In order to elucidate Cr behavior in soil and soil water it is necessary to clarify the factors controlling the Cr release from contaminated Cr-containing soil. The experiments on Cr release from the contaminated soils collected from factory ruins and the standard soils (mixing ratio=1:4(JSO-1: JSO-2 provided by the Geological Survey of Japan) which were added as K₂CrO₄ (1,000 mg kg^-1) were conducted. Chromium concentration in alkaline solution for the contaminated soils was high (i.e., 29.5 ∼ 33.9 mg kg^-1) but low (i.e. 11.2 ∼ 13.8 mg kg^-1) for JSO-1:JSO-2 mixed soil. After the experiments, Eh and pH of the solution for the JSO-1:JSO-2 mixed soil lies in Cr₂O₃ region in acidic to neutral region in Eh-pH diagram, while that for the contaminated soils along CrO₄^2-／Cr₂O₃ boundary in alkaline solution.
Eh and pH for the solution interacted with JSO^-1:JSO^-2 mixed soil and contaminated soils are plotted along Fe²⁺/Fe(OH)³ boundary and in Fe(OH)₃ region, respectively.
"FeO"(Fe²⁺) content and amorphous(allophane) and low crystalline phase (ferrihydrite) content in the JSO-1:JSO-2 mixed soil are higher than those of the contaminated soils. Therefore, it is considered that the lower Cr concentration in the solution reacted with the JSO-1:JSO-2 mixed soil is due to the more efficient reduction of Cr⁶⁺ to Cr³⁺ by "FeO" (Fe²⁺) in the soil samples and adsorption of Cr³⁺ by weathering product (mainly low crystalline iron oxyhydroxide and allophone ) in the soil than the contaminated soils.

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Tamagawa hot spring is a volcanic gas-bearing hydrothermal system derived from Quaternary andesitic to dacitic magma beneath Yakeyama volcano. Thermal waters and precipitates of Tamagawa Hot Spring in 2002 and 2007 were investigated to clarify the geothermal structure of the area. Thermal waters in Tamagawa Hot Spring area are divided into three types: Cl-SO₄type (Ohbuki Hot Spring: pH 1.2), SO₄type (pH 1.8 to 2.9) and neutral-type (pH 6.1). Concentrations such as F, Cl, SO₄, Na, K, Mg and Ca in Cl-SO₄type Ohbuki thermal water are ten to several hundred-times higher than those of elements in SO₄type thermal waters. The concentrations of elements in SO₄ type thermal waters also varied according to changes in geothermal structures supplying steam and the flow system of groundwater and vapor in Tamagawa geothermal system from 2002 to 2007.
The oxygen and hydrogen isotopic ratios of the thermal waters in the system suggest that SO₄ type thermal waters are formed by heating of shallow groundwater by the steam separated from Ohbuki thermal water below Tamagawa Hot Spring area. On the other hand, the small variation of chemistry and hydrogen and oxygen isotopic ratios of Cl-SO₄ type Ohbuki thermal water from 2002 to 2007 suggests that the Cl-SO₄ type Ohbuki thermal water originates from a deeper part of Yakeyama Volcano. The flow rate of Cl-SO₄ type Ohbuki thermal water below Tamagawa hot spring area was estimated to be 13,000 l/min.

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In the 10th SGA (Society for Geology Applied to Mineral deposits) meeting at Townsville, Australia, an interesting new discovery session was programmed. Most are reported from Australia by Ivanhoe Mining Co., which are unique types in Australia and unusual in other terrains.

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Excursion to the Miocene hydrothermal deposits in the Southwest Hokkaido has been conducted on October 3 and 4 as the SRG Autumn Seminar in 2008. Fifteen participants have visited the Akaiwa Acid Alteration Zone, the Kunitomi Kuroko deposit, the Ohe manganese deposit and the Niki diagenic zeolite deposit. We observed the characteristic field occurrences and ore mineral assemblages, and discussed about the genesis of above deposits and their hydrothermal alteration systems.

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