Assessment of metal contamination in surface sediments from Zhelin Bay,the South China Sea

Metals and biogenic elements were analyzed from surface sediments collected from Zhelin Bay in the South China Sea in December 2008. The high concentrations of TOC, TN and BSi indicate the high nutrient level and diatom productivity in Zhelin Bay. The concentrations of metals were generally far lower than the effects-range-low (ERL) values that define pollutant levels. Enrichment factors (EF) and geoaccumulation indices (I_geo) suggest there are pollution levels of Cd, Cu and Zn at some stations. As, Cu, and Pb are potentially biotoxic in some stations. Correlation and principal component analyses indicate that most of the metals primarily originate from natural sources, and from maricultural activities as well. Mariculture contributes considerable Cd and Cu contamination. As and Pb comes primarily from combustion of gasoline and diesel fuel by ships.     

Disequilibria between ~(210)Po and ~(210)Pb in surface waters of the southern South China Sea and their implications

Naturally occurring 210Po (half-life 138.4d) is the granddaughter of 210Pb (half-life 22.3a), both are members of 238U decay series and have been inten-sively utilized to study kinetic aspects of material cy-cling in the ocean[1]. Based on radioactive disequilibria in the 226Ra-210Pb-210Po system, oceanographical processes with different timescales have been widely studied. Rama et al.[2] first detected excess 210Pb rela-tive to its precursor 226Ra in surface waters, and considered this exc…     

基于磁力资料的南海及邻区磁性基底和居里面深度特征研究

磁性基底和居里面是研究地壳和岩石圈的地质构造和热演化过程的两个重要磁性界面.为了研究南海及邻区磁性基底和居里面所反映的深部构造及其热活动的地质效应,本文在对磁异常进行化极处理的基础上,采用最小曲率位场分离方法,获得了磁性基底和居里面引起的化极磁异常,利用双界面模型快速反演方法,反演了南海及邻区的磁性基底和居里面深度,研究了磁性基底、居里面深度及其分布特征,讨论了磁性基底、居里面与新生界深度之间相关性特征及其地质意义.研究表明,磁性基底深度5~20 km,洋盆南北两侧磁性基底走向分别以NE、NEE向为主,中南半岛周缘磁性基底呈NW、NNW走向.居里面深度15~32 km,宏观表现为"洋壳浅、周缘深"及周缘"北浅南深"的特征,洋盆地区居里面深度呈现"西南浅、东部深",洋壳与陆壳接触带在居里面深度上表现为梯级带特征.新生界深度与磁性基底深度相关性（Correlation between the depth of magnetic basement and Cenozoic,CDMBC）多以不规则形状分布,在盆地的沉积中心呈现正相关;新生界深度与居里面深度相关性（Correlation between the depth of Curie surface and Cenozoic,CDCSC）多呈NE、NEE向带状正相关分布,走向与盆地走向一致;莺歌海盆地、琼东南盆地、万安盆地南部和曾母盆地CDMBC呈正相关、CDCSC呈负相关,莺歌海相关性特征推测为：居里面随岩石圈变形隆起而抬升,磁性基底张裂下沉,发生大规模沉降引起;琼东南盆地相关性特征推测为：居里面随岩石圈变形下坳而下降,沉积中心与磁性基底下沉方向一致;万安盆地和曾母盆地相关性特征推测为：深部流体沿南海西缘断裂直接进入地壳,引起该处居里面深度变浅.     

The distribution of dissolved lead in the coastal waters of the East China Sea

The distribution of dissolved lead in the coastal waters of the East China Sea was investigated seasonally. The average concentrations in surface waters during the spring and autumn were 0.52 nM and 0.27 nM, respectively. In the spring, the concentration of dissolved Pb in the surface waters and bottom waters ranged from 0.13 to 1.86 nM and from 0.15 to 0.94 nM, respectively. For both the surface water and the bottom water, the highest values were observed at the Yangtze River Estuary. Seasonal variability of D-Pb between spring and autumn in the ECS was observed. These results suggested that riverine inputs and atmospheric inputs may be the main sources of lead in this area, while adsorption and co-precipitation on suspended particles at the river estuary and biological process may be the major sinks.     

