CHANGES IN CONTENT OF TRACE AND ULTRATRACE ELEMENTS WITH AN INCREASE IN NONCRYSTALLINE MATERIALS IN VOLCANIC ASH SOILS OF JAPAN

Abstract

A total of 57 elements in volcanic ash soils from 18 pedons distributed in Japan were analyzed and the relationships between noncrystalline material content and that of individual elements were examined. The content of the noncrystalline materials was estimated by using acid-oxalate extraction. Oxalateextractable Si (Si_o), Fe (Fe_o) and Al (Al_o) corresponds to the Si content in allophane-imogolite, Fe in ferrihydrite and Al in allophane-imogolite plus Al complexed with humus, respectively. Silicon and alkaline or alkaline-earth elements such as Na, K, Ca, and Sr tended to decrease during the process of volcanic ash soil formation, i.e., andosolization. In contrast, the contents of Al, Y, Zr and the first transition metals tended to increase with the increasing content of noncrystalline materials. The first transition metals showed a high correlation with Fe_o suggesting their similarity in chemical behavior during andosolization. The heavy lanthanoid elements tended to increase with the increasing content of allophane-imogolite.