In order to assess the radioactive level in the terrestrial and marine organisms in Yangjiang and the adjacent areas, ⁹⁰Sr, gross beta and gamma-emitting radionuclides (²³⁸U, ²²⁶Ra, ²²⁸Th, ²²⁶Ra, ⁴⁰K, ¹³⁷Cs, ⁵¹Cr, ⁵⁵Fe, ⁵⁴Mn, ⁵⁸Co, ⁶⁰Co and ⁶⁵Zn) were analyzed from 2011 to 2012. The annual effective doses were estimated in the high natural radioactive background areas in Yangjiang (HBRAYJ). The specific activities of ²³⁸U, ²²⁸Th, ²²⁶Ra, ⁴⁰K and ¹³⁷Cs in all organisms were <0.05–5.20, 0.30–14.50, 0.11–3.58, 11.1–148.0 and <0.003–0.088 Bq/kg, whilst ⁵¹Cr, ⁵⁵Fe, ⁵⁴Mn, ⁵⁸Co, ⁶⁰Co, ⁶⁵Zn and ^110mAg were below the minimum detectable activity. ⁹⁰Sr and gross beta specific activities were 20.0–143.0 and 0.021–0.316 Bq/kg. Results show that ²²⁸Th was significantly higher than ²³⁸U and ²²⁶Ra of natural U series in organisms due to the rich-Th soils in the HBRAYJ; ²²⁸Th, ²²⁶Ra, ⁴⁰K, ¹³⁷Cs and ⁹⁰Sr were greatly lower than the limited concentrations in Chinese foods. The internal dose mainly contributes to natural ⁴⁰K, ²²⁶Ra and ²²⁸Th. It is useful to provide some basic data and assess the radiological risk from the HBRAYJ and Yangjiang nuclear power plants in future.

The Huangmao Island dumping area is adjacent to the Pearl River Estuary in the South China Sea. From its first dumping activity in 1986 to 2017, 6750 × 10⁴ m³ dredged materials were dumped in this dumping area. Sediment pollution levels, ecological risk, and benthic communities in 2011–2017 were evaluated; the results showed that the concentrations of the heavy metals (HMs; except Hg) in surface sediments of the dumping area met the class I standard of marine sediment quality (GB 18668-2002). HMs in the surface sediments were relatively high in the northern and central areas but relatively low in the south of the dumping area. Speculation was that the spatial variation in HM concentrations might be caused by dumping activities. The Nemerow index implied that the contaminated area was mainly in the north of the dumping area (S1, S2, and S3), where the dumping amount was the largest. The potential ecological risk (Eⁱ_r) indices of Zn, As, Cu, and Pb indicate that these metals posed a low risk to the ecosystem of the dumping area, whereas Cd and Hg posed a high risk at some stations. The geoaccumulation indices (I_geo) of Zn, As, Cu, and Pb specified no pollution or light pollution in the study area, whereas those of Cd and Hg in most years indicated mild contamination levels. Benthic organisms in the study area were arthropods, chordates, annelids, mollusks, echinoderms, nemertinean, coelenterate, and echiuran, among which arthropods were the most abundant. The abundance of taxa and density of benthic organisms had a little difference among the stations within the dumping area, but were significantly lower than those of the stations outside the dumping area. In addition, non-metric multidimensional scaling analysis confirmed that the observed patterns separated the stations within the dumping area from stations outside the dumping area. The evaluation results of the HMs revealed that the dumping area with a large dumping amount was more severely polluted. Dumping dredged materials seemed to have a negative impact on the benthic community in the dumping area.

Mangrove ecosystems play a critical role in climate regulation, carbon sequestration, and pollution mitigation. However, their long-term resilience to accelerating sea-level rise (SLR) under global climate change scenarios remains uncertain. Vertical soil accretion is a critical factor in determining the vulnerability of mangrove wetlands to SLR. In this study, vertical soil accretion rates in a mangrove wetland in the Beilun estuary were measured using a ²¹⁰Pbex dating method. Based on recently acquired data and previously available data, we conducted the first systematic assessment of SLR risk in mangrove wetlands in the Guangxi coastal zone in the context of increasing global climate change and extreme weather. The results show that the vertical soil accretion rate of 6.72 ± 1.91 (4.22–10.54) mm/a in the Beilun estuary is slightly higher than SLR rate in the Guangxi coastal zone. Concurrently, our results indicate that mangroves with thriving root systems enhance soil accretion through biotic controls in the Beilun estuary, while significant changes in soil sources and hydrodynamic forces during the 1980s and 2000s contributed to adaptation to SLR. Additionally, by linking sedimentation dynamics with SLR projections, we reveal that current accretion rates in some mangrove areas in the Guangxi coastal zone are insufficient to offset the projected SLR by the end of 2050 and 2100. This finding offers a new perspective on the traditional assumption of inherent resilience in mangroves while revealing the adaptive capacity of mangroves in the Beilun estuary and Guangxi coastal zone under projected SLR scenarios. It underscores the need for integrated management strategies that balance sediment supply maintenance and ecological restoration, which are critical to ensuring the long-term resilience of mangrove ecosystems, in line with sustainability principles.

