TY - JOUR
T1 - Differences in stream water nitrate concentrations between a nitrogen-saturated upland forest and a downstream mixed land use River Basin
AU - Shinozuka, Ken'ichi
AU - Chiwa, Masaaki
AU - Tayasu, Ichiro
AU - Yoshimizu, Chikage
AU - Otsuki, Kyoichi
AU - Kume, Atsushi
N1 - Funding Information:
The cost of publication was supported in part by a Global COE Program from Kyushu University. This study was partly financially supported by Grants-in-Aid for Scientific Research (17H03833). We thank Tetsuji Ota (Kyushu University) and the members of the Tayasu laboratories (Center for Ecological Research, Kyoto University) who helped with the experiments. We also thank the members of the University of Kyushu University for their support in this study
Publisher Copyright:
© 2019 by the authors.
PY - 2017/1/1
Y1 - 2017/1/1
N2 - Nitrogen (N) saturation of upland forests has been assumed to be a substantial N source downstream. However, removal processes of N, including assimilation and denitrification in the downstream area, have not been clarified. To evaluate the N removal processes, nitrate (NO3 -) and organic N concentrations, as well as nitrogen isotope ratio (δ15N) and oxygen isotope ratio (δ18O) of NO3 - were measured along three rivers of Tatara River Basin, Japan where upland forests have already been N-saturated. Geographic information system (GIS) based topographical analysis was also conducted to evaluate the land use as urban area in relation to topography. In two of the three rivers, NO3 - concentrations did not increase from upstream to downstream, despite the potential non-point N sources of urban areas. In another river, NO3 - concentrations rather decreased. The values of δ15N and δ18O of NO3 - and organic N concentrations suggested the presence of denitrification and assimilation over N pollutants in the river whose watersheds have a lower percentage of urban area. The lower percentage of urban area could be explained by the lower topographic index. This study concluded that the NO3 - leaching from upland N-saturated forests was substantially assimilated or denitrified in the downstream area.
AB - Nitrogen (N) saturation of upland forests has been assumed to be a substantial N source downstream. However, removal processes of N, including assimilation and denitrification in the downstream area, have not been clarified. To evaluate the N removal processes, nitrate (NO3 -) and organic N concentrations, as well as nitrogen isotope ratio (δ15N) and oxygen isotope ratio (δ18O) of NO3 - were measured along three rivers of Tatara River Basin, Japan where upland forests have already been N-saturated. Geographic information system (GIS) based topographical analysis was also conducted to evaluate the land use as urban area in relation to topography. In two of the three rivers, NO3 - concentrations did not increase from upstream to downstream, despite the potential non-point N sources of urban areas. In another river, NO3 - concentrations rather decreased. The values of δ15N and δ18O of NO3 - and organic N concentrations suggested the presence of denitrification and assimilation over N pollutants in the river whose watersheds have a lower percentage of urban area. The lower percentage of urban area could be explained by the lower topographic index. This study concluded that the NO3 - leaching from upland N-saturated forests was substantially assimilated or denitrified in the downstream area.
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U2 - 10.3390/hydrology4030043
DO - 10.3390/hydrology4030043
M3 - Article
AN - SCOPUS:85046879713
VL - 4
JO - Hydrology
JF - Hydrology
SN - 2306-5338
IS - 3
M1 - 43
ER -
