2020 Volume 30 Pages 17-22
The mercury concentration of river waters in Niigata Prefecture was studied for regional distribution, fluctuation factors, and speciation. We investigated 11 rivers in Niigata Prefecture four times a year. As a result, average concentrations of total mercury (T-Hg), and dissolved T-Hg in the river waters were 1.7 ng/L, and 0.29 ng/L, respectively. The average ratio of dissolved alkyl mercury concentrations to dissolved T-Hg concentrations were about 15%. The dissolved T-Hg concentrations had no observable regional differences. On the other hand, the T-Hg concentration in suspended solids (SS) was highest in the Seki River. The average T-Hg concentration in SS (SS-Hg) in the Seki River was 0.34 μg/g, whereas those in the other rivers ranged from 0.11 to 0.23 μg/g. The factor that increased SS-Hg concentration in the Seki River is considered to be the sediment originated from volcano. We investigated long-term fluctuations of T-Hg concentration in the Shinkawa River during April 2017 to March 2019. As a result, the average concentrations of dissolved T-Hg and particulate T-Hg in the Shinkawa River were 0.40 ng/L and 2.3 ng/L, respectively. The particulate T-Hg concentration was highly correlated with SS concentration.
