Atsuyuki Ohta

Seasonal characterization of dust days, mass concentration and dry deposition of atmospheric aerosols over qingdao, china

The seasonal characterization of dust days, mass concentration and dry deposition of atmospheric aerosols were investigated using the historical data of dust days observed over Qingdao during the period from 1961 to 2001 and ground-based aerosol sampling data collected in the period from May 2001 to November 2002. In Qingdao most of the dust days occurred in spring and in winter and no dust days existed in summer. The seasonal variation of the uplifting dust day over Qingdao was in phase with that analyzed over North China. The mean mass concentration of the total suspended particles (TSP) in spring, summer, autumn and winter was respectively 300, 110, 113 and 185 μg·m−3. The values and phase of the seasonal oscillation for fine particles were very similar to those for coarse particles except for the month March, during which the concentration of the coarse particles was about 4 times as high as that of the fine particles. Comparison between seasonal variation of mass concentration of aerosols and dust days indicated that high frequency of uplifting dust day was accompanied by high TSP mass concentration. The TSP mass concentration measured by the low-volume instrument was about 30% lower than that measured by high-volume instrument, though the two data sets are highly correlated (correlation coefficient=0.89). The dry deposition flux during the observation period from May 2001 to November 2002 ranged from 0.06 to 0.2 g·m−2·d−1 with a mean value of 0.13 g·m−2·d−1, which was about 1/3 as that over Beijing.

Influence of multi-electron excitation on EXAFS spectroscopy of trivalent rare-earth ions and elucidation of change in hydration number through the series

Abstract We have made a detailed study of the extended X-ray absorption fine spectra (EXAFS) at the K edge of aqueous Y ion and at L3 edges of aqueous lanthanide ions and thereby elucidated the systematic changes in their hydration structures. Anomalous peaks arising from double-electron excitation (2p, 4d → 5d, 5d) appear in the EXAFS signals of La3+-Tb3+ between 5-7 Å−1. We established a removal process of double-electron excitation from EXAFS spectra. Using that process, we confirmed that the intensity and energy position of the extracted double-electron excitation are comparable to previously reported data. The presence of double-electron excitation engenders a smaller error than the errors estimated in the fitting process. Consequently, double-electron excitation does not seriously affect the determination of the structures of REE3+ aquo ions in the first coordination sphere. Subsequent EXAFS analyses of hydrated REE3+ ions suggest that the hydration numbers, the interatomic distances, and the Debye-Waller factors decrease from 9.7, 2.55 Å, and 9.0 × 10−3 Å2 for La3+ to 7.9, 2.31 Å, and 5.7 × 10−3 Å2 for Lu3+. These parameters change as a sigmoid curve with increasing atomic number. The hydration structures of REE3+ ions are inferred to change from the nonahydrated structure for La3+-Nd3+ to the octahydrated structure for Tb3+-Lu3+ through intermediate structures for Sm3+, Eu3+, and Gd3+. In addition, the hydration state of Y3+ closely resembles that of Ho3+ because the two have almost identical ionic radii.

Coordination study of rare earth elements on Fe oxyhydroxide and Mn dioxides: Part II. Correspondence of structural change to irregular variations of partitioning coefficients and tetrad effect variations appearing in interatomic distances

Abstract Experimental distribution coefficients of rare earth elements (REEs) between Fe oxyhydroxides (FeOOH) and Mn dioxide (δ-MnO2) and solutions [KD(REE)] exhibit anomalous variations: preferential uptake of light REEs by Mn dioxide, a step-like trend in KD(REE) in the Er-Tm-Yb-Lu region, and fractionation of KD(Y) from KD(Ho). Extended X-ray absorption fine structure (EXAFS) spectroscopy was applied to determine coordination states of Er, Tm, Yb, Lu, and Y adsorbed onto FeOOH and δ-MnO2 to assess structural changes around the REE site. The structures obtained, combined with previously determined structures of light REEs-sorbed Fe and Mn samples, corresponded to variations found in KD(REE). The structural parameters in the first coordination sphere suggest that La, Pr, and Nd adsorbed onto δ-MnO2 have a distorted tenfold-coordination sphere and differ greatly from La-, Pr-, Nd-, and Sm-sorbed FeOOH, which have a mixture of eightfold- and ninefold-coordination spheres. In contrast, heavy REEs including Y adsorbed onto Fe and Mn samples’ local structures have an eightfold-coordination sphere. The preferential uptakes of light REEs by δ-MnO2 are explained by the structural change. The irregular variations of heavy REEs and Y fractionation from Ho in KD(REE) do not, however, correspond to any change found in the coordination sphere. During characterization of the first coordination sphere, the W-type tetrad effect appears in the series variation of interatomic distances of REE3+aq and REE-sorbed FeOOH and δ-MnO2. The occurrence of a tetrad effect indicates that the interatomic distances relate not only to the electrostatic field but also to a quantum field.

