<sup>90</sup>Sr and <sup>89</sup>Sr in seawater off Japan as a consequence of the Fukushima Dai-ichi nuclear accident

Abstract

Abstract. The impact of the earthquake and tsunami on the east coast of Japan on 11 March 2011 caused a loss of power at the Fukushima Dai-ichi nuclear power plant (NPP) that resulted in one of the most important releases of artificial radioactivity into the environment. Although several works were devoted to evaluating the atmospheric dispersion of radionuclides, the impact of the discharges to the ocean has been less investigated. Here we evaluate the distribution of Fukushima-derived 90Sr (n = 57) and 89Sr (n = 19) throughout waters 30–600 km offshore in June 2011. Concentrations of 90Sr and 89Sr in both surface waters and shallow profiles ranged from 0.8 ± 0.2 to 85 ± 3 Bq m−3 and from 19 ± 6 to 265 ± 74 Bq m−3, respectively. Because of its short half-life, all measured 89Sr was due to the accident, while the 90Sr concentrations can be compared to the background levels in the Pacific Ocean of about 1.2 Bq m−3. Fukushima-derived radiostrontium was mainly detected north of Kuroshio Current, as this was acting as a southern boundary for transport. The highest activities were associated with near-shore eddies, and larger inventories were found in the closest stations to Fukushima NPP. The data evidence a major influence of direct liquid discharges of radiostrontium compared to the atmospheric deposition. Existing 137Cs data reported from the same samples allowed us to establish a 90Sr / 137Cs ratio of 0.0256 ± 0.0006 in seawater off Fukushima, being significantly different than that of the global atmospheric fallout (i.e., 0.63) and may be used in future studies to track waters coming from the east coast of Japan. Liquid discharges of 90Sr to the ocean were estimated, resulting in an inventory of 53 ± 1 TBq of 90Sr in the inshore study area in June 2011 and total releases of 90Sr ranging from 90 to 900 TBq, depending upon the reported estimates of 137Cs releases that are considered.

Cesium, iodine and tritium in NW Pacific waters – a comparison of the Fukushima impact with global fallout

“…This evaluation is, however, strongly dependent on the estimation of the 137 Cs liquid releases as the 90 Sr / 137 Cs activity ratios observed in seawater offshore Fukushima were used for the evaluation of the 90 Sr source term. Recently, Casacuberta et al (2013), analyzing 90 Sr in seawater samples collected in the NW Pacific Ocean during June 2011 (the KOK cruise, Buesseler et al, 2012), estimated the 90 Sr source term to be 0.09-0.9 PBq, which is very similar to that of Povinec et al (2012).…”

Short-term dispersal of Fukushima-derived radionuclides off Japan: modeling efforts and model-data intercomparison

“…This conclusion is further supported by the 90 Sr measurements at the KOK stations (Casacuberta et al, 2013). The distribution of 90 Sr, which is much less volatile than 137 Cs and thus came almost entirely from the oceanic source, is similar to that for 137 Cs, suggesting that both chemicals came from the same source.…”

“…This conclusion is supported by the radium-based analysis of Charette et al (2013), who reported a strong coastal signature in waters sampled during the KOK cruise. The result is further supported by the similarity between the measured 90 Sr and 137 Cs patterns, which suggests that both radionuclides came from the oceanic source (Casacuberta et al, 2013).…”

Hybrid Nanoparticle–Polymer Brush Composites for Detection of Low‐Level Radiostrontium in Water

“…Strontium‐90 is present in surface soil around the world mainly as a result of fallout from past atmospheric nuclear weapons tests, as well as nuclear plant accidents . Moreover, strontium as an element is relatively mobile and can move down with percolating water to underlying layers of soil and into groundwater . The maximum contaminant level allowable by the United States Environmental Protection Agency (EPA) for 90 Sr in public drinking water supplies is 0.33 Bq L −1 (USEPA, 2008) .…”