Isotope hydrograph separation for modeling of runoff mechanisms of atmospherically derived chemical and radioactive pollutants

Matsunaga, Takeshi; Yanase, Nobuyuki; Hanzawa, Yukiko  ; Tsuzuki, Katsunori  ; Naganawa, Hirochika  

In a tributary watershed of the Kuji River of Japan, the hydrological components of runoff associated with a rain storm event were investigated using isotope tracers of hydrogen (H) and oxygen (O) in precipitations and stream water. The runoff was separated into either "old water" (pre-existing in the ground before the storm) and "new water"(from the storm precipitation). It was found that the discharge of several hazardous trace elements (Sb, Cu, Cr) was largely (24-54%) attributable to that of the new water in spite of its small contribution to the total water discharge. These investigations suggest that the new water may play an important role in the migration of atmospherically derived, hazardous trace elements to streams during rain storms.