Masami Ohtsubo

Swelling and mineralogy of smectites in paddy soils derived from marine alluvium, Japan

Abstract A low-swelling smectite exhibiting little intra-crystalline swelling even after saturation with Na was found in paddy soils derived from marine alluvium of Ariake Bay in Kyushu, Japan. The low-swelling smectite was considered to be beidellite-nontronite mineral containing as much as 10% Fe2O3. The low-swelling characteristics of this smectite are ascribed to the considerable substitution of Fe2+ for Al3+ in the ochtahedral layer which depresses the dissociation of unit layers of smectite. Transformation of low-swelling to high-swelling smectite is believed to be due to the oxidation of Fe2+ to Fe3+ in the octahedral layer.

SMECTITE IN MARINE QUICK-CLAYS OF JAPAN

Clayey sediments of marine origin having sensitivities (ratio of undisturbed to remolded shear strength) as high as 1000 at a reduced salt concentration are found around Ariake Bay, Kyushu, Japan. The clay fraction of the sediments contains smectite as a principal mineral (33–42%) in contrast to the illitic composition of most previously described quick-clays. However, this smectite is a low-swelling type, and the Na-form expands only to about the same extent as the Ca-form and gives a sediment volume almost equal to that of the Ca-clay. This low-swelling smectite appears to consist of packets of unit layers even after saturation with Na, and thus reacts like the kaolinite or illite of conventional quick-clays.РезюмеГлиняные осадки морского происхождения, имеющие чувствительности (отношение несмущенной и смущенной прочностей при срезе) такие большие как 1000 при уменьшенной концентрации соли, находятся в районе бухты Ариаке, Кыусху, Япония. Глинистая фракция осадков содержит смектит как основной минерал 33-42%) в противоположность к иллитовому составу большинства ранее описанных зыбучих глин. Однако, этот смектит является мало-набухающего типа, и Nа-форма расширяется только до примерно такого же самого уровня как Са-форма и приводит к почти равному объему осадков как и Са-глина. Кажется, что этот мало-набухающий смектит состоит из пакетов элементарных слоев даже после насыщения натрием, и тогда он реагирует как каолинит либо иллит обычных зыбучих глин. [Е.С.]RésuméDes sédiments argileux d’origine marine ayant des sensitivités (proportion de la force non dérangée à la force remoulée) atteignant 1000 à une concentration de sel réduite sont trouvés autour de la Baie Ariake, Kyushu, Japon. La fraction argile des sédiments contient de la smectite comme minéral principal (33–42%) contrairement à la composition illitique de la plupart des argiles rapides décrits précédemment. Cette smectite est cependant du type à bas gonflement, et la forme-Na s’épand seulement approximativement autant que la forme-Ca et donne un volume de sédiment presqu’égal à celui de l’argile-Ca. Cette smectite à bas gonflement semble consister de paquets de couches unitaires même après avoir été saturée de Na, et par conséquent elle réagit comme la kaolinite ou l’illite d’argiles rapides conventionnels. [D.J.]ResümeeTonige Sedimente mariner Entstehung, die bei reduzierter Salzkonzentration Sensitivitäten (Verhältnis der ungestöten zur Scherfestigkeit der durchkneteten Probe) von etwa 1000 haben, wurden um die Ariake Bay, Kyushu, Japan, gefunden. Die Tonfraktion der Sedimente enthält Smektit als häufigstes Mineral (33–42%) im Gegensatz zur illitischen Zusammensetzung der meisten früher beschriebenen Quick-tone. Dieser Smektit quillt jedoch nur wenig, und die Na-Form quillt etwa nur so viel wie die Ca-Form und ergibt ein Sedimentvolumen, das dem von Ca-Tonen entspricht. Dieser schlechtquellende Smektit scheint aus Paketen von Einzellagen zu bestehen, sogar nach der Sättigung mit Na, und verhält sich daher wie der Kaolinit oder Illit von herkömmlichen Quicktonen. [U.W.]

Particle interaction and rheology of illite-iron oxide complexes

The Bingham yield stress for suspensions of illite-iron oxide complexes is examined as a function of pH and iron oxide content. Addition of iron oxides to illite increased the yield stress over a pH range of 3 to 10. With increasing pH the yield stress decreased for the complexes with iron oxides of 2 and 5% while the complexes with iron oxides of 7, 10, and 20% exhibited the maximum yield stresses at pH values from 6 to 8. The iron oxides which are not associated with the illite enhanced the yield stress more than the iron oxides precipitated on the illite surfaces. The yield stress for the complexes was correlated with their zeta potential, and the higher yield stress is considered due to smaller interparticle repulsion.

LOW-SWELLING SMECTITE IN A RECENT MARINE MUD OF ARIAKE BAY

Abstract A low-swelling smectite was found in a recent marine mud of Ariake Bay. The Na-clay of this mud swells but to the same extent as the Ca-clay and its dominant interparticle force is not repulsion between individual particles. The sediment volume at low salt concentration and the specific viscosity of the Na-clay were almost equal to those of the Ca-clay. The liquid limit of the Na-mud decreased with decreasing NaCl concentration and was lower than that of the Ca-mud.

