The construction project of a non-super high-rise public building in Guangzhou’s Nansha Free Trade Zone faces unique challenges.The project established a full-cycle technical management system,encompassing technical ...The construction project of a non-super high-rise public building in Guangzhou’s Nansha Free Trade Zone faces unique challenges.The project established a full-cycle technical management system,encompassing technical management across various sectors and BIM collaboration.Simultaneously,it introduced advanced technical management such as deep foundation pits and core tube construction,along with a risk management system and special weather response strategies.Through these measures,the project achieved numerous significant results,forming a unique management paradigm that offers valuable insights for similar engineering projects.展开更多
Coral sand is a unique material developed in the tropical ocean environment, which is mainly composed of coral and other marine organism debris, with the CaCO3 content up to 96 %. It has special physical and mechanica...Coral sand is a unique material developed in the tropical ocean environment, which is mainly composed of coral and other marine organism debris, with the CaCO3 content up to 96 %. It has special physical and mechanical properties due to its composition, structure and sedimentary environment. In this contribution, we discuss its specific gravity, porosity ratio compressibility, crushing, shearing and intensity for coral sand samples from the Nansha islands based on laboratory mechanical tests. Our results show distinct high porosity ratio, high friction angle and low intensity as compared with the quartz sand. We believe that grain crushing is the main factor that influences the deformation and strength of coral sand. Comprehensive study on the physical and mechanical properties of coral sands is significant in providing reliable scientific parameters to construction on coral islet, and thus avoids accidents in construction.展开更多
Nansha wetland plays a crucial role in ecological balance of the Pearl River Delta or even Guangzhou. The research, based on researches available, analyzed ecological benefits of Nansha wetland and proposed protection...Nansha wetland plays a crucial role in ecological balance of the Pearl River Delta or even Guangzhou. The research, based on researches available, analyzed ecological benefits of Nansha wetland and proposed protection measures in order to better protect urban wetlands and achieve sustainable development of ecological resources of Nansha wetland.展开更多
The accelerated corrosion behavior of copper T2 and brass H62 exposed in simulated Nansha marine atmosphere for different periods were investigated by weight loss method, SEM, XRD and potentiodynamic polarization meas...The accelerated corrosion behavior of copper T2 and brass H62 exposed in simulated Nansha marine atmosphere for different periods were investigated by weight loss method, SEM, XRD and potentiodynamic polarization measurements. The results indicate that copper T2 and brass H62 underwent severe corrosion, and the final corrosion rates at 32 days of exposure were 0.24 (μm/d and 0.10 (xm/d, respectively. Moreover, the overall corrosion type of copper T2 was uniform and the corrosion products Cu2O and Cu2C1(OH)3 played a vital role in the corrosion rate of copper. While the dezincification corrosion with zinc preferential dissolution was obvious in brass H62. The predominant phases were the zinc-rich compounds Zn5(OH)8Cl2 H2O, Zni2(SO4)3Cl3(OH)15 5H20 and NaZn4(SO4)Cl(OH)6.6H2O. There existed a large number of copper-rich holes with 20-50μm depth beneath the corrosion product layer.展开更多
Abstract The Nansha ultra-crust layer-block is confined by ultra-crustal boundary faults of distinctive features, bordering the Kangtai-Shuangzi-Xiongnan extensional faulted zone on the north, the Baxian-Baram-Yoca-Cu...Abstract The Nansha ultra-crust layer-block is confined by ultra-crustal boundary faults of distinctive features, bordering the Kangtai-Shuangzi-Xiongnan extensional faulted zone on the north, the Baxian-Baram-Yoca-Cuyo nappe faulted zone on the south, the Wan'an-Natuna strike-slip tensional faulted zone on the west and the Mondoro-Panay strike-slip compressive faulted zone on the east. These faults take the top of the Nansha asthenosphere as their common detachmental surface. The Cenozoic dynamic process of the ultra-crust layer-block can be divided into four stages: K2-E21, during which the northern boundary faults extended, this ultra-crust layer-block was separated from the South China-Indosinian continental margin, the Palaeo-South China Sea subducted southwards and the Sibu accretion wedge was formed; E22-E31, during which the Southwest sub-sea basin extended and orogeny was active due to the collision of the Sibu accretion wedge; E32-N11, during which the central sub-sea basin extended, the Miri accretion wedge was formed and “A-type” subduction of the southern margin of the north Balawan occurred; N12-the present, during which large-scale thrusting and napping of the boundary faults in the south and mountain-building have taken place and the South China Sea stopped its extension.展开更多
The area of the southwestern Nansha Trough is one of the most productive areas of the southern South China Sea.It is a typical semi-deep sea area of transition from shoal to abyssal zone.To understand distributions an...The area of the southwestern Nansha Trough is one of the most productive areas of the southern South China Sea.It is a typical semi-deep sea area of transition from shoal to abyssal zone.To understand distributions and roles of nitrogen forms involved in biogeochemical cycling in this area,contents of nitrogen in four extractable forms:nitrogen in ion exchangeable form(IEF-N),nitrogen in weak acid extractable form(WAEF-N),nitrogen in strong alkali extractable form(SAEF-N) and nitrogen in strong oxidation extractable form(SOEF-N),as well as in total nitrogen content(TN) in surface sediments were determined from samples collected from the cruise in April-May 1999.The study area was divided into three regions(A,B and C) in terms of clay sediment(<4 μm) content at <40%,40%-60% and >60%,respectively.Generally,region C was the richest in the nitrogen of all forms and region A the poorest,indicating that the finer the grain size is,the richer the contents of various nitrogen are.The burial efficiency of total nitrogen in surface sediments was 28.79%,indicating that more than 70% of nitrogen had been released and participated in biogeochemical recycling through sediment-water interface.展开更多
