测高重力场反演海底地形方法比较

根据重力异常与海底地形的相关性,利用日本西之岛附近海域内的重力异常和船测水深,分别采用SandwellSmith方法(SS,1994)和重力地质法(GGM)反演了该海域内1'×1'海底地形模型,并将反演的模型与格网化船测水深模型和ETOPO1模型进行了对比分析。在GGM中,使用了迭代法向下延拓确定密度差常数为5.7g/cm~3。与SS模型相比,GGM模型与格网化船测水深模型的差值的标准差达到了37.10m。     

渤海基底倒形结构形成机制

为了探讨渤海基底结构特征,中国科学院海洋研究所调查船“海燕号”用KЦГ—Ⅱ型海底石英重力仪和国产ZH641型金属弹簧海底重力仪在渤海进行了联合观测(范时清,江玉成),完成剖面四条,测点49个,控制面积1700平方公里,全区总测量精度为±1.06毫伽。为了得到单纯由地质不均匀体引起的海底重力变化状况,通过对观测数据的系统校正与运算,求出各测点的海底布格重力异常值,并作出各剖面的布格重力异常曲线。 海底构造的存在,会引起水下各地段密度分布的不均匀或相对的差异性,从而引起海底重力场相应的变化,在一般情况下,局部重力变化与地壳表层地质构造的差异有关,即同岩石成分及其成层条件不同有关,在较致密的岩层接近地表的地方,重力值就增大,反之,重力值就减小。海底重力测量结果表明,渤海中部存在着一个巨大的北北东向的重力低区和各断面布格异常曲线呈大凹陷的地段,反映这里乃是一个沉积盖层较     

南海北部陵水陆坡重力流沉积调查与分析

深水沉积环境复杂、浅层沉积物土质差异明显、重力流沉积多样,对深水海洋工程水下设施的设计、施工和运营安全提出了新的挑战。通过二维/三维数字地震等方式能够识别出数百米的滑坡体,但是对于海洋工程上所关注的浅层海底的重力流沉积体系,其分析能力有限。以南海北部陵水区块为例,通过船载多波束的后向散射成果、自主水下航行器(AUV)搭载的浅地层剖面资料,结合重力活塞取样器(JPC)取样和碳14测年(AMS14C)等资料综合分析,对深水海底浅层重力流沉积的形成和分布模式进行探讨。研究表明,船载多波束后向散射图能够较为准确地识别区域性重力流沉积区域,以及表层沉积物的变化,AUV搭载的浅地层剖面能够精确地识别地层的纵向差异,JPC取样能够获取重力流沉积样品及其物理力学参数,以上资料的综合分析,是准确识别、研究和认识现代重力流沉积体系的重要方法。研究区内最近的2期重力流沉积分别发生于5.5 kaBP左右和45 kaBP前,重力流的发生一般都是由上陆坡区海底峡谷的活动引起的。最近的一期重力流事件中,先后发生了浊流沉积和块状搬运体(MTDs)沉积,MTDs沉积过程中会对下伏地层产生明显的冲蚀现象。在重力流沉积区进...     

海底高精度重力测量系统及方法技术研究和应用

海底高精度重力测量系统及方法技术研究和应用罗壮伟，刘文锦，程振炎（地质矿产部物化探研究所）前言海洋重力测量对于海洋石油天然气资源勘查以及天然地震预报与震害预测、大地构造、军事科学研究等，都具有十分重要的意义。目前国内外海洋重力主要从事深海域重力勘测，...     

应用重力地质法反演马里亚纳海沟地形

根据重力地质法(Gravity Geological Method, GGM),利用6 736个已知水深点数据和卫星测高重力异常反 演了马里亚纳海沟(142^°36^''~147^°18^''E,23^°~27^°N)1^''×1^''分辨率的海底地形,该计算中的密度差常数为1.20 g/cm³。将反演的地形与实测检核水深数据相比,两者较差标准差为152.9 m,平均误差为(±3.0) m,均方差为153.0 m,优于ETOPO1模型和直接把船测水深控制点格网化后的模型。将重力地质法反演的模型、ETOPO1模型、直接格网模型进行功率谱密度分析,结果显示3种模型在中长波地形能量一致,但对于短波地形,重力地质法模型能量高于其他2个模型,说明重力地质法更能描绘细致的海底地形地貌。选取2条测线与重力地质法模型进行对比研究,结果表明重力地质法在海底地形起伏小的区域优于在海底地形起伏较大区域的反演效果。     

