The total deposition rates during NWT for 239 Pu and 240 Pu amount to 1.55 × 10 9 atoms·cm −2 and 3.1 × 10 8 atoms·cm −2 , respectively. With the higher undisturbed fallout of 239 Pu compared with values reported for glaciers from European Alps at Col du Dome and Colle Gnifetti as well as from the polar region, the eastern Tien Shan glacier would be an ideal site for defining the start of the Anthropocene. 236 U is a rather new environmental tracer, while little is known about its global fallout from NWT. The observed deposition flux of 236 U during NWT amounts to 3.5 × 10 8 atoms·cm −2 at the drill site. The average 236 U/ 239 Pu ratio of 0.27 ± 0.09 is in good agreement with literature values from global fallout.