Dynamics of major picoplankton groups, Synechococcus (Syn), Prochlorococcus (Pro), picoeukaryotes (Euk) and heterotrophic bacteria (Bact) was investigated by flow cytometry for the first time in the Nansha Islands are...Dynamics of major picoplankton groups, Synechococcus (Syn), Prochlorococcus (Pro), picoeukaryotes (Euk) and heterotrophic bacteria (Bact) was investigated by flow cytometry for the first time in the Nansha Islands area in the South China Sea. Averaged over the whole investigation area, depth-weighted integrated cell abundance (DWA) of Syn, Pro, Euk and Bact was 1.6 (0.4-5.7)×103, 5.4 (0.1-7.3)×104, 0.7 (0.2-2.2)×103, and 2.3 (1.4-3.2)×105 cells/mL respectively. Picoautotrophic cell abundance was low in the northwest part of the Nansha Islands where surface water temperature was low and the upper mixed layer was shallow. Concurrently, a surface maximum vertical distribution pattern was observed in this area. While in the southeast and east zones where temperatures were relatively higher and nitraclines were deeper, picoplankton is abundant and a subsurface maximum around 50-75 m is observed. Coupling of horizontal and vertical distribution patterns of picoplankton abundance and hydrological status was found, suggesting a strong influence of currents and water column structure on picoplankton distribution in the investigation area. Contrary to that in the shelf water in the East China Sea, the relationship between Pro and Bact in the Nansha Islands area in the South China Sea was not significantly negative but weakly positive. Moreover, a similar distribution pattern of Syn and Pro was observed. Possible reasons for these differences in the two marine regimes were discussed.展开更多
The corrosion and pitting behavior of pure aluminum 1060 exposed to Nansha Islands marine atmosphere for 34 months was investigated based on mass loss measurement,scanning electron microscopy(SEM),energy dispersive sp...The corrosion and pitting behavior of pure aluminum 1060 exposed to Nansha Islands marine atmosphere for 34 months was investigated based on mass loss measurement,scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),and electrochemical impedance spectroscopy(EIS).The results indicated that serious pitting corrosion occurred on the surfaces of pure aluminum.The corrosion rate after exposure for 13 months was approximately 1.28 g/(m^(2)·a).The XPS results showed that the corrosion products were Al_(2)O_(3),Al(OH)_(3),and AlCl_(3).Moreover,the corrosion product layer was more protective than the native oxide film,and the protectiveness first increased and then decreased.Finally,the shape of the pits was evaluated using statistical analysis.展开更多
A detailed survey of the reefs in the Nansha Islands＇ sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager（OLI） images were u...A detailed survey of the reefs in the Nansha Islands＇ sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager（OLI） images were used to analyze the geological features and spectral characteristics of the Nansha reefs. The exposed islands/sandbanks,reef flats and sub-tidal reefs were identified with the near-infrared band, the red and green bands, and the blue band, respectively. Based on the relationships among various characteristics and bands illustrated in the OLI images, the maximum between-cluster variance threshold algorithm（OTSU method） and the mathematical morphology were employed to extract characteristic parameters of the spatial geometry of the reefs from top to bottom, which were subsequently operated by a series of post-processing methods such as vectorization,simplification and topological analysis. Among the 132 standalone reefs and 16 atolls that are identified in the study, four reefs have yet to be named in the Standard Names of Various Islands in the South China Sea and the website Nansha Islands Online（http：//www.nansha.org/）. Another 24 ones are exposed to the atmosphere even during high tides. Taiping Island with an area of 0.57 km^2 represents the largest exposed geological feature. This study demonstrated the applicability of medium-resolution satellite images to derive the coral reef information effectively and thus provided information for the related departments that are responsible to manage the coast.An improved resolution of multispectral bands with the panchromatic band in higher spatial resolution（15 m for OLI image） is expected to provide an optimum satellite based approach to map marine habitats.展开更多
The corrosion behavior of pure copper exposed to the atmosphere of Nansha Islands for 21 months was studied by mass loss method,composition analysis,morphology observation and electrochemical measurements.The results ...The corrosion behavior of pure copper exposed to the atmosphere of Nansha Islands for 21 months was studied by mass loss method,composition analysis,morphology observation and electrochemical measurements.The results showed that the average corrosion rate of copper exposed for one year was approximately 7.85μm/a,implying that Nansha Islands was classified as a corrosion category of CX.The structure and properties of the corrosion product layer generated on the front and back sides of the exposed sample differed significantly.The inner corrosion product layer(Cu2O)on the front side was relatively thick and dense,whereas the outer product layer(Cu2Cl(OH)3)was extremely thin.However,the outer product layer on the back side was thicker than the inner layer.Electrochemical measurements indicated that the protection afforded by the corrosion product layer on the front side was improved gradually,while that on the back side was deteriorated.展开更多
