Characteristics of artificial radionuclides in sedimentary soil cores from a volcanic crater lake. (December 2018)

• Record Type: Journal Article
• Authors: Yim, Seong A.; Chae, Jung-Seok; Byun, Jong-In; Ko, Suk-Hyung
• Is Part Of: Journal of environmental radioactivity. Volume 192(2018)
• Page Start: 532
• Page End: 542
• Publication Date: 2018-12
• Subjects: Artificial radionuclide -- Sedimentation -- Crater-lake; Radioactivity -- Periodicals; Radiation, Background -- Periodicals; Radioecology -- Periodicals; Radioactive pollution -- Periodicals; Environmental Pollutants -- Periodicals; Radioactive Pollutants -- Periodicals; Radioactivity -- Periodicals; Radioécologie -- Périodiques; Pollution radioactive -- Périodiques; Fond de rayonnement -- Périodiques; 539.752
• DOI: 10.1016/j.jenvrad.2018.08.006
• Languages: English
• ISSNs: 0265-931X

Abstract

Abstract: The distributions of 137 Cs, 237 Np, and 239+240 Pu activity concentrations in sedimentary soil cores of the volcanic crater-lake have been studied. The 240 Pu/ 239 Pu atom ratios measured by MC-ICP-MS and mutual activity ratios were examined. These results were used to evaluate the sedimentation characteristics of the crater-lake (Baengnokdam of Mt. Halla, Korea). The 137 Cs, 237 Np, and 239+240 Pu activity concentrations showed similar distribution patterns and one maximum peak was observed in each sediment core, except at St.10. For all sediment cores, the activity concentrations were in the range 1.03 × 10 0 –1.92 × 10 2 Bq·kg −1 dw for 137 Cs, 7.56 × 10 −3 – 7.15 × 10 0 mBq·kg −1 dw for 237 Np, and 5.20 × 10 −3 – 5.13 × 10 0 Bq·kg −1 dw for 239+240 Pu, respectively. The averaged 240 Pu/ 239 Pu atomic ratio (0.159) was slightly less than the global fallout ratio (0.176). The averaged inventories were estimated to be 9.21 × 10 3 ±5.34 × 10 3 Bq·m −2 for 137 Cs, 2.27 × 10 2 ±1.58 × 10 2 Bq·m −2 for 239+240 Pu, and 3.22 × 10 −1 ±1.78 × 10 −1 Bq·m −2 for 237 Np. The averaged 239+240 Pu/ 137 Cs and 237 Np/ 239+240 Pu activity ratios were 2.21 × 10 −2 and 2.21 × 10 −3, respectively. The mean sedimentation rates calculated using 239+240 Pu activity concentrations at the central area (St.30 – St.45) and at all stations (St.5 – St.75) were estimated to be 0.844 cm yr −1, and 0.767 cm yr −1, respectively. In addition, the sedimentation rates calculated using 210 Pb and 226 Ra were 0.856 cm yr −1 at depths of 0–35 cm and 0.204 cm yr −1 at depths of 35–55 cm. These results imply that the sedimentation in Baengnokdam was relatively slow (0.204 cm yr −1 ) until about 44 years ago and then became faster (0.856 cm yr −1 ) to the present. The excess 210 Pb dating is consistent with the sedimentation rate calculated from the vertical 239+240 Pu profile. Graphical abstract: Image 1 Highlights: This is the first report of radionuclides and sedimentation in the Korean volcanic crater-lake (Baengnokdam of Mt. Halla). The distributions of 137 Cs, 237 Np, 239+240 Pu and 240 Pu/ 239 Pu atom ratios were investigated in sedimentary soil cores. Sedimentation characteristics were estimated using horizontal and vertical information of the radioactive isotopes.