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The purpose of this investigation is
to know the long-term characteristics of VOC concentrations in houses built before the building code
in 2003 and to clarify the countermeasures against indoor air pollution in the
houses already built. For example, the improvements of living habits,
ventilation and the remove of building materials. The concentrations of VOCs
were measured in these houses in summer and winter from 2000 to 2005. The
results showed that the concentration of formaldehyde decreased in the first
year. After that the decline of the concentration was not seen and the concentration
changed only with the temperature. The characteristics of decline were thought
to be caused by two sorts of emission. One is an emission of concealed
formaldehyde in the process of material production and the other is an emission
with the generation of formaldehyde from adhesives of urea resin and moisture.
The concentration of toluene decreased rapidly in the first year. The
concentrations of xylene, ethyl-benzene and styrene showed a similar change.
But the concentrations of acetaldehyde which were measured from the summer of
2002 did not decrease and its concentration in some houses was higher than the
guideline even in the winter of 2005.
Silica sinter developed on the northern shore of Lake Usoriyama in the Osorezan geothermal field was examined for the occurrence, texture, crystallinity of silica minerals, and the concentrations of trace elements and oxygen isotopes. The silica sinter consists of a thick eastern mound (layer A) and a thin western part (layer B). Most of the silica sinter is composed of alternating bands of thin layers of silica minerals with colors varying from white to yellow and reddish gray. There is a unique stromatolitic texture, an aggregate of stratified concentric layers that extends upward and is red to reddish gray in color in the middle of layer A. Silica minerals, mainly opal-A and opal-CT, dominate the mineralogical constituents of the sinter. The δ18O of the silica mineral in layer A varies between 13‰ and 26‰, while layer B has higher values, between 19‰ and 33‰. The hydrothermal fluid from which the silica sinter precipitated is dominated by meteoric water is similar to present-day hot spring water.