Yoshihiro Makide

Comparison of adsorption behavior of multiple inorganic ions on kaolinite and silica in the presence of humic acid using the multitracer technique

Abstract The influence of humate formation on the adsorption of various ions on kaolinite and amorphous silica was studied using the multitracer technique, i.e., the simultaneous application of a variety of radioactive tracers. The technique simultaneously provided the solid-aqueous distributions of 32 elements, namely, Be, Na, Sc, V, Cr, Mn, Fe, Co, Zn, Ga, As, Se, Rb, Sr, Y, Zr, Tc, Ru, Rh, Ag, Te, Ba, Ce, Pm, Eu, Gd, Tm, Yb, Lu, Hf, Re, and Pt, in the absence and presence of humic acid. Speciation calculations under our experimental conditions were also conducted for 19 elements among them, using our previous results on the stability constants of their humate complexes. Comparison of the pH dependences of each element and humic acid dissolved in the aqueous phase enabled us to evaluate the interaction between them. With the aid of the speciation calculation, we discussed the predominant species that would control the environmental behavior of each ion. Among the elements studied, it was suggested that humate formation greatly affects the behavior of rare earth elements, which would indicate that the environmental behavior of these ions is influenced by humic substances. For alkaline earth metals (Be, Sr, Ba), divalent transition metals (Mn, Co, Zn), trivalent transition metals (Cr, Fe), and Ag, the influence of the formation of humate complexes on their distribution behavior was observed. It was estimated that the organic-inorganic complex made up of inorganic particles (e.g., kaolinite and silica in this study) coated with humic substances, plays an important role in the behavior of various ions in the environment. For the other ions of V V , Ga, Rb, Zr, Ru, Rh, Te, Hf, and Pt, humate formation was not important, but other factors such as hydrolysis and adsorption on solid surfaces were predominant factors. Based on the present results and an equilibrium model expressed by stability constants of hydroxides and carbonates or oxalates, the environmental behaviors of various cations are compared. For the oxoanions found in this study, such as As V , Se IV , Tc VII , and Re VII , humate formation also was not important. The inhibiting effect, on the adsorption of ions onto the solid surface, of the humic acid coating on the surface was observed for the distributions of V V , As V , Se IV , Zr, Ru, Rh, Hf, and Pt. These results show that the adsorption of humic substances alters the nature of inorganic particles in adsorbing metal ions.

CO2 laser tritium isotope separation: Collisional effects in multiphoton dissociation of trifluoromethane

Multiphoton dissociation of ppm level CTF3 in CHF3 is reported. The effect of buffer gas pressure on the specific dissociation rates and the isotopic selectivity is investigated. Pulse energy dependence of the dissociation rates is converted to the intrinsic relation between the fractional conversion per pulse and the fluence by means of the new deconvolution technique. By addition of 100 Torr argon, the critical fluence of CTF3 was decreased from 136 to 34 J/cm2, while the intrinsic selectivity was increased from 34 to 580. In the absence of buffer gas argon, the fractional conversion per pulse exhibits two different pressure dependences. Unlike in the case below 15 Torr, the system shows strong pressure dependence and loss of the isotopic selectivity above 15 Torr. Possible application to the tritium removal process is also discussed.

A Survey of Trace Elements in Pteridophytes

Concentration of 11 trace elements (Ca, Sc, Cr, Fe, Co, Zn, Rb, Cs, Ba, La, and Ce) in 96 pteridophytes (fern and fern ally species) was determined by instrumental neutron activation analysis to evaluate a concentration range for each element and also to find species characteristic in the uptake of trace elements. Asplenium trichomanes was found to accumulate Sc, Cr, and Co to the highest concentrations among 96 pteridophytes. The highest concentration of Ca and Zn was observed for Asplenium obscurum. The other Pteridophytes exhibited only one element whose concentration was the highest. A positive correlation was found between the concentrations of Fe and Sc, and also between the concentrations of Cr and Co. The remarkable accumulation of lanthanides (La and Ce) was observed mainly in diversifying genera (Polystichum and Dryopteris in Dryopteridaceae, Diplazium in Woodsiaceae, and Asplenium in Aspleniaceae).

tritium isotope separation by CO2 laser-induced multiphoton dissociation of CTF3

Abstract Isotope separation of tritium at ppm concentration level was achieved by CO 2 laser-induced multiphoton dissociation of CTF 3 in CHF 3 with single-step separation factors exceeding 500. The effects of laser frequency, pulse energy, pulse duration, irradiation geometry, tritium concentration, sample pressure, and buffer gas were investigated.

