Hydroxy-interlayered minerals in Japanese soils influenced by eolian deposition

The influence of eolian dust deposition on the development of Red-Yellow soils and nonallophanic Andisols in Japan has been well documented. In these studies, it was reported that the clay fractions of these soils are dominated by fine-grained quartz, 2:1 layer silicates and their intergrades, and kaolinite. However, the nature and composition of hydroxy-interlayered minerals on these soils influenced by eolian dust addition from China is largely unknown. To address this problem, we collected and characterized 28 soil samples from seven pedons in Japan classified as Hapludalfs, Hapludults, or Melanudands, and two soil samples from a pedon in China classified as a Vermiboroll. These samples were extracted with 0.15 M acid oxalate and 0.3 M sodium citrate solutions and the amounts of Al, Fe, and Si present in the extracts were determined. This information was used in combination with x-ray diffraction patterns of the samples obtained before and after extraction to determine the mineralogy and estimate the composition of the interlayer material. Except for the Vermiboroll samples, which contained kaolinite and highly charged smectite, the dominant minerals in these soil samples were hydroxy-interlayered vermiculites (HIV) The citrate extracts yielded low Si/Al atomic ratios (i.e., 0.12-0.86 after 4 h and 0.39-0.90 after 24 h) suggesting that the interlayer materials of the HIV minerals were hydroxyaluminosilicate, hydroxy-Al, and/or hydroxy-Fe ions. Our results provide chemical and mineralogical evidence for the occurrence of hydroxy-interlayer materials in loess-derived Japanese soils developed under temperate, humid climates.