Abstract
Spatial and temporal distributions of arsenic and other heavy metals in river waters, river sediments and spring waters were investigated in the Ina River System flowing in the east area of Hyogo Prefecture during 1996-99. Arsenic showed the highest concentration at the water quality monitoring point of Gin-bashi, located in middle reaches, among the sampling points in the main stream. The concentration was found to be influenced from three tributaries, Nojiri River, Shio River and Yato River, and several springs containing arsenic in the order of 10-100μg·l-1. Other heavy metal concentrations in river waters did not differ from average in this prefecture. Dissolved As3+ was found as major arsenic component in most of the springs. In main stream, arsenic in river sediments also indicated similar distribution pattern as the pattern in river waters.
From these results and long-term monitoring data of arsenic, it is presumed that the distributions of arsenic in river waters and sediments are influenced basically by geological features, and temporarily by Hyogo-ken Nanbu Earthquake and Inagawa Earthquake Swarm.
