Mutsuo Koyama

The role of Mn2+-rich hydrous manganese oxide in the accumulation of arsenic in lake sediments

Arsenic is present at high concentrations in the upper layer of Lake Biwa sediments and shows a depth profile similar to that of Mn. Adsorption experiments of As onto synthetic hydrous Mn oxide (HMO) in the presence of Mn2+ and the speciation of Mn in the sediment cores, suggest that the accumulation of As at the sediment surface results from post-depositional migration of arsenite in the sediment pore water followed by oxidation to arsenate at the sediment surface and adsorption onto Mn2+-rich HMO.

Compositional change of settling particles with water depth in the Japan Sea

Abstract Settling particles at five different water depths (890–3240 m) and a box core sample were collected in September 1984 in the Japan Sea (40°49.4′N, 138°40.7′E; 3350 m deep), and analyzed for major components and 25 elements. According to the vertical changes in elemental concentrations (Me) and elemental concentration ratios to aluminum (Me/Al), these elements are grouped into four types: (1) the elemental concentration increases with water depth and the Me/Al ratio remains almost constant vertically (Al, Sc, La, Th, Hf, V, Ta, K, Rb, and Cs); (2) both the elemental concentration and the Me/Al ratio decrease with depth (I, Ba, Ca, Sr); (3) both the elemental concentration and the Me/Al ratio increase with depth (Mn); and (4) the elemental concentration remains almost constant or increases a little with depth and the Me/Al ratio decreases with depth (As, Sb, Se, and Ag). These four types are named refractory, biogenic, scavenged, and biogenic-scavenged, respectively; the fourth type is recognized here for the first time. Fe, Co, Zn, and Br show maximum Me/Al ratios within the water column but are grouped as scavenged (Fe and Co) and biogenic-scavenged (Zn and Br) elements. The concentration changes of elements in the settling particles at 3240 m relative to the surface sediment suggest that elements except those of the refractory type are regenerated or liberated on or near the sea floor.

Preparation of dithiocarbamatecellulose derivatives and their adsorption properties for trace elements

Tosylcellulose was treated separately with aniline, benzylamine, n-butylamine and piperazine to give four different aminocelluloses which were further treated with carbon disulfide to furnish four dithiocarbamatecelluloses (AND, BZD, BUD and PID). A comparative study was made of their performance as adsorbents for several kinds of metal ions. PID, which has the highest degree of substitution of the dithiocarbamate group of the four derivatives obtained, was investigated for its adsorption behavior towards Ag+, As5+, Cd2+, Co2+, Cr3+, Cr6+, Cu2+, Fe3+, Hg2+, Mn2+, Pb2+, Sb5+; Se4+, Te4+ and Zn2+. PID showed good adsorption characteristics with relatively large capacities for Ag+, Cr6+, Cu2+, Hg2+, Pb2+ and Se4+ ranging from 9.5 to 370 mg g-1 of resin.

Partition of divalent and total manganese in organs and subcellular organelles of MnCl2-treated rats studied by ESR and neutron activation analysis

The possibility that Mn2+ is converted to other valency states in vivo was examined by measuring the ratio of Mn2+, determined by ESR, to total manganese, determined by neutron activation analysis combined with chemical separation, in various organs of control rats and rats treated with MnCl2. In control rats, the total manganese content was high in the thyroid, hypophysis, adrenal, pancreas, liver and kidney, but the Mn2+ contents of these organs were low. In rats treated with Mn2+, the total manganese contents of all organs increased, but the Mn2+ contents still remained low. With regard to subcellular distribution, the total manganese content was high in the nuclear and mitochondrial fractions of the liver and kidney, and in the microsomal and supernatant fractions of the pancreas. The ratio of Mn2+ to total manganese was relatively high in the microsomes of the liver and kidney of control rats, and in the nuclear fraction of the pancreas of Mn2+-treated rats. Thus, the distribution and behavior of manganese in the pancreas were different from those in other organs. Purified liver nuclei and mitochondria were demonstrated to contain manganese, indicating that manganese is tightly bound in each cellular compartment.

