Removal of short‐range‐order minerals prior to grain‐size analysis of volcanic ash soils

Incomplete dispersion of aggregates is a well‐known difficulty when analyzing soil texture of Andosols, particularly if no fresh soil material is available. To facilitate such investigations, several dispersion procedures were carried out on air‐dried samples rich in short‐range‐order minerals, originating from selected Andosol profiles (S Mexico). As a result, we propose an improved method based on a sequential chemical treatment with K oxalate, NH₄ oxalate, and oxalic acid that reliably removes cementing agents and allows for a stable dispersion of soil particles after addition of Na pyrophosphate. This method was proved to be well reproducible and highly reliable for routine grain‐size determinations. The potential error caused by the inherent risk of dissolving primary minerals or fresh volcanic glass remains far beyond the analytical error resulting from the incomplete and irreproducible dispersion of highly resistant aggregates by other commonly used techniques.     

Clay minerals of sediments in the Yatsushiro bay

Since three decades ago it has been established by numerous investigators⁴,⁷,⁹⁾ that the general Process of formation of clay minerals is different between the marine and terrestrial conditions, and that the clays of the marine origin are, in general, of illitic type, whereas those of the terrestrial are of kaolin group. In previous communications,¹,²⁾ it was reported that clay fractions of the soil and mud from the Ariake Sea are characterized by the abundance of minerals of illite-montmorin series (montmorin refers to montmorillonite group after Jackson and Sherman⁸⁾, being different from most terrestrial soils in Kyushu. The matter seems to be of some importance because the Presence of montmorin, even in a relatively small quantity, is likely to exercise a considerable, influence on the behaviour and properties of the clay and the fertility of the soil. The soils of the reclaimed land of the Sea are not only productive, Whether they are clayey or sandy, but also they have been approved to be powerful improving materials for the degraded paddy soils, so-called “Akiochi” soils by several field experiments.     

Stability of allophane,allophanic clay,and allophane-halloysite floc in aqueous solutions of an anionic exocellular heteropolysaccharide (Gum Xanthan) from Xanthomonas campestris

Stability of allophane with positive and/or negative charges in the presence of gum xanthan (GX) was mainly investigated at three pH levels. At pH 4.5, allophane showed polymeric iocculation (PFL) at low GX concentrations, and polymeric stabilization (PST) at medium GX concentrations. Flocculated allophane (i.e.p.) at pH 6.5 showed polymeric weak-stabilization (PWST) at extremely low GX concentrations, besides PFL and PST described above. At pH 8.5, allophane did not exhibit any change in stability with GX addition. The PFL and PWST can be regarded as charge neutralization between allophane and GX. Allophanic clay with i.e.p. at pH 10 exhibited both PFL and PST but no PWST, even at pH 8.5. The PWST can be explained by the disintegration of the floc when interparticle attraction was weakened by the adsorption of GX. The lower PWST and PST of allophane-halloysite mutual floc strongly suggested the presence of a more stable arrangement among these dissimilar particles. Stability of crystalline clays was also studied for comparison. The above behavior was analyzed on the basis of (i) the suspended microaggregate of allophane, and (ii) the double-stranded wormlike structure of GX, which was taken in this study as a model substance of anionic microbial polysaccharide.     

Adsorption of xanthan polymer on allophane and effect on the changes in colloidal stability of allophane by heavy metal ions

The influence of divalent cations at concentrations of 10^-6.0 to 10^-4.0 M on the colloidal stability of partially deflocculated allophane by gum xanthan (GX) polysaccharide at pH 6.5 was investigated at two GX concentrations. Experiment in the presence of 10^-2.0 g L^-1 GX showed that the stability decreased by the addition of divalent cations and the effect of the decrease due to the cationic species was evident in a higher concentration range, i.e., 10^-5.0 to 10^-4.0 M. The order of the effect was Pb >Zn > Cd > Mg. Experiment in a 10^-4.5 g L^-1 GX solution revealed that (i) the stability increased by the addition of heavy metal cations at 10^-5.0 M (the order of the effect was Pb > Zn > Cd) and decreased at a concentration above 10^-4.5 M, (ii) whereas the stability decreased by the addition of Mg ion. The striking difference in the stability behavior due to the difference between the two GX-concentrations was attributed to the (i) degree of GX-adsorption (and hence negative charge from the carboxyl group in GX) onto allophane based on the electrophoretic mobility, (ii) complexation of heavy metal cations by organic ligand (carboxyl group) in GX which was adsorbed onto allophane, and (iii) surface complexation by heavy metal cations and hydroxyl groups on allophane. The results were discussed in relation to the characteristics of the particles of allophane, viz., (i) polymer-coated soft particles, and (ii) semi-soft particles on which the rigid (hard) surface of allophane substantially remained.     

