As urbanization accelerates, a growing influx of pollutants enters the sea through land runoff, posing a threat to coastal ecosystems. In this study, we systematically determined the concentrations of nutrients and heavy metals in the water and sediments of coastal areas (Yantai, China) and assessed their sources and ecological risks. The results showed that inland rivers transported large amounts of NO₃⁻ and PO₄³⁻ into coast water, which caused severe eutrophication. Regarding heavy metals, copper dominated in seawater, whereas plumbum and arsenic were dominant in sediment, which was sourced from aerosol deposition and mariculture. Zinc, chromium, copper, mercury, and cadmium contributed slightly to pollution, with low enrichment factors, mainly from natural sources. Further analysis showed that zinc, mercury, copper, and arsenic were significantly affected by the grain size composition in sediment. Ecological risk assessment indicated that the coastal zone of Yantai City is in a state of light heavy-metal pollution.

China’s sinuous coastline is increasingly threatened by land subsidence driven by complex geological conditions and intensive human activity. Using year-round Sentinel-1A acquisitions for 2023 and SBAS-InSAR processing, we generated the first millimetre-resolution subsidence velocity field covering the 50 km coastal buffer of mainland China. We elucidated subsidence patterns and their drivers and quantified the associated socio-economic risks by integrating 1 km GDP and population data. Our analysis shows that ~55.77% of the coastal zone is subsiding, exposing 97.42 million residents and CNY 16.41 billion of GDP. Four hotspots—Laizhou Bay, northern Jiangsu, the Yangtze River Delta (YRD) and the Pearl River Delta (PRD)—exhibit the most pronounced deformation. Over-extraction of groundwater is identified as the primary driver. The 15 m resolution subsidence product provides an up-to-date, high-precision dataset that effectively supports sustainable development research in coastal hazard prevention, territorial spatial planning, and sea-level rise studies.

Salinity and clay mineral types have been shown to influence the migration and settlement efficiency of microplastics (MPs) under restrictive experimental conditions. However, current research is limited to deep trenches or laboratory conditions, and studies in the semi-enclosed sea area of the continental shelf are still lacking. We investigated the effects of bottom seawater salinity and clay mineral types on MPs distribution in surface sediments using the western part of the North Yellow Sea as an example, where current conditions are complex and salinity changes rapidly over short distances. Under detection conditions with a minimum detection limit of 10 μm, the abundance range of MPs in the investigated sea area reached 24–1134 items/(g dry weight). The distribution of MPs was in good agreement with the isohaline of the bottom seawater, and MPs tended to converge in the high salinity area. However, there is an exceptional case in which the temperature and salinity difference caused by the cold water mass can create a frontal flow that blocks the transport of terrigenous materials to the middle of the cold water mass. This phenomenon causes MPs to settle at the edge of the cold water mass. A significant positive correlation exists between montmorillonite with expansive properties and fragment MPs and MPs with particle size > 100 μm, which have a larger surface area (p < 0.05). The negative charges on the surface of MPs and clay minerals are neutralized, promoting the heterogeneous aggregation between clay minerals and MPs and accelerating the sedimentation process of MPs in the ocean. This is another important reason for the accumulation of MPs in the high-salinity region. This study provides a basis for pollution prevention and control of MPs in the shallow sea, supplying new insights into the effects of bottom seawater salinity and clay mineral type on the distribution of MPs.