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Featured researches published by Chitoshi Mizota.


Geoderma | 1990

Oxygen isotope composition of quartz in soils developed on late Quaternary volcanic ashes in Japan

Chitoshi Mizota; Minoru Kusakabe; Masami Noto

Oxygen isotope compositions of quartz isolated from 25 soil samples developed on late Quaternary volcanic ashes in Japan were determined. The δ18O values for aerosol sized quartz (1–10 μm in diameter) ranged from +10.9 to +17.5%. The variation is attributed to mixing of long-distance aeolian dust (δ18O=+16 to +17%) with variable amounts of local volcanic quartz (δ18O=+6 to + 8%). The δ18O values of soil quartz decreased systematically with the increasing particle size. The contribution of quartz derived from long-distance aeolian dust is higher in fine fractions ( 53 μm). Fine-grained quartz is often associated with hornblende in soils derived from volcanic ashes. Because large oxygen isotope fractionations (∼ 79%) between fine quartz (δ18O=+13%) and hornblende (δ18O=+6%) in bulk soil samples are unlikely in a normal magmatic equilibrium process, such fractionations are considered to result from post-depositional (secondary) mixing of the fine quartz incorporated by the eolian process. On the other hand, small oxygen isotope fractionations (< 2%) between coarse-grained quartz (+8%) and hornblende (+6%) indicate a volcanic origin.


Geoderma | 1988

Clay mineralogy and chemistry of seven pedons formed in volcanic ash, Tanzania

Chitoshi Mizota; I. Kawasaki; Toshiyuki Wakatsuki

Abstract Clay mineralogy and chemistry of seven pedons developed in Quaternary volcanic ashes under different moisture regimes in northern Tanzania have been studied. Total carbon, nitrogen and acid-oxalate soluble aluminum contents of soils increased and pH (H 2 O, M -KCl), exchangeable basic cations and available phosphorus contents decreased with increasing mean annual rainfall. High contents of clays in soil samples (410–860 g/kg) are believed to indicate advanced stages of weathering. An aluminum-humus complex, allophane and gibbsite predominated in soils under a perudic moisture regime, kaolinite and halloysite (0.7 and 1.0 nm) in those under udic to ustic moisture regimes. Resilication resulting from the seasonal drying of moisture regimes is considered to inhibit the release of “active” aluminum in the weathering of volcanic materials but to favour the authigenic formation of kaolinite and halloysite. Substantial amounts of vermiculite-chlorite intergrades were observed associated with fine-grained quartz in a perudic soil and mica in an aridic soil. Oxygen isotopic composition of fine aerosol-sized quartz suggests an eolian origin. Origin of clay mica is also discussed in the light of the oxygen isotope composition.


Clays and Clay Minerals | 1986

Curved smectite in soils from volcanic ash in Kenya and Tanzania; a low-angle X-ray powder diffraction study

S. J. van der Gaast; Chitoshi Mizota; J.H.F Jansen

Low-angle X-ray powder diffraction (XRD) measurements of soil samples, made at controlled relative humidities, showed the presence of major reflections at 20–33, 10–27, and 7–8 Å. The first reflection, which increased in intensity but did not shift in spacing with decreasing relative humidity, represents curved smectite layers. This spacing was also observed by high-resolution transmission electron microscopy. The value of 10–27 Å for the second reflection, the 001 reflection of smetite, is unusually high, probably due to poorly stacked, irregularly curved layers. The 7–8-Å reflection originates from kaolinite or dehydrated halloysite, which also contain curved layers. The more curved the layer structure of the smectite, the more difficult it is to detect this phase; therefore the XRD relative peak heights are not directly proportional to the percentages of the smectite.


Geoderma | 1980

Implications of clay mineralogy to the weathering and chemistry of AP horizons of ando soils in Japan

Chitoshi Mizota; Koji Wada

Abstract The clay mineralogy of 22 samples of the Ap horizons of Ando soils was determined by a combination of methods. Of these samples, 15 did and 7 did not contain allophane and imogolite. Opaline silica was found in 4 samples, whereas aluminum—humus complexes, iron oxides and layer silicates were found in all samples. The presence of allophane and imogolite and the absence of opaline silica in a few Ap horizons was related to mixing of A 1 horizons and subsoils by cultivation and to lower supplies of organic matter relative to the amounts of aluminum released from volcanic ash by weathering. The contents of 2:1 and 2:1:1 layer silicates and their intergrades were larger in soils in which quartz predominated in fine fractions. It was inferred that aluminum bound with humus and in allophane-like constituents, rather than aluminum in allophane and imogolite, is important in reactions with phosphate and fluoride.


