Distribution and Characteristics of Hazardous Geological Features in the Marine Coastal and Offshore Areas of Zhejiang Province, East China Sea

Newly acquired high-resolution shallow seismic profiles(7069 km in length) in the coastal and offshore areas of Zhejiang Province, East China Sea, China, have revealed eight marine hazardous geological features: shallow gas, sand ridges, erosion ditches, scarps, irregular bedrock features, underwater shoals, buried paleo-channels, and submarine deltas. Based on the seismic profiles, we have constructed a marine geological map of these hazardous features. Shallow gas accumulations are common and occur mainly in two separate nearshore regions that cover 4613 and 3382 km^2 respectively. There are also scattered shallow gas accumulations in the offshore area, typically accompanied by paleo-channels that occur mainly in the middle of the study area. Sand ridges, erosion ditches, scarps, and irregular bedrock features are found mainly in the northeast of the study area in association with each other. In the southeastern part of the study area, the sand ridges have a linear form and trend NW–SE, representing the western part of the linear sand ridges in the East China Sea. The maximum slope gradient is 1?, which suggests that this area is prone to landslides. These hazardous marine geological features are important to marine and engineering activities in this region.

Validation and application of multi-source altimeter wave data in China＇s offshore areas

Studies of offshore wave climate based on satellite altimeter significant wave height（SWH） have widespread application value. This study used a calibrated multi-altimeter SWH dataset to investigate the wave climate characteristics in the offshore areas of China. First, the SWH measurements from 28 buoys located in China＇s coastal seas were compared with an Ifremer calibrated altimeter SWH dataset. Although the altimeter dataset tended to slightly overestimate SWH, it was in good agreement with the in situ data in general. The correlation coefficient was 0.97 and the root-mean-square（RMS） of differences was 0.30 m. The validation results showed a slight difference in different areas. The correlation coefficient was the maximum（0.97） and the RMS difference was the minimum（0.28 m） in the area from the East China Sea to the north of the South China Sea.The correlation coefficient of approximately 0.95 was relatively low in the seas off the Changjiang（Yangtze River） Estuary. The RMS difference was the maximum（0.32 m） in the seas off the Changjiang Estuary and was0.30 m in the Bohai Sea and the Yellow Sea. Based on the above evidence, it is confirmed that the multialtimeter wave data are reliable in China＇s offshore areas. Then, the characteristics of the wave field, including the frequency of huge waves and the multi-year return SWH in China＇s offshore seas were analyzed using the23-year altimeter wave dataset. The 23-year mean SWH generally ranged from 0.6-2.2 m. The greatest SWH appeared in the southeast of the China East Sea, the Taiwan Strait and the northeast of the South China Sea.Obvious seasonal variation of SWH was found in most areas; SWH was greater in winter and autumn than in summer and spring. Extreme waves greater than 4 m in height mainly occurred in the following areas： the southeast of the East China Sea, the south of the Ryukyu Islands, the east of Taiwan-Luzon Island, and the Dongsha Islands extending to the Zhongsha Islands, and the frequency of extreme waves was 3%-6%. Extreme waves occurred most frequently in autumn and rarely in spring. The 100-year return wave height was greatest from the northwest Pacific seas extending to southeast of the Ryukyu Islands（9-12 m）, and the northeast of the South China Sea and the East China Sea had the second largest wave heights（7-11 m）. For inshore areas, the100-year return wave height was the greatest in the waters off the east coast of Guangdong Province and the south coast of Zhejiang Province（7-8 m）, whereas it was at a minimum in the area from the Changjiang Estuary to the Bohai Sea（4-6 m）. An investigation of sampling effects indicates that when using the 1°×1°grid dataset, although the combination of nine altimeters obviously enhanced the time and space coverage of sampling, the accuracy of statistical results, particularly extreme values obtained from the dataset, still suffered from undersampling problems because the time sampling percent in each 1°×1°grid cell was always less than33%.

Utilization and Management of Small Fishery Population Resources in Coastal and Offshore Areas of China

There are numerous types of living resources in coastal and offshore areas of China. In recent years,both the population type and quantity structure have significant changes,and the stock of small fishery population resources is increasing. This population is precious protein resource. It is urgent to study how to take prompt and effective fishing and take full advantage of processing,utilization and management. Traditional utilization methods are limited by many factors. The utilization efficiency is extremely low. The feed conversion rate of some mariculture fishes with fresh small trash fishes as feeds is even as low as 0. 2. Innovative production and management organization model with aquatic enterprises as leaders greatly increases the utilization efficiency of small fish resources with the aid of marine processing mother ship. In order to further accelerate developing and utilizing small fishery population resources in coastal and offshore areas,China should launch survey and utilization researches of small fishery population resources in coastal and offshore areas,formulate practical and feasible laws,regulations and policies,actively encourage and support autonomous innovative management mode of enterprises,and promote effective utilization and management of coastal and offshore fishery resources.

