Abstract
The purpose of this study is to clarify the sources structure of Organic Halogens Precursor (OXP) in a whole river basin. First, runoff characteristics of OXP on three non-point sources (precipitation, urbanized area, forest area) were surveyed and their mechanisms were grouped into two categories, one was the STORM model type (precipitation, urbanized area) and another was the direct proportionate type to cumulative flow (forest area). Organics from urbanized area was abundant in OXP. Second, the runoff load at the confluence of three branch rivers were divided into four components (direct runoff, indirect runoff, the Lake Biwa, point sources). Expressed in the product of flow by water quality coefficient, cumulative load of each component was calculated throughout a year. As results, the load of OXP at the confluence amounted to 1.91 × 106kg and about 76% of that was attributed to both direct runoff and the Lake Biwa. Organics by direct runoff was abundant in OXP. Lastly, some factors related to sources control were mentioned as to direct runoff and point sources.
