Ministry of Environment of Japan made the Soil Contamination Countermeasures Law (referred to hereafter as the Law) on 29 May 2002, in order to prevent health damage which toxic substances in soils could cause by oral ingestion. The pollutants in many cases are toxic metals as Pb, As, Cr(VI) and Hg. The administration of the Law obliges landowners, managers and occupiers of sites of business establishments handling these toxic metals to examine soil contamination by field survey and chemical analysis to determine toxic metal concentrations and their leachabilities when they close their facilities. Because As, Se, Cd, Hg, and Pb are very important metals for economic geologists, they have a lot of knowledge and techniques on geochemistry and mineralogy of these metals. Therefore, economic geologists should be able to contribute to develop techniques surveying toxic metals in contaminated lands, as well as controlling their leachabilities.
The followings are important subjects economic geologists have advantages to develop;
1) Mapping natural levels of toxic heavy metal concentrations in soils
2) Clarifying whether soils have high toxic metal concentrations or high leachabilities caused by anthropogenic or natural processes.
3) Determining chemical interactions between toxic metals and soil materials for fixing toxic metals in soils.
4) Developing on-site chemical analytical techniques for surveying contaminated sites.

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Soil Contamination Countermeasures Law (referred to hereafter as the Law) was made on 29 May 2002, for preventing health damage which toxic substances as Pb, As, Cr(VI) and Cd in soils could cause by oral ingestion.
In order to carry out the Law, we must judge whether soils have high toxic metal concentrations or high leachabilities caused by anthropogenic or natural processes. If high toxic metal concentrations or high leachabilities are caused by natural processes, the administration of the Law should not oblige landowners, managers and occupiers of contaminated sites to remedy them.
Therefore, it is essential to determine natural levels of Pb, As, Cr(VI) and Cd concentrations and their leachabilities of Japanese soils which have a wide range of chemical and mineralogical composiotion. It is also very important to develop chemical and mineralogical analytical methods to judge whether soils have high toxic metal concentrations or high leachabilities caused by anthropogenic or natural processes.
We obtained Pb, As, Cr(VI) and Cd concentrations and leachabilities of stream and marine sediments, as well as soils formed by weathering of volcanic ashes and granite and granitoid, using XRF and conventional wet chemical analytical methods. We also obtained mineralogical data of these sediments and soils, using XRD, TG-DTA and analytical TEM. Furthermore, we obtained lead isotope ratios of these sediments and soils, using ICP-Mass.

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Migration behavior of base metal elements in volcanic ash soil (Andosols) profile at two (A and B) sites in Hadano, Kanagawa Prefecture, central Japan was investigated. It was found that the base metal elements in A site which is composed only of Andosols and B site which is composed of Andosols and Loam dissolve considerably from the parent-rock but partially adsorb onto secondary minerals in Andosols.
The order of elemental mobility in A site is similar to the adsorption tendency of base metal elements onto iron oxyhydroxides. It is thought that the migration behavior in A site is controlled by the adsorption onto iron oxyhydroxide, but that in B site is fractionation of solution composition influenced by the adsorption onto iron oxyhydroxide and the ion exchange reaction between downward migrating soilsolution and clay minerals.

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In recent years, soil pollution and groundwater pollutions, caused by hazardous materials, have become a major problem in Japan. Thus, people and corporations as well, conduct soil pollution investigations of the land to accurate grasp of actual conditions of soil pollution, and remediation of lands. Examples of soil and groundwater contamination investigation and remediation of contaminated lands are explained.

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In the last decade, arsenic contaminated groundwater (>0.01 mg/L) has frequently been detected from place to place in Japan, and has caused serious social problems. The comprehensive surveys and researches have demonstrated that arsenic of natural origin dissolves from the aquifer to groundwater under specific environmental conditions. Concerning the aquifer geology, the arsenic-bearing groundwater is divided into S-type (sediment hosted type) and M-type (metamorphic rock hosted type). Meanwhile, from the viewpoint of dissociation mechanism, the arsenic contamination is classified into three types; .Type 1: Reductive dissolution of iron oxyhydroxide (goethite) and release of adsorbed arsenic into groundwater; Type 2: Oxidation of arsenic pyrite, and Type 3: Arsenic release by the decomposition of organic matter in an alluvial peat layer under reducing condition of the aquifer.
Because arsenic takes various forms as source and sink in nature and is sensitive to the environmental conditions, it is important that we should consider the geochemical cycle of arsenic for elucidating the dissolution mechanism and also for the remediation of groundwater at the contaminated sites.

