抄録
A follow-up study was carried out on secular changes from 1974 to 1977 of mercury concentrations in bottom sediments of the Suimon River and other rivers polluted by the effluent from a chemical plant which had been manufacturing acetaldehyde with mercurial catalyst. The results obtained were summarized as follows.
1) Mercury concentrations in sediments from each sampling station were found to have fairly changed in the period.
2) There was no possibility of additional pollution by other industrial sources.
3) There was very little possibility of release of mercury from bottom sediments.
4) The changes of mercury concentrations in sediments appeared to relate closely to the state of rainfalls, especially outbreak of torrential downpours in the catchment area.
5) Torrential downpours were observed to exert a considerable influence on the change of particle size distribution of sediments.
6) Mercury concentrations in sediments correlated significantly to the contents of fine particle fraction of sediments.