南海磁性基底分布特征的地球物理研究

利用南海最新的磁力资料,在岩石物性分析基础上,选择南海一条典型剖面拟合反演其密度与磁性结构并以拟合结果作为约束,反演全海域磁性基底的宏观分布.对南海磁力数据进行了低纬度化极处理,利用Halo小波基对化极磁异常进行了多尺度分析并依据磁力异常特征进行了磁场分区.根据剖面与全海域磁性基底反演结果认为：南海北部陆缘更倾向于非火山型的构造属性.磁性基底对浅部沉积作用的控制关系在莺歌海一带表现得非常明显.中—西沙和南沙块体的磁性基底特征十分相似,推测在海盆拉张之前,二者为同一块体.     

Disequilibria between 210Po and 210Pb in surface waters of the southern South China Sea and their implications

Activities of the naturally occurring radionuclides, ²¹⁰Pb and ²¹⁰Po, were measured in both dissolved (<0.45 μm) and particulate (>0.45 μm) phases from surface waters of the southern South China Sea. The average activity of particulate ²¹⁰Pb, 0.23 Bq/m³ (n=23), accounted for about 12% of the total ²¹⁰Pb, which corresponds with values of open oceans. Particulate ²¹⁰Po, with an average activity of 0.43 Bq/m³, accounted for about 40% of the total ²¹⁰Po, which was much higher than those of open and eutrophic oceans. The residence times of total ²¹⁰Po and ²¹⁰Pb in surface waters estimated from an irreversible steady-state model were 0.82 a and 1.16 a, respectively. The consistently high fractionation factor calculated either by scavenging rate constants (5.42) or K_d values (6.69) suggested that a significant fractionation occurred between ²¹⁰Po and ²¹⁰Pb during their removal from solution to particles and that the two radionuclides had different biogeochemical cycling pathways in the oligotrophic South China Sea. Furthermore, our results indicated that there exist different fractionation mechanisms between ²¹⁰Po and ²¹⁰Pb in different marine environments: in eutrophic ocean, plankton detritus and fecal pellets are the main carrier of ²¹⁰Po and ²¹⁰Pb, by which ²¹⁰Po and ²¹⁰Pb have been scavenged and removed; while in oligotrophic ocean, microbes could become the main carrier of ²¹⁰Po and fractionate ²¹⁰Po and ²¹⁰Pb significantly as a result of scarce plankton detritus and fecal pellets. These results suggest the use of ²¹⁰Po to trace marine biogeochemical processes relating to microbial activities and the cycling of sulfur group elements (S, Se, Te and Po).     

Occurrence of persistent organic pollutants in marine fish from the Natuna Island,South China Sea

Five marine fish species were collected from the Natuna Island, South China Sea to investigate the occurrence of polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs). Concentrations of PBDEs, PCBs, and DDTs in marine fish ranged from 2.85 to 7.82, 14.3 to 48.1, and 7.99 to 40.3 ng/g lipid weight, respectively. Higher concentrations of PBDEs, PCBs, and DDTs were observed in Snakefish (Trachinocephalus myops), which might be attributed to their different feeding and living habits. PCBs were the predominant POPs in all marine fish, followed by DDTs and PBDEs. BDE 47 and PCB 153 were the predominant congener of PBDEs and PCBs, respectively. Compositional distribution of DDTs indicated the possible presence of fresh input sources around the Natuna Island. The ratios of o,p′-DDT/p,p′-DDT being less than 1 in fish samples suggested that DDT contributions from dicofol seemed considerably low. New input sources of DDT in South China Sea are worth further research.     

A record of Miocene carbon excursions in the South China Sea

High-resolution δ¹³C records are presented for the Miocene benthic foraminifersCibicidoides wuellerstorfi andC. kullenbergi (24-5 Ma) and the planktonic foraminiferGlobigerinoides sacculifer (18-5 Ma) from ODP Site 1148A (18° 50.17’N, 116° 33.93’E, water depth 3308.3 m), northern South China Sea. The general pattern of parallel benthic and planktonic δ¹³C shows a decrease trend of δ¹³C values from the early-middle Miocene to the middle-late Miocene. Two distinct δ¹³C positive excursions at 23.1-22.2 and 17.3-13.6 Ma, and two negative excursions at 10.2-9.4 and 6.9-6.2 Ma have been recognized. All these events are cosmopolitan, providing the good data for the stratigraphic correlation of the South China Sea with the global oceans as well as for studying the changes of the global carbon reservoir and its corresponding climate.     