Layer-block tectonics （LBT） concept, with the core of pluralistic geodynamic outlook and multilayer-sliding tectonic outlook, is one of new keys to study 3-dimensional solid and its 4-dimensional evolution history o...Layer-block tectonics （LBT） concept, with the core of pluralistic geodynamic outlook and multilayer-sliding tectonic outlook, is one of new keys to study 3-dimensional solid and its 4-dimensional evolution history of global tectonic system controlled by global geodynamics system. The LBT concept is applied to study the lithospheric tectonics of the southern South China Sea （SCS）. Based on the analysis of about 30 000 km of geophysical and geological data, some layer-blocks in the Nansha micro-plate can be divided as Nansha ultra-crustal layer-block, Zengmu crustal layer-block, Nanwei （Rifleman bank）-Andu （Ardasier bank） and Liyue （Reed bank） North Palawan crustal layer-blocks, Andu-Bisheng and Liyue-Banyue basemental layer-blocks. The basic characteristics of the basemental layer-blocks have been dicussed, and three intra-plate basin groups are identified. The intra-plate basins within Nansha micro-plate can be divided into three basin groups of Nanwei- Andu, Feixin-Nanhua, and Liyue-North Palawan based on the different geodynamics. In the light of pluralistic geodynamic concept, the upheaving force induced by the mid-crust plastic layer is proposed as the main dynamical force which causes the formation of the intra-plate basins within the Nansha micro-plate. Finally, models of a face-to-face dip-slip detachment of basemental layerblock and a unilateral dip-slip-detachment of basemental layer-block are put forward for the forming mechanisms of the Nanwei Andu and Liyue-North Palawan intra-plate basin groups, respectively.展开更多
Based on the feature of the growth and the local limitation of the Nansha reef's closed atoll, also the related remote sensing information of it, the composite analysis is made. The closed atoll conception remote ...Based on the feature of the growth and the local limitation of the Nansha reef's closed atoll, also the related remote sensing information of it, the composite analysis is made. The closed atoll conception remote sensing system is constructed through the formation mechanism, development law and the space-time distribution of the closed atoll. Solution of the equation consisting of information function value and isostatic value of closed atoll and half-closed atoll using this system, and topologic analysis on the two kinds of atoll's morphologic growth are the basic foundation for the research of their evolutionary comparative model.展开更多
Sand cay is a special kind of islet formed by coral detritus and bioclast, which is common in Nansha Islands of China. Some sand cays play an important role in ocean strategy and economy, but surprisingly we know litt...Sand cay is a special kind of islet formed by coral detritus and bioclast, which is common in Nansha Islands of China. Some sand cays play an important role in ocean strategy and economy, but surprisingly we know little about them, especially those recently formed sand cays. In this research, we monitor migration of a new sand cay in Nanxun Jiao（Gaven Reef） using a series of Quick Bird and World View-2 satellite images between June 2006 and August 2013. We conduct a regression between migration distance and wind observational data to examine the migration patterns of the new sand cay. The migration distance is calculated based on the sand cay locations extracted based on Normalized Difference Water Index（NDWI）. The wind observational data downloaded from NOAA are reformed into four wind direction vectors. Based on the results of regression, we concluded that the migration of the new sand cay on Nanxun Jiao was significantly associated with the east, west and north wind.East wind was the main influence factor of the migration; its impact strength was almost twice as the west and north wind. The south wind has little effect on the migration of the sand cay, which is partly blocked by the artificial structure in the south.展开更多
As is well-known, Nansha Islands in the South China Sea(SCS) are of important strategic position and invaluable ecological value. Therefore, many attentions are paid to either the political and legal aspects of expose...As is well-known, Nansha Islands in the South China Sea(SCS) are of important strategic position and invaluable ecological value. Therefore, many attentions are paid to either the political and legal aspects of exposed features that matter in the maritime delimitation, or the physical and geographical characteristics of coral reefs that are the predominant structures of these islands. However, it seems that they consistently lose the connection of sciences and humanities in the research of Nansha Islands in the SCS. In this study, we carry out a combinative research, based on remote sensing data using satellite imagery analysis together with historical materials using literature investigation, so as to reconsider to the geographical characteristics of Nansha Islands from a standpoint of the United Nations Convention on the Law of the Sea(UNCLOS). After thoroughly appraising the statuses of these newly formed sand cays, several high tide features of Nansha Islands are identified. By means of the comparison of satellite images coupled with reference to nautical charting and sailing directions during different time periods, we can conclude that the statuses of these high tide features formed on reef platforms are relatively stable due to the growth of reef-building organisms although their migration patterns are subject to external disturbances, and hence the cursory judgment pursuant to the relevant provisions of the UNCLOS about whether a coral reef belongs to a low tide elevation only based on outdated references or ex parte evidences is not reliable. Moreover, it is accordingly justified to improve further development and perfection of the maritime legislation by eliminating such ambiguities with the growth of coral reefs and the evolution of sand cays being both taken into account.展开更多
On the basis of interpretation of comprehensive geophysical data and foreign data analysis,there existed a lot of overburden detachment shear thrust faults along the southeastern margin of Nansha Trough,which composed...On the basis of interpretation of comprehensive geophysical data and foreign data analysis,there existed a lot of overburden detachment shear thrust faults along the southeastern margin of Nansha Trough,which composed imbricated overthrust nappe structure.Thrust-faulted nappe structure pattern is determined in this area,which consists of frontal fault zone,thrust fault-folded zone and root zone structures,and presents regularly zonation on plane.The detail description of the structural geometrical characteristics is given in shallow thrust fault zone,and the kinematical mechanism of thrust fault nappe structure is furtherly discussed.Overthrnst nappe structure in this area is resulted from island arc-continent collision and orogenic activities.展开更多
