南海颗粒物质的通量、组成及其与沉积物积累率的关系初探

通过大孔径时间系列沉积物捕获器的多年测量及对样品的多学科综合分析表明:南海北部与中部深海区1000m左右水深颗粒通量大约为90mg·m-2·d-1,在多数情况下,季风期间的颗粒通量有比较明显的增高。颗粒物主要组成为钙质生物来源的CaCO₃、生物硅、岩源物质及海洋生物来源的有机质。颗粒通量与组成在水柱中的垂向变化表明,生源组分中CaCO₃及有机质随深度具有较为明显的减少。颗粒物侧向运动可能是造成某些时段南海中部深层颗粒通量增加的主要原因。颗粒物质在进入深海沉积物之前,CaCO₃、生物硅均在深层水与沉积物界面之间发生大量的溶解作用。有机质在沉降过程中的减少,一方面是由于硅质与钙质壳体的溶解而使结合在壳体内部的有机质随之溶解造成;另一方面可能与生物及生物地球化学作用有关。岩源物质除水柱沉降之外,还可以通过浊流等底层搬运机制进入南海北部及中部海盆,其中在南海北部这种搬运作用更为明显。     

南海北部深水区沉积物稀土元素特征及其物源指示意义

对南海北部白云深水区沉积物稀土元素的研究表明,渐新世至中新世的物源发生较大变化。渐新世时期,白云深水区不同区域稀土元素的分布特征差异明显,表明沉积物物源不同。深水区北部沉积物主要来自古珠江物源区,深水区东、西部沉积物中含有较多中基性火山物质,南部则主要包含基性火山物质,说明当时南海北部地区构造活动较强,存在较多火山活动,火山活动由北向南基性成分增多。渐新世末的白云运动使南海北部深水区产生强烈持续沉降,造成陆架坡折带北移,白云深水区从渐新世浅海陆架环境演化为中新世陆坡深水环境,中新世期间沉积物主要来自深水区北部的珠江三角洲物源,深水区东部存在东沙隆起源区,而深水区南部沉积物在中新世仍受到基性火山活动的影响。     

南海北部深水区新生代盆地三层结构及其构造演化

位于陆壳与洋壳之上的大陆边缘记录了大陆裂解-大洋打开的全部过程,是研究地球动力学的重要场所.南海北部深水区盆地位于南海北部大陆边缘,新生代盆地表现为裂陷期盆地、裂后拗陷期盆地及裂后洋盆沉降期盆地3层结构.裂陷期盆地表现为一系列地堑及半地堑结构,拗陷盆地表现为中间厚两侧薄的“碟形”盆地特征,裂后拗陷期盆地表现为大陆坡局部加厚,向南海洋盆方向厚度逐渐减薄的“挠曲”盆地形态.南海北部深水区盆地经历了3期构造演化过程,盆地表现出不同的动力学机制.裂陷期盆地受地幔物质上涌影响表现为水平伸展作用为主,盆地内普遍发育伸展构造样式,裂后拗陷期盆地表现为区域均匀沉降特征.而裂后洋盆沉积期受南海强烈沉降作用的影响表现出明显的向南海洋盆倾斜特征.大陆架-陆坡-深海平原的构造格局主要形成于裂后洋盆沉降期.南海及其北部盆地下伏地幔物质活动的差异性决定了盆地内的3层结构的形成演化过程.     

南海北部1987～1988年颗粒物质和硅藻通量的季节性变化:季风气候与 El Nino的响应

南海北部1987年9月～1988年10月沉积物捕获器中颗粒物质和硅藻通量的季节性变化受到季风气候的控制.颗粒物质与硅藻在东北和西南季风盛行期增加,在季风转变期减少.浅层和深层的颗粒总通量、蛋白石通量、碳酸钙通量、蛋白石/颗粒总通量比值、碳酸钙/颗粒总通量比值、有机碳/磷的比值以及浅层硅藻Thalassionema nitzschioides、Coscinodiscus excentricus、Coscinodiscus nodulifer、Nitzschia marina和Rhizosolenia bergonii的通量在东北季风期间明显地增加了,这些变化可能与1987年～1988年发生的EINino事件相关.     