OPTIMAL HARVESTING AND STABILITY FOR FISHING MODELS WITH STAGE STRUCTURE IN INSHORE-OFFSHORE AREAS

A fishing model with stage structure in inshore and offshore areas is considered.Steady states of the dynamical system representing fishery are derived and their local,as well as global,stability is discussed.The optimal harvest policy is formulated and solved as an optimal control problem.A numerical example is given to illustrate the solution procedure.

Numerical simulation and inversion of offshore area depth based on x-band microwave radar

A detection method of offshore area depth utilizing the x-band microwave radar is proposed. The method is based on the sea clutter imaging mechanism of microwave radar, and combined with dispersion equation of the liner wave theorem and least square method （LSM）, consequently get the inversion results of water depth in the detected region. The wave monitoring system OSMAR-X exploited by the Ocean State Laborato-ry, Wuhan University, based on a microwave radar has proven to be a powerful tool to monitor ocean waves in time and space. Numerical simulation and inversion of offshore area depth are carried out here; since JONSWAP model can give description of stormy waves in different growth phase, it is suitable for simulation. Besides, some results from measured data detected by OSMAR-X x-band radar located at Longhai of Fujian Province, China, validates this method. The tendency of the average water depths inferred from the radar images is in good agreement with the tide level detected by Xiamen tide station. These promising results suggest the possibility of using OSMAR-X to monitor operationally morphodynamics in coastal zones. This method can be applied to both shore-based and shipborne x-band microwave radar.

Coral Ba/Ca and Mn/Ca Ratios as Proxies of Precipitation and Terrestrial Input at the Eastern Offshore Area of Hainan Island

Geochemical ratios in coral reef skeletons could be used as proxies to reconstruct past climatological and environmental records in data-poor regions. Using a 103-year data set(1902 to 2005), the annual variations in Ba/Ca and Mn/Ca ratios of Porites lutea skeletons at an eastern offshore area of Hainan Island(19?12'28.4''N, 110?37'38.8''E) were analyzed using inductively coupled plasma-optic emission spectrometry(ICP-OES). The analysis results showed that Ba/Ca ratios varied from a minimum of 3.120 μmol mol^(-1) in 1903 to a maximum of 10.064 μmol mol^(-1) in 1944, with an average of 5.256 μmol mol^(-1). Mn/Ca ratios varied from 0.206 to 5.708 μmol mol^(-1) with an annual average of 1.234 μmol mol^(-1), with peak values in 2001, 1964 and 1932, that correlated with strong rainfall events caused by typhoons. Variation in Ba/Ca and Mn/Ca ratios were compared with available river discharge and precipitation records, providing insight into past climatological events. Human activities and their indirect effects could impact the strength of the relationship between Ba/Ca and Mn/Ca ratios and observed precipitation and terrestrial input in the future.

Distribution Characteristics of Nutrients and Eutrophication Assessment in the Offshore Area of Northern Shandong

According to the survey data of three voyages in the offshore area of northern Shandong in May,August and October 2018,the distribution characteristics and water qualities of DIN,PO_(4-)P and COD in different seasons were analyzed,and the eutrophication status of the sea area was assessed by single factor index,eutrophication index and organic pollution comprehensive index.The results showed that the seawater in the surveyed area mainly belonged to class I and class II seawater,and DIN was the maximum factor influencing seawater quality.The planar distribution of DIN concentrations showed a decreasing trend from west to east,and high value areas appeared near the Yellow River Estuary and Xiaoqing River Estuary.The concentrations of PO_(4-)P were lower,and the planar distribution law was not obvious.The concentrations of COD were high near shore and low offshore,high in the western sea area and low in the eastern sea area.The eutrophication status of the sea area was not up to the eutrophication level,and red tides were less likely to occur,but there was a possibility of organic pollution.

