The hypothesis that the product of discharge and concentration of nitrogen (N) in river water is equal to the atmospheric deposition was verified in the mountainous basin of the Tedori River in Japan. To verify this r...The hypothesis that the product of discharge and concentration of nitrogen (N) in river water is equal to the atmospheric deposition was verified in the mountainous basin of the Tedori River in Japan. To verify this relationship, long-term data?are required to eliminate the effect of short-term variation of the N components. The basin has very high mountains, including Mount Hakusan (2702 maltitude), which is covered with deep snow in winter. Therefore, limited data were used for the estimation of the deposition of the entire basin by assuming a linear relationship of altitude. As a result, it was found that the estimated N concentration coincided well with observed concentrations at six sites—the Shiramine and Kuwajima (upper stream), Nakajima (lower stream) and Dainichi dam, Tedori dam and Senami sites (middle stream). The seasonal variation of N concentrations was low in the snowmelt period and high in autumn through to winter. This was not due to the larger discharge in snowmelt season as it was also found that N deposition was high in winter and low in spring, which indicated a clear relationship between N concentration and monthly atmospheric deposition including N storage in snow pack.展开更多
Quantitative analysis of the rate of geochemical weathering of sulfur (S) from sedimentary rocks (GeoS) was conducted using concentration (Cs) and discharge (Qs) data from the Tedori River and atmospheric deposition (...Quantitative analysis of the rate of geochemical weathering of sulfur (S) from sedimentary rocks (GeoS) was conducted using concentration (Cs) and discharge (Qs) data from the Tedori River and atmospheric deposition (AtdepS) in the basin. First, S fluxes were calculated using 16 years of Cs and Qs data. The annual average discharge of S (TotalS) was estimated at 8597 ton·year-1 (117.3 kg·ha-1·year-1). Of this, 1331 ton·year-1 was AtdepS (18.2 kg·ha-1·year-1) and another 7266 ton·year-1 was GeoS (99.1 kg·ha-1·year-1). Monthly changes in TotalS were investigated, which showed that GeoS was highest in summer, because of the air temperature, while AtdepS peaked in winter because of seasonal wind. Using Qs and AtdepS corrected for altitude, TotalS, AtdepS and GeoS were estimated at six sites, and among these sites we found that the TotalS per unit area values were random, depending on the site characteristics. In particular, the discharge from the Kuwajima site was remarkably high suggesting that the sedimentary rocks at this site had higher pyrite content than at the other sites. Finally, we also assessed the relationship between the characteristics of sedimentary rocks and GeoS in a range of rivers in the Hokuriku Region, and found that there was a close relationship between concentrations of SO42- greater than 10 mg·l-1 and sedimentary rocks containing the pyrite group. In addition, we estimated that the influence of GeoS was present when the concentration of SO42- in river water was greater than 2 - 3 mg·l-1 in the Hokuriku region.展开更多
To evaluate the nitrogen pollution load in an aquifer, a water and nitrogen balance analysis was conducted over a thirty-five year period at five yearly intervals. First, we established a two-horizon model comprising ...To evaluate the nitrogen pollution load in an aquifer, a water and nitrogen balance analysis was conducted over a thirty-five year period at five yearly intervals. First, we established a two-horizon model comprising a channel/soil horizon, and an aquifer horizon, with exchange of water between the aquifer and river. The nitrogen balance was estimated from the product of nitrogen concentration and water flow obtained from the water balance analysis. The aquifer nitrogen balance results were as follows: 1) In the aquifer horizon, the total nitrogen pollution load potential (NPLP) peaked in the period 1981-1990 at 1800 t·yr-1;following this the NPLP rapidly decreased to about 600 t·yr-1 in the period 2006-2010. The largest NPLP input component of 1000 t·yr-1 in the period 1976-1990 was from farmland. Subsequently, farmland NPLP decreased to only 400 t·yr-1 between 2006 and 2010. The second largest input component, 600 t·yr-1, was effluent from wastewater treatment works (WWTWs) in the period 1986-1990;this also decreased markedly to about 100 t·yr-1 between 2006 and 2010;2) The difference between input and output in the aquifer horizon, used as an index of groundwater pollution, peaked in the period 1986-1990 at about 1200 t·yr-1. This gradually decreased to about 200 t·yr-1 by 2006-2010. 3) The temporal change in NPLP coincided with the nitrogen concentration of the rivers in the study area. In addition, nitrogen concentrations in two test wells were 1.0 mg·l-1 at a depth of 150 m and only 0.25 mg·l-1 at 50 m, suggesting gradual percolation of the nitrogen polluted water deeper in the aquifer.展开更多
Recently severe damage of flooding by urbanization was frequently occurred. To prevent this damage, small reservoir was constructed in the urbanized residential area. This paper describes an effect of flood peak disch...Recently severe damage of flooding by urbanization was frequently occurred. To prevent this damage, small reservoir was constructed in the urbanized residential area. This paper describes an effect of flood peak discharge control by a small reservoir (control reservoir) caused by rapidly developed urbanization. Although work for this purpose was conducted, research on the effects of the control reservoir was not conducted until now. This research, conducted by simulation, was a case study in the Kurabe River Basin in the Tedori River Alluvial Fan Area, Japan, based on the precise investigation of the reservoir in the actual field. The study was conducted to determine not only the actual control reservoir capacity for the newly developed residential area but also the ideal capacity for all present residential areas and the largest capacity allowable for a maximum rainfall event that recently occurred. The control reservoir effects between individual blocks and the entire basin area were compared by dividing the test basin into 15 blocks (sub-basins). The results showed that the effects on the capacity per unit area of the residential area in blocks have close relationship with the decreasing ratio of peak discharge in blocks. Consequently, the effects of control reservoir capacity and the limitation were clarified. In the future, control reservoirs should be constructed for all of the already developed residential areas, for example, by utilizing underground car parking lot. The results of this research can contribute to the design of the control reservoir for protection against flooding damage in urbanized areas.展开更多
文摘The hypothesis that the product of discharge and concentration of nitrogen (N) in river water is equal to the atmospheric deposition was verified in the mountainous basin of the Tedori River in Japan. To verify this relationship, long-term data?are required to eliminate the effect of short-term variation of the N components. The basin has very high mountains, including Mount Hakusan (2702 maltitude), which is covered with deep snow in winter. Therefore, limited data were used for the estimation of the deposition of the entire basin by assuming a linear relationship of altitude. As a result, it was found that the estimated N concentration coincided well with observed concentrations at six sites—the Shiramine and Kuwajima (upper stream), Nakajima (lower stream) and Dainichi dam, Tedori dam and Senami sites (middle stream). The seasonal variation of N concentrations was low in the snowmelt period and high in autumn through to winter. This was not due to the larger discharge in snowmelt season as it was also found that N deposition was high in winter and low in spring, which indicated a clear relationship between N concentration and monthly atmospheric deposition including N storage in snow pack.