长江口-杭州湾及其邻近海域不同粒级沉积有机碳分布特征

通过对长江口、杭州湾、舟山海域及东海陆架4个海区表层沉积物样品的粒度敏感组分分析,发现东海陆架与长江口具有相似的三级组分物质组成,杭州湾与舟山海域具有相似的两级组分物质组成.综合4个区域粒级组分分布特征,采用湿分法将4个海域表层沉积物样品分成6个粒级:＜0.004 mm,0.004～0.025 mm,0.025～0.063 mm,0.063～0.125 mm,0.125～0.250 mm和＞0.250 mm,分别提取各级组分和全样进行有机碳及同位素测试.定量分析各级组分有机碳含量、来源及物质组分,除杭州湾海域粗粒级外,基本上＜0.004 mm的粘土组分有机碳含量最高;富集在杭州湾海域粗颗粒中的有机质主要来源于陆源植物碎屑.沉积物颗粒大小、物质组成类型是不同粒级有机质富集的主要控制因素.     

深海钻探与南海

本文从南海北部陆缘，南部陆缘和南海中央海盆的地质构造与地球物理主要特下及尚未解决的重要地质问题来阐述在南海进行深海钻探的意义。南海北部陆缘是离散型大陆边缘，在陆壳与洋壳之间的磁静区是两者的过渡区。对它的研究直接关系到南海的形成演化与沉积盆地的成因，深海钻探需要解决的主要问题是了解磁静区基底下的物质是减薄的过渡壳还是古洋壳。地海南部南缘与北部陆缘不同，是聚敛型大陆边缘，它的构造与地球物理场特征与北部     

南海北部1987～1988年颗粒物质和硅藻通量的季节性变化:季风气候与El Nio的响应

南海北部１９８７年９月～１９８８年１０月沉积物捕获器中颗粒物质和硅藻通量的季节性 变化受到季风气候的控制。颗粒物质与硅藻在东北和西南季风盛行期增加，在季风转变期减 少。浅层和深层的颗粒总通量、蛋白石通量、碳酸钙通量、蛋白石／颗粒总通量比值、碳酸钙／颗 粒总通量比值、有机碳／磷的比值以及浅层硅藻Ｔｈａｌａｓｓｉｏｎｅｍａ ｎｉｔｚｓｃｈｉｏｉｄｅｓ、Ｃｏｓｃｉｎｏｄｉｓｃｕｓ ｅｘｃｅｎｔｒｉｃｕｓ、Ｃｏｓｃｉｎｏｄｉｓｃｕｓ ｎｏｄｕｌｉｆｅｒ、Ｎｉｔｚｓｃｈｉａ ｍａｒｉｎａ和Ｒｈｉｚｏｓｏｌｅｎｉａ ｂｅｒｇｏｎｉｉ的通量在东北 季风期间明显地增加了，这些变化可能与１９８７年～１９８８年发生的ＥＩ Ｍｉ　ｏ事件相关。     

南海表层沉积物与沉降颗粒物中有机碳的δ~(13)C对比研究及其古环境再造意义

对南海表层沉积物与沉降颗粒物有机碳的δ13C进行了对比研究,从古环境再造方面探讨了陆源和海源对南海表层沉积物的贡献。南海表层沉积物有机碳的δ13C比沉降颗粒物中有机碳的δ13C偏重表明,Suess效应对南海现代过程的影响不可忽视,两者的δ13C差值反映了Suess效应对南海现代过程的影响程度。利用两者的δ13C差值,对现代陆源和海源有机碳的δ13C进行修正后,计算得到,在南海陆架周围表层沉积物的有机碳中,陆源的比例为48%,海源的比例为52%;在远离陆架的表层沉积物的有机碳中,陆源的比例为14%,海源的比例为86%。     

