Archive

Sediments from the site GC16 of Haiyang IV, the South China Sea show anomalous values of δ¹³C_org, δ¹⁵N and δ¹³C_inorg. The sulfate methane transition zone (SMTZ) is a key biochemical interface in CH₄ fluid flowing area. The values of δ¹³C_org and δ¹⁵N show obviously depleted in STMZ. Comparing with the date above the STMZ, depleted 1.4‰PDB and 0.93‰ respectively within the zone. The data of δ¹³C_inorg also identify the authigenic carbonates as microbially-mediated methane-derived precipitates. The 2 times of vigorous methane-rich fluid expulsion had occurred since the bottom sediments deposition of the core. The depth of methane fluid arriving coincident with the up limited of STMZ.

Using the data from the 3th version of U.S. Navy Generalized Digital Environment Model(GDEM), we diagnosed the intermediate circulation and deep circulation in the west of Luzon Island with the P-vector method. The diagnosed result shows that it is an anticyclonic circulation in the west of Luzon Island in the intermediate layer (1 000~2 000 m vertical-averaged), different from the deep layer circulation (2 400 m to bottom vertical-averaged) in the same region, which has been reported as cyclone in the previous studies. These two eddies both correspond with the low salinity water in geographical location. The results further show that the velocity of anticyclonic circulation reduces as the depth increases, and the velocity of cyclonic circulation is stronger in the deeper layer. The current at the depletion layer (about 2 200 m) is weak and disorder. Further research demonstrates that low salinity water and anticyclonic circulation in the intermediate layer have distinct seasonal variation, they both become stronger in May to July, which may suggests that the anticyclonic circulation is influenced by the upper layer circulation to some degree.

Luzon Strait is an important water exchange channel between South China Sea and Philippine Sea. As a famous western boundary current in the North Pacific, the Kuroshio has an important impact on the South China Sea circulation. In this research, we extracted the salinity-maximum at density of 23.0~25.5 kg/m³ and studied further the relation between the Kuroshio intrusion and bifurcation of the North Equatorial Current with CTD data of 1991—2011 and the satellite altimeter data. The results show that: (1) The ways of Kuroshio intrusion in SCS are diverse, including branch, bending and loop. (2) In different years, Kuroshio intrusion is quite different and the range of salinity-maximum can be more than 0.3 in the 120°E section. (3) The bifurcation of North Equatorial Current has a great effect on the intrusion of Kuroshio in South China Sea: When the bifurcation of North Equatorial Current moves to north, the Kuroshio intrusion in South China Sea is strong; when it moves to south, the Kuroshio intrusion is weak.

The cohesive sediment dynamics have great potential engineering and environmental impacts in the Pearl River Estuary (PRE). In this study, we established a 3D unstructured triangular grid hydrodynamics model by using the SELFE (Semi-implicit Eulerian-Lagrangian Finite Element) model for the PRE, considering the baroclinic current, tidal current and wind current. On the basis of the hydrodynamics model, we then developed a cohesive sediment model including a bed change module. From the numerical results which are in good agreement with the field data obtained in the wet season, the characteristics of turbidity maximum (TM) in the PRE can be well reproduced, and the relevant sediment dynamics can be explained. The results show that the suspended sediment concentration (SSC) in the west side is higher during the wet season, which indicates that the suspended sediment in the PRE is terrigenous. The TM is found in all “three shoals”, and the suspended sediment concentration is up to 0.5 g/L. The tidal dynamics, gravitational circulation and sediment resuspension and deposition processes are the primary formation mechanisms of TM in the PRE. TM in the middle shoal is mainly caused by the sediment resuspension and deposition processes, on the other hand, the gravitational circulation is the predominant formation mechanisms of TM in the west shoal.

The ditching probability caused by typhoon wave was analyzed by using WAVEWATCH-III (WW3) wave model. Results show that: (1) The WW3 wave model can simulate the typhoon wave well with CCMP (Cross-Calibrated, Multi-Platform) wind data as driving field, and the simulation significant wave height (SWH) has high precision. (2) The ditching probability field has good agreement with the wave field, and the large areas mainly locate in the quadrants of 1st and 4th. (3) When the flying height is at 10 m, ditching probability in big wave area is above 20%, and it is even more than 35% in the large center, ditching probability is about 15%~20% in the wake of typhoon, and 10%~15% in other waters. When the flying height is at 15 m, ditching probability is greatly reduced and ditching probability in big wave area is 5%~15%, while it is below 5% in other waters.

Marine surface sediments from the Fuzhou Bay, the western Liaodong Peninsula, were obtained for sedimentary analysis. The characteristics of grain size are corresponding to the sedimentary environment. The grain size parameters show a significant difference among samples from various positions, as the average grain sizes range from 1.2Φ to 6.5Φ. The grain sizes are all poor sorted (1.4~2.6) with fine to coarse skewness, and display a spatial change as fine to coarse to fine from the estuary to the shallow sea. The 5 m and 10 m isobaths mark the edge of these boundaries, probably resulting from sediment transport and submarine topography. Most of river sediments can be transported to the 5 m isobath, and sediments in the area between 5 m to 10 m isobaths are mainly from river and outer sea, while little river sediments can get to west of 10 m isobaths. With the evidence of both Weibull function and mineralogy, most of the sediments in Fuzhou Bay are from the erosion of Liaodong Bay and Fuzhou Bay.