联合重力异常和重力垂直梯度异常数据反演皇帝山海域海底地形

海底地形对开展海洋科学调查和研究十分重要。以多波束为主的回声测深技术测量成本高且效率低,几十年来仅实现了全球约20%的海床测绘。对于空白区（特别是深海区域）,可以借助重力异常和重力垂直梯度异常进行回归分析反演得到,但该方法得到的比例因子鲁棒性不强。为了解决这一问题,同时考虑到两种重力数据在表征海底地形长短波长的不同优势,本文结合滑动窗口赋权和稳健回归分析来反演海底地形。在太平洋皇帝山海域（35°～45°N,165°～175°E）的实验结果表明：在船测检核点处,本文构建模型的标准差为61.02 m,相比于单一重力数据反演模型,精度分别提高了14.92%（重力异常）和2.08%（重力垂直梯度异常）,能较好地反映皇帝海山链的地形走势。     

基于地形单元分区的BP神经网络反演海底地形

海底地形和海洋重力场在一定波段频率域上存在相关性,传统海底地形反演方法主要考虑海底地形与重力数据之间的线性关系,而忽略非线性项作用对反演结果的影响。基于此,提出了基于海底地形单元分区的BP神经网络反演方法,改善海底地形反演精度。选取东印度洋北部东经90°海岭附近海域(83°E～92°E,10°S～10°N)为实验区,利用船测水深、卫星测高重力等数据,根据地形特征将实验区分为海盆区和海岭区,使用BP神经网络方法分别进行海底地形反演,构建了实验区1′×1′局部海底地形模型。结果表明,基于地形单元分区的反演结果模型平均相对误差精度可达1.45%,比未分区的反演结果均方根误差降低了42 m,验证了本文方法的有效性和可行性。     

近海底调查的拖曳式海洋重力仪

目前海洋重力主要为海面和海底测量。海面重力测量受水深影响,观测点远离重力源,其分辨率降低;海底测量分辨率不受水层影响,但由于逐点测量的耗时,其覆盖性较差。我们制作了一个重力测量系统,该系统在近海底具有高分辨率、高速采集重力数据的能力,其探头用船拖曳在海底附近的正上方。     

两种测高重力异常反演海底地形方法比较

针对基于测高重力异常反演海底地形理论众多、选取标准无法确定的情况,利用中国南海海域内的测高重力异常和船测水深数据研究比较了重力地质法(GGM)和SmithSandwell (SAS)法两种精度高、计算速度相对较快的海底地形反演理论。其中,GGM方法的密度差异常数Δρ由向下延拓技术确定为2.15 g·cm-3,SAS方法采用移去-恢复技术得到反演波段内重力异常和水深数据。结果表明:测线分布条件一定时,水深多在-1 000 m左右或反演区域岛礁、海山等复杂海底地形较多时选取SAS方法,水深主要在-3 000 m以深的区域或海底地形复杂程度不高时选取GGM方法则能获取更好的效果,其效果最优处与船测水深在检核点处的差值最优平均值能达-0.61 m,标准差可达14.67 m。     

高精度测高重力场反演南海海底地形

随着测高技术的不断发展,测高海洋重力场的精度不断提高,由其反演计算的海底地形精度也相应提高。利用Sandwell 2014年最新发布主要由Jason-1末期大地测量任务和Cryosat-2观测资料反演的测高重力场V23.1,采用重力地质法(GGM)反演了中国南海海域海底地形模型,并对结果进行了精度评价。该过程中首先直接计算一系列密度差下的反演结果,并通过船测数据检核选定优化的密度差范围,然后利用向下延拓的方法确定了最优密度差异常数为7g/cm3。与船测水深数据相比,反演得到的GGM模型与检核点船测水深数据差值的标准差达到了±70.32m;此外,还计算了由测高重力异常V15.2反演的海底模型,比较这两个模型发现:测高重力场短波部分的改善对海底地形反演精度的提升作用有限,为得到更高精度的海底地形模型,需引入短波更为敏感的重力梯度资料。     

Biocorrosion by Bivalves

Abstract. A survey of the historical background of chemically boring bivalves and the proposed methods of boring, indications for biocorrosion, observations, and experimental results are provided. The regional impact to the ecosystem is discussed with examples from the N. Adriatic, Caribbean, and E. Pacific. The fossil record of the geologically oldest biocorroders extends back into the Mesozoic, i.e ., U. Triassic for Lithophaga and Jurassic for gastrochaenids.     

