Susumu Osaki

Isotope geochemistry and petrology of African carbonatites

The carbonatite bodies examined are the Palabora, Spitskop and Premier Mine carbonatites of Precambrian age, the Mbeya carbonatite of Mesozoic age, Tertiary Homa Mountain carbonatite and the Recent eruptions of the Oldoinyo Lengai carbonatite. The field of oxygen and carbon isotopic ratios of the Palabora carbonatite, especially of the older carbonatite, coincides with that of primary igneous carbonatites. Spitskop carbonatite shows a slight deviation in oxygen and carbon isotopic ratios from primary igneous carbonatites. The Spitskop carbonatite forms a pipe-like body whose composition was modified after emplacement in several stages by circulating fluids which showed progressive enrichment in magnesium and iron. In the Premier Mine, the main carbonatite dyke mass intruded the centre of the black kimberlite. The oxygen isotopic compositions show a significant enrichment in their 18O compared to the “sub-volcanic” type carbonatites. Carbon and especially oxygen isotopic compositions show a considerable range in the Mbeya carbonatite. The fractionation factors of oxygen and carbon isotopes between the coexisting calcites and dolomites in the primary Mbeya carbonatites suggest that the carbonates crystallized at temperatures from 800°C to 380°C and > 700°C to 380°C, respectively. Carbon and oxygen isotopic compositions of the Homa Mountain carbonatite show a considerable spread and this is probably due to interaction with atmospheric oxygen and meteoric water during eruption. Sodium carbonate lava from Oldoinyo Lengai is deliquescent and readily alters in air. The lower value of δ13C in the sodium carbonate lava is thought to be due to the partitioning of heavy carbon into a CO2 gas phase during vulcanicity. It appears to suggest that no genetical relationship exists between sodium carbonatite lava and evaporite trona.

Determination of chromium(vi) in natural waters by the sorption of chromium-diphenylcarbazone with xad-2 resin.

The sorption of the chromium(III)-diphenylcarbazone complex (Cr-DPC) with XAD-2 has been investigated, for use in the separation of Cr(VI) from Cr(III) species in natural waters. Cr-DPC is formed from the reaction of Cr(VI) with diphenylcarbazide, but Cr(III) species give no reaction in aqueous solution. The addition of sodium chloride or sodium beta-naphthalenesulphonate markedly enhances the sorption. The Cr-DPC sorbed on XAD-2 can be almost completely eluted with organic solvents, especially methanol, but about 5% of it is irreversibly sorbed and cannot be eluted. The excess of diphenylcarbazide and some of the organic matter in natural waters are also sorbed on XAD-2 but most of this can also be eluted with methanol. Organic matter which interferes with measurement of the absorbance of Cr-DPC can almost all be removed by extraction with chloroform. By use of these techniques, Cr(VI) in sea-water has been determined by the standard-addition method. Although about 50 litres of sea-water are necessary for the analysis, organic and colloidal Cr(III) species do not interfere.

The effect of organic matter and colloidal particles on the determination of chromium(VI) in natural waters.

The chromium(VI) contents of two water samples, a river water and a sea-water, were determined by means of solvent extraction with APDC (ammonium pyrrolidinedithiocarbamate) into chloroform and by co-precipitation with iron(III) hydroxide. The analytical results depended on the separation method used, possibly because of differences in the behaviour of the chemical species of chromium in natural waters. Various chromium species, including simple inorganic ions, organic complexes, Cr(III) adsorbed on inorganic colloids and Cr(III) combined with organic polymers, were prepared, and their analytical characteristics were investigated.

Adsorption of Fe(III), Co(II) and Zn(II) onto particulates in fresh waters on the basis of the surface complexation model I. Stabilities of metal species adsorbed on particulates

Abstract Particulates, fine sediments and residue from evaporation of the filtrate from fresh waters were sequentially extracted with several reagents, and concentrations of iron, manganese, cobalt and zinc were determined. Iron(III) and Co(II) in particulates were similar to those in fine sediments in both their contents and chemical forms. Concentrations of Zn(II) and Mn in particulates were higher than those found in fine sediment, and considerably different in their chemical speciation. The difference between Fe and Mn may be due to the difference in their oxidation potentials. The difference between Co and Zn may depend on their affinity for Fe or Mn oxides. Distributions of Fe(III), Co(II) and Zn(II) between particulates and water were determined and compared with those predicted on the basis of the surface complexation model. These results are generally consistent with theories that metal species dissolved in water exist as free ions or are considerably less stable than their surface complexes on particulates.

Biologically induced Po emission from fresh water

Behavior of Po in fresh waters was examined in laboratory culture experiments using fresh water collected from a small pool, Xi river and Xiqing lake, showing formation of volatile Po compounds followed by emission to air. Addition of tryptone to the fresh water cultures increased the emission of Po considerably along with a growth of microorganisms, suggesting a connection of chemoheterotrophs to Po emission. Participation of photoautotrophs was also considered because Po emission was increased when NaHCO3 was added to the fresh water cultures. The emission behavior of Po and S in these experiments appeared in different ways. The quantity of Po emitted was comparable to the previous culture experiments (Momoshima, Song, Osaki & Maeda, Environ. Sci. Technol., 35, 2956-2960, 2001) in which artificial culture medium containing 3% NaCl was used and inoculated with sea sediment extract. The biological support for Po emission, thus, would be a general phenomenon in fresh water as well as a seawater environment and is possibly a source for atmospheric Po.

