A total of 200 kg wet mass of sediment was collected from the Pacific Ocean (22o23’ N, 152°40' E) on 16 November 1997 during the ‘IAEA '97 Pacific Ocean Expedition’ to the NW Pacific Ocean with the research vessel Bosei Maru. The sediment was collected using box coring down to 35 cm of sediment depth. The sediment was first dried in open air and subsequently freeze dried leaving a total dry mass of 18 kg. The sample was then ground into powder, sieved through a 250 µm mesh, homogenized by mixing in a nitrogen atmosphere, bottled in polyethylene sealed bottles, (100 ± 5) g units, and coded as IAEA‑412 (for a total of 175 bottles). All bottles were sterilized at 25 kGy (60Co) in an irradiation facility.
Reference date for decay correction: 2019-01-01
Certified values for activity concentrations
(based on dry mass)
| Radionuclide | Certified value [Bq kg⁻¹] | Expanded uncertainty* [Bq kg⁻¹] |
| 40K | 561 | 26 |
| 137Cs | 5.66 | 0.17 |
| 210Pb‡ | 88.2 | 3.2 |
| 210Po† | 89.7 | 3.8 |
| 226Ra¤ | 27.4 | 1.0 |
| 228Ra# | 36.2 | 2.3 |
| 228Th+ | 36.3 | 1.1 |
| 232Th | 36.3 | 3.5 |
| 235U | 1.38 | 0.05 |
| 238U | 31.2 | 1.7 |
| 239Pu | 0.358 | 0.012 |
| 240Pu | 0.240 | 0.011 |
| 239/240Pu | 0.611 | 0.016 |
*The uncertainty is expressed as an expanded uncertainty using a coverage factor k = 2 estimated in accordance with the JCGM 100:2008 'Evaluation of measurement data - Guide to the expression of uncertainty in measurement' [1] and ISO Guide 35 [2].
†Polonium-210 is in secular equilibrium with 210Pb.