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The sealing plug for mine drainage is located at the penetralia part of the 3M level adit that is at the bottom of the old Matsuo mine in the northern part of Japan. In evaluating the safety of the plug concrete, a direct evaluation method would cause harm to the safety of the plug. As a consequential evaluation method, a hydrogechemical method was undertaken to compare the water quality of seepage and inflow water instead.
Seepage and inflow water was identified at ten locations in the 3M level adit. Except for the water in front of the plug, the pH values of the identified water samples were in the middle range and their water qualities were characterized as Ca-HCO₃ type (within the range of unconfined groundwater). The Sr isotopic ratios (⁸⁷Sr/⁸⁶Srr) were between 0.7040 and 0.7044, which are close to the values of pyroxene-andesite and propyrite. These results suggest that the water qualities were affected by the andesite nearby sulfur ore.
On the other hand, the pH values of the water samples in front of the plug were within the acidic range. Their water qualities were characterized by Ca-SO₄ type (within the range of acid mine drainage) and the Sr isotopic ratios in a range between those of sulfur ore and plug concrete (0.7047-0.7052). These results suggest that the origins of the water samples in front of the plug are acid mine drainage or groundwater nearby sulfur ore. In addition, high concentration of Ca is considered to be due to the dissolution of Ca from the plug concrete or calcium carbonate.
It can be deduced from the hydrogechemical survey that a large part of seepage and inflow water in the 3M level adit originates in unconfined groundwater, and is hardly affected by acid mine drainage. Therefore, it can be described that the plug maintains the capability to seal mine water drainage.

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Traditional drainage survey has been used mainly for geochemical exploration and evaluation of anthropogenic metal contamination. To carry out the survey properly, some technical consideration should be paid besides just following related technical guidelines. Recently developed some. methods such as tracer-injection synoptic quantification of discharge, ng/l order Hg analysis, and high-resolution survey on first and second order streams enable the drainage survey to treat wider range of environmental issues.

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Studies on natural analogues are indispensable ways to define geological disposal concepts, and to provide convincing support for the performance assessment of long-term radioactive isolation. Long-term predictions on the behavior of the natural environment are recognized to be fraught with uncertainty if based solely on information from limited and short-term observations or experiments. In this context, natural analogue studies have been extensively carried out by many researchers in the world. However, natural analogue studies have been recently scaled down and financially limited due to: (1) limited study areas that are systematically analogous to disposal sites, which is the primary prerequisite for analogue studies; (2) deficiency in defining natural analogues; and (3) lack of clarity on the utilization of data obtained in the studies and how it can contribute to performance assessment.
Recent issues surrounding the performance assessment that should be addressed urgently in assessing the impacts on the disposal systems include: (1) retardation of anionic species such as ¹⁴CO₄^2-, H⁷⁹SeO₃^-, ⁹⁹TcO₄^-; and (2) bentonite-hyper alkaline fluid (i.e. cement pore fluid) interactions. If the criteria for natural analogue studies are strictly defined, it would be very difficult to find suitable study areas. In this review, the required conditions and strategies for future natural analogue studies are discussed and summarized based on case studies of natural attenuation of arsenic in acid mine drainage and mineral paragenesis under hyper alkaline condition in Oman ophiolite.

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For the safety assessment of geological disposal of high level nuclear waste it is essentially important to elucidate the long-term migration behavior of radioactive elements in shallow geologic environment as well as in deep environment. For this purpose in mind, the migration behavior of chemical analogue elements (REEs, U, and Th) during the chemical weathering of several types of rocks and soils (e. g., Andosols, Loam, sedimentary rocks) was investigated. REEs are depleted in Andosols compared with parent volcanic ash. However, they accumulate or do not remove from the Loam underlying the Andosols. REEs migrate significantly in the sedimentary rocks (shale) but they adsorb onto secondary minerals (e. g., iron oxyhydroxides).

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Goldich′s weathering series (Goldich, 1938) is consistent with the results of thermochemical calculation on solubility of silicates as a function of partial pressure of carbon dioxide and also the rate of dissolution of silicates experimentally determined.
However, it was found that this weathering series, solubility and dissolution rate of silicates are inconsistent with the rate of dissolution of Ca·Na-feldspar and pyroxene in Kanto-loam. Goldich′s weathering series, solubility and dissolution rate of Ca·Na-feldspar and pyroxene indicate that Ca·Na-feldspar is more stable or similar to Mg-pyroxene in the weathering series. However, Ca·Na-feldspar in the Kanto-loam was suffered more intense weathering than pyroxene. This inconsistency is interpreted in terms of the rapider rate of dissolution of Ca·Na-feldspar than pyroxene in organic ligand-rich soil water in near-surface environment, suggesting that organic acids are important for controlling the dissolution of Ca·Na-feldspar.

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Plio-Pleistocene paleostress field that allowed the deposition of Au-and-Ag-bearing, quartz vein-type ore in southwestern Kyushu, Japan, is still controversial. We studied mesoscale faults to understand temporal and spatial variation of stress in mid Pliocene sedimentary sequence, called the Hitoyoshi Formation, just to the northeast of the metallogenic province. Consequently, extensional and transtensional tectonic regimes were found from the fault-slip data, and both of them have the common minimum compressive stress axis in a NW-SE to NNW-SSE trend. The stress regimes are concordant with the known paleostresses found from mesoscale faults in the Pliocene Miyazaki Group on the Pacific side of Kyushu, suggesting that they represent regional stress fields in southern Kyushu. The observed minimum compressive axis is trending perpendicular and, therefore, concordant to known preferred orientation of the mineral veins in southwestern Kyushu. The coincidence suggests that the formation of veintype ore deposits was accompanied by extensional or transtensional tectonics.

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