南海及邻近地区面波层析成像和S波速度结构

本文介绍由面波层析成像得到的南海和邻近地区地壳上地幔三维S波速度结构.研究区域介于100°E ~130°E和0°~30°N之间,南海位于区域中心,其北、西、南三面通过大陆架和陆坡分别与华南、印支和巽它地块相连,东面邻接台湾—菲律宾岛弧和西菲律宾海盆.由面波层析成像得到的速度结构横向变化与研究区内构造单元的划分基本相符,给出了各个单元的主要结构特征.(1)扬子地块具有厚而高速的岩石圈,华南褶皱带和印支地块具有活动陆块的结构特征,西菲律宾海盆表现为一个较老的稳定的海盆,而岛弧地带显示低速的岩石圈和俯冲板片引起的高速.(2)南海海盆岩石圈厚度60~70 km,横向变化不大,软流圈内低速不显著,整体上表现出一个已停止扩张的年轻海盆的结构特点.与东部中央海盆相比,西南次海盆的上地幔盖层速度和软流圈速度都较低.(3)在南海海盆周边的陆缘地区,岩石圈厚度变化较大,上地幔盖层和软流圈速度较低,明显低于海盆和外围的大陆地区.红河断裂带也表现类似现象,说明这些地区的岩石圈新生代以来经历了长期的构造作用.     

Sediment mass and distribution in the South China Sea since the Oligocene

The sediment macro-distribution patterns and their evolutionary characteristics in the South China Sea (SCS) are discussed based on a quantification of the sediment mass from the be- ginning of seafloor spreading in the Oligocene to the Present. Above the pre-Oligocene base, the total sediment mass for the whole SCS is estimated to be 1.44×1016 t, with the highest average accumulation rate of ~22 g·cm-2·ka-1 in the Oligocene. Having no large abyssal fans but fast accumulation in sedimentary basins on the continental shelf and slope, the SCS shows quite different sedimentary characters not only from the open ocean but also from small backarc basins along the marginal West Pacific, apparently controlled by the coupling between local tectonics and global climate changes.     

Carbon and nitrogen cycling in the Zhubi coral reef lagoon of the South China Sea as revealed by Po and Pb

The radionuclides ²¹⁰Po and ²¹⁰Pb were examined to trace the cycling of particulate organic carbon (POC) and particulate organic nitrogen (PON) in the Zhubi coral reef lagoon. The net export flux of POC to the open sea is 14 mgC m⁻² d⁻¹. However, the net exchange of PON has not yet been observed. On average, the vertical export fluxes in the lagoon of POC and PON, as derived from ²¹⁰Po/²¹⁰Pb disequilibria, are 43 mgC m⁻² d⁻¹ and 13.8 mgN m⁻² d⁻¹, respectively. The deficit of ²¹⁰Po relative to ²¹⁰Pb in particulate matter provides evidence for the degradation of particulate organic matter. According to the mass balance budgets, 310 mgC m⁻² d⁻¹ and 121 mgN m⁻² d⁻¹ were recycled into dissolved fractions. Based on a first-order kinetics model, the degradation rate constants of POC and PON are 0.28 and 0.30 m⁻¹, respectively. Thus, ²¹⁰Po and ²¹⁰Pb can quantify the cycling of carbon and nitrogen in this coral lagoon.     

