The Cd Content Provided By Sources Affected the Bottom Waters in Various Ways

Abstract

According to the investigation data of Jiaozhou Bay in 1992, this paper studies the level of Cd content and its horizontal distribution in the bottom waters from the center of the bay to the south of the bay mouth. The result indicates that the Cd content in the bottom waters of the bay ranged from 0.09 to 0.72μg/L in May, 0.08 to 1.08μg/L in August and 0.30 to 1.19μg/L in October, which means that waters of the bay were not polluted at all by Cd in May but some waters were mildly contaminated in both August and October. In a word, the bottom bay waters from the center of the bay to the south of the bay mouth were slightly polluted or not polluted at all by Cd in May, August and October. In May, surface runoff and rivers together transported Cd content of 1.07-1.53μg/L to Jiaozhou Bay waters. In the bottom waters from the southeast to the center of the bay, the Cd content decreased from 0.72μg/L to 0.09μg/L. The Cd content in the bottom waters of the southeast of the bay is relatively high for the sources of Cd could reach its surface waters there. However, much little Cd content is found in the bottom waters of the center of the bay due to the lack of Cd access to its surface waters. In August, rivers and main sea currents together transported Cd content of 0.96-1.11μg/L to Jiaozhou Bay waters. According to transporting mechanism of substance content in Jiaozhou Bay introduced by the author, high Cd content area of 1.08μg/L exists in the bottom waters of the center of the bay, while low-content area of 0.08μg/L was in the southwest of the bay where currents are about to leave the bay. In October, rivers transported Cd content of 1.04-1.10μg/L to Jiaozhou Bay waters. The Cd content decreased from 1.19μg/L to 0.30μg/L along the content gradient from the high-content area of the southeast of the bay to the waters of the south of the bay mouth. In the waters of the southeast of the bay, relatively high Cd content transported to the surface waters by sources leads to high level of Cd in its bottom waters. It’s the exact opposite in the waters of the south of the bay mouth. The Cd content provided by sources affects the law of the bottom waters in various ways, and the horizontal variation of Cd content reveals its changing process in the bottom waters.