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海洋地球化学若干领域的研究进展 总被引：1，自引：0，他引：1
海洋地球化学是20世纪中期形成的一门新兴边缘科学，是在海洋科学飞速发展和取得了一系列重大成果的基础上产生的。从海洋同位素地球化学的发展、海洋元素的循环与示踪技术的研究、短周期气候变化与突变事件的发现以及海底矿产资源的大面积勘测等方面论述了海洋地球化学若干领域的研究进展。 相似文献
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氮(N)是生物生命活动的基本营养元素，N循环是整个生物圈物质和能量循环的重要组成部分。近几十年来，环境和资源问题的日益突出促进了人们对海洋生态系统的研究及对海洋资源的开发和利用，海洋中的N循环亦受到了广泛关注。尤其是20世纪90年代以来，随着国际地圈与生物圈计划(IGBP)、全球海洋通量联合研究(JGOFS)、全球海洋生态系统动力学研究(GLOBEC)等重大国际合作计划的实施，海洋中的N循环研究取得了重大进展。
本文主要对海洋沉积物中的N循环过程进行了阐述，包括海洋沉积物中N的生物地球化学循环(海洋中N与生物生产过程的关系、早期成岩作用及N的去营养化、沉积物中N循环及其控制机制、颗粒N的形成及其功能、N与其他生源要素循环的关系)及沉积物中N循环的研究方法等，以期对进一步开展N循环的研究有所帮助。 相似文献
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工业革命以来,大气CO_2浓度呈现快速增加的趋势,随之而来的问题是海洋酸化的程度越来越明显。与工业革命前相比,目前海洋表层海水pH降低了0.1个单位,到本世纪末估计会降低0.4个pH单位。本文综述了海洋酸化对碳、氮和硫循环的影响,包括碳循环中的溶解度泵、碳酸盐泵、软组织泵和微型生物碳泵,海洋酸化对氮循环中氮的固定、硝化作用、反硝化作用、N_2O的产生的影响,海洋酸化与硫循环中二甲基硫(DMS)的产生及其与食物网结构之间的关系。海洋酸化无论是以直接或间接方式均会在一定程度上对碳、氮和硫的生物地球化学循环产生影响,最终改变海洋系统的结构与功能。在自然界中,海洋酸化不是一个独立的过程,而是与其他物理、化学、生物变化因素相偶联共同作用于碳、氮和硫的生物地球化学循环。 相似文献
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大陆架边缘陆地与海洋之间过渡带是地球上最重要的界线之一，海洋地球化学家们经常把大陆架边缘作为一个“生物地球化学反应器”。Turchyn与Schrag的研究显示，在大陆架边缘存在化学物质循环的新的重要的信息。 相似文献
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海洋沉积物作为生源要素氮的重要源与汇，在其生物地球化学循环中起着至关重要的作用。该项研究旨在查清海洋沉积物中氮的存在形态及其生态学意义。氮是生物生命活动必需的营养要素，海洋中的氮往往是海洋初级生产力的限制因子，氮的吸收与再生释放在估算海洋新生产力和生源要素的生物地球化学循环率上也有重要贡献。海洋沉积物中的氮作为海水中氮的重要供给源是海洋生物赖以生存的重要物质基础，对维持海洋生态平衡、修复失衡的海洋生态环境具有重要意义。但由于不同海区海洋沉积物的来源和环境不同，氮的形态和含量亦不相同，可被生物吸收和利用的数量就不相同，因此造成了不同海区生物种群和环境不同，进而影响生态环境。因此，研究海洋沉积物中氮的形态，了解各个形态与沉积物中生物种群及与环境的关系，确定其生物和化学活性，査清氮不同形态的生态学功能，对于深入探讨海洋生物资源可持续利用的方法和策略具有重要意义。本文主要阐述海洋沉积物中氮的存在形式与分布、氮的早期成岩和去营养化作用、硝化和反硝化作用以及氮与生物特定种群的关系等，探讨了影响海洋沉积物中的氮循环的主要因素，并分析了海洋沉积物中的氮与生态系的关系，以期对研究氮的海洋生物地球化学过程有所帮助。 相似文献
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海洋中DMSP的研究进展 总被引：6，自引：2，他引：6
DMSP(dimethylsulfoniopropionate，β-二甲基巯基丙酸内盐)作为DMS(dimethylsulfide,二甲基硫)的前体，是1种重要的生源硫化物。根据其在海洋生态系统和生物地球化学循环中所起着的重要作用，作者综述了国内外海洋科学工作者十几年来在EMSP研究方面的进展。 相似文献
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碳中和是应对气候变化的必由之路,海洋负排放是实现碳中和的重要途经。海洋作为地球最大碳库,研究发现越来越多的海洋和海岸带生物参与碳循环,并对海洋碳汇产生重要贡献。鱼类作为海洋生态系统中最重要组成部分之一,其在海洋碳循环中的作用还没有引起足够的重视。最新研究表明海洋鱼类在无机碳循环中发挥了重要作用,深化对鱼类参与碳循环过程的认识、量化其固碳潜力将有助于丰富海洋碳循环研究。本文首先系统梳理了鱼类参与碳循环的过程和机制等研究进展。鱼类通过产生碳酸盐粪便、水平和垂直迁移运输、生物扰动、生物碳和“尸体”碳以及食物网消耗与传输等方式参与海洋碳循环。鱼类参与碳循环的证据和参与海洋碳循环的重要性逐渐凸显。其次,本文提出目前鱼类参与碳循环研究存在的问题与挑战,包括渔业捕捞源汇之争、水产养殖业的机遇和挑战以及准确量化鱼源碳酸盐的困难,仍有待理论和方法学的深化研究和技术的革新去解决。最后本文提出鱼类参与碳循环的研究展望,及其在全球气候变化背景下的潜在机遇,同时结合当前渔业碳汇的发展进程以及行业需求,提出渔业减排固碳发展路径建议。本文旨在提升鱼类在海洋碳循环贡献和服务生态系统的潜力的认识,为海洋碳汇和渔业碳汇研究提供新的视角。 相似文献
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This study presents new geochemical and isotope data on igneous rocks of the Vetlovaya marginal sea paleobasin (part of the Late Mesozoic–Cenozoic margin of the northwestern Pacific). The results show that the rock complexes of this marginal sea basin comprise igneous rocks with geochemical compositions similar to those of normal oceanic tholeiites, enriched transitional tholeiites, and ocean island and back-arc basin basalts. Island-arc tholeiitic basalts are present only rarely. The specific geochemical signatures of these rocks are interpreted as being related to mantle heterogeneity and the geodynamic conditions in the basin. 相似文献
