Abstract: Sediment pollution in closed bays is directly impacts the ecological security of coastal environments. As a closed bay, Xinglin bay faces ongoing challenges in achieving stable water quality standards, even after the implementation of pollution control measures. This instability poses a risks to the regional urban economy and social development. In response, we analyzed and evaluated sediment samples from the bay, proposing appropriate control measures. The analysis results indicate that the organic matter content of surface sediments ranged from 1.93% to 15.40%, total nitrogen(TN) from 650 to 3980 mg·kg^-1, and total phosphorus(TP) from 311 to 2470 mg·kg^-1. These pollutants exhibited higher concentrations in the eastern and western bay rims and the northern inlet estuary, while lower levels were observed in the center and near the seawall. The organic index of the surface sediments ranged 0.07 to 2.53, with 54.3% of the sites showing moderate to severe pollution levels, predominantly near the northern inlet estuary, bay rims; the TP single factor index of surface sediments ranged from 0.52 to 4.12, with 30% of sites showing moderate to severe pollution levels, and the distribution characteristics were similar to those of the former. The vertical distribution analysis showed that the content gradually decreased with depth, with significant enrichment in surface layers, particularly in the eastern and western bay rim and the northern inlet estuary areas. Based on the spatial distribution characteristics and pollution evaluation results, a combination of conventional dredging and in-situ ecological restoration was proposed to provide crucial support for the comprehensive water environment improvement in the Xinglin Bay Area.

Key words: Closed bay, sediments, pollution evaluation, internal pollution control