Biodiffusion of 7Be and 210Pb in intertidal estuarine sediment

Abstract The profiles of 7 Be and 210 Pb in three kinds of sediments from the intertidal zones of the Tatara-Umi estuary, Fukuoka, Japan were measured. In a silty area, they were fitted on a simple biodiffusion model with the diffusion coefficients of (1–8) × 10 −7 cm 2 s −1 . Radioactive tracers of 22 Na, 85 Sr, 134 Cs, 59 Fe, 54 Mn, 57 Co and 65 Zn were added to the untreated or heated cores of the undisturbed sediments to examine bioactivity on the transfer of the radionuclides In the heated cores, paniculate tracers were hardly transferred. In the untreated cores, they were diffused heterogenously and showed peaks at intermediate depths, which suggested biodiffusion with conveyor-belt deposit feeders. Paniculate radionuclides in estuarine sediment in the silty area are supposed to be biodiffused mainly with macroorganisms such as crabs and bivalves.

Transfer of 7Be, 210Pb and 210Po in a forest canopy of Japanese cedar

The concentrations of 7Be, 210Pb and 210Po of ca. 60 parts of a whole tree of Japanese cedar and of underlying litter and soil samples were determined for studying their transfer in a forest canopy. The results suggest that the mean residence times of 7Be and 210Pb in the forest canopy were ca. 20 and 900 days, respectively, and the dry deposition rate of 7Be on the forest canopy was about a half of the total deposition rate.

Crystal structures and Mössbauer spectra of mixed-valence dinuclear iron(II,III) complexes: detrapped valence states†

Mixed-valence µ-phenolate bis(µ-carboxylate) diiron(II,III) complexes [FeIIFeIII(bpmp)(L)2][BF4]2 have been prepared, where Hbpmp represents 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol and HL is benzoic acid (Hba) 1, phenylacetic acid (Hpaa) 2, 3-phenylpropionic acid (Hppa) 3, 4-phenylbutyric acid (Hpba) 4, 5-phenylvaleric acid (Hpva) 5, 6-phenylhexanoic acid (Hpha) 6 or p-methoxybenzoic acid (Hmba) 7. The Mossbauer spectra were measured for the complexes and the crystal structures of 4 and 7 determined. Complexes 1, 2 and 4 show trapped Mossbauer spectra due to iron(II) and iron(III), 5–7 show detrapped Mossbauer spectra at 293 K and trapped ones at 78 K and 3 shows a similar temperature dependence to that of 1, but differs in some points. The quadrupole splittings and isomer shifts of 3 increase on rising temperature. The spectra are explained in terms of intramolecular electron exchange between two energetically inequivalent vibronic states FeA2+FeB3+ and FeA3+Fe B2+: the apparent valence states of the iron atoms are 2.2 and 2.8 on the Mossbauer timescale at 293 K. At both 293 and 130 K the cations of complex 7 sit on a center of symmetry, and the two irons in this cation are crystallographically equivalent. The mean Fe–O length is intermediate between FeII–O and FeIII–O values, which indicates that both iron atoms are in an averaged valence state at 293 and 130 K when considered in terms of a static description. However, Mossbauer spectra of the complex show that the valence states of the irons are localized to iron-(II) and -(III) at 130 K and are delocalized at 293K on the characteristic Mossbauer timescale. Complex 4 is composed of iron-(II) and -(III) moieties, in accordance with the observation that the valence states of the irons are localized on the Mossbauer timescale (10–7 s) at 293 K.

Atmospheric deposition of35S

The35S content in atmospheric deposition, aerosol and rain water was determined about every 10 days for a year with7Be,32P and some stable elements. Average35S concentrations were 110 mBq·m−2·d−1 for atmospheric deposition, 0.078 mBq·m−3 for aerosol in surface air and 45 mBq·l−1 for rain water. The ratios of7Be/35S were abnormally low, although most of32P/7Be showed the reasonable values corresponding to the residence times from 10 to 60 days. The excess35S suggests an external source of35S or/and a faster cycle of35S than that of7Be and32P.

Effects of metal ions and organic ligands on the adsorption of Co(II) onto silicagel

Cobalt(II) ions were adsorbed onto silicagel from solutions containing metal ions and organic ligands. Levels of < 10−4M Ca(II), Zn(II), Fe(III) and Mn(II) did not affect adsorption, while 10−3M Fe(III) and Mn, as hydroxides, enhanced adsorption in the low pH region. Glycine, nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) lower the rate of adsorption, as the surface complexation model predicts, but ethylenediamine did not interfere with adsorption. Humic and fulvic acids lowered the rate of adsorption in approximately the same manner as glycine. These effects are discussed in relation to the application of the surface complexation model to the adsorption of trace metal ions on particulates in fresh waters.