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Results from laboratory studies indicated that low molecular weight (LMW) carbonyl compounds, especially formaldehyde, acetaldehyde, acetone and glyoxal, can be formed in seawater by photochemical processes. Once formed, these compounds appear to be readily consumed by biota. These results suggest that concentrations of LMW carbonyl compounds should undergo diurnal variations in the illuminated layer of the sea. In support of this, diurnal fluctuations of LMW carbonyl concentrations were observed in humic-rich surface waters off the west coast of Florida over a three day sampling period using a shipboard HPLC system. Fluctuations in acetaldehyde were particularly strong and reproducible, with steady night-time concentrations of 2–3 nM and day-time concentrations reaching a maximum of 20–30 nM in the early afternoon. In contrast, diurnal fluctuations in formaldehyde were less distinct, ranging from 15 to 50 nM.The laboratory and field results are discussed in terms of biotic/abiotic sources and sinks of LMW carbonyl compounds in surface seawater. It is speculated that photooxidative cleavage of biologically refractory dissolved organic matter (DOM) in seawater to yield LMW organic fragments, such as carbonyl compounds, may be important in the breakdown and geochemical cycling of DOM in the ocean. 相似文献
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V. S. Savenko 《Oceanology》2012,52(2):191-193
The geochemical balance of carbon in the ocean is considered for the conditions of constant carbonate alkalinity. It is shown
that the intrabasin processes result in the annual transformation of 487 million t of organic carbon into calcium-magnesium
carbonates, which is accompanied by the extraction of 1628 million t of calcium from silicates. It is concluded that the hypothesis
of the reverse weathering based upon the notion of the inversion of the mineral formation processes in the ocean against the
overland weathering processes requires a substantial correction. 相似文献
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Einaudi Florence Pezard Philippe A. Cochemé Jean-Jacques Coulon Christian Laverne Christine Godard Marguerite 《Marine Geophysical Researches》2000,21(3-4):387-408
As opposed to ocean crustal drilling that often yields a discontinuous core, ophiolites provide a unique opportunity to study continuous sections of oceanic basalts. In order to provide high frequency constraints on the construction of the upper oceanic crust, a continuous 280 m thick volcanic transect was sampled in the Semail ophiolite in Oman. The analyzed section is located in the Sarami Massif, in the central part of the ophiolite, and exposed along Wadi Shaffan. A multidisciplinary study was carried out after sampling in the field. Core measurements including porosity, grain density, compressional velocity, magnetic susceptibility and electrical resistivity for over 100 samples from this transect have been made. Geochemical analyses including major, trace and Rare Earth Elements were also