This work yielded an improved method for extracting and analysing benzothiophene in marine sediment.The detation limit was 0.05 ng S of benzothiophene, with precision of 8%. Benzothiophene was found in Nansha Islands ...This work yielded an improved method for extracting and analysing benzothiophene in marine sediment.The detation limit was 0.05 ng S of benzothiophene, with precision of 8%. Benzothiophene was found in Nansha Islands sea area sediments and ranged from 1.1 -6.8 ng per gram dry sediment. Its concentration was closely correlated to hte organic carbon content in the sediment.Several source processes of benzohtiophene are discussed in this paper.展开更多
Landscapes of the Nansha Islands may be divided into five types: tropical marine organismbreeding landscape of reef knoll like Zengmu Shoal, Wan'an Bank and so on; tropical marine organismbreeding landscape of ato...Landscapes of the Nansha Islands may be divided into five types: tropical marine organismbreeding landscape of reef knoll like Zengmu Shoal, Wan'an Bank and so on; tropical marine organismbreeding landscape of atoll including all emerged reefs and most submerged reefs; tropical evergreen arborbush forest and phosphorous lime soil landscape of limesand Islets like Taiping Islet, Nanwei islet and so on; tropical shallow sea marine organismbreeding landscape of southern continental shelf; tropical oceanic and deepsea marine organism landscape in middle and north parts of the Nansha Islands area. These five landscape types may be also summed up as two categories, one is tropical sea landscape including those in shallow and deep sea, the other is tropical coral reef landscape including those of reef knoll, atoll and limesand islet. This paper outlines the evolutional model of landscapes of the Nansha Islands. The distribution and evolution of landscape types are related with palaeogeography and modern environmental conditions. The former shallow sea of the Nansha islands was coastal zone in the Late Pleistocene epoch. Deep sea is evolved from shallow sea due to long and slow subsidence of crust. Modern coral reefs develop on old reef top of the Late pleistocene epoch or on baserock of continental shelf in the Holocene due to the rise of sea level in postglacial. Limesand islet is in the peak of developmental stage.展开更多
Based on the remote sensing information feature of Nansha coral islets and reefs that controlled by the Nansha Islands local area's goological structure and growth law, by means of mathematical model and PC, the N...Based on the remote sensing information feature of Nansha coral islets and reefs that controlled by the Nansha Islands local area's goological structure and growth law, by means of mathematical model and PC, the Nansha Islands coral islets and reefs' top geological data' spatial distribution and local change trend are simulated by using the trend surface system on the remote sensing composite information, and an scientific interpretation and local comparison of Nansha coral islands and islets' spatial distribution feature are made.展开更多
Changes in vegetation status generally also represents changes in the ecological health of islands and reefs(IRs).However,studies are limited of drivers and trends of vegetation change of Nansha Islands,China and how ...Changes in vegetation status generally also represents changes in the ecological health of islands and reefs(IRs).However,studies are limited of drivers and trends of vegetation change of Nansha Islands,China and how they relate to climate change and human activities.To resolve this limitation,we studied changes to the Normalized Difference Vegetation Index(NDVI)vegetation-greenness index for 22 IRs of Nansha Islands during normal and extreme conditions.Trends of vegetation greenness were analyzed using Sen's slope and Mann-Kendall test at two spatial scales(pixel and island),and driving factor analyses were performed by time-lagged partial correlation analyses.These were related to impacts from human activities and climatic factors under normal(temperature,precipitation,radiation,and Normalized Difference Built-up Index(NDBI))and extreme conditions(wind speed and latitude of IRs)from 2016 to 2022.Results showed:1)among the 22 IRs,NDVI increased/decreased significantly in 15/4 IRs,respectively.Huayang Reef had the highest NDVI change-rate(0.48%/mon),and Zhongye Island had the lowest(–0.29%/mon).Local spatial patterns were in one of two forms:dotted-form,and degradation in banded-form.2)Under normal conditions,human activities(characterized by NDBI)had higher impacts on vegetation-greenness than other factors.3)Under extreme conditions,wind speed(R^(2)=0.2337,P<0.05)and latitude(R^(2)=0.2769,P<0.05)provided limited explanation for changes from typhoon events.Our results provide scientific support for the sustainable development of Nansha Islands and the United Nations‘Ocean Decade’initiative.展开更多
A reduced vertically integrated upper mixed layer model is set up to numerically study the thermodynamic process of the formation of the 'Nansha warm water'(NWW) in the Nansha Islands sea areas in spring. Acco...A reduced vertically integrated upper mixed layer model is set up to numerically study the thermodynamic process of the formation of the 'Nansha warm water'(NWW) in the Nansha Islands sea areas in spring. According to the numerical experiments, it is shown that, in spring, the formation of the NWW is mainly due to the sea surface net heat flux and the local weak current strength; the contribution from temperature advection transport and warm water exchange with the outer seas (Sulu Sea or south of Sunda shelf) is very little. In the sea areas where the current is strong, the advection may also play an important role in the temperature field.展开更多
文摘The construction project of a non-super high-rise public building in Guangzhou’s Nansha Free Trade Zone faces unique challenges.The project established a full-cycle technical management system,encompassing technical management across various sectors and BIM collaboration.Simultaneously,it introduced advanced technical management such as deep foundation pits and core tube construction,along with a risk management system and special weather response strategies.Through these measures,the project achieved numerous significant results,forming a unique management paradigm that offers valuable insights for similar engineering projects.