Geological evolution of offshore pollution and its long-term potential impacts on marine ecosystems

Populations and metropolitan centers are accumulated in coastal areas around the world.In view of the fact that they are geographically adjacent to coasts and intense anthropogenic activities,increasing global offshore pollution has been an important worldwide concern over the past several decades and has become a very serious problem that needs to be addressed urgently.Due to offshore pollution,various geological disasters occur in high frequency,including intensified erosion and salinization of coastal soils,frequent geological collapses and landslides and increasing seismic activities.Moreover,offshore pollution shows increasingly serious impacts on the topography and geomorphology of offshore and coastal areas,including coastal degradation,retreating coastlines and estuary delta erosion.Offshore sedimentation processes are strongly influenced by the pH changes of terrestrial discharges,and sedimentary dynamics have become extremely acute and complex due to offshore pollution.The seabed topography and hydrodynamic environment determine the fate and transport of pollutants entering offshore regions.Coastal estuaries,port basins and lagoons that have relatively moderate ocean currents and winds are more likely to accumulate pollutants.Offshore regions and undersea canyons can be used as conduits for transporting pollutants from the continent to the seabed.It is particularly noteworthy that the spatial/temporal distribution of species,community structures,and ecological functions in offshore areas have undergone unprecedented changes in recent decades.Due to increasing offshore pollution,the stable succession and development trend of marine ecosystems has been broken.It is thus important to identify and regulate the quantity,composition and transportation of pollutants in offshore regions and their behavior in marine ecosystems.In particular,crucial actions for stabilizing marine ecosystems,including increasing species and biodiversity,should be implemented to enhance their anti-interference capabilities.This review provides an overview of the current situation of offshore pollution,as well as major trends of pollutant fate and transportation from continent to marine ecosystems,transformation of pollutants in sediments,and their bioaccumulation and diffusion.This study retrospectively reviews the long-term geological evolution of offshore pollution from the perspective of marine geology,and analyses their long-term potential impacts on marine ecosystems.Due to ecological risks associated with pollutants released from offshore sediments,more research on the influence of global offshore pollution based on marine geology is undoubtedly needed.

A POSSIBLE IMPACT OF EL NINO MODOKI ON SEA SURFACE TEMPERATURE OF CHINA'S OFFSHORE AND ITS ADJACENT REGIONS

El Nio Modoki,similar to but different from canonical El Nio,has been observed since the late1970s.In this paper,using HadISST and NCEP/NCAR wind data,we analyze the relationship between El Nio Modoki and Sea Surface Temperature(SST)in the offshore area of China and its adjacent waters for different seasons.Our results show a significant negative correlation between El Nio Modoki in summer and SST in autumn in the offshore area of China and its adjacent waters,particularly for regions located in the east of the Kuroshio.It is also found that during El Nio Modoki period,anomalous northerlies prevail over the regions from the northern part of the Philippines to the offshore area of China,indicating that the northerlies are unfavorable for the transport of warm water from the western tropical Pacific to the mid-latitude area.Consequently,El Nio Modoki in summer may play a substantial role in cold SST anomalies in the offshore area of China and its adjacent waters in autumn through the influence of the Kuroshio,with a lagged response of the ocean to the atmospheric wind field.

海域地震动强度包络模型研究

人工模拟地震动是目前开展海洋工程结构抗震分析的主要地震输入分析。强度包络函数是人工模拟地震动的重要参数,决定了地震动的强度非平稳性特性,并对地震动持时起控制作用。目前的地震动强度包络模型均是基于陆域地震动记录统计分析得出,无法准确反应海域地震动的强度特性。因此,基于日本K-Net强震动观测台网的实测地震数据库,分析海域地震动在时域中强度分布特性;提出适用于海域地震动的三段式强度包络模型,回归得到震级M、震中距R及关键参数上升段t_(1)、强震平稳段ts、下降段衰减率c(无量纲)的计算表达式;研究震级、震中距对海域地震动强度包络模型的影响规律,并探讨海域地震动与陆域地震动强度包络模型的异同。研究结果表明:海域地震动强度包络模型中关键参数上升段t_(1)、强震平稳段ts、下降段衰减率c的取值范围分别为[13~52 s],[12~79 s],[0.037~0.173];震级对关键参数(t_(1)、t_(s)、c)的影响要大于震中距;与陆域地震动相比,海域地震动的强度包络模型的下降段衰减率c相差显著,且各关键参数的分布范围更大。

海洋平台振动设备所在区域结构优化设计分析

海洋平台上有很多振动设备如压缩机、泵等,这些设备内部转子的往复运动导致高频振动,对平台结构、杆件的稳定造成影响,长期振动下使平台结构出现疲劳,同时设备振动会产生噪音和震感,对平台上的人员身心健康也造成严重影响。文章基于渤海某平台,相关数据均来源于该平台。通过对该平台在压缩机作用下的振动响应,研究压缩机振动对平台的影响,优化该区域结构设计。

