Masaharu Tanimizu

JNdi-1 : a neodymium isotopic reference in consistency with LaJolla neodymium

Abstract A neodymium oxide with relative 143Nd/144Nd ratio 1.000503±1(1 σm) to LaJolla Nd was prepared as a new isotopic reference. The neodymium reagent was selected from two points of view as follows. The first is low abundance of neighboring elements Ce and Sm, which affects isobaric interference. The second is high 143Nd/144Nd ratio, which is closer to those of chondritic and mantle-derived materials. The 143Nd/144Nd ratio of the reagent was measured alternately with LaJolla Nd to get a coherency with LaJolla Nd using 12 mass spectrometers in 11 laboratories in Japan. Aliquots of this neodymium oxide reagent named JNdi-1 are available upon request from the Geological Survey of Japan and may be useful for precise interlaboratory calibration of Nd isotopes.

Anthropogenic lead inputs to the western Pacific during the 20th century.

Unlike in the North Atlantic, no continuous record of anthropogenic lead (Pb) has been available in the western Pacific. We reconstructed historical changes in anthropogenic Pb on the basis of Pb isotope ratios recorded in annually-banded coral retrieved from Ogasawara Island, Japan. Whereas the predominant natural source of Pb to the surface of the western Pacific apparently is Chinese loess, anthropogenic Pb has affected the western Pacific at least since the late 19th century. From the late 19th to the early 20th century, Australian Pb used in Japan was an important source of anthropogenic Pb. During 1920-1940, Pb emitted from parts of the world other than Japan contributed somewhat to the western Pacific, and the amount of Pb imported from Australia declined. Alkyl Pb used in Japan became the main source from 1950 until the mid-1970s, when leaded gasoline began to be regulated in Japan. Since the mid-1980s, aerosols from China have been the predominant source of Pb in the western Pacific. During the 1990s, around 60% of Pb in the surface of the western Pacific was from Chinese aerosols. We also investigated the present spatial distribution and likely sources of Pb in the western Pacific by using coral samples. Enrichment in 208Pb, which is a characteristic of Pb from China, was found in all coral samples except that from Pohnpei, Micronesia, suggesting that at present anthropogenic Pb is transported to the western Pacific mainly from China via westerly winds.

Determination of ultra-low 236U/238U isotope ratios by tandem quadrupole ICP-MS/MS

Isotope ratios of 236U/238U were measured at levels below 10−7 by single collector ICPMS with a tandem quadrupole mass separation mechanism. Peak tailing of the prominent 238U+ ion beam on the 236U+ peak was reduced to the level of ∼10−10 by use of two quadrupole mass filters. The 235UH+ interference on 236U+ was efficiently reduced to a UH+/U+ ratio of 1 × 10−8 by an ion–molecule reaction between UH+ and O2 in a collision/reaction cell placed between the two quadrupoles. The resultant detection limit for 236U/238U measurement was better than those reported by any other ICPMS study. The 236U/238U ratios, measured as 236U16O+/238U16O+, were determined in the range 10−9 to 10−7 without correction for spectral interference. Accurate measurements of 236U/238U to as low as 1 × 10−10 are projected.

Isotopic constraints on biogeochemical cycling of copper in the ocean

Trace elements and their isotopes are being actively studied as powerful tracers in the modern ocean and as proxies for the palaeocean. Although distributions and fractionations have been reported for stable isotopes of dissolved Fe, Cu, Zn and Cd in the ocean, the data remain limited and only preliminary explanations have been given. Copper is of great interest because it is either essential or toxic to organisms and because its distribution reflects both biological recycling and scavenging. Here we present new isotopic composition data for dissolved Cu (δ(65)Cu) in seawater and rainwater. The Cu isotopic composition in surface seawater can be explained by the mixing of rain, river and deep seawater. In deep seawater, δ(65)Cu becomes heavier with oceanic circulation because of preferential scavenging of the lighter isotope ((63)Cu). In addition, we constrain the marine biogeochemical cycling of Cu using a new box model based on Cu concentrations and δ(65)Cu.

Determination of isotopic composition of dissolved copper in seawater by multi-collector inductively coupled plasma mass spectrometry after pre-concentration using an ethylenediaminetriacetic acid chelating resin.

Copper is an essential trace metal that shows a vertical recycled-scavenged profile in the ocean. To help elucidate the biogeochemical cycling of Cu in the present and past oceans, it is important to determine the distribution of Cu isotopes in seawater. However, precise isotopic analysis of Cu has been impaired by the low concentrations of Cu as well as co-existing elements that interfere with measurements by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The objective of this study is to develop a simple Cu pre-concentration method using Nobias-chelate PA1 resin (Hitachi High Technologies). This extraction followed by anion exchange, allows precise analysis of the Cu isotopic composition in seawater. Using this method, Cu was quantitatively concentrated from seawater and >99.9999% of the alkali and alkaline earth metals were removed. The technique has a low procedural blank of 0.70 ng for Cu for a 2L sample and the precision of the Cu isotopic analysis was ±0.07‰ (±2SD, n=6). We applied this method to seawater reference materials (i.e., CASS-5 and NASS-6) and seawater samples obtained from the northwestern Pacific Ocean. The range of dissolved δ(65)Cu was 0.40-0.68‰.

