Shizuko Ambe

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.

“Multitracer” a new tracer technique — Its principle, features, and application

We established “Multitracer”, a new versatile radiotracer technique, for simultaneous tracing of a number of elements in various chemical, environmental, and biological systems. Metal foil targets (typically Au, Ag, Ge, Cu and Fe) are irradiated with C, N, or O ions accelerated up to 135 MeV/nucleon by RIKEN Ring Cyclotron. Radiochemical procedures have been developed to remove the target material leaving the nuclides as Multitracer solutions containing various radionuclides of Be, Na, Mg, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Te, I, Ba, Ce, Pm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, W, Re, Os, Ir, Pt, and Hg. Multitracers enable efficient tracing of a number of elements, and comparison of their behavior under strictly identical experimental conditions. Such features will be demonstrated by means of an example of application to a model experiment for the study of removal mechanism of various elements from the ocean.

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).

Effects of soil acidity on the uptake of trace elements in soybean and tomato plants

The effects of soil acidity on the uptake of trace elements (Co, Zn, Se, Rb, Sr, Y, Zr, Tc, Ru, Rh and Re) in soybean and tomato were studied by a multitracer technique. The soybean and tomato plants were cultivated on soils at pH 6.4 (normal soil) and 4.2 (acid soil) and administered with a multitracer for 15-60 d. In general, the uptake of cationic elements in the leaves and stems of soybean plants cultivated on acid soil became higher than those of plants cultivated on normal soil during the late period of growth. However, the effect of soil acidification on the uptake of the anionic element. Se, was quite different from that on the cationic elements. The uptake of Se by the plants cultivated on normal soil was higher than that of the plants cultivated on acid soil at all four harvest points. The uptake behavior of these elements in soybean was discussed in relation to their adsorption behavior on the same soil as was used for soybean cultivation. The growth of tomato plants was seriously affected by the soil acidity and lowering of uptake of elements was observed for the plants cultivated on acidified soil.

Multitracer study on transport and distribution of metal ions in plants

Transport and distribution of metal ions in rice and soybean plants were studied using multitracers produced by irradiating an Au target by 135 MeV/nucleon12C,14N, or16O ions accelerated by RIKEN Ring Cyclotron. The multitracer consisted of radioisotopes of the following elements: Be, Na, Sc, Mn, Fe, Co, Zn, Se, Rb, Sr, Y, Zr, Nb, Ag, Te, Ba, Ce, Pm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, Ir, and Pt. Rice and soybean plants were grown in a nutrient solution and also on soil containing a multitracer. γ-ray spectroscopy of different parts of the plants showed that all the elements were more or less taken up by roots, while appreciable transport to leaves and seeds was observed only for Mn, Zn, Se, Rb, Sr, and Ba.

Screening of plant species for comparative uptake abilities of radioactive Co, Rb, Sr and Cs from soil

In case of radioactive fallout, persistence of long lived nuclides in soil and subsequent transfer into the food chain through plants over a long period is the key factor. The possibility of “phytoremediation” is suggested to reduce the radionuclides in soil. To exploit the natural potential of some plants in absorbing or accumulating certain radionuclides and depleting the soil radioactivity, thirty-two plant species were tested under laboratory conditions for their comparative ability in taking up radioactive Rb, Co, Sr and Cs. Broccoli and tomato for Co, tomato, chard, sunflower and cucumber for Rb; cucumber, sunflower and turnip (Kyona) for Sr, and tomato, chard and cucumber for Cs were found to be effective compared to other species tested.

The use of a multitracer technique for the studies of the uptake and retention of trace elements in rats

The uptake by, and distribution and retention of radioactive isotopes in various organs of Wistar rats were examined using the multitracer technique. A hydrocholoric acid solution (pH 3) of a carrier-free radioactive multitracer was prepared from gold foil irradiated with a 14N beam of 135 MeV nucleon. The solution was administered orally to 12 7-week-old male rats. Urine and faeces were collected and each group of three rats was killed at 1, 2, 3 or 6 days after administration. The percentage of administered dose of the 17 elements, Mn, Co, Zn, As, Rb, Sr, Y, Eu, Gd, Er, Tm, Yb, Lu, W, Re, Ir and Pt in the organs blood and excreta were determined using gamma-ray spectrometry. Each element revealed its characteristic distribution among the different organs, including the blood. These results are discussed and compared with those of single-tracer experiments, and the advantages of the multitracer technique are presented.

FORMATION OF METALLOFULLERENES WITH HIGHER GROUP ELEMENTS

Abstract The formation of metallofullerenes was examined for 23 elements, and some experimental evidence was obtained for metallofullerenes with group-4, Zr and Hf, and group-5, Nb, elements. Relative yields of the metallofullerenes eluted at the retention time around those for M@C 82 (M=group-2 and -3 elements) were found to decrease exponentially as the group number increased. The yields for Fe and Co, namely group-8 and -9 elements, were estimated to be less than one hundredth of that for M@C 82 (M=lanthanoid)

Multitracer study on uptake and excretion of trace elements in rats

The multitracer technique was first applied to the investigation of the uptake and excretion behaviour of trace elements in rats. A multitracer solution, prepared by irradiation of a gold target with a 14N-beam from the RIKEN Ring Cyclotron, was orally administered to male Wistar rats. The uptake and excretion rates of 23 elements, Be, Mn, Co, Zn, As, Rb, Sr, Y, Zr, Ce, Pm, Eu, Gd, Tb, Er, Tm, Yb, Lu, Hf, W, Re, Ir and Pt, were simultaneously determined under strictly identical experimental conditions. For some of the elements, the results obtained were consistent with previous reports on uptake and excretion of the elements in animals. For the other elements, unique behaviour was revealed for the first time as described in the present work. These results show that the multitracer technique has excellent reliability and versatility for a comparative study of the uptake and excretion of many different elements in animals.

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.