Abstract:

Sediment pollution in closed bays poses a direct threat to the ecological security of coastal environments. As a closed bay, Xinglin Bay faces ongoing challenges in maintaining stable water quality despite implemented pollution control measures, posing risks to regional economic and social development. To address this issue, we analyzed and evaluated sediment samples collected from Xinglin Bay and proposed corresponding control strategies. Our analysis indicated that the surface sediments in the bay area contain organic matter (OM) ranging from 1.93% to 15.40%, total nitrogen (TN) ranging from 650 to 3980 mg·kg^-1, and total phosphorus (TP) ranging from 311 to 2470 mg·kg^-1. These pollutants were more concentrated in the eastern and western rims of the bay and the northern estuary, while lower concentrations were detected in the central area and near the seawall. The organic pollution index of surface sediments ranged from 0.07 to 2.53, with 54.3% of sampling sites showing moderate to severe pollution, particularly near the northern estuary and bay rims. Similarly, the TP single-factor index ranged from 0.52 to 4.12, with 30% of sites showing moderate to severe pollution, following a distribution pattern similar to OM and TN. Vertical distribution analysis indicated that OM, TN, and TP concentrations gradually decreased with depth, with significant enrichment in the surface layers, especially in the eastern and western bay rims and the northern estuary. Based on these pollution evaluation results, we recommend a combination of conventional dredging and in-situ ecological restoration measures. This integrated approach can provide technical support for the comprehensive improvement of the water environment in Xinglin Bay.

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