Journal of the Japan Society of Engineering Geology

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Column experiments consisting of crushed rock containing arsenic (As) and boron (B), and volcanic ash with high amorphous aluminum and iron contents were conducted to evaluate the leaching behaviors and adsorption characteristics of these toxic elements from the rock. The results showed that the As and B concentrations in the effluent were much higher than the environmental standards, and that the addition of a bottom adsorption layer decreased the concentrations of As and B and delayed their peak appearances in the leachate. The pHvalues of the effluent from the rock layer were alkaline ranging from 10 to 11, but interactions between the pore water and minerals in the volccanic ash layer buffered the pHvalues (approximately pH7). The As and B migration in the columns were simulated using an advective-dispersive equation with a Henry type adsorption model. As a result, the model expressed the leaching behavior of B well whereas the model did not express that of As. The distribution coefficient, K_d, of B evaluated from the column experiments also agreed well with that obtained from batch adsorption experiments. This indicates that the model is effective in evaluating B migration. However, since As adsorption was affected by many factors, such as pH, coexisting ions, and other experimental conditions, simulated K_d values of As did not agree with the observed ones. The above results suggest that a bottom adsorption layer is effective in the reduction and retardation of heavy metals leached from a rock layer and in the neutralization of the effluent pH. Furthermore, the B migration can be predicted using the K_d value derived from batch experiments.

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This paper has focused on Land-use change to clarify spatial distribution of human impacts on terrain as a viewpoint of vulnerability mapping to natural disasters. First, the technique of making 100m-mesh land-use maps, which divides into farm lands, forest, urban, river, sea shore and sea, has been developed using the old editions' 1/50,000 topological maps of Geospatial Information Authority of Japan. Then, the land-use change from 1900 to 1997 in the Fukuoka Prefecture area has been analyzed using the geographical information systems (GIS) in comparison with distribution of regional geology and terrain.
The results are as follows. (1) The relationship between land use and terrain changed significantly after 1950 in comparison with land use of 1900 that harmonized with local relief. (2) The lands of plutonic rocks had already been developed widely before 1900, and its use shifted to urban use from farm land after 1950. (3) The characteristics of elevation and slope angle in urban and farm lands indicate that the urban lands which adjoin mountainous area increased by about ten times from 1900 to 1997. (4) The difference of 4 to 8 degrees in slope angle has been estimated on plutonic rocks' terrain that changed from forest as human impacts, based on the relationship between land use and its geology.
These results imply that the proposed method would enable mapping of anthropogenic terrain.

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