TY - JOUR
T1 - Assessment of global nitrogen pollution in rivers using an integrated biogeochemical modeling framework
AU - He, Bin
AU - Kanae, Shinjiro
AU - Oki, Taikan
AU - Hirabayashi, Yukiko
AU - Yamashiki, Yosuke
AU - Takara, Kaoru
N1 - Funding Information:
This study was supported by the Kyoto University Global COE program “Sustainability/Survivability Science for a Resilient Society Adaptable to Extreme Weather Conditions” and the JSPS Grants-in-Aid for Scientific Research . This work was also partially supported by JSPS KAKENHI, Grants-in-Aid for Scientific Research (S)( 19106008 ). We wish to thank Dr. Lex Bouwman for providing us with global data on N input including sewage effluents, net N input via fertilizer and manure, etc., and Mr. Leif Harum for giving us good comments about this article. The authors are grateful for their supports.
PY - 2011/4
Y1 - 2011/4
N2 - This study has analyzed the global nitrogen loading of rivers resulting from atmospheric deposition, direct discharge, and nitrogenous compounds generated by residential, industrial, and agricultural sources. Fertilizer use, population distribution, land cover, and social census data were used in this study. A terrestrial nitrogen cycle model with a 24-h time step and 0.5° spatial resolution was developed to estimate nitrogen leaching from soil layers in farmlands, grasslands, and natural lands. The N-cycle in this model includes the major processes of nitrogen fixation, nitrification, denitrification, immobilization, mineralization, leaching, and nitrogen absorption by vegetation. The previously developed Total Runoff Integrating Pathways network was used to analyze nitrogen transport from natural and anthropogenic sources through river channels, as well as the collecting and routing of nitrogen to river mouths by runoff. Model performance was evaluated through nutrient data measured at 61 locations in several major world river basins. The dissolved inorganic nitrogen concentrations calculated by the model agreed well with the observed data and demonstrate the reliability of the proposed model. The results indicate that nitrogen loading in most global rivers is proportional to the size of the river basin. Reduced nitrate leaching was predicted for basins with low population density, such as those at high latitudes or in arid regions. Nitrate concentration becomes especially high in tropical humid river basins, densely populated basins, and basins with extensive agricultural activity. On a global scale, agriculture has a significant impact on the distribution of nitrogenous compound pollution. The map of nitrate distribution indicates that serious nitrogen pollution (nitrate concentration: 10-50 mg N/L) has occurred in areas with significant agricultural activities and small precipitation surpluses. Analysis of the model uncertainty also suggests that the nitrate export in most rivers is sensitive to the amount of nitrogen leaching from agricultural lands.
AB - This study has analyzed the global nitrogen loading of rivers resulting from atmospheric deposition, direct discharge, and nitrogenous compounds generated by residential, industrial, and agricultural sources. Fertilizer use, population distribution, land cover, and social census data were used in this study. A terrestrial nitrogen cycle model with a 24-h time step and 0.5° spatial resolution was developed to estimate nitrogen leaching from soil layers in farmlands, grasslands, and natural lands. The N-cycle in this model includes the major processes of nitrogen fixation, nitrification, denitrification, immobilization, mineralization, leaching, and nitrogen absorption by vegetation. The previously developed Total Runoff Integrating Pathways network was used to analyze nitrogen transport from natural and anthropogenic sources through river channels, as well as the collecting and routing of nitrogen to river mouths by runoff. Model performance was evaluated through nutrient data measured at 61 locations in several major world river basins. The dissolved inorganic nitrogen concentrations calculated by the model agreed well with the observed data and demonstrate the reliability of the proposed model. The results indicate that nitrogen loading in most global rivers is proportional to the size of the river basin. Reduced nitrate leaching was predicted for basins with low population density, such as those at high latitudes or in arid regions. Nitrate concentration becomes especially high in tropical humid river basins, densely populated basins, and basins with extensive agricultural activity. On a global scale, agriculture has a significant impact on the distribution of nitrogenous compound pollution. The map of nitrate distribution indicates that serious nitrogen pollution (nitrate concentration: 10-50 mg N/L) has occurred in areas with significant agricultural activities and small precipitation surpluses. Analysis of the model uncertainty also suggests that the nitrate export in most rivers is sensitive to the amount of nitrogen leaching from agricultural lands.
KW - Anthropogenic sources
KW - Global rivers
KW - Nitrogen pollution load
KW - Terrestrial ecosystem
KW - Water quality
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U2 - 10.1016/j.watres.2011.02.011
DO - 10.1016/j.watres.2011.02.011
M3 - Article
C2 - 21402394
AN - SCOPUS:79953212894
SN - 0043-1354
VL - 45
SP - 2573
EP - 2586
JO - Water Research
JF - Water Research
IS - 8
ER -