Integrated biogeochemical modelling of nitrogen load from anthropogenic and natural sources in Japan

Source Apportionment of Annual Water Pollution Loads in River Basins by Remote-Sensed Land Cover Classification

“…Table 2 shows the statistical description of the collected water quality data. For all 30 sites over Japan, large variations of annual concentration of TN, TP, and BOD were observed between rivers, with a smallest coefficient of variation as 10.3% for DO and highest value as 162.6% for TP [14]. The large spatial variation of TP concentration are corresponding to the large differences in regional characteristics including population, topography, geology, agricultural activities, and land use in 30 river basins.…”

“…The large spatial variation of TP concentration are corresponding to the large differences in regional characteristics including population, topography, geology, agricultural activities, and land use in 30 river basins. Furthermore, significant correlation coefficients from the Pearson correlation analysis [32] for detecting the relationships between water pollutant loads and land cover have been found [14]. As for the hydrochemical datasets, we collected available long-term observation data of river discharge, TN, TP, BOD, COD, and DO concentration for 30 selected river outlets (Figure 2), which represented different regions of Japan, for 11 years (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004).…”

“…The large spatial variation of TP concentration are corresponding to the large differences in regional characteristics including population, topography, geology, agricultural activities, and land use in 30 river basins. Furthermore, significant correlation coefficients from the Pearson correlation analysis [32] for detecting the relationships between water pollutant loads and land cover have been found [14]. For a clearer understanding of the spatial distribution of water pollution loads in Japan, the basin area and river mouth discharge for each catchment are listed in Table 3.…”

“…As for the hydrochemical datasets, we collected available long-term observation data of river discharge, TN, TP, BOD, COD, and DO concentration for 30 selected river outlets (Figure 2), which represented different regions of Japan, for 11 years (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004). Statistical analysis has been conducted for the collected monthly hydrochemical database from the National Land with Water Information (http://www1.river.go.jp/) monitoring network [14]. Table 2 shows the statistical description of the collected water quality data.…”

“…Generally, a river's water quality is linked to the land cover in the watershed and is degraded by changes in the land cover patterns on their watersheds as human activities increase [5][6][7][8]. Different studies have increasingly recognized that human action at the landscape scale is a principal threat to the ecological integrity of river ecosystems and water quality [9][10][11][12][13][14][15]. However, the information on the sources of pollutants in catchments and on the response of water quality to changing land use practices is still limited in many catchments [16][17][18][19][20].…”