Dana Lee Biddulph

Iodine-129 in Seawater Offshore Fukushima: Distribution, Inorganic Speciation, Sources, and Budget

The Fukushima nuclear accident in March 2011 has released a large amount of radioactive pollutants to the environment. Of the pollutants, iodine-129 is a long-lived radionuclide and will remain in the environment for millions of years. This work first report levels and inorganic speciation of (129)I in seawater depth profiles collected offshore Fukushima in June 2011. Significantly elevated (129)I concentrations in surface water were observed with the highest (129)I/(127)I atomic ratio of 2.2 × 10(-9) in the surface seawater 40 km offshore Fukushima. Iodide was found as the dominant species of (129)I, while stable (127)I was mainly in iodate form, reflecting the fact that the major source of (129)I is the direct liquid discharges from the Fukushima NPP. The amount of (129)I directly discharged from the Fukushima Dai-ichi nuclear power plant to the sea was estimated to be 2.35 GBq, and about 1.09 GBq of (129)I released to the atmosphere from the accident was deposited in the sea offshore Fukushima. A total release of 8.06 GBq (or 1.2 kg) of (129)I from the Fukushima accident was estimated. These Fukushima-derived (129)I data provide necessary information for the investigation of water circulation and geochemical cycle of iodine in the northwestern Pacific Ocean in the future.

Geomagnetic modulation of the late Pleistocene cosmic-ray flux as determined by 10Be from Blake Outer Ridge marine sediments

Abstract The cosmic-ray flux incident upon the Earth during the late Pleistocene, 20–60 kyr B.P., was studied by measuring the cosmogenic radionuclide 10 Be from a marine sediment core at site CH88-10P on the Blake Outer Ridge. The paleointensity of the geomagnetic field for this core was determined by various methods. The variance in the concentration of 10 Be in the authigenic fraction of the sediments from Blake Ridge closely correlates with the inverse of the variance in the paleointensity of the geomagnetic field. The 10 Be signal lags, up to 1000 years of sedimentation, the measured paleointensity of the sediments. In contrast, the data from several other elements, some climatically sensitive, and from beryllium show relationship neither to 10 Be nor to the paleomagnetic data. The relationship between 10 Be concentration and the dipole field intensity ( M / M o ) as measured in the sediments is consistent with theoretical models.

Iodine-129, 87Sr/86Sr, and trace elemental geochemistry of northern Appalachian Basin brines: Evidence for basinal-scale fluid migration and clay mineral diagenesis

Evidence for basin scale brine migration and clay mineral diagenesis in the northern Appalachian Basin was investigated using elemental and isotope (129I/I, 87Sr/86Sr) geochemistry of formation waters collected from the Middle to Upper Devonian section of the northern basin margin in western New York, northwest Pennsylvania, and eastern Kentucky. One sample from each of the Mississippian Berea sandstone and the Silurian Medina sandstone were analyzed for comparison. Measured iodine ratios range between 28 to 1,890 × 10−15 and are anomalously high compared to cosmogenic iodine sourced from Devonian age organic matter. Iodine-129 in the waters was largely derived from fissiogenic sources, the spontaneous fission of 238U to produce 129I, with estimated 129I/I values up to 270 × 10−15, which occur locally in the organic-rich shales. There are three water samples that have values of 490 × 10−15, 860 × 10−15, and 1,890 × 10−15, which are above the range for local fissiogenic 129I and may be accounted for by topographically driven, basin scale fluid flow through a regionally high fissiogenic source. Relatively large uranium occurrences lie along the structural front of the Appalachian Basin in the Blue Ridge Province and are situated within hypothesized flow paths parallel to the main compressional direction of the Alleghanian orogeny. Estimated 129I/I values for these uranium occurrences are in excess of 55,000 × 10−15. The strontium isotope composition and Sr concentration of brines display a mixing trend between a highly radiogenic end-member (0.7210) with low Sr (51 mg/L) and a non-radiogenic (0.7100), high Sr (4789 mg/L) end-member. Potassium and boron concentrations are notably depleted relative to evaporated Paleozoic seawater, the hypothesized source of Appalachian Basin brines. The K/Rb values of formation waters are depleted relative to seawater values, but in some cases are well above values indicative of water-rock reactions. The Sr isotopic composition, K and B depletion, and intermediate K/Rb ratios are consistent with smectite diagenesis and paleo-temperatures that are likely greater than approximately 150 °C. These temperatures may be high given the burial history of the study area and support the flow of formation waters from deeper within the basin. The combined isotopic and elemental results of formation waters provide compelling evidence for basin scale fluid migration in the northern Appalachian Basin and are consistent with previously published evidence documented from the rock record, including clay mineral diagenesis and ore deposition.

Accelerator mass spectrometry at Arizona: geochronology of the climate record and connections with the ocean.