基于数值模拟的近海广阔区域办公区风环境研究与改善

近海广阔区域由于缺乏地形遮挡,海洋气流对建筑区域影响显著,导致风速较大,进而引起人员不适,当强/台风来临时还可能会引起人员伤亡。以暖温带东亚季风区大陆性气候、近海广阔区域——胶东半岛的一办公区为例,利用CFD(计算流体力学)软件对办公区的风环境进行研究,以目标区域空旷平坦地面10年一遇10 m高度处10 min平均的风速观测数据为依据,风向以目标区域冬季季风主导方向为主,获得建筑区域的风速云图,确定不利风速区域。进一步,采用10年一遇10 m高度处3 s阵风风速进行极端风速下的研究,结合地形环境,提出风场环境改善方案,定量与定性地分析改善后的风场环境。研究结果可为近海广阔区域风环境的研究与改善提供依据。

长江口及其近岸海域抗生素的时空分异特征与生态风险评估

海洋作为河流抗生素的最终归宿,其在河流到海洋迁移过程的机制和变化规律尚未得到系统研究.2023年分别于丰水期和枯水期,在长江口及其近岸海域采集表层水样,采用固相萃取技术和超高效液相色谱-串联质谱法,对水样中5类20种抗生素的含量进行测定,分析其含量水平、时空分异以及潜在的生态风险.研究结果显示,20种抗生素检出浓度范围为ND(not detected)~63.32 ng·L^(–1),自长江口近口段(平均108 ng·L^(–1))—河口段(平均50 ng·L^(–1))—口外海滨段(平均40 ng·L^(–1))—近岸海域(平均29 ng·L^(–1))呈现出从内陆到海洋的递减趋势.5类抗生素的含量水平由高到低依次为氯霉素类>大环内酯类>磺胺类>喹诺酮类>四环素类,抗生素检出种类及含量具有明显的季节差异性,枯水期大环内酯类抗生素含量显著高于丰水期,而丰水期四环素类含量显著高于枯水期.研究区水体主要受到磺胺甲恶唑、环丙沙星、金霉素、红霉素、氯霉素、氧氟沙星等抗生素的潜在威胁,其生态风险不容忽视.

海上固定式光伏薄壁型钢桁架耐腐蚀性研究

采用热盐水实验、盐雾实验对4~6 mm薄壁型钢结构的腐蚀情况进行研究,通过对比实验分析喷砂钢板、镀锌钢板、镀锌+涂层钢板、涂层钢板的耐腐蚀性,通过海上实证实验挖掘各腐蚀方案在实际施工中易出现的问题。结果表明,从对比实验腐蚀情况上看,喷砂钢板和镀锌钢板在900 h盐雾和920 h60℃热盐水实验后已形成明显腐蚀,镀锌+涂层钢板和涂层钢板无腐蚀。从实证实验上看,钢结构桁架在焊接的过程中会破坏其表面的镀锌层,不易进行修补,涂层在焊接前涂装可预留焊接头,焊接后可进行补涂。因此推荐使用涂层设计方案进行海上薄壁型光伏桁架涂装。

复杂及特异性海洋油气生产设施用海范围界定探讨

随着海上油气开采规模的不断扩大,我国海上油气开发的海域使用需求日益强烈。通过收集梳理某海域149个海洋油气生产设施的结构形式、甲板布置等资料,结合近年来的权属核查、勘测数据,在现行《海籍调查规范》《宗海图编绘技术规范》《海域使用论证技术导则》的基础上,从海域管理的角度,重点对《海籍调查规范》未明确或未包含的海上设施用海范围界定方法进行探索,提出主轴法、用海范围规则化等用海界定的新方法,在此基础上完善各类设施用海界定方法。研究提出的界定方法可有效解决现阶段部分海洋油气生产设施用海界定无依据、界定成果与管理部门权属数据管理方式衔接性差,以及界定成果多样化等问题,为我国海洋油气生产设施海域使用的规范化管理及相关技术规范的修订提供参考。

Development characteristics and controlling factor analysis of the Neogene Minghuazhen Formation shallow water delta in Huanghekou area, Bohai offshore basin