Geoderma | 1991

The eolian origin of silty mantle in sedentary soils from Korea and Japan

Chitoshi Mizota; H. Endo; K.T. Um; Minoru Kusakabe; Masami Noto; Y. Matsuhisa

Abstract The concentration, particle-size distribution and oxygen isotope composition ( δ 18 O SMOW ) of quartz were examined in order to determine the extent to which the accretion of long-distance eolian dusts from the interior of China had formed the sedentary soils overlying diverse parent materials in Korea and Japan. The quartz content of the surface soils developed on quartz-free basaltic materials varies from 8.9 to 47.7%. Generally, the soil quartz found in surface horizons is finer than of the subsurface horizons and/or substrata. The particle-size of the soil quartz decreases from the west coast to eastern coastal margins of Korea and to the Japanese islands. This follows the major trajectory of westerly winds which carry the eolian dusts from the interior of China to mid-latitude regions of the North Pacific. The oxygen isotope composition of the fine quartz (1–10 μm in diameter) when separated from surface and subsurface horizons, is found in a relatively narrow range of + 15.9 to + 17.7‰ The values are indiscernible from those of recent eolian dusts from the interior desert and loess plateau of China. The δ 18 O values from the same sized quartz found in C horizons, + 10.4 and + 19.2%, consisting of saprolitic andesites and shales, respectively, differ from those of the overlying soils. The δ 18 O values of soil quartz developed on igneous materials systematically decrease with increasing particle-size to 53 μm (∼ 14%). They abruptly decrease to + 8 to + 12% for fractions larger than 53 μm. A large apparent oxygen isotope fractionation (up to 10%) - between fine (+ 17%) and coarse (+ 8 to + 12%) grained quartz observed in the samples - does not represent an equilibrium oxygen isotope fractionation for normal magmatic processes. The data provide evidence for an eolian origin of the fine quartz incorporated during soil development.


Soil Science and Plant Nutrition | 1982

Mineralogy of the tropospheric dusts in rainwater collected in Fukuoka, Northern Kyushu

Chitoshi Mizota

Abstract The mineralogical composition of the tropospheric dusts deposited by rainfall was examined during February to May, 1981 in Fukuoka. The dusts (0.5 to 37 mg/liter rainwater) contained quartz, mica, feldspar and some day minerals as common constituents. The dusts showed a definite mineralogical variation, serpentine minerals and talc witb appreciable amounts of amphibole being found in some. The mineralogical variation of the dusts during the collection periods was correlated with the surrace geology of the windward, arid to semi-arid regions in north China, from where the dusts derive. The integrated amounts of dusts incorporated by rainfall and dust storms (10 mm/102 years) indicated their importance to development of soil on old and stable landscape in northern Kyushu.


Soil Science and Plant Nutrition | 1975

Relationships between the petrological nature and the clay mineral composition of volcanic ash soils distributed in the suburbs of Fukuoka-City, Kyushu

Chitoshi Mizota; Shigenori Aomine

Abstract A contrasting occurrence of clay minerals was found within a soil profile which was derived from volcanic materials in the suburbs of Fukuoka-city, Northern Kyushu. The soil profile is located on an isolated terrace, and the morphological characteristics of the soil correspond exactly to Andosols, so-called Kuroboku soils or Humic Allophane soils. The clay fraction of upper horizons of the soil consists largely of alumina-rich gel-like materials, gibbsite, and layer silicates such as chlorite and chloritevermiculite intergrades, while that of lower horizons is composed of allophane and gibbsite or halloysite. There was no positive indication of allophane in the upper horizons. Corresponding with the clay mineralogical composition, quartz is abundant in the fine sand fraction of the upper horizons, while the mineral is very scarce or none in the lower horizons, suggesting a close relation between the petrological nature of parent volcanic materials and the mineralogical composition of weathering p...


Soil Science and Plant Nutrition | 1982

CLAY MINERALOGY OF SPODIC HORIZONS FROM CRYORTHODS IN JAPAN

Chitoshi Mizota

Abstract Clay mineralogy of thirteen spodic horizon samples from seven Cryorthods developed on diverse materials (peridotite, andesite, lapilli, volcanic ash, slate, granite and granodiorite) in Chubu and Kanto, Japan was determined by successive chemical dissolutions with dithionitecitrate and 0.5 m NaOH-differential infrared spectroscopy in combination with chemical, X-ray diffraction, electron microscopic and thermogravimetric analyses. Thc major part of the soluble iron was found to be crystalline goethite. Presence of allophane (and imogolite) in the lower parts of the spodic horizons, but not in the upper parts, was interpreted as indicating a relatively limited supply of complexing fulvic acid from the overlying organic-rich horizons. The well-developed Al interlayers in the 2 : 1 type minerals associated with gibbsite suggest that the environment of the lower sub-horizons is rich in active aluminium,


Geoderma | 1982

Clay mineralogy and some chemical properties of Ap horizons of Ando soils used for paddy rice in Japan

Chitoshi Mizota; Maria Adriana Carrasco; Koji Wada

Abstract The clay mineralogy of the Ap horizons of Ando soils in Japanese paddies was determined by a combination of methods and compared with that of Ando soils of uplands. Six of 13 paddy soil samples contained allophane and imogolite and none contained gibbsite, whereas parallel figures were 15 and 7 for 22 upland soil samples. Substantial numbers of diatoms were found in 5 paddy and 1 paddy-converted upland soil samples. The lack of gibbsite was related to the stage of soil formation rather than the paddy condition, whereas the presence of diatoms was related to both. Regarding layer silicates, there was no particular difference between the paddy and upland soil samples but one unidentified mineral with unique morphology and infrared spectrum was found in two paddy soil samples. There was no particular difference in phosphate adsorption between the paddy and upland soil samples.


Geoderma | 1988

Characterization of some Andepts and andic soils in Rwanda, Central Africa

Chitoshi Mizota; Jean Chapelle

Abstract The morphology, chemistry and clay mineralogy of ten pedons developed on Quaternary basic volcanic ashes in the northwestern highlands of Rwanda under perudic to udic marginal to ustic moisture regimes are reported. Eight pedons have abundant Al(Fe)-humus complexes, allophane and imogolite and thus qualify as Andepts, whereas the other two pedons do not because of their halloysitic clays. These last two soils are thought to be in a more advanced stage of pedogenesis and to have been formed in parent materials consisting of volcanic ash mixed with residuum from the underlying granitic and metamorphic rocks. Their physical, chemical and clay mineralogical properties are distinctive from those of soils in Kenya and Tanzania. The differences are discussed in relation to soil moisture regimes and petrological nature of parent ashes.

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