CO2-laser isotope separation of tritium with pentafluoroethane-T (C2TF5)

Isotope separation of tritium by CO2 laser-induced multiphoton dissociation (MPD) of C2TF5 is reported for the first time. The MPD spectrum obtained for C2TF5 comprised a broad peak at about 940 cm−1 where C2HF5 was nearly transparent. The unimolecular dissociation of C2TF5 was induced with much lower laser fluence than that for CTF3, another working molecule we proposed for laser isotope separation of tritium. The mechanisms and kinetics of the dissociation of C2TF5 and C2HF5 were investigated under various experimental conditions: laser frequency, pulse energy, pulse duration, tritium concentration, sample pressure, buffer gas pressure and irradiation geometry. Single-step separation factors exceeding 500 were achieved with the most efficientP(20) line in 00o–10o0 transition at 944.2 cm−1.

Beneficial effect of rare earth elements on the growth of Dryopteris erythrosora

Summary Lanthanum was demonstrated to be beneficial to the growth of Dryopteris erythrosora , a fern species which accumulates rare earth elements (REEs) under natural conditions. The enhancement of its growth by La was much greater than that by Ca. The uptake rates of REEs were evaluated to be higher than that of Zn and almost equal to those of Sr and Co. The region in the mesophyll where REEs were concentrated was not the same as that of Ca. In mesophyll cells, REEs were observed mainly in chloroplasts. These observations suggest that REEs do not behave as a ‹super Ca› as was suggested for some plants, but that they are transferred to chloroplasts by special mechanisms, possibly for fulfilling yet unknown functions or being stored as a mechanism of detoxification.

Multitracer study on the uptake mechanism of yttrium and rare earth elements by autumn fern

Summary Irrespective of low bioavailability, some plant species accumulate Y and rare earth elements (REEs) to a great extent (accumulator species). The uptake mechanisms of Y and REEs were investigated for autumn fern, one of accumulator species. For comparison, plant species which accumulated poorly REEs (non-accumulator species) were also studied. In the present investigation, two noticeable phenomena were observed. (I) Autumn fern showed no ionic-radius dependence of Y-REE uptake by leaves, while non-accumulator species showed an extremely high uptake for Y compared with REEs. (II) Y-REE uptake by autumn fern was influenced by the addition of chelating reagents to the uptake solution, while no effect was observed for non-accumulator species.

Variations of stratospheric trace gases measured using a balloon-borne cryogenic sampler

Abstract For a better understanding of the cycles of atmospheric trace gases, we have continued to systematically collect air samples in the stratosphere over Japan since 1985, using a balloon-borne cryogenic sampler. The collection of the stratospheric air samples was also made twice over the Scandinavian Peninsula in 1997 and once over Japanese Antarctic station, Syowa in 1998. The air samples collected were analyzed not only for the concentrations of CO2, CH4, N2O and various halocarbons but also for their isotopic ratios. These measurements revealed that, in general, the concentrations of all gas components decreased and their isotopic ratios increased with increasing height, due to influence of atmospheric transport and photochemical destruction in the stratosphere. However, detailed inspection of the results indicated that the observed vertical profiles of the respective components were quantitatively different, depending on location and time. Stratospheric CO2 over Japan showed the secular increase with an average rate of 1.4 ppmv/year for the period 1985–1999.

Laser-induced fluorescence study on the interaction of Eu(III) with polycarboxylates

AbstractLaser-induced fluorescence spectroscopy was applied to obtaining hydration structure of Eu(III) complexes with synthetic polycarboxylates of poly(acrylic acid), poly(maleic acid), poly(methacrylic acid), and poly(a-hydroxyacrylic acid). Dependence of