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A study of organo-mineral complexes in some gleysolic soils : their isolation and the mineralization of nitrogen, sulphur and phosphorus Hinds, Aston Alexander

Abstract

A detailed study of the factors affecting the efficiency of ultrasonic dispersion of five Gleysolic soils by the Biosonik BP-III probe type ultrasonic vibrator was conducted. Various soil/water ratios, lengths of vibration time and intensity settings were investigated and it was found that a soil suspension (1:10 or 1:5 soil/water ratio) not exceeding a total volume of 125 ml could be effectively dispersed by vibration for 20 minutes at a probe setting of 80. The efficiency of soil dispersion was reduced by 30-40 percent unless there was a "cooling off" period for the probe of 25-30 minutes between consecutive dispersions. The condition of the probe tip exerted a major influence on the effectiveness of dispersion and severe pitting which developed after about 70 hours of use, reduced the output of energy from the probe by nearly 70 percent. The heating effects of sonication was found to be a useful index of the energy output of the probe, and a technique for comparing the energy delivered to a suspension, which was equally effective and simpler than radiation pressure measurements, is described. A major finding which emerged from this study was that relatively large amounts of Fe, Al, Si, and C were solubilized during the vibration of soils in water, and that this effect could be suppressed by dispersing soils in a dilute electrolyte solution, notably 0.01 M CaCl₂. A fractionation scheme for the isolation in bulk of organo-mineral complexes was developed based on ultrasonic dispersion of the soil and a system of continuous flow centrifugation. The method reduces considerably the time involved in obtaining various particle-size fractions, and gives quantitative separation of the size groups, (an average of 98 percent of the soil material was recovered). The amounts of C, N, S, and P in the soils and their particle-size fractions (2-50μm, l-2μm, 0.2-lμm, and

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