Vertical settlement results in homogeneous of Hg between surface and bottom waters in Jiaozhou Bay

Abstract

Using investigation data on Mercury (Hg) in waters between the bay center and the bay mouth in Jiaozhou Bay in May and August 1990, this paper analyzed the vertical settlement process and the influence on the vertical variation of Hg contents. Results showed that Hg contents in surface waters in May and August 1990 were 0.189-0.204 μg L−1 and 0.053-0.063 μg L−1, compared to 0.194-0.208 μg L−1 and 0.055-0.055 μg L−1 in bottom waters. The pollution level in May was moderate, compared to slight polluted in August. There were high settlement processes in the bay center in May and August 1990. Hg contents in bottom waters would be high/low in case that Hg contents in surface waters were high/low. By means of vertical water’s effect, the settlement processes of Hg in waters were rapid in different space and time, resulting in the homogeneous of Hg contents between surface and bottom waters.