The dynamic change in the shorelines reflects an important sign to the socio-economic development of coastal areas. The Huizhou–Shanwei region of China has experienced rapid socio-economic development over the past 33 years. The study of the dynamic change in the shorelines in this region can provide basic data support for the marine environmental protection and regional development planning in this region. Based on Landsat RS (remote sensing) images from 1990 to 2023, this study obtained the length and structure data of the shorelines in eight periods by manual visual interpretation. DSAS (Digital Shoreline Analysis System) and other methods were also used to calculate indices such as EPR (End Point Rate) and fractal dimension of the shorelines The results show that, during 33 years, the length of the shorelines increased 15.83 km, with an average growth rate of 0.48 km/y; the value of the intensity of change in the shorelines was 0.08%; the average EPR was 3.66 (m/y), and the artificiality index of the shorelines increased from 0.2895 to 0.4295; the greatest intensity of change was in the estuarine shorelines, with an intensity of change of −2.69%. The overall change in the fractal dimension of the shorelines was small, both between 1.0395 and 1.0673; the shorelines became slightly more curved. As far as the influencing factors are concerned, the influence of the natural environment is a long process, and human activities are more capable of changing the length and shape of the shorelines in a short period of time, with factors such as the degree of economic development having a greater impact on the shorelines.

This paper presents a comprehensive analysis of the distribution characteristics and environmental assessment of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) in the surface sediments of the Chaoshan estuary and nearshore waters from 2020 to 2021. By measuring surface sediment samples from 114 stations in Chaoshan near-shore waters, analyzing their TOC, TN and TP contents and distribution characteristics, and evaluating the pollution status by using two methods, namely, Nemero's Comprehensive Pollution Index Method and Ecotoxicity Effect, the sources of organic matter in surface sediments were initially. By comparing the content of TOC, TN, TP and the source of organic matter in the local area of the study area in the past 15 years, and summarizing the change rule, it is of great significance to comprehensively understand the current situation of surface sediment and the ecological risk of pollution in the study area. The results show:The contents of TOC, TN and TP in the surface sediments of the Chaoshan near-shore waters ranged from 0.05–1.36%, 0.006–0.210%, and 0.015–0.112%, respectively; The distribution is higher in the bay than outside the bay, higher at the mouth of the river than in the near-shore area, and gradually decreasing from the shore to the sea.;34.2% of the stations in the study area are at cleaner and above levels, 65.8% of the stations are at light to moderate pollution levels, 71.9% of the area is heavily polluted by TN and meets the criteria for Class II pollution, and 28.1% of the area is polluted by TOC and TP, which are Class I polluted༛Based on the C/N ratio to determine the source of organic matter, the source of organic matter in the surface sediments in the study area is dominated by input from marine sources, and there is a significant correlation between the various factors༛Comparison of localized surface sediments in the study area in the last 15 years revealed that TOC and TN content decreased compared to the historical period, TP content increased, C/N ratio increased compared to the historical period and was greater than 8, and the source of organic matter was dominated by a mixture of inputs from both marine and terrestrial sources.