文摘Quantitative analysis of the rate of geochemical weathering of sulfur (S) from sedimentary rocks (GeoS) was conducted using concentration (Cs) and discharge (Qs) data from the Tedori River and atmospheric deposition (AtdepS) in the basin. First, S fluxes were calculated using 16 years of Cs and Qs data. The annual average discharge of S (TotalS) was estimated at 8597 ton·year-1 (117.3 kg·ha-1·year-1). Of this, 1331 ton·year-1 was AtdepS (18.2 kg·ha-1·year-1) and another 7266 ton·year-1 was GeoS (99.1 kg·ha-1·year-1). Monthly changes in TotalS were investigated, which showed that GeoS was highest in summer, because of the air temperature, while AtdepS peaked in winter because of seasonal wind. Using Qs and AtdepS corrected for altitude, TotalS, AtdepS and GeoS were estimated at six sites, and among these sites we found that the TotalS per unit area values were random, depending on the site characteristics. In particular, the discharge from the Kuwajima site was remarkably high suggesting that the sedimentary rocks at this site had higher pyrite content than at the other sites. Finally, we also assessed the relationship between the characteristics of sedimentary rocks and GeoS in a range of rivers in the Hokuriku Region, and found that there was a close relationship between concentrations of SO42- greater than 10 mg·l-1 and sedimentary rocks containing the pyrite group. In addition, we estimated that the influence of GeoS was present when the concentration of SO42- in river water was greater than 2 - 3 mg·l-1 in the Hokuriku region.
文摘To evaluate the nitrogen pollution load in an aquifer, a water and nitrogen balance analysis was conducted over a thirty-five year period at five yearly intervals. First, we established a two-horizon model comprising a channel/soil horizon, and an aquifer horizon, with exchange of water between the aquifer and river. The nitrogen balance was estimated from the product of nitrogen concentration and water flow obtained from the water balance analysis. The aquifer nitrogen balance results were as follows: 1) In the aquifer horizon, the total nitrogen pollution load potential (NPLP) peaked in the period 1981-1990 at 1800 t·yr-1;following this the NPLP rapidly decreased to about 600 t·yr-1 in the period 2006-2010. The largest NPLP input component of 1000 t·yr-1 in the period 1976-1990 was from farmland. Subsequently, farmland NPLP decreased to only 400 t·yr-1 between 2006 and 2010. The second largest input component, 600 t·yr-1, was effluent from wastewater treatment works (WWTWs) in the period 1986-1990;this also decreased markedly to about 100 t·yr-1 between 2006 and 2010;2) The difference between input and output in the aquifer horizon, used as an index of groundwater pollution, peaked in the period 1986-1990 at about 1200 t·yr-1. This gradually decreased to about 200 t·yr-1 by 2006-2010. 3) The temporal change in NPLP coincided with the nitrogen concentration of the rivers in the study area. In addition, nitrogen concentrations in two test wells were 1.0 mg·l-1 at a depth of 150 m and only 0.25 mg·l-1 at 50 m, suggesting gradual percolation of the nitrogen polluted water deeper in the aquifer.
文摘Recently severe damage of flooding by urbanization was frequently occurred. To prevent this damage, small reservoir was constructed in the urbanized residential area. This paper describes an effect of flood peak discharge control by a small reservoir (control reservoir) caused by rapidly developed urbanization. Although work for this purpose was conducted, research on the effects of the control reservoir was not conducted until now. This research, conducted by simulation, was a case study in the Kurabe River Basin in the Tedori River Alluvial Fan Area, Japan, based on the precise investigation of the reservoir in the actual field. The study was conducted to determine not only the actual control reservoir capacity for the newly developed residential area but also the ideal capacity for all present residential areas and the largest capacity allowable for a maximum rainfall event that recently occurred. The control reservoir effects between individual blocks and the entire basin area were compared by dividing the test basin into 15 blocks (sub-basins). The results showed that the effects on the capacity per unit area of the residential area in blocks have close relationship with the decreasing ratio of peak discharge in blocks. Consequently, the effects of control reservoir capacity and the limitation were clarified. In the future, control reservoirs should be constructed for all of the already developed residential areas, for example, by utilizing underground car parking lot. The results of this research can contribute to the design of the control reservoir for protection against flooding damage in urbanized areas.