利用反射地震和多波束资料研究南海西北部麻坑的结构特征与成因

麻坑通常是由海底流体逸散形成的一种海底表面的残留地貌.本文所研究的区域主要位于南海的西北部,包括琼东南盆地的西南部和中建南盆地的中北部.该区域海底表面主要覆盖细粒沉积物,并且底流活动强烈,底流水道发育,为麻坑的形成和发育提供了有利条件.麻坑发育的主要因素是流体逸散系统,本文通过反射地震资料在本区发现了断层、气烟囱、泥火山、泥底辟、声空白/声混浊、强反射等多种与流体逸散相关的指示特征.麻坑的几何特征随着区域的不同会有较大变化.首先本区麻坑的尺寸跨度较大,与底流水道伴生的麻坑和广乐隆起的麻坑表面宽度通常是几十米到数百米,其他区域麻坑的表面宽度通常可达数千米,被称为巨型麻坑.其次本区麻坑的表面形态复杂多样,有圆形、椭圆形、新月形、环形等.各种不同的形态有可能指示了麻坑的不同发育阶段,新月形麻坑可能发育程度较低,其次是环形,圆形则相对较为成熟.据此推断发育程度较低的新月形麻坑有可能是活动麻坑,而地震海洋学的资料也倾向于证实这一点.     

南海三维热岩石圈结构及地表构造响应

为系统了解南海海底热流特征和岩石圈热结构与地表构造的关系,本文首先以最新海底热流为约束,采用三维数值模拟方法计算得到整个南海的"热"岩石圈底部边界（底界）的埋深,然后开展详细分析壳、幔热流贡献以及岩石圈热结构与地表不同构造单元之间的对应关系.结果显示南海岩石圈底部边界埋深为30~100 km,最浅埋深集中分布在南海海盆水深大于3000 m的区域（如南海西北次海盆、西南次海盆和东部次海盆西侧）,以及南海北部陆缘中部、莺歌海盆地、中建南盆地和南薇西盆地,体现了南海深部结构对地表不同构造单元的控制作用;靠近海盆东侧的马尼拉海沟具有较低的海底热流,对应岩石圈底界埋藏也较深,可能与南海和古南海洋壳俯冲有关;吕宋岛弧（119°E-122°E和13°N-17°N）表现出较高的海底热流,同时具有较浅的热岩石圈底界埋深,可能与南海板块和菲律宾海板块双向俯冲有关.     

Pollen record of the last 280 ka from deep sea sediments of the northern South China Sea

Environmental history of the northern continental shelf of the South China Sea during the last 280 ka BP, e.g. Marine Isotope Stages 1–8 (MIS 1–8) was reconstructed based on pollen record from the top 225m of ODP 1144 Site. During the interglacial periods, pollen assemblages are predominated by pine similar to those of the present day indicating that the environment of the interglacial periods was more or less close to that of today. Nevertheless, those from glacial periods are characterized by a large amount of herbaceous pollen, e.g.Artemisia, Gramineae, Cyperaceae, etc. inferring that grassland covered the merged continental shelf when the sea level lowered and the continental shelf was exposed. The exposed areas of the shelf were insignificant before MIS 5, but enlarged since MIS 4 and reached its maximum during MIS 2 according to ratios of pollen percentages between pine and herbs. The history of different exposure of the shelf can be compared with transgression records of the coastal areas of China and might result from neotectonic movement of Chinese continent. Some changes also took place in the components of grassland growing on the shelf during glaciations. Gramineae is the main element at MIS 8. ThenArtemisia increased upwards the profile and at last became the main component at the Last Glacial Maximum (MIS 2). Such changes in vegetation might be in response to cooler and drier climate.     

Stable isotopic records of the glacial deep-water properties in the South China Sea

Based on the oxygen and carbon stable isotopic records of benthic foraminifera in nine deep-sea cores of the South China Sea (SCS), the bathymetric profiles of δ¹⁸O and δ¹³C since the last glacial maximum (LGM) are preliminarily established. The bathymetric gradients of deep-water δ¹⁸O and δ¹³C in the SCS are obviously greater during the LGM than during the Holocene, showing the existence of the deep thermocline and nutricline at water depth of about 2 000 m. Particularly, the differences in δ¹⁸O and δ¹³C between the LGM and Holocene, from which the ice-volume effect and the global mean shift have been subtracted respectively, are positive values at water depths of 1 000–2 500 m in the SCS. This indicates the existence of deep-water mass with relatively cool temperature or higher salinity, better ventilation and more δ¹³C within the water depth range of the SCS during the LGM, which is distinctly different from that at present. These changes further confirm the existence of the glacial “North Pacific Deep Water” which, however, is possibly confined to the water depth range of 1 000–2 500 m. Project supported by the National Natural Science Foundation of China (Grant Nos. 49576286 and 49732060).     

