Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Iodine 129 data collected from paired Niskin-CTD rosette.

Sampling onboard the KOK was conducted using paired Niskin bottles on a CTD/rosette. Sample bottles (HDPE, acid-cleaned with 2% nitric acid) were rinsed several times with sample water prior to filling. Bottles were filled, sealed, and taped, and stored in the dark.

129I analyses were made on total inorganic iodine. Iodine was extracted from seawater in a dedicated low-level 129I preparation laboratory, using an adapted version (Tumey et al. 2013) of a commonly-used solvent extraction procedure (Fehn et al., 1992; Michel et al., 2012; Moran et al., 1998; Schnabel et al., 2007; Suzuki et al., 2008). Briefly, 0.5 mg of a very low 129I iodine carrier (Woodward Iodine Corporation; ~2x10-14 129I/127I) was added to a 250ml aliquot of each seawater sample: i.e., a carrier to sample ratio of ~40:1. Through the addition of sodium sulfite and hydroxylamine hydrochloride dissolved inorganic iodine was reduce to iodide. The procedure calls for the addition of nitric acid following the sulfite and hydroxylamine additions. This addition reduces the pH and enables the reduction of iodate to iodide. The resulting iodide was oxidized to molecular iodine by the addition of nitric acid and sodium nitrite. Molecular iodine was extracted into chloroform and then back-extracted into an aqueous solution of sodium sulfite and potassium hydroxide. 129I analyses were made on silver iodide precipitated by the addition of silver nitrate. The precipitated silver iodide was rinsed with MQ water (3X), dried, and mechanically mixed with niobium powder prior to being loaded into individual stainless steel target holders.

Accelerator mass spectrometric analyses were made at the Center for Accelerator Mass Spectrometry (CAMS), Lawrence Livermore National Laboratory. Targets were analyzed in a sequence similar to that for 14C at CAMS (e.g., Guilderson et al., 2003) and normalized against an in-house prepared dilution of NIST SRM 4949C with Woodward Iodide. Targets were analyzed such that samples with a 129I/127I ratio of ≥1 x 10-11 were counted to ~3% counting statistics. 129I/127I ratios for process blanks, prepared by running MQ water run through the full extraction procedure, averaged 3.8 x 10-14 and were not subtracted from unknowns (ie., consistent with how data are reported in the literature).

In much of the open ocean, total dissolved iodine (speciated between iodate and iodide) is constant to a few percent of a concentration of ~60 ugI- l-1 (Barkley and Thompson, 1960; Elderfield and Truesdale, 1980; Nakayama et al., 1989). Such a value is consistent with iodine concentrations in waters off Japan with salinities > 30 psu (Zheng et al., 2012). Salinities observed in the R/V KOK hydrocasts had a limited range: 33.5-34.8 psu. For the data reported here, the salinity was 34.18 ± 0.29 psu (1-sigma sd). We expect a limited range in total dissolved iodine concentrations and use 60ugI-l l-1 estimated uncertainty of 2ugI-l-1 (1-sigma sd) in calculating the 129I/127I ratios derived from our measurements of seawater samples. All uncertainties during dilution and processing are considered independent and added in quadrature.

Individual replicates (n=15) were made on random samples spanning the range of values and analyzed across ~8 months of time. The average relative difference for all of the pairs was -0.3 percent.

We believe that Station 18, taken right after inclement weather with two aborted stations, had sample collection issues.
The bottles had two sets of labels on them. The 129I data imply that there are at least one pair of mislabeled bottles.
We recommend not using data from Station 18.
Station 32, bottle 16 - bad target. Anomalously low current. Redone

BCO-DMO Processing:
* Converted data to BCO-DMO standardized file format
* Created applicable BCO-DMO header.
* Mapped appropriate terms to BCO-DMO terminology

The March 11, 2011 earthquake in Japan and the subsequent tsunami damaged and disrupted cooling systems at the Fukushima Daiichi nuclear power facility causing contamination of land and seas surrounding the site, as well as food supplies and drinking water. Small but measurable quantities of radioactivity have been detected in the atmosphere over the United States, including aerosol samples collected at the Woods Hole Oceanographic Institution, where I-131 was seen to increase to detectable levels as of March 21-22, 2011.

With major funding from the Moore Foundation, as well as a contribution from the National Science Foundation through a 2011 Grant for Rapid Response Research (RAPID) and support from the Woods Hole Oceanographic Institution, collaborating investigators from the United States, Japan, Spain, Monaco, and the United Kingdom were able to obtain samples off Japan for an early assessment of impacts.

From June 4 through June 19, 2011, a research cruise was carried out aboard the RV Kaimikai-O-Kanaloa, a research vessel operated by the University of Hawaii. During the cruise, hundreds of samples were collected in an area off the coast of Japan as close as 30 kilometers from the Fukushima Nuclear Power Plant and extending as far out as 600 kilometers off shore. The essential components of the program include: radionuclide measurements of water and particles; a radioecological study of biota, especially species at the base of the food chain and key fish species and a physical oceanographic study to characterize transport and water masses. A baseline radionuclide data set for the Atlantic and Pacific was obtained along an east to west network of sampling stations. Three hundred sampling events took place at thirty major stations for a total of more than 1500 samples. Along with 41 CTD stations, bottle samples of salinity, oxygen, radionuclides, and particulates were taken to depths of about 1000 meters. A list of the radionuclides sampled and a sampling summary map is available. One hundred net tows resulted in approximately fifty pounds of biological samples, including plankton and small fish. Daily samples of aerosol were also taken.

Early investigation following an accidental release of man-made radionuclides is key to understanding the magnitude of the release and the relationship to public health issues The research results also set the stage for the use of the longer lived radionuclides as tracers in subsequent studies by the community to understand ocean processes.