著者

石塚 成宏 小野寺 真一

出版者

一般社団法人日本土壌肥料学会

雑誌

日本土壌肥料學雜誌 (ISSN:00290610)

巻号頁・発行日

vol.68, no.1, pp.1-7, 1997-02-05

参考文献数

31

被引用文献数

19

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In order to determine processes of decreasing nitrate concentration in shallow groundwater in a forest on a suburban upland, we investigated the spatial distribution of δ^<15>N values of nitrate and nitrate concentrations in groundwater and soil water on Joso Upland, 60 km northeast of Tokyo. The water samples were collected at four plots along the direction of groundwater flow, which existed in farm land, forest, the boundary between farm land and forest, and grassland near a spring, respectively. Soil water samples were collected at depths of 0.2 m, 1 m and 3 m in the forest. The nitrate concentrations of shallow groundwater in farm land, forest and grassland were from 8 to 11, 6 and 2 mg L^<-1>, respectively. The nitrate concentration of shallow groundwater remarkably decreased throughout the forest. This suggested dilution of shallow groundwater with soil water which had a lower nitrate concentration. The δ^<15>N values of shallow groundwater in the forest (12 ‰) and grassland (more than 14 ‰) were higher than those of the shallow groundwater in the farm land (6 ‰), and the soil water in the forest (about 2 ‰). These results indicated that the nitrate concentration decreased not only by the dilution process with soil water, but also by the denitrification process of shallow groundwater in the forest and grassland.