南黄海南部与东海北部之间的深部构造

针对南黄海南部与东海之间的深部构造，根据前一段地球物理研究的结果，与有关文献进行对比探讨，发现其差异．在重力和三维地震层析成像结果基础上，探讨分析了该海域的深部构造，给出分布在南黄海南部与东海北部之间的苏浙-济州岛构造带的分布位置、形态特征，并讨论了该构造带的性质、与周边构造体系和构造演化的关系．并指出这一构造由于朝鲜半岛西缘断裂带的存在而并未延伸进入朝鲜半岛．     

Planktonic foraminifera and sea surface temperature (SST) of the Xisha Trough, South China Sea since Last Glaciation

South China Sea is the largest marginal sea of the Western Pacific between the Pacific Ocean and Asia Continent. It has been influenced by both the Pacific Ocean and continental climate. Its continental margins are broad in north and south, narrow in west. There are many islands in east. A large amount of siliciclastic sediments derived from peri-continents and islands were trans-ported into the sea[1], in which significant information of paleoceanography and paleoclimate and paleoenvironm…     

南海夏季风爆发与南大洋海温变化之间的联系

利用1979-2009年NCEP第二套大气再分析资料和ERSST海温资料,分析南海夏季风爆发时间的年际和年代际变化特征,考察南海夏季风爆发早晚与南大洋海温之间的联系.主要结果为:(1)南海夏季风爆发时间年际和年代际变化明显,1979-1993年与1994-2009年前后两个阶段爆发时间存在阶段性突变;(2)南海夏季风爆发时间与前期冬季(12-1月)印度洋-南大洋(0-80°E,75°S-50°S)海温、春季(2-3月)太平洋-南大洋(170°E -80°W,75°S-50°S)海温都存在正相关关系,当前期冬、春季南大洋海温偏低(高)时,南海夏季风爆发偏早(晚).南大洋海温信号,无论是年际还是年代际变化,都对南海夏季风爆发具有一定的预测指示作用;(3)南大洋海温异常通过海气相互作用和大气遥相关影响南海夏季风爆发的迟早.当南大洋海温异常偏低(偏高)时,冬季南极涛动偏强(偏弱),同时通过遥相关作用使热带印度洋-西太平洋地区位势高度偏低(偏高)、纬向风加强(减弱),热带大气这种环流异常一直维持到春季4、5月份,位势高度和纬向风异常范围逐步向北扩展并伴随索马里越赤道气流的加强(减弱),从而为南海夏季风爆发偏早(偏晚)提供有利的环流条件.初步分析认为,热带大气环流对南大洋海气相互作用的遥响应与半球际大气质量重新分布引起的南北涛动有关.     

Stepwise paleoceanographic changes during the last deglaciation in the southern South China Sea Records of stable isotope and microfossils

Quantitative analyses of microfossils and stable isotopic analysis were carried out for Core SCS-12 in the southwestern slope of the South China Sea (SCS). A high-resolution paleoceanographic record for the last 13 ka was revealed with the AMS¹⁴C dates. The southern SCS has experienced stepwise paleoceanographic changes since the last deglaciation. The oxygen isotopic stage 1/2 boundary around 12.05 ka B. P. and the end of the last deglaciation around 7.70 ka B.P. are two rapid change periods (corresponding to the terminationIa and terminationIb, respectively), in between is a slow change period. The authors infer that the sea level stood at - 110 m before the terminationIa, roughly the same as today after the termination I_B, and about - 50 m in between. Subsequently, the average winter sea surface temperature and salinity obviously increased while paleo-productivity decreased since 12.05 ka B.P. The early Holocene CaCO₃ preservation spike, coupled with a high abundance of pteropoda and CaCO₃ content, occurred around 7.70 ka B. P. Project supported by the National Natural Science Foundation of China (Grant Nos. 49576286 and 49732086).     

Latitudinal distribution of iodine in sediments in the Chukchi Sea and the Bering Sea

Iodine is a trace element playing an important role in vital activities of organisms. It is im-portant for human bodys thyroid gland. Deficient or excessive iodine will not only influence hu-man health but also cause feeblemindedness, so great attention h…