酶解褐藻胶寡糖的HPCE分析方法研究

采用高效毛细管电泳法（HPCE）对酶解褐藻胶寡糖进行了分离分析,考察了缓冲液浓度、pH、电压及温度等参数对寡糖分离的影响.实验结果表明在pH=2.5,100mmol/L 磷酸盐缓冲液中,运行电压20kV,电泳由负极到正极,温度30℃,235nm紫外检测条件下,酶解褐藻胶寡糖获得了高效分离.     

Production of Domoic Acid by Pseudo-nitzschia multiseries Hasle, Affected by Lithium

Abstract. Upon enrichment with lithium 385.6 μM Li, culture of Pseudo-nitzschia multiseries H asle produces substantially higher level of the neurotoxin domoic acid DA 230 fg · cell^-1 than the control 135 fg · cell^-1. We hypothesize that in Cardigan Bay, where the first domoic acid episode was reported, high levels of Li could have originated via a massive freshwater run-off involving an adjacent dump. Lithium enrichment may have played a part in enhancing DA production leading to the intoxication episodes of 1987. Thus, anthropogenic activities may play a role as a sustainer of algal blooms and should be included in habitat management considerations involving coastal and inshore algal blooms, both toxigenic and non-toxigenic.     

Degradation of lubricating oils by marine bacteria observed by quantitative mass spectrometry

Bacterial degradation of the hydrocarbons of lubricating oils was investigated by mass spectrometric analysis which gives both total amount and the composition of hydrocarbon types of residual oil. An unused lubricating oil, which mainly consisted of hydrocarbon types with only a small percentage ofn-alkanes, was degraded by marineBacillus sp. andPseudomonas sp. with 55 % and 25 % decreases in 10 days, respectively. Susceptibility of respective hydrocarbon types to biodegradation was in the following order: alkanes > non-condensed cycloalkanes, mono-aromatics > condensed cycloalkanes. A used lubricating oil of different brand showed a larger decrease than the unused oil. Both species of bacteria degraded large portions of alkane fraction of Arabian light crude oil.     

Long-term changes in the production by estuarine macrobenthos affected by multiple stressors

The macrobenthic production of an estuarine system was evaluated over a 14-year study period in a seagrass bed and in a sandflat. Over this period, the estuary suffered severe eutrophication and extreme weather events with important impacts on the community, impairing system functioning and ultimately the goods and services provided by the estuary (decline in the seagrass bed, decreased community production and/or a boost in the production by opportunist species, such as Hydrobia ulvae). Following the anthropogenic impacts, management measures were introduced which allowed a gradual recovery of the seagrass bed and a new macrobenthic community structure manifested by production increases of slow-growing species, such as Scrobicularia plana and Hediste diversicolor. There was a gradual re-orientation of energy into population biomass instead of population density but this was not translated into higher community production, mainly due to the decreased production of opportunist species (H. ulvae and several polychaetes). Several weather extreme events occurred during this post-mitigation phase - floods, heatwaves and droughts, all of which had negative impacts on macrobenthic dynamics and production. The heatwaves led to the greatest decreases in macrobenthic production, mainly due to S. plana perhaps associated with its physiological intolerance of higher temperatures. The prolonged drought that followed the heatwaves maintained low levels of production by S. plana and H. ulvae. With climate change, the frequency and intensity of extreme weather events are likely to increase worldwide so that the recovery of impacted/disturbed systems from impacts such as eutrophication may be seriously affected by these additional stressors, compromising attempts to improve the ecological quality of estuarine ecosystems.     

Numerical simulation of sediment lifted by waves and transported by tidal currents

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浮游生物来源溶解有机物的三维荧光特征研究

应用三维激发-发射荧光光谱技术,研究了中肋骨条藻和采集水样中浮游植物在光照和避光条件下培养实验过程中产生的溶解有机物,分析了三维荧光光谱中荧光峰数目、位置和荧光强度的变化,探讨了浮游植物和细菌在有机物产生中的作用.结果表明,光照条件下浮游植物生长产生类蛋白和类腐殖质荧光有机物,在衰亡期2类有机物的荧光强度迅速增加;而在避光条件下,类蛋白有机物荧光强度明显降低,类腐殖质有机物的荧光强度保持不变.2类有机物的荧光峰位置和荧光强度变化与初始有机物的性质及光照环境有关.