Radionuclides and heavy metals pose potential risks to marine ecosystems and human health. Daya Bay, the site of China’s first commercial nuclear power plant, has experienced significant anthropogenic impacts, yet the extent of radionuclide and heavy metal contamination remains unclear. Nineteen surface sediment samples were collected in January 2024 and analyzed for natural (²¹⁰Pb, ²²⁸Th, ²²⁶Ra, ²²⁸Ra, and ⁴⁰K) and anthropogenic (¹³⁷Cs) radionuclides, heavy metals (Cu, Pb, Zn, Cd, Cr, Mn, Hg, and As), grain size, and total organic carbon (TOC). The surface sediments of Daya Bay were predominantly fine-grained, with TOC levels ranging from 0.41% to 1.83%, influenced significantly by riverine input from the Dan’ao River. Natural radionuclides exhibited distinct spatial patterns: ²¹⁰Pb and ²²⁸Th activity levels were higher in fine-grained sediments, and correlated with TOC, indicating adsorption and sedimentation controls. In contrast, anthropogenic ¹³⁷Cs activity was low and showed no significant impact from the nuclear power plant. Notably, the absence in the samples of key anthropogenic radionuclides typically associated with nuclear power plant operations further confirmed the negligible impact of the power plant on local sediment contamination. The results indicated that the baseline levels of both natural and anthropogenic radionuclides and heavy metals were predominantly influenced by natural processes and local anthropogenic activities rather than the operation of the nuclear power plant. This study establishes critical baselines for radioactivity and heavy metals in Daya Bay, underscoring effective pollution control measures and the resilience of local ecosystems despite anthropogenic pressures.

In response to the intensification of global warming, extreme weather events, such as tropical cyclones (TCs) and cold waves (CWs) have become increasingly frequent near the eastern Guangdong coast, significantly affecting the structure and material transport of coastal waters. Based on nearshore-measured and remote sensing reanalysis data in the winter of 2011 and summer of 2012 on the eastern Guangdong coast, this study analyzed the nearshore hydrodynamic evolution process, influencing mechanism, and marine environmental effects under the influence of TCs and CWs, and further compared the similarities and differences between the two events. The results revealed significant seasonal variations in the hydrological and meteorological elements of the coastal waters, which were disrupted by the passage of TCs and CWs. The primary influencing factors were TC track and CW intensity. The current structure changed significantly during the TCs and CWs, with the TC destroying the original upwelling current and the CW affecting the prevailing northeastward current. Wind is one of the major forces driving nearshore hydrodynamic processes. According to the synchronous analysis of research data, the TC-induced water level rise is primarily attributed to the combined effects of wind stress curl and the Ekman effect, whereas the water level rise associated with CW is primarily linked to the Ekman effect. The water transport patterns during the TC and CW differed, with transport concentrated on the right side of the TC track and within the coastal strong-wind zones, respectively. Additionally, the temporal frequency domain of wavelet analysis highlighted the distinct nature of TC and CW signals, with 1–3 d and 4–8 d, respectively, and with TC signals being short-lived and rapid compared to the more sustained CW signals. This study enhances our understanding of the response of coastal hydrodynamics to extreme weather events on the eastern Guangdong coast, and the results can provide references for disaster management and protection of nearshore ocean engineering under extreme events.

High-energy, short-lived typhoon deposition can disrupt particle–water interactions, raising the question of whether rare earth elements (REEs) in event deposits still reflect equilibrium-controlled partitioning or instead capture transient, non-equilibrium geochemical states. We sampled a ~0.5–1 cm surface storm layer and underlying background sediments at 11 stations in the northeastern Beibu Gulf on 29–30 September 2024 (20–21 days after Typhoon Yagi), and quantified major/trace elements and REEs by ICP-OES and ICP-MS, integrating grain size/TOC and statistical correlations. Storm deposits show systematically lower ∑REE and LREE concentrations and slightly lower LREE/HREE ratios than background sediments, accompanied by weaker negative Eu anomalies and a shift toward slightly negative Ce anomalies relative to the mild positive Ce anomaly in background deposits. Despite finer textures and elevated TOC in the storm deposits, the canonical grain-size/adsorption control collapses, with ∑REE exhibiting little to no correlation with grain-size under storm conditions. Critically, storm deposits display pronounced LREE–HREE decoupling: LREE behave quasi-conservatively with “event-scale inertia”, whereas HREE respond more sensitively to non-equilibrium carrier reorganization and rapid settling. This selective decoupling provides a diagnostic geochemical fingerprint for identifying event-driven sedimentation and highlights the need to incorporate kinetic/time-scale effects when interpreting REE-based proxies in dynamic environments.