Mangrove wetlands, acting as significant traps for marine debris, have received insufficient attention in previous research. Here, we conduct the first comprehensive investigation into the magnitude, accumulation, source, and fate of marine debris across seven mangrove areas in the northern South China Sea (MNSCS) during 2019–2020. Systematic field surveys employed stratified random sampling, partitioning each site by vegetation density and tidal influence. Marine debris were collected and classified in sampling units by material (plastic, fabric, styrofoam), size (categorized into small, medium, and large), and origin (distinguishing between land-based and sea-based). Source identification and potential risk assessment were achieved through the integration of debris feature analysis. The results indicate relatively low debris levels in MNSCS mangroves, with plastics dominant. More than 70% of all debris weight with plastics (48.34%) and fabrics (14.59%) is land-based, and more than 70% comes from coastal/recreational activities. More than 90% of all debris items with plastics (52.50%) and Styrofoam (36.32%) are land-based, and more than 90% come from coastal/recreational activities. Medium/large-sized debris are trapped in mangrove wetlands under the influencing conditions of local tidal level, debris item materials, and sizes. Our study quantifies marine debris characteristics, sources, and ecological potential risks in MNSCS mangroves. From environmental, economic, and social sustainability perspectives, our findings are helpful for guiding marine debris management and mangrove conservation. By bridging research and policies, our work balances human activities with ecosystem health for long-term sustainability.

Inert construction and demolition waste from Hong Kong (HK public fills) has been used for marine trial reclamation in the Guanghai Bay (GHWT) of the Chinese Mainland. However, an environmental assessment of HK public fills is necessary due to higher radioactivity in HK soils than typical global levels. Here, radiation dose rate, gamma radionuclides and gross beta of HK public fills were analyzed. The origin information was explored using natural primordial radionuclides as fingerprints. Our data show that radiation dose rate of HK public fills before disposal was 0.14-0.54 (0.33 ± 0.03) μSv/h (n = 16,722 data with 2787 ships) in 2014, which is less than the GHWT background. Monthly detection of ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³²Th, ²²⁸Th, ⁴⁰K, and gross beta in HK public fills was conducted on three random ships. Their specific activities were <6.27-155.5, 58.7-98.7, <7.83-238.2,97.9-168.6, 87.1-136.0, 463.1-1,018, and 1047-1658 Bq/kg_DW, respectively. These results suggest that the radioactivity levels of HK public fills are essentially the same as the GHWT background. The study assessed potential risks using various indices icluding Ra_eq (Radium equivalent activity), H_ex (External radiation hazard index), H_in (Internal radiation hazard index), I_γ (Gamma index), AUI (Activity utilization index), AUI (Activity utilization index), E (Annual effective dose), AGDE (Annual gonadal dose equivalent), RLI (Representative level index), D_in (Indoor air absorbed dose rate), D_out (Outdoor air absorbed dose rate), and ELCR (Excess lifetime cancer risk). The study suggests that HK public fills should be used for the trial reclamation rather than building-house materials. This provides valuable insights for the resource utilization and minimizing environmental pollution of HK public fills. The aim is to offer fundamental technical assistance for future waste resource utilization, ecological protection, and restoration in the Guangdong-Hong Kong-Macao Greater Bay Area.

Mangrove wetlands as debris traps should receive more attention. Here, we assessed that the magnitude, accumulation, source and fate of marine debris in seven mangrove areas in the north South China Sea (MNSCS) (2019–2020). Marine debris with plastic dominating is invading the MNSCS at the low level. More than 70% of all debris weight with plastics (48.34% ) and fabrics (14.59%) is land-based, and more than 70% comes from coastal/recreational activities. More than 90% of all debris items with plastics (52.50%) and styrofoam(36.32%) is land-based, and more than 90% comes from coastal/recreational activities. The medium/large size debris are trapped in mangrove wetlands under the influenced conditions of local tidal level, debris item materials, and sizes. We expect that our study is helpful to determine the nature and significance of their risk and future marine debris management and the mangrove conservation and restoration.