The Slowly Rising Cadmium Content at Bottom

Based on investigation data of Cd content in Jiaozhou Bay in May, August and October of 1991, this paper studied the variation and sedimentation of Cd content at surface and bottom. According to the definition and model of Dongfang Yang's content changing angle, the results showed that at surface layers, Dongfang Yang's content changing angle was -7.96° from May to August and 9.09° from August to October, and at bottom, it was 1.71° and 2.86° correspondingly. In temporal variation, Cd content discharged by human activities to ocean slowly decreased to low value from May to August and slowly increased to high value from August to October. Further, through waters, bottom sediment amount increased slowly and less from May to August and from August to October. In spatial variation, whether Cd content transported by ships and wharfs increased or decreased, Cd content at bottom slowly increased all the time. It showed that from May to October, Cd content at surface rapidly and constantly sedimented to seafloor, causing the accumulation at bottom and slowly rising Cd content at bottom. Thus, with human's emphasis on the safe environment, Cd content transported by ships and wharfs decreased, causing no pollution to water quality.