Comparative Survey on Non-Point Source Pollution among Three Regions in Japan

降雨径流含有多种污染物，可能导致公共水体水质恶化。近年来，许多研究人员试图对非点源污染进行定量评价，以明确污染物径流的机制。但是，NPS很大程度上依赖于区域特征，因此尚未进行系统的研究。本研究的目的是明确不同区域特征的NPS污染物径流特征。在船桥市和千代田市等城市地区，道路径流可能是主要的NPS。由于实验的困难，大多数的研究都是对沉积过程或径流过程进行研究。我们试图把每次调查所得的结果联系起来。因此，粒径和溶解度是影响污染物径流机制的关键因素。在郡山市，因洪水导致的NPS污染物流入Abukuma河和三春湖是主要问题。研究了洪水过程中污染物的运移机制。连续观测表明，污染物运移特征与区域特征相关。并建立了一个数学模型来表达本研究中所观察到的现象。模型还考虑了沉积过程、再悬浮过程以及河流沉积物与营养物之间的相关性。

Rainfall runoff contains several types of pollutants and possibly causes deterioration of water quality in public water bodies. Recently many researchers have tried to evaluate non-point source (NPS) pollution quantitatively and to make clear the mechanism of pollutant runoff. But NPS depends so much on the regional characteristics that systematic research has not been done. The purpose of this study is to make clear the characteristics of NPS pollutant runoff from areas with different regional characteristics.In urban area like Funabashi City and Chiyoda City, road runoff is possibly the main NPS. Most of researches were conducted to investigate either sedimentation process or runoff process, because of the experimental difficulties. We tried to link the results obtained from each investigation together. Consequently, particle size and solubility were suggested to be the key factors in the mechanism of pollutant runoff.In Koriyama City, NPS pollutant runoff into Abukuma River and Miharu Lake caused by floods is major problem. Transportation mechanisms of pollutants during floods were investigated. Continuous observation revealed that the pollutant transportation characteristics were correlated with the regional properties. And mathematical model to express the phenomena, which were observed in this study, was developed. Sedimentation process, re-suspension process, and the correlation between river sediments and nutrients were also considered in the model.