Electron transfer reactions and the nature of the solvent effect on tris-toluene-3,4-dithiolates of rhenium, tungsten, molybdenum and technetium

Abstract The electron transfer reactions of the tris-toluene-3,4-dithiolates of Re, W, Mo and Tc with organic bases have been investigated by means of spectrophotometry and voltammetry. The resultant salts such as [Ph3PH+] [Re(tdt)3−], [o-phenH+] [Re(tdt)3−] were isolated. The so-called solvent effect which is observed on dissolving the complex in a polar solvent such as acetone and dimethylformamide was successfully interpreted in terms of redox reactions between the complex and the dissolved water or solvent.

TRACE ELEMENTS IN LAND PLANTS! CONCENTRATION RANGES AND ACCUMULATORS OF RARE EARTHS, Ba, Ra, Mn, Fe, Co AND HEAVY HALOGENS

More than 2000 samales of land plant leaves, mostly of tree, have been analyzed by neutron activation analysis in order to find out macroscopic relations between distributions of chemical elements in plants and soil characteristics. The distributions of the elements in plants were also examined from the view point of botanical taxonomy or phylogeny. New species which accumulate Co, rare earths, Ba, Ra, heavy halogens and some other elements have been found. Capability or potentiality for accumulating elements could be related to higher ranks of taxonomy, that is, genus or family. The nature of soil is also found to have profound effects on the extent of accumulation of elements in plants.

Mechanisms of precipitation of manganese(II) in Lake Biwa, a fresh water lake

Abstract The precipitation mechanisms of Mn(II) were studied from the viewpoint of adsorption onto suspended solids (SS) and microbial oxidation of Mn in Lake Biwa. In aerobic water samples maintained in the laboratory, the concentration of dissolved Mn [Mn(II)] decreased at pH > 7 by microbially mediated oxidation. Filtration, autoclaving and irradiation of u.v. light of the water samples and the addition of NaN 3 inhibited the precipitation of Mn(II). The adsorption of Mn(II) onto SS was also appreciable at pH > 7, and attained equilibrium within at least 30 min. The oxidation rate of Mn(II) was much less than the adsorption rate. In various environments of the lake (bottom water, sediment surface, river mouth, etc.) the initial adsorption of Mn(II) and subsequent slow oxidation mediated by bacteria may be essential to the mechanisms of Mn(II) precipitation.

RADIOACTIVATION ANALYSIS OF ALUMINIUM, VANADIUM, COPPER, MOLYBDENUM, ZINC AND URANIUM IN NATURAL WATER SAMPLES USING ORGANIC COPRECIPITANTS

A method is described for the determination of trace metal ions, V, Al, Cu, Mo Zn, and U, in natural water samples by neutron activation analysis, using organic coprecipitation as a preconcentration method. The preconcentration of trace elements was accomplished by converting the dissolved trace metal ions into the oxine chelates atpH 5.2 and extraction of the chelates witho-phenylphenol which is a liquid above 56 °C and solidifies at room temperature. After cooling the extraction system, the fine particles of the organic phase were collected on a millipore filter and the precipitate was air-dried in a clean environment. The solid extract was wrapped up in a sheet of clean polyethylene and subjected to neutron irradiation in a reactor for less than 10 min at a thermal flux of 2·1013 n·cm−2·sec−1. γ-Ray spectrometry by a coaxial Ge(Li) detector connected to a 1024-channel PHA was performed on the irradiated sample without further chemical separation, and thus the ppb level concentration of the elements in natural water samples could be determined. The fundamental study of the collection of the trace elements is also described.

Aquation of hexahalogenotechnetium(IV)

Abstract Kinetic and equilibrium studies on the aquation of TcX62− were performed in ionic media which contained HX, LiX, NaX and/or KX (X = Cl, Br). The observed rate constant, κobs, was fount to be of the first-order with respect to [H+] and [X−] in the solution where Li+ ion was substituted for a part of H+ ion. Strong effect of cations on the reaction rates were observed with the Na+ or K+ substituted solutions.

Radioactivation analysis of hair a means of biological monitoring of the environment

With the aim of indicating environmental pollution effects by heavy metals on humans using hair, nondestructive activation analysis was applied to 382 normal Japanese hair samples (background level). Elemental contents of hair could be determined for Ag, Al, As, Br, Ca, Cd, Cl, Co, Cr, Cu, Fe, Hg, I, K, La, Mg, Mn, Na, S, Sb, Sc, Se, Sm, Ti, V and Zn. As these elements in hair have wide concentration ranges, the differences in concentrations distribution between groups (sex, age, permanent treatment and regional difference) are discussed. A method for hair sampling is presented.