文摘Coral sand is a unique material developed in the tropical ocean environment, which is mainly composed of coral and other marine organism debris, with the CaCO3 content up to 96 %. It has special physical and mechanical properties due to its composition, structure and sedimentary environment. In this contribution, we discuss its specific gravity, porosity ratio compressibility, crushing, shearing and intensity for coral sand samples from the Nansha islands based on laboratory mechanical tests. Our results show distinct high porosity ratio, high friction angle and low intensity as compared with the quartz sand. We believe that grain crushing is the main factor that influences the deformation and strength of coral sand. Comprehensive study on the physical and mechanical properties of coral sands is significant in providing reliable scientific parameters to construction on coral islet, and thus avoids accidents in construction.
文摘Nansha wetland plays a crucial role in ecological balance of the Pearl River Delta or even Guangzhou. The research, based on researches available, analyzed ecological benefits of Nansha wetland and proposed protection measures in order to better protect urban wetlands and achieve sustainable development of ecological resources of Nansha wetland.
基金supported by the National Natural Science Foundation of China (No. 51671197)Special Project of Chinese Academy of Sciences (No. XDA130040502)
文摘The accelerated corrosion behavior of copper T2 and brass H62 exposed in simulated Nansha marine atmosphere for different periods were investigated by weight loss method, SEM, XRD and potentiodynamic polarization measurements. The results indicate that copper T2 and brass H62 underwent severe corrosion, and the final corrosion rates at 32 days of exposure were 0.24 (μm/d and 0.10 (xm/d, respectively. Moreover, the overall corrosion type of copper T2 was uniform and the corrosion products Cu2O and Cu2C1(OH)3 played a vital role in the corrosion rate of copper. While the dezincification corrosion with zinc preferential dissolution was obvious in brass H62. The predominant phases were the zinc-rich compounds Zn5(OH)8Cl2 H2O, Zni2(SO4)3Cl3(OH)15 5H20 and NaZn4(SO4)Cl(OH)6.6H2O. There existed a large number of copper-rich holes with 20-50μm depth beneath the corrosion product layer.
文摘Abstract The Nansha ultra-crust layer-block is confined by ultra-crustal boundary faults of distinctive features, bordering the Kangtai-Shuangzi-Xiongnan extensional faulted zone on the north, the Baxian-Baram-Yoca-Cuyo nappe faulted zone on the south, the Wan'an-Natuna strike-slip tensional faulted zone on the west and the Mondoro-Panay strike-slip compressive faulted zone on the east. These faults take the top of the Nansha asthenosphere as their common detachmental surface. The Cenozoic dynamic process of the ultra-crust layer-block can be divided into four stages: K2-E21, during which the northern boundary faults extended, this ultra-crust layer-block was separated from the South China-Indosinian continental margin, the Palaeo-South China Sea subducted southwards and the Sibu accretion wedge was formed; E22-E31, during which the Southwest sub-sea basin extended and orogeny was active due to the collision of the Sibu accretion wedge; E32-N11, during which the central sub-sea basin extended, the Miri accretion wedge was formed and “A-type” subduction of the southern margin of the north Balawan occurred; N12-the present, during which large-scale thrusting and napping of the boundary faults in the south and mountain-building have taken place and the South China Sea stopped its extension.