There are many diverse uses of accelerator mass spectrometry (AMS). Carbon-14 studies at our laboratory include much research related to paleoclimate, both with 14C as a tracer of past changes in environmental conditions as observed in corals, marine sediments and many terrestrial records. Terrestrial records such as forest fires can also show the influence of oceanic oscillations, whether they are short-term such as ENSO, or on the millennial time scale. In tracer applications, we have developed the use of 129I as well as 14C as tracers for nuclear pollution studies around radioactive waste dump sites, in collaboration with IAEA. We discuss some applications carried out in Tucson for several of these fields and hope to give some idea of the breadth of these studies.

Application of accelerator mass spectrometry to environmental and paleoclimate studies at the University of Arizona

Abstract A wide range of climatic, geologic and archaeological records can be characterized by measuring their 14 C and 10 Be concentrations, using accelerator mass spectrometry (AMS). These records are found not only in the traditional sampling sites such as lake sediments and ice cores, but also in diverse natural records. The purpose of this paper is to highlight some selected applications of AMS at the University of Arizona, including sample preparation, applications of AMS radiocarbon dating to learning about climatic changes in the past, modern 14 C studies, and 10 Be and 129 I measurements.

Two 60-year records of 129I from coral skeletons in the South Pacific Ocean

129I is an important radionuclide tracer for certain natural and anthropogenic nuclear processes. 129I has a half-life of 15.7 Myr and can be measured by accelerator mass spectrometry (AMS). This paper presents 129I results made at the University of Arizona with a NEC 3 MV Pelletron accelerator. For this study, we selected living corals from the Solomon Islands and Easter Island to monitor increases in anthropogenic 129I in the surface waters of the Pacific Ocean. 129I/127I values were measured in cores taken from massive Porites head coral skeletons. Typical sample sizes for this study were 10 g for the Solomon Islands corals, and 30 g for the Easter Island corals. Temporal resolution was semi-annual at the Solomon Islands, and annual at Easter Island. Iodine was extracted from the corals without the use of carrier iodine. Results of our study produced records at both sites from roughly 1935 to 1996. While 129I/127I values have increased at both locations since the beginning of atmospheric nuclear weapons testing, different bomb-pulse curves at these sites suggest different transport mechanisms and/or 129I inputs at the two sites. The implications of these measurements are discussed below.

STATUS OF THE NSF-ARIZONA AMS LABORATORY

Abstract The operation of the NSF-Arizona Laboratory is summarized. The methods used to determine accuracy and precision of radiocarbon measurements, and to make corrections for background contaminations are presented. An insulating support which has been installed, and a new heavy-ion beam line which is under construction, are described.

Accelerator mass spectrometry of long-lived light radionuclides

Abstract Many different kinds of paleoclimatic, geological and archaeological records can be characterized by measuring their radionuclide concentrations using accelerator mass spectrometry (AMS). The purpose of this paper is to highlight some applications of AMS, using studies conducted at the Arizona AMS Facility as examples. These include studies of 14 C, 10 Be, 26 Al, and 129 I. The work can be generally divided into two types: (1) methodological studies designed to refine and improve the capabilities of AMS, and (2) studies which utilize radiogenic isotopes as geochronometers or as geochemical tracers. Studies of the first type include the development of our 26 Al measurement capabilities, the construction on an automated sample preparation line and the construction of a plasma oxidation line. Studies of the latter type include 14 C dating of corals, speleothems and bones; new records of 10 Be from marine sediments and extraterrestrial materials; and 129 I studies of the pathways of this isotope in the surface ocean.

Measurement of the radioisotope 129I at the NSF-Arizona AMS laboratory

Abstract With the recent addition of a high-energy analysis beam line, the capability to measure 129I has been developed at the NSF-Arizona AMS Laboratory. Preliminary measurements have been made using the +4 and +5 charge states at 2.1 MV with a gas stripper. The current system employs a 90° injection magnet (r=0.36 m) following the ion source. Analysis components following the accelerator include an electrostatic quadrupole doublet lens, a 15° electrostatic deflector (r=1.25 m), a 90° analysis magnet (r=1.27 m) and a 77° spherical electrostatic analyzer (r=2.0 m). Detection of 129I is accomplished with a silicon surface barrier detector. Operation of this system with various iodine samples will be discussed.

Accelerator mass spectrometry at Arizona: geochronology of the climatic record and connections with the ocean.

There are many diverse uses of accelerator mass spectrometry (AMS). C studies at our laboratory include much research related to paleoclimate, with C as a tracer of past changes in environmental conditions as observed in corals, marine sediments, and many terrestrial records. Terrestrial records can also show the influence of oceanic oscillations, whether they are short term, such as ENSO (El Niño/Southern Oscillation), or on the millennial time scale. In tracer applications, we have developed the use of I as well as C as tracers for nuclear pollution studies around radioactive waste dump sites, in collaboration with IAEA. We discuss some applications carried out in Tucson, AZ, for several of these fields and hope to give some idea of the breadth of these studies.