南海表层沉积物中细粒组分的稀土元素地球化学特征

对南海表层沉积物中的细粒组分进行电感耦合等离子体质谱法测试, 探讨南海稀土元素分布特征及其影响因素.结果表明, 南海表层沉积物中稀土元素分布主要与陆源物质输入、生物活动和火山物质补给密切相关.南海细粒组分的配分模式与中国黄土的接近, 与周边的珠江、湄公河等河流输入物质也有相似性, 而与南海碱性玄武岩存在显著差异, 表明南海沉积物主要来自于周边大陆.稀土元素趋势分析表明, 珠江口往外至海南岛南部海域中沉积物朝东南方向向陆坡输送; 台西南至珠江口往外海域沉积物大多向南输运; 吕宋岛西部海域包括黄岩岛附近海域的火山物质主要向西北方向输送, 向西可达113°E、向北可至20°N附近; 南海南部沉积物整体上向南沙海槽西北部附近海域输送.      

南海表层沉积物与沉降颗粒物中有机碳的δ13C对比研究及其古环境再造意义

对南海表层沉积物与沉降颗粒物有机碳的δ13C进行了对比研究,从古环境再造方面探讨了陆源和海源对南海表层沉积物的贡献。南海表层沉积物有机碳的δ13C比沉降颗粒物中有机碳的δ13C偏重表明,Suess效应对南海现代过程的影响不可忽视,两者的δ13C差值反映了Suess效应对南海现代过程的影响程度。利用两者的δ13C差值,对现代陆源和海源有机碳的δ13C进行修正后,计算得到,在南海陆架周围表层沉积物的有机碳中,陆源的比例为48%,海源的比例为52%;在远离陆架的表层沉积物的有机碳中,陆源的比例为14%,海源的比例为86%。     

Organic geochemical characteristics of time-series settling particles in northern South China Sea and their implications

Organic carbon, total nitrogen, amino acids, sugars, and chlorophyll were determined in < 1 mm fractions of the samples collected by successive large aperture time-series sediment traps (Honjo-Mark M) in northern South China Sea during September 1987 to October 1988. The ratio of C/N and the relative abundance of amino acids and sugars show that organic matter in the settling particles from northern South China Sea is derived mainly from marine plantkon (especially phytoplankton). The organic carbon fluxes in our sediment traps are lower than those in other sediment traps. But the relative contents of C_org/total particulate matter are generally similar to those in the Panama Basin, Arabian Sea and Subarctic Pacific. It is suggested that monsoon-caused changes of physical and chemical conditions in the upper euphotic layer would control the fluxes of organic matter as well as its composition and transport in northern South China Sea. This project was financially supported by both Sino-German Scientific Cooperation Program and National Natural Science Foundation of China (No. 49070269, 49776297).     

Amino acid composition of suspended particles,sediment-trap material,and benthic sediment in the Potomac Estuary

Sediment trap deployments in estuaries provide a method for estimating the amount of organic material transported to the sediments from the euphotic zone. The amino acid composition of suspended particles, benthic sediment, and sediment-trap material collected at 2.4 m, 5.8 m, and 7.9 m depths in the Potomac Estuary was determined in stratified summer waters, and in well-mixed oxygenated waters (DO) in late fall. The total vertical flow, or flux, of material into the top traps ranged from 3 g m^?2 d^?1 in August to 4.9 g m^?2 d^?1 in October. The carbon and nitrogen fluxes increased in the deepest traps relative to the surface traps during both sampling periods, along with that of the total material flux (up to 47.3 g m^?2 d^?1 in the deepest trap), although the actual weight percent of organic carbon and organic nitrogen decreased with depth. Amino acid concentrations ranged from 129 mg g^?1 in surface water particulate material to 22 mg g^?1 in particulate material in 9-m-deep waters and in the benthic sediment. Amino acid concentrations from 2.4-mg-depth sediment traps averaged 104±29 mg g^?1 in stratified waters and 164±81 mg g^?1 in well-mixed waters. The deep trap samples averaed, 77.3±4.8 mg g^?1 amino acids in summer waters and 37±16 mg g^?1 in oxygenated fall waters. Amino acids comprised 13% to 39% of the organic carbon and 12% to 89% of the orgnaic nitrogen in these samples. Analysis of the flux results suggest that resuspension combined with lateral advection from adjacent slopes can account for up to 27% of the material in the deep traps when the estuary was well-mixed and unstratified. When the estuary was stratified in late summer, the amino acid carbon produced by primary productivity in the euphotic zone decreased by 85% (86% for total organic carbon) at the pycnocline at 6 m depth, leaving up to 15% of the vertical organic flux available for benthic sediment deposition.     

