Characteristics of Nutrient discharge in the major river basins of Hiroshima Prefecture.

To estimate the nutrient discharge from land to the sea, we conducted hydrochemical investigations of the major rivers at the 15 catchments located in Hiroshima-Prefecture. The results are summarized as follows:1) Seasonal variations of TN load in Ohta river and Ashida river indicate that precipitation have a large effect on the river runoff and TN load change with the amount of river discharge. It also suggests the characteristics of TN discharge with the difference of precipitation.2) The DOC and DN load from the middle-scale and small-scale catchments are estimated to be not small. We confirmed that the DOC and DN load per unit area are relatively large in the small catchments with low urban infrastructure, such as waste water system.3) DOC and DN fluxes mainly changed with the variation of river runoff and land use