The coupling of physical transport and phase-transfer processes represents a fundamental mechanism governing metal cycling in estuarine systems under tidal oscillations. Taking Quanzhou Bay as a model system, we conducted continuous observations and sample collection at the river channel (Q1), the turbidity maximum zone (Q2), and the outer bay channel (Q3). The metals (Al, Ti, Ba, Cu, Mn, and Zn) were measured by ICP-MS to systematically investigate the distribution, transport, and inter-media transfer across multiple water layers under varying estuarine processes. Our findings demonstrate that particulate metal concentrations in Quanzhou Bay exhibit strong synchrony with suspended sediment concentrations (SSC) over tidal cycles, displaying a distinct sediment-following pattern controlled by alternating end members. Particulate metal fluxes during flood and ebb-tides generally followed the hierarchy Q1 > Q2 >> Q3. Notably, stations Q1 and Q2 were dominated by flood-tide fluxes with net transport directed landward, whereas Q3 was characterized by ebb tide dominance with net flux directed seaward—revealing a spatial division of labor between “inner bay retention/reallocation” and “outer bay channel export”. In contrast, dissolved metals exhibited marked element-specific responses to tidal forcing: Al and Ti increased during flood tides at stations Q1 and Q2, while Ba and Cu showed opposite trends, and Mn and Zn displayed more conservative behavior. Concurrently, solid/liquid partition coefficient (logKd) values for Al, Ti and Ba, Cu exhibited inverse patterns over tidal cycles, suggesting divergent adsorption–desorption regulation under identical hydrodynamic conditions that drives differential phase-transfer dynamics. These disparities likely reflect intrinsic chemical properties and source variations among the elements. This study elucidates, at the tidal timescale, the coupled processes of “alternating end-member control—estuarine filter modulation—concurrent channelized export and inner bay retention” in Quanzhou Bay, providing critical process-level insights for metal flux quantification and bay pollution remediation initiatives in an ecological restoration project.

Storm-generated surface deposits can preserve short-lived sedimentary and geochemical signals, but their interpretation requires careful distinction between event-layer contrasts and true pre–post storm changes. Here we examine the sedimentary and heavy-metal characteristics of a post-storm surface drape and the underlying reference sediment in the northeastern Beibu Gulf after Super Typhoon Yagi. Grain size, total organic carbon (TOC), aluminum (Al), and heavy metal concentrations were analyzed, and interlayer differences were evaluated using correlation analysis and a Surface–Subsurface Contrast Index (SSCI). Because sediment samples were collected 20–21 days after Typhoon Yagi and no directly observed pre-typhoon surface baseline was available, the observed differences are interpreted as post-event surface–subsurface contrasts rather than direct pre–post storm concentration changes. The surface drape is laterally persistent, finer grained, and enriched in TOC and Al, indicating that it primarily records post-storm settling of fine particles rather than deposition under peak storm energy. Most metals, including V, Cr, Co, Ni, Zn, Pb, Mn, and As, show higher concentrations in the surface drape than in the subsurface reference layer, with mean surface–subsurface contrasts of 35–61%, whereas Cu shows only a limited contrast and Cd remains broadly unchanged. V, Cr, Co, Ni, Zn, and Pb exhibit spatially coherent high-value zones in the surface drape, broadly consistent with the distribution of fine-grained and Al-rich sediments. These contrasts suggest that the post-storm surface drape preferentially preserved fine-grained, Al-rich, and organic-bearing particles that acted as metal carriers. Our results highlight that post-storm surface sediments in tropical–subtropical bays should be interpreted as event-layer archives of short-term sedimentary and geochemical reworking rather than as simple indicators of long-term background seabed conditions. These findings provide insight into how extreme storms may imprint short-term source-to-sink signals in coastal event deposits.