Coordination study of rare earth elements on Fe oxyhydroxide and Mn dioxides: Part I. Influence of a multi-electron excitation on EXAFS analyses of La, Pr, Nd, and Sm

Abstract Coordination states of rare earth elements (REEs) adsorbed by iron oxyhydroxide (FeOOH) and manganese dioxide (δ-MnO2) (REE = La, Pr, Nd, and Sm) were determined using extended X-ray absorption fine structure (EXAFS) spectroscopy. Multi-electron excitation, resulting in double-electron excitation (2p, 4d → 5d, 5d) for REE-LIII edge EXAFS spectra, possibly causes a considerable error in EXAFS analyses for light REEs. To obtain reliable structural parameters this study elucidates the effects of double-electron excitation on the local structure determination of light REEs on poorly crystallized FeOOH and δ-MnO2. For this study, anomalous features attributable to excitation are superimposed on EXAFS signals of La, Pr, Nd, and Sm samples in the 5.0-7.0 Å-1 k range. The relative intensity of the double-electron excitation to the LIII adsorption edge is <1.1%. Consequently, the double-electron excitation engenders a smaller error than those estimated in fitting for Pr, Nd, and Sm samples. However, significant correction is necessary for the determination of local coordination states of La samples: interatomic distances are 0.007-0.036 Å shorter after correction. The EXAFS analyses of REE-sorbed Fe samples show that adsorbed La, Pr, Nd, and Sm have a mixture of eightfold and ninefold coordination structures and form inner sphere complexes at the FeOOH surface. The determined structural parameters of light REE-sorbed δ-MnO2 suggest that adsorbed light REEs have distorted tenfold-coordination spheres consisting of six short and four long REE-O bonds and form inner sphere complexes. Their coordination structures are more disordered than those of aquo ions and FeOOH samples.

Comprehensive Survey of Multi-Elements in Coastal Sea and Stream Sediments in the Island Arc Region of Japan: Mass Transfer from Terrestrial to Marine Environments

The dispersion of sediments across terrestrial areas, estuaries, shelves, slopes, and basins in island arc regions is extremely active. Because Japan is surrounded by vast oceans, it is fundamentally important to know sediment characteristics and dispersal systems upon the shelf and slope in terms of the erosion, transport, and deposition of sediments. Coastal seas, especially inner bays, often sustain severe damage from anthropogenic activities. Geochemical characteristics of marine sediments provide valuable clues regarding the dispersion of sediments. So far, the diffusion and fixation process of elements in the vertical direction and the past sedimentary environment found in core samples have attracted considerable scientific interest. However, regional spatial distributions of the chemical compositions of sediments in land, estuaries, and coastal areas are less understood (e.g., Balls et al., 1997; Degens et al., 1991; Ibbeken & Schleyer, 1991; Irion et al., 1995; Karageorgis et al., 2005; Voutsinou-Taliadouri & Varnavas, 1995; Wang et al., 2008). To better understand the spatial distribution of the elements in the earth’s surface, a geochemical map is used. The purpose of the map is to obtain natural geochemical baselines on the earth’s surface because the geochemical history of the earth’s surface is a fundamental part of geo-information. Many countries have produced national geochemical atlases to explore mineral recourses and address growing concerns about environmental problems (Fauth et al., 1985; Gustavsson et al., 2001; Lis & Pasieczna, 1995; Shacklette & Boerngen, 1984; Thalmann et al., 1988; Weaver et al., 1983; Webb et al., 1978; Xie et al., 1997; Zheng, 1994). Simultaneously, cross-boundary and sub-continental geochemical mapping projects have actively been carried out (e.g., Bolviken et al., 1986; Reimann et al., 1998; Salminen et al., 2005). Furthermore, the International Geochemical Mapping Project (IGCP 259) was initiated in 1988 under the auspices of the UNESCO to compile data on the global geochemical composition of the earth’s surface (Darnley et al., 1995). Thus, geochemical mapping has been undertaken globally, but it is restricted to terrestrial areas because surveys of soils, stream sediments, and river water samples are easy. However, 70% of the earth’s surface is covered by water. Surveying marine sediments is important to elucidate the mass transfer from land to sea. The Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, has conducted research on the fundamental

