The research focuses on the complex stratification of the seabed, which is consistent with real marine geological conditions. This article presents the effects of four parameters—seabed shear modulus, permeability coefficient, porosity, and saturation—on the distribution of excess pore water pressure within the seabed by internal solitary waves (ISWs). Additionally, the changes in excess pore water pressure distribution in layered seabed are analyzed. The findings indicate that increases in saturation and permeability coefficient lead to deeper penetration of excess pore water pressure into the seabed by ISWs. Conversely, the effects of shear modulus and porosity are relatively minor and inversely related to the depth of influence of excess pore water pressure. When stratification occurs in the permeability coefficient and saturation of the seabed, significant alterations are observed in the downward propagation of excess pore water pressure. Saturation stratification exhibits similar effects, with soil layers exhibiting higher saturation levels being more conducive to the transmission of excess pore water pressure by ISWs. These research findings hold substantial implications for assessing seabed liquefaction and surface erosion processes induced by ISWs.

For the first time, we present the rare earth element (REE) and sulfur isotopic composition of hydrothermal deposis recovered from Tangyin hydrothermal field, Southern Okinawa Trough at 1206 m water depth. The natural sulfur samples exhibit the lowest ΣREE (ΣREE = 0.654 × 10-6 ~ 4.580 × 10-6) followed by metal sulfides (ΣREE = 1.712 × 10-6 ~ 11.627 × 10-6), and the natural sulfur-sedment samples had the maximum ΣREE (ΣREE = 11.538 × 10-6 ~ 33.064 × 10-6), far lower those of the volcanic rock and sedment. But the dEu, dCe, (La/Yb)N, La/Sm, (Gd/Yb)N, and normalized patterens of the natural sulfur and metal sulfide show the most similarity to the sediment. Most hydrothermal samples are characterized by enrichment of LREE (LREE/HREE = 10.089 ~ 24.533) and slight negative Eu anomalies or no anomaly (δEu = 0.477 ~ 0.989), of which differ from the hydrothermal fluid from sediment-free midoceanic ridges and back-arc basins and Okinawa Trough, but similar to the sulfide from Jade hydrothermal field. The obvious negative anomaly of sulfide is may due to the larger ionic radii of Eu2+ than Fe, Cu, and Zn, preventing into sulfide radii. The lower temperature and more oxidizing conditions preduced by the mixing of seawater and hydrothermal fluid further weak the leaching ability of hydrothermal fluid and induce the lower REE concentrations for natural sulfur compare with metal sulfide, meanwhile the negative Eu anomaly weakened or be almost absent as well. The sulfur isotopic compositions of the natural sulfur (δ34S = 3.20‰ ~ 5.01‰, mean 4.23‰) and metal sulfide (δ34S = 0.82‰ ~ 0.89‰, mean 0.85‰) samples reveal that the sulfur of the chimney originated by magmatic degassing.

Utilizing seawater samples collected during the summer of 2025 in the Dingzi Bay region, South Yellow Sea, this study conducted a comprehensive analysis of the contents and concentrations of dissolved gases (N₂, O₂, Ar, CO₂), hydrocarbon gases (such as methane, ethane, and propane), and noble gases (including helium, neon, krypton, and xenon). The findings reveal that the dissolved gases in the study area are predominantly composed of N₂ and O₂, with average proportions of 77.8% and 21.6%, respectively. Notably, significant CO₂ anomalies were detected at certain stations, with concentrations reaching as high as 58.46%, which may indicate intense organic matter degradation or the introduction of external fluids. Furthermore, hydrocarbon gases, including methane and propane, were identified in several samples, with methane concentrations peaking at 37.9 mg/L, suggesting potential submarine oil and gas seepage or microbial activity. Spatial analysis revealed that anomalous points were primarily concentrated at stations CJ01, CJ08, CJ10, and CQ01, with no significant correlation to water depth, suggesting that their distribution may be influenced by local geological structures or bottom currents. This study elucidates the complexity and heterogeneity of dissolved gas composition in the waters of Dingzi Bay, thereby providing a novel scientific foundation for regional carbon cycle research, seabed resource exploration, and marine environmental monitoring.

Utilizing seawater samples collected during the summer of 2025 in the Dingzi Bay region, South Yellow Sea, this study conducted a comprehensive analysis of the contents and concentrations of dissolved gases (N₂, O₂, Ar, CO₂) and hydrocarbon gases (such as methane, ethane, and propane). The findings reveal that the dissolved gases in the study area are predominantly composed of N₂ and O₂, with average proportions of 77.8% and 21.6%, respectively. Notably, significant CO₂ anomalies were detected at certain stations, which may indicate intense organic matter degradation or the introduction of external fluids. Furthermore, wet gas constituents, including propane, butane, and isobutane, were identified in several samples, suggesting potential submarine oil and gas seepage or subsurface thermogenic gas input. Spatial analysis revealed that anomalous points were primarily concentrated at stations CJ01, CJ08, CJ10, and CQ01, with no significant correlation to water depth, suggesting that their distribution may be influenced by local geological structures or bottom currents. This study elucidates the complexity and heterogeneity of dissolved gas composition in the waters of Dingzi Bay, thereby providing a novel scientific foundation for regional carbon cycle research, seabed resource exploration, and marine environmental monitoring.