Coupled Ce-Nd isotope systematics and rare earth elements differentiation of the moon

Abstract 138Ce/142Ce and 143Nd/144Nd isotope ratios of lunar samples are determined to constrain the petrogenetic differentiation and evolution of the moon. High-precision Ce–Nd isotope data, well-defined Rb–Sr isochrons, and rare earth elements (REE) abundances of lunar samples show that unexpectedly low La/Ce ratios of evolved lunar highland samples are preserved from at least 3.9 Ga. Precise analysis of REE abundances indicates that the low La/Ce ratio results from a depletion of La relative to other REE. This depletion can be seen in pristine KREEP basalts and Mg-suite rocks from 3.85 to 4.46 Ga. As REE abundances of all these samples are controlled by the presence of a KREEP component, the depletion was probably inherited from a late crystallization sequence of the lunar magma ocean related to the production of the original KREEP component.

Identification of sources of lead in the atmosphere by chemical speciation using X-ray absorption near-edge structure (XANES) spectroscopy

Sources of Pb pollution in the local atmosphere together with Pb species, major ions, and heavy metal concentrations in a size-fractionated aerosol sample from Higashi-Hiroshima (Japan) have been determined by X-ray absorption near-edge structure (XANES) spectroscopy, ion chromatography, and ICP-MS/AES, respectively. About 80% of total Pb was concentrated in fine aerosol particles. Lead species in the coarse aerosol particles were PbC2O4, 2PbCO3 Pb(OH)2, and Pb(NO3)2, whereas Pb species in the fine aerosol particles were PbC2O4, PbSO4, and Pb(NO3)2. Chemical speciation and abundance data suggested that the source of Pb in the fine aerosol particles was different from that of the coarse ones. The dominant sources of Pb in the fine aerosol particles were judged to be fly ash from a municipal solid waste incinerator and heavy oil combustion. For the coarse aerosol particles, road dust was considered to be the main Pb source. In addition to Pb species, elemental concentrations in the aerosols were also determined. The results suggested that Pb species in size-fractionated aerosols can be used to identify the origin of aerosol particles in the atmosphere as an alternative to Pb isotope ratio measurement.

Determination of natural isotopic variation in nickel using inductively coupled plasma mass spectrometry

In this study, we measured natural isotopic variation of terrestrial nickel using multiple-collector inductively coupled plasma mass spectrometry. External precisions in 58Ni/62Ni, 60Ni/62Ni, 61Ni/62Ni, and 64Ni/62Ni ratios of 0.02%, 0.01%, 0.04%, and 0.09% (2 × standard deviation), respectively, were routinely obtainable for a Ni isotopic reference standard by correcting the mass discrimination effect with a 65Cu/63Cu ratio of 0.4456. Only a small isotopic variation of ±0.15‰ amu−1 was observed among seven commercially available reagent-grade nickel metals, while variation of ±0.20‰ amu−1 was observed for two nickel sulfide samples from Canada. The isotopic compositions of the two types of samples overlap. The overall variation of ±0.25‰ amu−1 corresponds to an uncertainty of 0.000 37 for the atomic weight of nickel; this uncertainty is twice the currently recommended value (56.6934 ± 0.0002) for the standard atomic weight of terrestrial nickel as proposed by IUPAC.

Heavy element stable isotope ratios : analytical approaches and applications

AbstractContinuous developments in inorganic mass spectrometry techniques, including a combination of an inductively coupled plasma ion source and a magnetic sector-based mass spectrometer equipped with a multiple-collector array, have revolutionized the precision of isotope ratio measurements, and applications of inorganic mass spectrometry for biochemistry, geochemistry, and marine chemistry are beginning to appear on the horizon. Series of pioneering studies have revealed that natural stable isotope fractionations of many elements heavier than S (e.g., Fe, Cu, Zn, Sr, Ce, Nd, Mo, Cd, W, Tl, and U) are common on Earth, and it had been widely recognized that most physicochemical reactions or biochemical processes induce mass-dependent isotope fractionation. The variations in isotope ratios of the heavy elements can provide new insights into past and present biochemical and geochemical processes. To achieve this, the analytical community is actively solving problems such as spectral interference, mass discrimination drift, chemical separation and purification, and reduction of the contamination of analytes. This article describes data calibration and standardization protocols to allow interlaboratory comparisons or to maintain traceability of data, and basic principles of isotope fractionation in nature, together with high-selectivity and high-yield chemical separation and purification techniques for stable isotope studies. FigureIsotope ratios of the elements can vary through almost all the chemical and biochemical reactions in nature

Correction to “A chemical kinetic approach to estimate dynamic shear stress during the 1999 Taiwan Chi-Chi earthquake”

[1] In the paper ‘‘A chemical kinetic approach to estimate dynamic shear stress during the 1999 Taiwan Chi-Chi earthquake’’ by T. Hirono et al. (Geophysical Research Letters, 34, L19308, doi:10.1029/2007GL030743), the equation for estimation of dynamic shear stress, the calculations provided for stresses normal to the fault, and the resultant shear stresses and frictional coefficients were incorrect. [2] The fourth sentence of paragraph 1 should read as follows. [3] The dynamic shear stress during the Chi-Chi earthquake was deduced to be 1.37 MPa, and the frictional coefficient to be 0.03–0.08. [4] The second sentence of paragraph 11 including equation (9) should read as follows. [5] From equations (2), (4), (8), and f(a) = (1 a), a in the center of the fault zone (x = 0) is expressed as