Transport of radionuclides by sea-ice and dense-water formed in western Kara Sea flaw leads

摘要

A transport assessment of particle-bound and dissolved artificial radionuclides (Cs-137 and Pu-239,Pu-240) by sea-ice and dense-water formed in western Kara Sea flaw leads close to the Novaya Zemlya dumping sites is presented in this study. We both performed a "best estimate" based on available data, and a "maximum assessment" relying on simulated constant releases of 1 TBq Cs-137 and Pu-239,Pu-240 from individual dumping bays. The estimates are based on a combination of (i) the content of particulate matter in sea-ice; (ii) analytical data and numerical simulations of radionuclide concentrations in shelf surface deposits, suspended particulate matter (SPM), and the dissolved phase; and (iii) estimates of lead-ice and dense-water formation rates as well as modeling results of local ice drift pathways. In the "best estimate" case, 2.90 GBq Cs-137 and 0.51 GBq Pu-239,Pu-240 attached to sea-ice sediments can be exported from the lead areas toward the central Arctic basin. The radionuclide burden of the annually formed dense lead water in the "best estimate" amounts to 4.68 TBq Cs-137 and 0.014 TBq Pu-239,Pu-240. In the "maximum assessment", potential export-rates of ice-particle bound Cs-137 and Pu-239,Pu-240 toward the central Arctic would amount to 0.64 and 0.16 TBq, respectively. As much as approximate to 900 TBq Cs-137 and approximate to 6.75 TBq Pu-139,Pu-240 could be annually taken up by 34.75 dense-water rejected in the lead area. Assuming the (unlikely) instantaneous release of the total Cs-137 and Pu-239,Pu-240 inventories (approximate to 1 PBq and 10 TBq, respectively) from the Novaya Zemlya dumping sites into the dissolved phase, the dense lead water locally formed during one winter season could take up approximate to 90% of the Cs and approximate to 68% of the Pu released. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 42]