A series of experiments about dynamic triaxial apparatus were carried out to study the dynamic response behavior of silt from Hangzhou Bay. We studied the influence of structure, loading frequency, dynamic stress on dynamic strain, critical cyclic stress ratio, and the dynamic strength. The test results implied that, under the same loading conditions,the remoded samples are more likely to undergo structural failure than the undisturbed ones in smaller cycles. However, the dynamic strength of undisturbed soil is greater than that of remoded ones. Structural impact become an important factor influencing the dynamic strength of soil samples, the influence increased with the increase of dynamic stress, and decreased with the increase of frequency. On the other hand, the variation of loading frequency has significant effect on the dynamic characteristics of silt, the more frequency increased, the more cycles sample required to reach a failure, at the same time, the critical cyclic stress ratio of silt is also enlarged.

Coastline is of great importance for coast protection and management. Traditional coastline draughting methods are mainly based on field mapping and remotely sensed images. Field mapping is usually time consuming and difficult to carried out in complicated area. Coastline interpretation requires high criterion for operators and the proper coastline is hard to extract. Aiming at the problems mentioned above, a coastline extraction method for natural coastline based on airborne LiDAR data and tidal estimation was proposed and Feiyantan and Zhifu Island were chosen as study area in this research. Instantaneous water edge was firstly extracted from ortho-rectified images acquired by airborne LiDAR system. Coastline of study area was estimated through tidal data, by utilizing inter-conversion model of elevation system and DEM retrieved by airborne LiDAR system. Compared with “908 coastline”, the RMSE of 3 types of natural coastline (sandy coastline, rocky coastline and silty coastline) extracted using this method are 1.66 m, 5.23 m and 32.48 m, individually. Results show that the method established in this research is efficient and capable of extracting sandy coastline and rocky coastline, without the need of field mapping.

The aim of this study is to develop the exploitative intensity evaluation for the residential islands, and set the evaluation processes which are suitable for the residential islands on account of land resources specificity. In addition, Donghai Island was taken as an example, while 2006 SPOT images and 2010 ALOS images were used as data sources, and finally, the evaluation on land resources exploitative intensity from 2006 to 2010 was given. The assessment results can be divided into 6 degrees: they are weak, less weak, medium, less strong, strong and extremely strong. Each level accounted for 94.00%, 3.28%, 1.98%, 0.59%, 0.04% and 0.11%, respectively. The results show that the land resources exploitative intensity for Donghai Island was less weak from 2006 to 2010. More importantly, the evaluation results can service for the managerial and decision-making departments.

Due to the fact that oil spill has been increasing damage to the marine environment, to quickly detect the oil spill is certainly of significance for preventing and alleviating the disasters. Currently using polarized SAR in the detection of the oil spill is an important approach of remote sensing. In this paper, the SIR-C data were employed in the monitoring of oil spills, in which the polarized parameters entropy, scattering angle and anti-entropy were first extracted and then used to retrieve the oil spill information using the support vector machine (SVM) classifier. The assessment showed that SVM-based classification can achieve more accurate result than that of H-α decomposition based oil spill identification of SAR data.

Using HPLC-CHEMTAX method, pigments data collected from the nearshore surface water of the East China Sea in spring of 2008 were analyzed for understanding phytoplankton community structure and relationships with environmental factors. Results showed that the dominant groups are diatoms and dinoflagellates, which averagely contributed to chlorophyll a (Chl a) up to 42% and 32%, respectively. Both diatoms and dinoflagellates preferred in the environment with lower temperature, lower salinity, and higher N/P ratio, but the diatoms bloom occurred in the salinity front formed by the interaction of the Changjiang diluted water and the open ocean water which is higher in salinity and lower in temperature and N/P ratio, while the dinoflagellates bloom occurred in the temperature front formed by the interaction of the Changjiang diluted water and the Taiwan Warm Water which is higher in temperature, lower in salinity and N/P ratio. LOWESS results revealed that both Chl a and dinoflagellates increased incipiently and then decreased as temperature or salinity increasing, while relationships between diatoms and temperature or salinity showed a larger fluctuation. Both Chl a and diatoms increased as N/P ratio increasing, while the relationship between dinoflagellates and N/P ratio displayed a larger fluctuation.

Based on the three-dimensional hydrodynamic and water exchange numerical model——FVCOM, the water exchange numerical model of Bohai Bay was established, then the observed tide and currents data was used to validate the model result. Using this model, Bohai Bay water exchange was simulated, and the water exchange regularity of Bohai Bay was also studied. The results showed that: Bohai Bay water exchange rate was low, the half period of water exchange was 323 days; the water exchange rate of central Bohai Bay was higher, while the water exchange rate was lower at northwest and southern area; due to the role of the barrier strip, the water exchange rate in the southwest area was the lowest. Therefore, the place and time should be selected before discharging pollutant.

The distribution and enrichment characteristics of seven dispersed elements ( Ga, Ge, Rb, Tl, Cd, Te and Se ) in the surface sediments around Hainan Island waters were analyzed and their correlations with sediment grain size, total organic carbon and organic nitrogen were also studied. Nemerow Comprehensive Evaluation Index and Pollution Load Index methods were used respectively to preliminarily evaluate the contamination of these elements. The results show that the dispersed elements enrichment has close relation with sediment grain size, organic carbon and organic nitrogen content. Except Te, the other six kinds of dispersed elements have shown high enrichment in silt or clay sediments, and they tend to concentrate in the sediment where organic carbon and organic nitrogen contents are high. In general, the dispersed element pollution degree is a slight, but in some sediments (such as the sediments from northwest, west, southeast coastal waters and from Lingshui and Sanya waters of Hainan Island), the pollution reaches to the moderate degree, indicating that these areas have been impacted by human activities seriously, which should attract the attention of the competent authorities for the marine environment protection.