PRESENCE STATE OF TRACE ELEMENTS IN THE OHTAKIGAWA RIVER WATERSHED FROM THE FOOT OF Mt. ONTAKE

This paper is aimed at understanding the influence of Mt. Ontake volcanic activity on the water quality of the Ohtakigawa River watershed. For this purpose, various properties of trace elements are obtained. The Ohtakigawa, which flows along the southern foot of Mt. Ontake, has several tributaries such as Nigorigawa River, Shirakawa River, Shimokurosawa River, and Uguigawa River. Seven sampling stations were selected in the four tributaries (four points) and the Ohtakigawa (three points). Filtration of samples was carried out with teflon filter paper (PTFE, 0.5μm, φ 47mm), and the samples were separated into dissolved and suspended matters. Trace elements contained in them were analyzed by using the ICPE. The concentrations of the trace elements were high in the following order: the Nigorigawa (Al: 6.16mg L), the Ohtakigawa after the confluence of the Nigorigawa (Al: 1.92mg L and 0.88mg L), and the others (Al: 0.06-0.70mg L). This result indicates that among the four tributaries, the Nigorigawa plays a predominant role in the change in the water quality of the Ohtakigawa.