Center for Promotion of Interdisciplinary Education and Research, Educational Unit for Adaptation and Resilience for a Sustainable Society, Kyoto University, Kyoto, Japan.
Water Res. 2011 Apr;45(8):2573-86. doi: 10.1016/j.watres.2011.02.011. Epub 2011 Feb 19.
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.
本研究分析了大气沉积、直接排放以及居民、工业和农业源产生的含氮化合物导致的全球河流氮负荷。本研究使用了肥料使用、人口分布、土地覆盖和社会普查数据。开发了一个具有 24 小时时间步长和 0.5°空间分辨率的陆地氮循环模型，以估计农田、草地和自然土地中土壤层的氮淋失。该模型中的氮循环包括氮固定、硝化、反硝化、固定化、矿化、淋失以及植被对氮的吸收等主要过程。先前开发的总径流综合途径网络用于分析从自然和人为源通过河道输送的氮以及通过径流向河口收集和输送氮的过程。通过在世界几个主要河流流域的 61 个地点测量的养分数据对模型性能进行了评估。模型计算的溶解无机氮浓度与观测数据吻合较好，证明了所提出模型的可靠性。结果表明，大多数全球河流的氮负荷与流域面积成正比。预测低人口密度流域（如高纬度或干旱地区）的硝酸盐淋失减少。硝酸盐浓度在热带湿润河流流域、人口稠密的流域和农业活动广泛的流域中尤其高。在全球范围内，农业对含氮化合物污染的分布有重大影响。硝酸盐分布图表明，在农业活动显著且降水盈余较小的地区发生了严重的氮污染（硝酸盐浓度：10-50mgN/L）。对模型不确定性的分析还表明，大多数河流的硝酸盐输出对农业用地的氮淋失量敏感。
