Large amount of settlement brought by the river

Abstract

Utilizing the survey dataset of Pb in waters from south of bay mouth to southeast of bay in October 1992, and applying the horizontal and vertical change models of matter content put forward by authors, we would calculate the horizontal loss amount, vertical diluted amount and vertical sediment amount of Pb in surface and bottom layers and set up the model diagram on the Pb content horizontal and vertical changes. The research results unveiled that in October, the absolutely horizontal loss amount of Pb content in surface layer and bottom layer was 3.58–7.89μg/L, and the relatively horizontal loss amount of Pb content in surface layer and bottom layer was 27.01–51.30%. In the southern waters of bay mouth, the absolutely vertical sediment amount of Pb was 2.13μg/L, and the relatively vertical sediment amount was 13.84%. In the southeastern waters of the bay, Pb content in the surface layer and bottom layer had an absolutely vertical diluted amount of 6.61μg/L and a relatively vertical diluted amount of 22.54%. In October, in the surface waters, after the main sea current brought high Pb content to the southern waters of the bay mouth, the Pb content began to settle to the seabed in large quantities, leading to a horizontal loss amount of almost one third 27.01% of the Pb content on surface when the current entered the bay. Pb content in the bottom layer of the seabed also reduced greatly by 51.30%, which was more than half. It revealed that Pb content in the surface layer could settle to the bottom rapidly and continuously when the current entered the bay, causing a large loss amount of Pb content in the surface layer. At the same time, the Pb content on the bottom was largely buried in the seabed, causing a lot of losses. In October, in the process of vertical migration, the vertical sediment amount of Pb in the surface and bottom layers 13.84% was shifted to the vertical diluted amount of Pb in the surface and bottom layers 22.54% before and after the main sea current entered the bay. The high Pb content transported by the main sea current had a large amount of settlement in the southern waters of the bay mouth and accumulated in the seabed. However, when the current reached the bay with Pb content, there was also a large amount of settlement in the southeastern part of the bay, but no accumulation in the seabed.