Regional geochemical mapping in eastern Japan including the nation's capital, Tokyo

ABSTRACT For use in a nationwide geochemical mapping project, 496 stream sediment samples were collected in eastern Japan including the nations capital, Tokyo. The 51 elements were determined using ICP-AES and ICP-MS; their spatial distribution maps were created using geographic information system (GIS) software. Spatial distribution patterns of elemental concentrations in stream sediments are consistent with the distribution of surface geology. Heavy metals and toxic elements are highly elevated in the sediments associated with mineral occurrences, but their distributions are limited to a small area. Surveying for nationwide geochemical mapping avoids collection of samples near contamination sources. Nevertheless, high concentrations of P (P2O5), Cr, Ni, Cu, Zn, Sn, Sb, Hg, and Pb were found in populated areas. Results of statistical analyses – analysis of variance and a multiple comparison test – suggest that the enrichments are not coincidental phenomena, rather these sediment samples accurately represented contamination.

Preliminary Evaluation of Local Structure and Speciation of Lanthanoids in Aqueous Solution, Iron Hydroxide, Manganese Dioxide, and Calcite Using the L3-Edge X-ray Absorption Near Edge Structure Spectra

We elucidate the application of L3-edge X-ray absorption near edge structure (XANES) spectra to the local structural analysis of lanthanoids in aqueous solution, iron hydroxide, manganese dioxide, and calcium carbonate. The L3-edge XANES spectra of lanthanoid compounds showed sharp white lines. The full width at half-maximum (FWHM) values of lanthanoid aqua ions exhibited a convex tetrad curve in the series variation across the lanthanoid series. The variation is attributable to 4f electron orbitals and can be explained by the refined spin-pairing energy theory. For each lanthanoid, the FWHM values of lanthanoid compounds roughly decreased with increasing local coordination numbers. However, they did not faithfully reflect the local coordination sphere of the lanthanoid complex having a high and distorted coordination sphere and were rather sensitive to their chemical forms. The relationship between the magnitude of the FWHM values was determined by the crystal field splitting or degeneracy of 5d orbitals. The systematic variation of FWHM can be explained by the ligand strength of the ligand molecules (-H2O0, -O-, -OH-, -CO32-, -Cl-, and -O2-) that cause the crystal field splitting. Therefore, the FWHM values of L3-edge XANES of lanthanoid compounds may be more useful in speciation analysis rather than structural analysis.

Less impact of limestone bedrock on elemental concentrations in stream sediments

Abstract: Geological survey of Japan, National Institute of Advanced Industrial Science and Technology has created the nationwide geochemical maps of 53 elements using fine stream sediments (< 180 μm) in Japan. The spatial distribution patterns of elemental concentrations of stream sediments reflect faithfully the distribution of geology and mineral deposits. However, the exception is limestone bedrock, which insignificantly influences on elemental concentrations of stream sediments. To clarify the reason, we collected stream sediments from Akiyoshi-dai, where is underlain by the largest-scale limestone bedrock. Fine stream sediments (< 180 μm), whose drainage basins are occupied by limestones, have high CaO and Sr concentrations and intensive peak of calcite obtained by X-ray diffractometry. Examining variation of elemental concentrations against the particle size of sediments, the finer particle contains a higher proportion of calcite and has higher CaO concentration. However, CaO concentration (10–20 wt. %) in stream sediments is much lower than expected values (~50%); nevertheless limestone outcrops in more than 70 % in their watersheds. The contradictory finding is explained by less contribution of limestone clastics to river system because limestone bedrocks are easily dissolved by water (chemical weathering) but not susceptible to physical weathering and erosion process. In other words, the supply quantity of clastic materials from limestone bedrocks is much smaller than those of other rock types. In addition, Sr concentration in some samples does not correlate with either CaO concentration or the peak intensity of calcite; nevertheless Sr is expected to have similar chemical properties to CaO. The fact suggests that calcite formed from water oversaturated for calcium carbonate is supplied to river system; it has the different Sr concentrations from Akiyoshi Limestone.