In the bottom layer the Hg content controlled by both Seasonal variation and transportation source

Abstract

Based on the investigation data of Jiaozhou Bay in 1992, the vertical distribution and seasonal variation of Hg in the surface and bottom layers from the center of the bay to the southeast of the bay were studied, and the seasonal distribution, variation range and horizontal distribution trend of Hg content in the surface and bottom layers were determined. The results showed that in May, August and October, in Jiaozhou Bay, from the central water area to the coastal water area in the southeast of the Bay, from the surface layer to the bottom layer, the range of Hg content in the bottom layer and the surface layer was: 0.007-0.040 μg/L, which conformed to the national water quality standard of class I seawater, and the water was not polluted by any Hg content. From May to October, in the central waters of Jiaozhou Bay, the seasonal changes of Hg content in the surface layer from low to high were spring, summer and autumn, and the seasonal changes of Hg content in the bottom layer from low to high were autumn, spring and summer. In the surface of the coastal waters in the southeast of Jiaozhou Bay, the seasonal changes of Hg content in the surface and bottom layers from low to high were autumn, spring and summer. The author put forward the law of Hg deposition: in summer, marine organisms propagated in large numbers, but in spring and autumn, there was no large number of marine organisms propagated. In this way, the Hg content sediment depended entirely on the combination of zooplankton, phytoplankton and floating particles in the sea water. Therefore, in summer, a large amount of Hg was taken to the seabed, while in spring and autumn, no large amount of Hg was taken to the seabed. In May, August and October, the change of Hg content in the surface and bottom layers fully confirmed the settlement law. Moreover, it was believed that a large number of marine organisms in the water were the main carriers to bring a large number of Hg to the seabed. Therefore, the variation of Hg content in the bottom was determined by the surface Hg content and the vehicles that transport Hg content vertically to the sea bottom, which resulted in the fact that the horizontal distribution trend of Hg content in the surface and bottom was same.