Heavy‐Metal Contamination of Soil and Vegetables in Wastewater‐Irrigated Agricultural Soil in a Suburban Area of Hanoi, Vietnam

The To Lich and Kim Nguu Rivers, laden with untreated waste from industrial sources, serve as sources of water for irrigating vegetable farms. The purposes of this study were to identify the impact of wastewater irrigation on the level of heavy metals in the soils and vegetables and to predict their potential mobility and bioavailability. Soil samples were collected from different distances from the canal. The average concentrations of the heavy metals in the soil were in the order zinc (Zn; 204 mg kg−1) > copper (Cu; 196 mg kg−1) > chromium (Cr; 175 mg kg−1) > lead (Pb; 131 mg kg−1) > nickel (Ni; 60 mg kg−1) > cadmium (Cd; 4 mg kg−1). The concentrations of all heavy metals in the study site were much greater than the background level in that area and exceeded the permissible levels of the Vietnamese standards for Cd, Cu, and Pb. The concentrations of Zn, Ni, and Pb in the surface soil decreased with distance from the canal. The results of selective sequential extraction indicated that dominant fractions were oxide, organic, and residual for Ni, Pb, and Zn; organic and oxide for Cr; oxide for Cd; and organic for Cu. Leaching tests for water and acid indicated that the ratio of leached metal concentration to total metal concentration in the soil decreased in the order of Cd > Ni > Cr > Pb > Cu > Zn and in the order of Cd > Ni > Cr > Zn > Cu > Pb for the ethylenediaminetetraaceitc acid (EDTA) treatment. The EDTA treatment gave greater leachability than other treatments for most metal types. By leaching with water and acid, all heavy metals were fully released from the exchangeable fraction, and some heavy metals were fully released from carbonate and oxide fractions. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the vegetables exceeded the Vietnamese standards. The transfer coefficients for the metals were in the order of Zn > Ni > Cu > Cd = Cr > Pb.

Assessment of the water quality of two rivers in Hanoi City and its suitability for irrigation water

The To Lich and Kim Nguu Rivers in Hanoi City are the main sources of irrigation water for suburban agricultural land and fish farm. Wastewater from the industrial plants located along these rivers has been discharged, and has degraded the water quality of the rivers. This study describes the chemical properties of water from the rivers, focusing on heavy metal pollution and the suitability of water quality for irrigation water. Water from the rivers was heavily polluted with organic matter and heavy metals such as Pb, Cu, Zn, Cr, Cd and Ni. Dissolved oxygen, chemical oxygen deman, and total suspended solids, and the concentrations of all heavy metals exceeded the Vietnamese standard for surface water quality in all investigated sites. The concentrations of some heavy metals such as Cu, Cd, Cr and Ni were above the internationally recommended WHO maximum level for irrigation water. A wide variation in the heavy metal concentration of water due to metal types is the result of wastewater discharged from different industrial sources.

Mineralogy and chemistry, and their correlations with the geotechnical properties of marine clays in Ariake bay, Japan: Comparison of quick and nonquick clay sediments

This article describes the mineralogy, chemistry, and geotechnical properties of quick and nonquick clay profiles in Ariake Bay, Japan, and the correlations of the mineralogy and chemistry of the clays with their geotechnical properties. The chemistry is discussed in terms of saline environment at the time of deposition, and postdepositional weathering processes. The principal clay minerals identified were smectite, mica, and kaolinite. The salinity in pore water of nonquick clay varied, according to changes in sea level, from brackish to marine, and then brackish toward the surface. The higher iron oxide contents of the clay profiles were attributed to the production of iron hydroxide by pyrite oxidation, due to exposure of the clays to atmosphere for the nonquick clay sediment, and due to the supply of oxygen from fresh water permeating through the clays during leaching process for the quick clay sediment. The major factors which increase the activity of the clay were both smectite and salinity in pore ...

Particle-size characterization of flocs and sedimentation volume in electrolyte clay suspensions

The variation of the particle-size of flocs in clay suspension with the salt concentration and the correlation of the particle-size with the sediment behaviour of the suspensions have been studied. The particle-size distribution of flocs was determined by means of the sedimentation balance. Due to the increase of the salt concentration in the suspensions, the particle-size of flocs showed marked increases for the salt concentration range of 0 to 0.01M, followed by smaller increases for the salt concentrations higher than 0.01M. A negative correlation was observed between the mean particle-diameter of flocs in the suspensions and the zeta potential. The sediment volume of the clay suspensions of pH 7 was found to be positively correlated with the mean particle-diameter of flocs. The void ratio of the sediment exhibited a rapid decrease with increasing depth at the surface zone and a subsequent slow decrease at greater depths.

Settling velocity of a sodium montmorillonite floc under high ionic strength

Abstract The settling velocity of a single floc of sodium montmorillonite coagulated under a condition of high ionic strength was analyzed as a function of floc diameter to determine the fractal dimension of the floc. The obtained values of the fractal dimension were found to be approximately 2.0 irrespective of ionic strength and pH values. This result clearly demonstrated that the difference of the viscosity of coagulated montmorillonite suspension against ionic strength earlier reported is not affected by the difference of the fractal structure of a floc but by that of the attractive force between individual clay particles in a floc.

Influence of various factors on the difference in the liquid limit values determined by Casagrande’s and fall cone method

As there are many correlations linking the liquid limit directly or indirectly with various engineering properties of the soil, the accurate determination of the liquid limit is quite essential. Generally, two methods, i.e. Casagrande’s and fall cone are adopted to determine the liquid limit of soil. Research was carried out to study the influence of the properties of bentonite and the presence of the salt solution on the liquid limit values of soil-bentonite mixtures determined by the Casagrande’s and fall cone methods. The results showed that irrespective of the presence of the type of bentonite or salt solution, a higher value of the liquid limit was obtained by the Casagrande’s method as compared to the fall cone method. However, the difference between the two methods decreased with the decrease in the liquid limit, clay fraction, specific surface area and free swelling capacity of the bentonite present in the mixture. Similarly, the difference in the liquid limit values obtained by both these methods is reduced with an increase in the salt concentration.