福井県大野盆地における扇状地湧水中の硝酸態窒素濃度の変動

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The concentration changes of nitrate nitrogen (NO_<3->N) and other ions were examined in 4 springs called "Shohzu" of Konomoto Alluvial Fan and the water of Takinami River in Ohno Basin, Fukui Prefecture. The outline of results is as follows : The waters of these springs and the river were supplied from the same source, judging from the measurement of lead isotope ratios and the results of previous studies. The concentrations of NO_<3->N and other ions in these waters were quite low, in spite of a little pollution from fertilizer applications. The NO_<3->N concentration increased relatively between Konomoto-yakushido spring located at the top of fan and Shinokura-jinja upstream of an urban area, and many fields distributed between them. Its concentration in the latter spring increased a little in July when midsummer drainage is carried out in rice fields and fertilizers are applied to upland crops, and in October to November at the time of drainage after rice cultivation. The changing pattern of NO_<3->N concentration coincided with that of sulfate, a component of fertilizers, at Shinokura-jinja spring. This suggested that the fertilizer application in fields had a small effect on ground water. The concentration changes of NO_<3->N and other anions in Nakano-shohzu downstream from the urban area, where small fields are scattered, were similar to those of Shinokura-jinja spring. In O-shohzu, within the urban area, the ion concentrations were hardly different from those of Shinokura-jinja spring located at the upper end of the groundwater system. On the other hand, the seasonal changes of NO_<3->N concentration were very small, and might have been caused by the installation of pavement and sewerage.
2001-10-05

福井県大野盆地における扇状地湧水中の硝酸態窒素濃度の変動

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