A Study on scheme of stream discharge of hazardous metals in rainfall events
Matsunaga, Takeshi; Yanase, Nobuyuki; Hanzawa, Yukiko ; Tsuzuki, Katsunori ; Naganawa, Hirochika
Stream discharge of metallic elements from the ground was investigated in a forested catchment in the Oda River watershed in the central Japan. The investigation revealed that several hazardous metals such as Cu, Sb and Cr in dissolved form and also rare earth elements are peculiar elements whose stream discharges are always accelerated in a rainfall event. Further, two different schemes of elemental transport in this peculiar discharge were suggested. They were (1) a coincidently occurring discharge with an initial increase in a flow rate of a stream, and (2) a discharge with slower increase and prolonged decrease, which are poorly corresponding to the change in the stream flow rate. An analysis of hydrological discharge, using chemical signatures of natural organic materials (NOM) and isotopic signatures of deuterium and oxygen of water suggested that the latter discharge is associated with that of NOM of the soil layer. The latter discharge was also effective for rare earth elements.