Fluxes of material in the Arabian Sea and Bay of Bengal — Sediment trap studies

In order to investigate how monsoons influence biogeochemical fluxes in the ocean, twelve time-series sediment traps were deployed at six locations in the northern Indian Ocean. In this paper we present particle flux data collected during May 1986 to November 1991 and November 1987 to November 1992 in the Arabian Sea and Bay of Bengal respectively. Particle fluxes were high during both the SW and NE monsoons in the Arabian Sea as well as in the Bay of Bengal. The mechanisms of particle production and transport, however, differ in both the regions. In the Arabian Sea, average annual fluxes are over 50gm^-2y^-1 in the western Arabian Sea and less than 27gm^-2 y^-1 in the central part. Biogenic matter is dominant at sites located near upwelling centers, and is less degraded during peak flux periods. High particle fluxes in the offshore areas of the Arabian Sea are caused by injection of nutrients into the euphotic zone due to wind-induced mixed layer deepening. In the Bay of Bengal, average annual fluxes are highest in the central Bay of Bengal (over 50gm^-2y^-1) and are least in the southern part of the Bay (37gm^-2y^-1). Particle flux patterns coincide with freshwater discharge patterns of the Ganges-Brahmaputra river system. Opal/carbonate and organic carbon/carbonate carbon ratios increase during the SW monsoon due to variations in salinity and productivity patterns in the surface waters as a result of increased freshwater and nutrient input from rivers. Comparison of S years data show that fluxes of biogenic and lithogenic particulate matter are higher in the Bay of Bengal even though the Arabian Sea is considered to be more productive. Our results indicate that in the northern Indian Ocean interannual variability in organic carbon flux is directly related to the strength and intensity of the SW monsoon while its transfer from the upper layers to the deep sea is partly controlled by input of lithogenic matter from adjacent continents.     

Amino acid biogeo- and stereochemistry in coastal Chilean sediments

The spatial distribution of total hydrolysable amino acids (THAA) and amino acid enantiomers (d- and l-forms) was investigated in sediments underlying two contrasting Chilean upwelling regions: at ∼23 °S off Antofagasta and at ∼36 °S off Concepción. The contribution of amino acids to total organic carbon (%T_AAC: 7-14%) and total nitrogen (%T_AAN: 23-38%) in surface sediments decreased with increasing water depth (from 126 to 1350 m) indicating that organic matter becomes increasingly decomposed in surface sediments at greater water depth. Changes in the ratio between the protein amino acid aspartate and its non-protein degradation product β-alanine confirmed this observation. Furthermore, estimates of THAA mineralization showed that sedimentary amino acid reactivity decreased with both increasing water depth as well as progressive degradation status of the organic matter that was incorporated into the sediment. Reactivity of organic matter in the sediment was also assessed using the Degradation Index (DI) developed by [Dauwe, B., Middelburg, J.J., 1998. Amino acids and hexosamines as indicators of organic matter degradation state in North Sea sediments. Limnol. Oceanogr.43, pp. 782-798.]. Off Concepción, DI was successfully applied to examine the degradation status of sedimentary organic matter at different water depths. However, unexpected results were obtained at the Antofagasta stations as DI increased with sediment depth, suggesting more degraded organic matter at the surface than deeper in the cores. The contribution of peptidoglycan amino acids to THAA was estimated from the concentrations of d-aspartate, d-glutamic acid, d-serine, and d-alanine. Peptidoglycan amino acids accounted for >18% of THAA in all investigated samples. In surface sediments peptidoglycan amino acids accounted for a progressively larger fraction of THAA at increasing water depths (up to >26%). Further, the contribution of peptidoglycan amino acids to THAA increased with increased sediment depth and age (up to 288-year-old) reaching up to 59%. Independent estimates based on d-amino acid concentrations in selected laboratory strains, bacterial counts and the sedimentary concentrations of d-amino acids indicate that a large fraction of the measured d-amino acids (>47 to >97%) originated from cell wall residues rather than from enumerated cells.     