基金Supported by the National Basic Research Program of China (973 Program, No. 2007CB407305)Qingdao Special Project for Outstanding Scientists (No.05-2-JC-90)the 100 Talents Project of Chinese Academy of Sciences (No.2003-202)
文摘The area of the southwestern Nansha Trough is one of the most productive areas of the southern South China Sea.It is a typical semi-deep sea area of transition from shoal to abyssal zone.To understand distributions and roles of nitrogen forms involved in biogeochemical cycling in this area,contents of nitrogen in four extractable forms:nitrogen in ion exchangeable form(IEF-N),nitrogen in weak acid extractable form(WAEF-N),nitrogen in strong alkali extractable form(SAEF-N) and nitrogen in strong oxidation extractable form(SOEF-N),as well as in total nitrogen content(TN) in surface sediments were determined from samples collected from the cruise in April-May 1999.The study area was divided into three regions(A,B and C) in terms of clay sediment(<4 μm) content at <40%,40%-60% and >60%,respectively.Generally,region C was the richest in the nitrogen of all forms and region A the poorest,indicating that the finer the grain size is,the richer the contents of various nitrogen are.The burial efficiency of total nitrogen in surface sediments was 28.79%,indicating that more than 70% of nitrogen had been released and participated in biogeochemical recycling through sediment-water interface.
文摘Dynamics of major picoplankton groups, Synechococcus (Syn), Prochlorococcus (Pro), picoeukaryotes (Euk) and heterotrophic bacteria (Bact) was investigated by flow cytometry for the first time in the Nansha Islands area in the South China Sea. Averaged over the whole investigation area, depth-weighted integrated cell abundance (DWA) of Syn, Pro, Euk and Bact was 1.6 (0.4-5.7)×103, 5.4 (0.1-7.3)×104, 0.7 (0.2-2.2)×103, and 2.3 (1.4-3.2)×105 cells/mL respectively. Picoautotrophic cell abundance was low in the northwest part of the Nansha Islands where surface water temperature was low and the upper mixed layer was shallow. Concurrently, a surface maximum vertical distribution pattern was observed in this area. While in the southeast and east zones where temperatures were relatively higher and nitraclines were deeper, picoplankton is abundant and a subsurface maximum around 50-75 m is observed. Coupling of horizontal and vertical distribution patterns of picoplankton abundance and hydrological status was found, suggesting a strong influence of currents and water column structure on picoplankton distribution in the investigation area. Contrary to that in the shelf water in the East China Sea, the relationship between Pro and Bact in the Nansha Islands area in the South China Sea was not significantly negative but weakly positive. Moreover, a similar distribution pattern of Syn and Pro was observed. Possible reasons for these differences in the two marine regimes were discussed.
基金the National Natural Science Foundation of China(No.51671197)Special Project of Chinese Academy of Sciences(No.XDA130040502).
文摘The corrosion and pitting behavior of pure aluminum 1060 exposed to Nansha Islands marine atmosphere for 34 months was investigated based on mass loss measurement,scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),and electrochemical impedance spectroscopy(EIS).The results indicated that serious pitting corrosion occurred on the surfaces of pure aluminum.The corrosion rate after exposure for 13 months was approximately 1.28 g/(m^(2)·a).The XPS results showed that the corrosion products were Al_(2)O_(3),Al(OH)_(3),and AlCl_(3).Moreover,the corrosion product layer was more protective than the native oxide film,and the protectiveness first increased and then decreased.Finally,the shape of the pits was evaluated using statistical analysis.
基金The National High Technology Research and Development Program of China(863 Program)under contract No.2012AA12A406the National Natural Science Foundation of China under contract Nos 41471068,41171325,and J1103408+1 种基金the Program for New Century Excellent Talents in University under contract No.NCET-12-0264the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘A detailed survey of the reefs in the Nansha Islands＇ sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager（OLI） images were used to analyze the geological features and spectral characteristics of the Nansha reefs. The exposed islands/sandbanks,reef flats and sub-tidal reefs were identified with the near-infrared band, the red and green bands, and the blue band, respectively. Based on the relationships among various characteristics and bands illustrated in the OLI images, the maximum between-cluster variance threshold algorithm（OTSU method） and the mathematical morphology were employed to extract characteristic parameters of the spatial geometry of the reefs from top to bottom, which were subsequently operated by a series of post-processing methods such as vectorization,simplification and topological analysis. Among the 132 standalone reefs and 16 atolls that are identified in the study, four reefs have yet to be named in the Standard Names of Various Islands in the South China Sea and the website Nansha Islands Online（http：//www.nansha.org/）. Another 24 ones are exposed to the atmosphere even during high tides. Taiping Island with an area of 0.57 km^2 represents the largest exposed geological feature. This study demonstrated the applicability of medium-resolution satellite images to derive the coral reef information effectively and thus provided information for the related departments that are responsible to manage the coast.An improved resolution of multispectral bands with the panchromatic band in higher spatial resolution（15 m for OLI image） is expected to provide an optimum satellite based approach to map marine habitats.
基金The authors are grateful for the financial supports from National Natural Science Foundation of China(51671197)Strategic Priority Research Program of Chinese Academy of Sciences(13040502).
文摘The corrosion behavior of pure copper exposed to the atmosphere of Nansha Islands for 21 months was studied by mass loss method,composition analysis,morphology observation and electrochemical measurements.The results showed that the average corrosion rate of copper exposed for one year was approximately 7.85μm/a,implying that Nansha Islands was classified as a corrosion category of CX.The structure and properties of the corrosion product layer generated on the front and back sides of the exposed sample differed significantly.The inner corrosion product layer(Cu2O)on the front side was relatively thick and dense,whereas the outer product layer(Cu2Cl(OH)3)was extremely thin.However,the outer product layer on the back side was thicker than the inner layer.Electrochemical measurements indicated that the protection afforded by the corrosion product layer on the front side was improved gradually,while that on the back side was deteriorated.
