Nonexchangeable potassium in a 1.4-nanometer mineral and mica in a Korean ultisol
1993
Wada, K. | Kakuto, Y.
Eleven cations, Na+, NH4+, Cs+, Ag+, Mg2+, Ca2+, Sr2, Ba2+, Cu2+ Pb2+, and Al3+, were used individually to extract K from clay fractions of a Korean Ultisol in order to provide information on non-exchangeable K in a 1.4-nm mineral and mica. The 1.4-nm mineral and mica. The 1.4-nm mineral exhibited X-ray diffraction patterns of partially interlayered vermiculite. The associated change in mineral structure following K extraction was determined by X-ray diffraction analysis to improve the understanding of the 1.4-nm mineral structure. Potassium extraction conducted with solutions containing 0.5 M Mg2+ and Ba at 25 and 100 degrees C showed that nonexchangeable K was extracted only with Ba2+ at 100 degrees C. The associated intensity of the 1.4-nm reflection after K extraction suggested that more than one-half of the K was present in the mineral. The cumulative amount of nonexchangeable K extracted with 0.5 M Pb2+ at 100 degrees C (10.5, 40.5, and 75 cmol kg-1) and its proportion to the total K (35, 69, and 89%) increased in the order < 0.2-micrometer < 0.2-0.5-micrometer < 0.5-2-micrometer fractions. There was little effect of the interlayer material on the K extraction from the 1.4-nm mineral. The associated intensity increase of the 1.4-nm reflection and no change in its d spacing suggest that the nonexchangeable K resides at the opened interlayer rather than as mica layers in the 1.4-nm mineral. Single of nonexchangeable K at 100 degrees C for 50 h showed that Ag+, Ba2+ and Pb2+ were effective, whereas Na+, NH4+, Cs+, Mg1+, Ca2+, Sr2+, Cu2+, and were not, indicating that the atomic weight and hydration energy of a cation are important in determining its K-extraction ability.
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