2007 Volume 116 Issue 6 Pages 864-876
We have developed a GIS-based geosphere integration information system named Geosphere Environmental Informatics for evaluating heavy metal distribution on a national-scale. Geosphere Environmental Informatics includes various geosphere environmental information such as geological map, soil map, vegetation topography, locations of mineral deposits, alteration zone, anomalies of heavy metals, satellite images, groundwater information, and concentrations of heavy metals in rocks, soils and river-bed sediments. The system has some new geoprocessing tools. The Map integration tool integrates various geosphere maps. The River catchment tool creates individual stream networks with their features. The Intelligence search refinement tool extracts the objective characteristics of geosphere information from the GIS database.
Heavy metal concentrations of several kinds of rock and river-bed sediments distributed in the model field (Kuroko deposits district in Akita Prefecture, Japan) were examined to evaluate heavy metal concentrations caused by mining and those in a natural state. Hydrothermal alteration zones related to are mineralization show the strong effects of heavy metal concentrations in river-bed sediments. It is difficult to distinguish artificial pollution from the natural abundance of heavy metals in altered rocks and river-bed sediments around a mine. A field survey over a wide area and detailed analyses of items including transport and precipitation mechanisms are required to evaluate artificial heavy metal pollution in a mining district.
Chemical species of heavy metals in extracted solutions from rocks were examined by successive filtration. Heavy metals extracted from black slate existed in the solution as truly dissolved species. On the other hand, the amounts of truly dissolved species in solutions extracted from weathered slate decreased, and dominant chemical species of heavy metals were adsorbates on fine and coarse colloidal particles. In addition, colloidal particles show different REEs affinities. These results imply possible fractionation among REEs during chemical weathering and transport processes by colloidal particles.