基金The National Basic Research Program of China ("973") under contract Nos 2009CB2194 and 2007CB411700the Major Knowledge Innovation Programs of the Chinese Academy of Sciences under contract No. kzcx2-yw-203-01+2 种基金the National Natural Science Foundation of China of China under contract No. 40676039the National Program of Sustaining Science and Technology of China under contract No. 2006BAB19B02the Program of the Ministry of Land and Natural Resources of China under contract No. GT-YQ-QQ-2008-1-02
文摘Layer-block tectonics （LBT） concept, with the core of pluralistic geodynamic outlook and multilayer-sliding tectonic outlook, is one of new keys to study 3-dimensional solid and its 4-dimensional evolution history of global tectonic system controlled by global geodynamics system. The LBT concept is applied to study the lithospheric tectonics of the southern South China Sea （SCS）. Based on the analysis of about 30 000 km of geophysical and geological data, some layer-blocks in the Nansha micro-plate can be divided as Nansha ultra-crustal layer-block, Zengmu crustal layer-block, Nanwei （Rifleman bank）-Andu （Ardasier bank） and Liyue （Reed bank） North Palawan crustal layer-blocks, Andu-Bisheng and Liyue-Banyue basemental layer-blocks. The basic characteristics of the basemental layer-blocks have been dicussed, and three intra-plate basin groups are identified. The intra-plate basins within Nansha micro-plate can be divided into three basin groups of Nanwei- Andu, Feixin-Nanhua, and Liyue-North Palawan based on the different geodynamics. In the light of pluralistic geodynamic concept, the upheaving force induced by the mid-crust plastic layer is proposed as the main dynamical force which causes the formation of the intra-plate basins within the Nansha micro-plate. Finally, models of a face-to-face dip-slip detachment of basemental layerblock and a unilateral dip-slip-detachment of basemental layer-block are put forward for the forming mechanisms of the Nanwei Andu and Liyue-North Palawan intra-plate basin groups, respectively.
基金This study was supported by the National Natural Science Foundation of China.
文摘Based on the feature of the growth and the local limitation of the Nansha reef's closed atoll, also the related remote sensing information of it, the composite analysis is made. The closed atoll conception remote sensing system is constructed through the formation mechanism, development law and the space-time distribution of the closed atoll. Solution of the equation consisting of information function value and isostatic value of closed atoll and half-closed atoll using this system, and topologic analysis on the two kinds of atoll's morphologic growth are the basic foundation for the research of their evolutionary comparative model.
基金National Sea Islands Protection and Management Programme
文摘Sand cay is a special kind of islet formed by coral detritus and bioclast, which is common in Nansha Islands of China. Some sand cays play an important role in ocean strategy and economy, but surprisingly we know little about them, especially those recently formed sand cays. In this research, we monitor migration of a new sand cay in Nanxun Jiao（Gaven Reef） using a series of Quick Bird and World View-2 satellite images between June 2006 and August 2013. We conduct a regression between migration distance and wind observational data to examine the migration patterns of the new sand cay. The migration distance is calculated based on the sand cay locations extracted based on Normalized Difference Water Index（NDWI）. The wind observational data downloaded from NOAA are reformed into four wind direction vectors. Based on the results of regression, we concluded that the migration of the new sand cay on Nanxun Jiao was significantly associated with the east, west and north wind.East wind was the main influence factor of the migration; its impact strength was almost twice as the west and north wind. The south wind has little effect on the migration of the sand cay, which is partly blocked by the artificial structure in the south.
基金Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA13010401
文摘As is well-known, Nansha Islands in the South China Sea(SCS) are of important strategic position and invaluable ecological value. Therefore, many attentions are paid to either the political and legal aspects of exposed features that matter in the maritime delimitation, or the physical and geographical characteristics of coral reefs that are the predominant structures of these islands. However, it seems that they consistently lose the connection of sciences and humanities in the research of Nansha Islands in the SCS. In this study, we carry out a combinative research, based on remote sensing data using satellite imagery analysis together with historical materials using literature investigation, so as to reconsider to the geographical characteristics of Nansha Islands from a standpoint of the United Nations Convention on the Law of the Sea(UNCLOS). After thoroughly appraising the statuses of these newly formed sand cays, several high tide features of Nansha Islands are identified. By means of the comparison of satellite images coupled with reference to nautical charting and sailing directions during different time periods, we can conclude that the statuses of these high tide features formed on reef platforms are relatively stable due to the growth of reef-building organisms although their migration patterns are subject to external disturbances, and hence the cursory judgment pursuant to the relevant provisions of the UNCLOS about whether a coral reef belongs to a low tide elevation only based on outdated references or ex parte evidences is not reliable. Moreover, it is accordingly justified to improve further development and perfection of the maritime legislation by eliminating such ambiguities with the growth of coral reefs and the evolution of sand cays being both taken into account.
