Intercalibration of selected anthropogenic radionuclides for the GEOTRACES Program

Abstract

As part of the GEOTRACES Program, six laboratories participated in an intercalibration exercise on several anthropogenic radionuclides of interest. The effort was successful for 239,240Pu activity, 240Pu/239Pu isotope ratio, and 137Cs activity measured in filtered seawater samples from the Bermuda Atlantic Time Series station (BATS) and a site on the continental slope of the Northeastern U.S. A limited number of analyses were reported for 237Np, 241Am, 90Sr, and 238Pu in filtered seawater. Intercalibration of any of the isotopes of interest in filtered particulate matter was unsuccessful due to insufficient size of the samples distributed. Methods used were based on traditional radio-counting techniques and inductively coupled plasma mass spectrometry (ICP-MS). Although the majority of analyses were performed on samples ≥60 L, one lab demonstrated the ability to analyze several of the anthropogenic radionuclides on 10-20 L sample volumes using ICP-MS

Rapid Method To Determine 137Cs, 237Np, and Pu Isotopes in Seawater by SF-ICP-MS

“…4,53 They were lower than those affected by the Sellafield nuclear fuel reprocessing plant (NRP) discharge such as in the Irish Sea (0.1−1.0 mBq L −1 ), 54 an area near the Sellafield NRP (9 mBq L −1 ), 55 and in the Danish Sea (0.65−1.69 μBq L −1 ), 8 etc., while they were higher than the estimated global deposition values (0.03−0.065 μBq L −1 ) (Table S5). 8,10 Moreover, the 237 Np/ 239 Pu atom ratios (9.0−19.2) were comparable to those in surface waters of the Western Atlantic Ocean (10) and Northwestern Mediterranean Sea (4), which are mainly influenced by global fallout, 4,53 but significantly lower than those of the Danish seawater (24.2−84.8) influenced by the Sellafield NRP discharge. 8 These results indicated that 237 Np in the northwest Pacific Ocean around the FDNPS site mainly originated from global fallout; however, the 240 Pu/ 239 Pu atom ratio (0.178−0.273) as a fingerprint for Pu source identification indicated that Pu in the study area was not only derived from global fallout but also from the Pacific Proving ground (PPG)-Pu input.…”

“…These values were consistent with the 237 Np activity concentrations in the Mediterranean (0.14−0.20 μBq L −1 ) and Western Atlantic Ocean (0.07−0.20 μBq L −1 ) that are mainly affected by global fallout. 4,53 They were lower than those affected by the Sellafield nuclear fuel reprocessing plant (NRP) discharge such as in the Irish Sea (0.1−1.0 mBq L −1 ), 54 an area near the Sellafield NRP (9 mBq L −1 ), 55 and in the Danish Sea (0.65−1.69 μBq L −1 ), 8 etc., while they were higher than the estimated global deposition values (0.03−0.065 μBq L −1 ) (Table S5). 8,10 Moreover, the 237 Np/ 239 Pu atom ratios (9.0−19.2) were comparable to those in surface waters of the Western Atlantic Ocean (10) and Northwestern Mediterranean Sea (4), which are mainly influenced by global fallout, 4,53 but significantly lower than those of the Danish seawater (24.2−84.8) influenced by the Sellafield NRP discharge.…”

Changes in liquid and atmospheric inputs to the marine environment from land (including through groundwater), ships and offshore installations

“…The programme also includes anthropogenic radionuclides. As part of the programme, intercalibration efforts have demonstrated the ability to identify plutonium-239, plutonium-240 and caesium-137 from relatively small samples (Kenna and others, 2012). Radioisotope data collected through the GEOTRACES programme have also contributed substantially to the understanding of movements of material in the ocean (Malakoff, 2014).…”