Advances in Seasonal Variations and Controls of the Air-sea CO2 Flux in the South China Sea

Marine carbon cycle of the South China Sea is an important part of global carbon cycle. Researches on the air-sea CO₂ flux in the South China Sea will help us understand the global carbon cycle and improve the global carbon system parameter database. This paper concisely summarized the changes of partial pressure of CO₂ (pCO₂), air-sea CO₂ fluxes (FCO₂), and related environmental factors in four regions in domains in the South China Sea. The low-salinity area of the upper reaches of the Pearl River estuary in the northern of South China Sea shelf area acted as a strong source of atmospheric CO₂, with high pCO₂（405.3~810.6 Pa）all year round. The lower area of the Pearl River estuary (salinity > 33.7) acted as a weak sink of CO₂ in winter, with relatively low pCO₂ （35.2~37.0 Pa). The northern slope/basin in the South China Sea acted as a source of CO₂ in warm seasons with a relatively high pCO₂ (45.0 Pa), and acted as a sink of CO₂ in cold seasons with a relatively low pCO₂ (34.7 Pa). The west of the Luzon Strait acted as a sink of CO₂ in spring, while it acted as a source of CO₂ in other seasons, with relative high pCO₂ (38.4~47.5 Pa) in winter. The central/southern basin in the South China Sea acted as sources of CO₂, with relative high pCO₂ (41.0 Pa) all the year. Generally, the estimation of annual sea-air CO₂ fluxes showed that most domains in the South China Sea served as weak sources of atmospheric CO₂. In the future, more researches should be focused on the time-series of sea surface pCO₂ and the remote sensing of the sea-air CO₂ fluxes.     

楚科奇海-加拿大海盆表层沉积物中的氨基酸

对2003年中国第二次北极科学考察所获得的部分表层沉积物样品进行了总水解氨基酸(THAA)、氨基糖(HA)的测定。不同区域氨基酸主要成分不同,楚科奇海站位的氨基酸主要成分为甘氨酸(Gly)、谷氨酸(Glu),位于加拿大海盆的B80、B11、P27站THAA的主要成分为丝氨酸(Ser)。沉积物的总有机碳(TOC)、总氮(TN)、THAA、HA含量等特征随区域不同有较大差别,白令海峡的BS11站TOC、HA含量最低,加拿大海盆的B80站THAA、TN含量最低。楚科奇海R03站TOC、TN为最高,THAA在R11含量达最大值,HA在楚科奇海台的P11站最高。初步讨论了楚科奇海—加拿大海盆表层沉积物中氨基酸的空间分布,根据氨基酸选择性降解和主成份分析结果引入DI”指标,并对七个站位表层沉积物有机质新鲜程度进行了比较,新鲜度由大至小顺序为C15>BS11>R11>S11>P11>R03>B80,这与表层沉积物来源、水动力条件等有关,由此推测楚科奇海陆架、白令海峡沉积物有机质较楚科奇海台、加拿大海盆较为新鲜。