文摘On the basis of interpretation of comprehensive geophysical data and foreign data analysis,there existed a lot of overburden detachment shear thrust faults along the southeastern margin of Nansha Trough,which composed imbricated overthrust nappe structure.Thrust-faulted nappe structure pattern is determined in this area,which consists of frontal fault zone,thrust fault-folded zone and root zone structures,and presents regularly zonation on plane.The detail description of the structural geometrical characteristics is given in shallow thrust fault zone,and the kinematical mechanism of thrust fault nappe structure is furtherly discussed.Overthrnst nappe structure in this area is resulted from island arc-continent collision and orogenic activities.
文摘This work yielded an improved method for extracting and analysing benzothiophene in marine sediment.The detation limit was 0.05 ng S of benzothiophene, with precision of 8%. Benzothiophene was found in Nansha Islands sea area sediments and ranged from 1.1 -6.8 ng per gram dry sediment. Its concentration was closely correlated to hte organic carbon content in the sediment.Several source processes of benzohtiophene are discussed in this paper.
文摘Landscapes of the Nansha Islands may be divided into five types: tropical marine organismbreeding landscape of reef knoll like Zengmu Shoal, Wan'an Bank and so on; tropical marine organismbreeding landscape of atoll including all emerged reefs and most submerged reefs; tropical evergreen arborbush forest and phosphorous lime soil landscape of limesand Islets like Taiping Islet, Nanwei islet and so on; tropical shallow sea marine organismbreeding landscape of southern continental shelf; tropical oceanic and deepsea marine organism landscape in middle and north parts of the Nansha Islands area. These five landscape types may be also summed up as two categories, one is tropical sea landscape including those in shallow and deep sea, the other is tropical coral reef landscape including those of reef knoll, atoll and limesand islet. This paper outlines the evolutional model of landscapes of the Nansha Islands. The distribution and evolution of landscape types are related with palaeogeography and modern environmental conditions. The former shallow sea of the Nansha islands was coastal zone in the Late Pleistocene epoch. Deep sea is evolved from shallow sea due to long and slow subsidence of crust. Modern coral reefs develop on old reef top of the Late pleistocene epoch or on baserock of continental shelf in the Holocene due to the rise of sea level in postglacial. Limesand islet is in the peak of developmental stage.
文摘Based on the remote sensing information feature of Nansha coral islets and reefs that controlled by the Nansha Islands local area's goological structure and growth law, by means of mathematical model and PC, the Nansha Islands coral islets and reefs' top geological data' spatial distribution and local change trend are simulated by using the trend surface system on the remote sensing composite information, and an scientific interpretation and local comparison of Nansha coral islands and islets' spatial distribution feature are made.
基金Under the auspices of National Key Research and Development Program of China (No.2022YFC3103103)。
文摘Changes in vegetation status generally also represents changes in the ecological health of islands and reefs(IRs).However,studies are limited of drivers and trends of vegetation change of Nansha Islands,China and how they relate to climate change and human activities.To resolve this limitation,we studied changes to the Normalized Difference Vegetation Index(NDVI)vegetation-greenness index for 22 IRs of Nansha Islands during normal and extreme conditions.Trends of vegetation greenness were analyzed using Sen's slope and Mann-Kendall test at two spatial scales(pixel and island),and driving factor analyses were performed by time-lagged partial correlation analyses.These were related to impacts from human activities and climatic factors under normal(temperature,precipitation,radiation,and Normalized Difference Built-up Index(NDBI))and extreme conditions(wind speed and latitude of IRs)from 2016 to 2022.Results showed:1)among the 22 IRs,NDVI increased/decreased significantly in 15/4 IRs,respectively.Huayang Reef had the highest NDVI change-rate(0.48%/mon),and Zhongye Island had the lowest(–0.29%/mon).Local spatial patterns were in one of two forms:dotted-form,and degradation in banded-form.2)Under normal conditions,human activities(characterized by NDBI)had higher impacts on vegetation-greenness than other factors.3)Under extreme conditions,wind speed(R^(2)=0.2337,P<0.05)and latitude(R^(2)=0.2769,P<0.05)provided limited explanation for changes from typhoon events.Our results provide scientific support for the sustainable development of Nansha Islands and the United Nations‘Ocean Decade’initiative.
基金This work was supported by the Knowledge Innovation Frontier Project of South China Sea Institute of OceanologyChinese Academy of Sciences under contract No,LYQY200310+1 种基金National Science Foundation of China under contract Nos 40376003 and 40276004 National Special Key Project of China under contract No.2001DIA50041.
文摘A reduced vertically integrated upper mixed layer model is set up to numerically study the thermodynamic process of the formation of the 'Nansha warm water'(NWW) in the Nansha Islands sea areas in spring. According to the numerical experiments, it is shown that, in spring, the formation of the NWW is mainly due to the sea surface net heat flux and the local weak current strength; the contribution from temperature advection transport and warm water exchange with the outer seas (Sulu Sea or south of Sunda shelf) is very little. In the sea areas where the current is strong, the advection may also play an important role in the temperature field.
