The influence of Cd Content Transported by Different Sources on Different Surface and Bottom Layers

Abstract

According to the investigation data of Jiaozhou Bay in 1992, the vertical distribution, horizontal distribution and seasonal variation of Cd in the surface and bottom waters from the center of the bay to the south of the mouth of Jiaozhou Bay are studied, and the seasonal distribution, range of distribution and horizontal distribution trend are determined. The results show that in May, August and October, in the waters from southern mouth to the center of the bay, the Cd content of surface and bottom waters ranged from 0.12-1.19μg/L, in line with the national water quality standards for Class I and Class II seawater, which indicates that water quality was slightly polluted by the Cd content orwas not polluted. The surface levels of Cd vary seasonally from low to high: spring, summer, and fall, the same was true for Cd seasonal variation in bottom waters. In the surface and bottom waters of Jiaozhou Bay from the south of the bay mouth to the center of the bay, in May, August and October, when the Cd content in surface waters was relatively low, and the corresponding bottom layer was relatively low; when the Cd in surface waterswas relatively high, the corresponding bottom layer was relatively high; this shows that the loss of Cd content both from the surface and the bottom was relatively high. In May, August and October, in the waters from the southeast of the bay to the center of the bay, the horizontal distribution of Cd in the surface and the bottom waters have an opposite trend. From May to October, the seasonal variation of Cd content in surface waters in the southeast of the bay was mainly affected by the Cd content transported by main sea currents, while the bottom waters are mainly affected by river-transported Cd content. From May to October, in the central waters of Jiaozhou Bay, the seasonal changes of surface and bottom Cd content are not consistent withthat of Cd content transported by main sea currents. On the temporal scale, in the waters of Jiaozhou Bay from the south of the bay to the center of the bay, in May, August and October, the Cd content in the surface and bottom watersvariateswithin the same range, maintaining the consistency. On the spatial scale, in the waters from the southeast of the bay to the center of the bay, in May, August and October, according to the comparison between the Cd content transported by main sea currents and that transported by rivers, it can be proved that the horizontal distribution of Cd content in the surface waters was opposite to that of in the bottom waters.