Mineralogical properties of andisols of the Kitakami mountain range,Northeastern Japan

We studied the mineralogical properties of Andisols of the Kitakami mountain range. Soils of the northern and central parts of the mountain range contained higher levels of acid oxalate extractable silicon (Si_o), aluminum (A1_o), and iron (Fe_o) but smaller amounts of sodium pyrophosphate-extractable aluminum (Al_p), iron (Fe_p), and carbon (C_p) than those of the southern part. Consequently, the soils of the northern and central parts of the mountain range contained large amounts of allophane and ferrihydrite whereas in the soils of the southern part A1 (Fe)-humus complexes and 2:1 and 2:1:1 clays predominated. The amount of sand (20-2,000 μm) in the soils tended to decrease sharply from the north to the south of the mountain range. The soils of the northern and central parts of the mountain range contained larger amounts of heavy minerals in their fine sand fraction (20-200 μm). The soils of the southern part, on the other hand, contained larger amounts of fine-grained quartz (2-20 μm). All the soils of the mountain range contained substantial amounts of volcanic glass in their sand fraction. However, on a total soil basis, the amount of volcanic glass in the soils decreased from the north to the south of the mountain range and the trend was parallel to that of the sand content of the soils. From these results, we concluded that (i) the soils of the northern and central parts of the mountain range were derived mainly from tephras and (ii) the soils of the southern part were strongly influenced by long-range eolian dust.     

Nitrate adsorption in some andisols developed under different moisture conditions

Nitrate leaching from agricultural lands is one of the most critical problems related to both environmental quality and human health. Although in many studies surfacecharge properties of and nitrate adsorption in soils have been analyzed in tropical and subtropical regions, fewer studies have been conducted on the nitrateretention properties of allo phanic Andisols. The objectives of the present study were to examine the potential nitrate adsorption capacity and the factors affecting nitrate retention in topsoils and subsoils of three Andisols Tokaachi, Hokkaido. Nitrate adsorption at pH 6.0 was found to be low or negligible even in the subsoil of a Haplic Wet Andisol (Melanaquands), despite the high clay content, Nitrate adsorption maxima calculated from the Langmuir equation were higher in the lower horizons of a Haplic Andisol (Melanudands) and a Lowhumic Andisol (Hap ludands), which were developed under moderate to moderately dry moisture conditions and displayed a high allophane content and a low total carbon content. The nitrate adsorption of the aliophanic Andisols was much higher than that reported from other studies conducted in Ultisols and Oxisols, which are rich in iron oxides. The potential capacity to adsorb nitrates and retard nitrate movement should be taken into account in predicting the fate of nitrate in soils and the consequent mitigation of groundwater contamination.     

Radioactive contamination of plants in Japan covered with rain-out from H-bomb detonations in March-May 1954 at Bikini Atoll,Marshall Isls. (Part 1) Distribution of deposited radioactivity

Introduction

New H-bombs detonated from March-May 1954 at Bikini atoll not only gave unexpected disaster to crew on board No. 5 Fukuryu-Maru, a tunafishing boat which happened to be in the neighbourhood (43 miles away from) the dangerous area, but also brought a somewhat high radioactive fall-out all over Japan.     

Desalination of sea water by akadama soil and akadama soil-inorganic adsorbents mixtures

(pp. 33–39)

The purpose of this study is to investigate utilization of Akadama soil and evaluate its ion removal efficiency for seawater desalination. The chemical composition of the Akadama soil was Al₂₀₃ 0.334 kg kg^?1, SiO₂ 0.470 kg kg^?1, Fe₂₀₃ 0.157 kg kg^?1 by weight. X-ray powder diffraction pattern, electron diffraction pattern and IR spectrum of Akadama soil showed that allophane was the main phase and low crystallinity kaolin was generated from the allophane. The column method was carried out to evaluate seawater desalination efficiency, the best mixture ratio of the Akadama soil (particle size was less than 250 m), aluminum silicate adsorbent, aluminium magnesium adsorbent, and magnesium oxide adsorbent was 3:1:1:1. Removal percentages of Na⁺, Mg²⁺, Ca²⁺, K⁺ and Cl^? from artificial seawater were 87.7, 84.4, 91.1, 97.3 and 90.7%, respectively. In the batch method, where the mixed adsorbent was used for removal of heavy metals from 20 mg L^?1 solution, the removal percentages of Cu²⁺, Ni²⁺, Mn²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ were higher than 98%. The removal percentage of PO₄ from river water was 100%.     

Andosol clay re‐aggregation observed at the microscale during physical organic matter fractionation

The high aggregate stability of Andosols and the direct effects of sample drying led to several inconsistencies during physical soil organic matter fractionation. We have determined that NaCl addition displayed little influence on clay dispersion. At the microscale, we observed the re‐aggregation of the clay fraction caused by freeze‐drying. This issue was avoided by analyzing aliquots of soil suspension. Thus, we recommend reserving a small soil liquid aliquot to be subjected to microscopy analysis.     

Flocculation and Stabilization of Allophane in the Presence of an Anionic Microbial Polysaccharide (Gum Xanthan) and Several of Its Hydrolytic Intermediates

The polymeric effect of gum xanthan (GX) on the stability of allophane at pH 4.5 and 6.5 was compared with the effect of several of its hydrolytic intermediates (hGX). The polymeric effect of GX was manifested by (i) the effective flocculation at low GX concentrations, (ii) the higher stabilizing ability above the flocculation concentration (FC), and (iii) the appreciable ability of deflocculation of (a) flocculated allophane and (b) allophane-halloysite floc, at extremely low concentrations of GX solution at pH 6.5. In contrast to GX, in the presence of sodium polyacrylate, there was a complete lack of deflocculation of the flocculated allophane at pH 6.5. This fact suggests that effective deflocculation is due to the double-stranded wormlike structure of the GX chain with a small but finite flexibility. The fact that flocculated allophane by GX at pH 4.5 still exhibited a positive electrophoretic mobility can be ascribed to the flocculation of allophane particles by bridging with this biopolymer. The relationship between FC of GX and the allophane content in soil clays was also examined.