Based on a combination of high resolution 3-D seismic, drilling and well logging and core data, this study focuses on describing the depositional features of the Neogene Minghuazhen Formation shallow water delta in Huanghekou area(HHKA), Bohai offshore basin and discussing the evolution and controlling factors of shallow water delta sandbody. An obvious meandering fluvial delta system developed in sequence 1(SQ1) of the Neogene in HHKA with thinner sandbody of distributary channels and poor development of mouth bar. The sequence texture obviously influences the vertical development and stacking pattern of sandbodies and controls the distribution of sandbodies in plain view as well. In shallow water lacustrine basins, relative topographic height difference leads to change of distribution of accommodation space, and sandbodies of distributary channels usually develop well in local low-lying areas where accommodation space increases. The delta is dominated by distributary channel sandbodies during the early period of base level rising. Sandbodies contact with each other in a lateral stacking pattern and are characterized by a fan shape in plain view. Distributary channels gradually narrow and tend to shift during the mid-late-period of base level rising, while the sandbodies are characterized by a net shape in plain view. During the period of base level slow falling, the multistory/multilateral channel sandbodies dominated the inner front of shallow-water delta and the delta sand dispersal distributes as a lobe shape.

中欧漂浮式海上风电关键技术与产业链合作路径研究

基于中国完善的装备制造体系与欧洲丰富的项目经验优势互补现状,首先,围绕漂浮式海上风电机组、浮式基础、系泊及锚固系统、动态海缆、勘察设计、施工运输与安装、运行维护等产业链和关键技术进行研究,建立了纵向深层剖析和横向拓展对比的产业链评价体系;然后,结合不同细分领域中欧对比结果提出了18项重点合作领域;最后,探讨了试验交流、合作建设、规模应用、全球推广的中欧合作路径,期望解决国内示范样机浮式基础形式单一、成本高昂、产业链不成熟的问题,并为中欧漂浮式海上风电合作提供一定思路和启发。

近海盐渍地区大体积混凝土耐久特性研究

近海盐渍地区湿度大、腐蚀多元化,亟需提高混凝土抗腐蚀等耐久性。结合连云港某热电厂工程腐蚀环境,解决大体积混凝土的内外温差应力开裂风险和防腐耐久性问题,进行了配置混凝土的抗压强度、绝热温升、体积稳定性、抗氯离子侵蚀和抗硫酸盐侵蚀特性研究。结果表明近海盐渍地区大体积混凝土宜采用S95级矿粉和粉煤灰等防腐混合材,其中矿粉掺量30%~35%,粉煤灰+早强激发剂掺量20%~25%。基于新型地聚合物碱激发原理制备的激发剂能够有效避免大掺量混合材对混凝土早期强度的不良影响,从而避免其遭受腐蚀破坏的风险。大掺量掺合料的合理使用可以提高混凝土的工作性能和耐腐蚀性能,降低水泥用量,满足盐渍地区抗侵蚀及耐久性要求。研究可为近海盐渍地区抗腐蚀低收缩高性能混凝土的制备提供借鉴。

基于交能融合的分布式海上风电选址与布置

[目的]在近海浅水海上风电场场址资源日益稀缺,场址逐步向深远海、大型化、基地化发展的背景下,探讨一种交能融合的分布式海上风电,以规避开放式水域的大型海上风电场常出现的涉海范围广、征海面积大、影响通航安全等问题。[方法]基于已建或正在规划的大型港区配套建设的防波堤进行优选场址,在分析港池与防波堤的功能与布置的基础上,通过对海上风力发电机组及海底电缆的优化布置,可实现技术与经济、政策与环境等多方面的提升。[结果]对比国内数十个开放式水域已建海上风电工程,基于交能融合的分布式海上风电场可显著地缩小场址涉海范围、减少征海面积,并降低对周边区域船舶海上通行的影响,是一种相对安全、经济、环保的海上风电场址类型。[结论]通过对交能融合的分布式海上风电选址与布置的探讨,阐述了该类型海上风电场在节约用海、减少海上碍航物、捆绑送出和就地消纳、施工与运维等多方面的优点,并可将其作为现阶段单一海上风电类型的重要补充,成为一种新的增量海上风电场址资源。

海上L区稀疏井网沉积微相刻画研究

海上L区井网稀疏井数少、目标储层地震分辨率差、制约储层沉积微相刻画精度,为解决小层沉积微相刻画难的问题,建立了以沉积模式为指导、单井微相作约束、多地震属性综合对比的沉积微相刻画方法,完成稀疏井网小层沉积微相识别刻画研究,明确工区微相展布特征,相演化模式验证结果可靠。形成的稀疏井网沉积微相刻画方法,为海上稀疏井网储层沉积微相刻画提供参考和借鉴意义。