performed on 23 selected samples from this transect. The Wadi Shaffan transect appears as composed of two main petrological and geochemical members providing the main lithostratigraphic signal. The boundary between the two sequences is marked by the presence of a massive flow unit equating to the most primitive lava and across which significant changes in mineralogy and texture are observed. The physical properties equally record significant changes. In all, the section is characterized by chemical compositions coherent with that of V1-Geotime volcanism and appears as built through two main sequences of volcanic activity. The magnetic susceptibility profile correlated to geochemical variations present the most detailed evolution allowing to individualize a succession of at least 4 volcanic phases. These phases are interpreted as magmatic cycles characterized by differentiation processes, allowing one to place high frequency constraints on the volcanic behavior of fast spreading ridges. Some of the physical properties also reflect this series of differentiation trends, as noticed in the past from downhole measurements recorded in the context of deep ocean drilling into the crust. 相似文献
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The dual isotopes of deep nitrate as a constraint on the cycle and budget of oceanic fixed nitrogen 总被引：1，自引：0，他引：1
Daniel M. Sigman Peter J. DiFiore Mathis P. Hain Curtis Deutsch Yi Wang David M. Karl Angela N. Knapp Moritz F. Lehmann Silvio Pantoja 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(9):1419-1439
We compare the output of an 18-box geochemical model of the ocean with measurements to investigate the controls on both the mean values and variation of nitrate δ15N and δ18O in the ocean interior. The δ18O of nitrate is our focus because it has been explored less in previous work. Denitrification raises the δ15N and δ18O of mean ocean nitrate by equal amounts above their input values for N2 fixation (for δ15N) and nitrification (for δ18O), generating parallel gradients in the δ15N and δ18O of deep ocean nitrate. Partial nitrate assimilation in the photic zone also causes equivalent increases in the δ15N and δ18O of the residual nitrate that can be transported into the interior. However, the regeneration and nitrification of sinking N can be said to decouple the N and O isotopes of deep ocean nitrate, especially when the sinking N is produced in a low latitude region, where nitrate consumption is effectively complete. The δ15N of the regenerated nitrate is equivalent to that originally consumed, whereas the regeneration replaces nitrate previously elevated in δ18O due to denitrification or nitrate assimilation with nitrate having the δ18O of nitrification. This lowers the δ18O of mean ocean nitrate and weakens nitrate δ18O gradients in the interior relative to those in δ15N. This decoupling is characterized and quantified in the box model, and agreement with data shows its clear importance in the real ocean. At the same time, the model appears to generate overly strong gradients in both δ18O and δ15N within the ocean interior and a mean ocean nitrate δ18O that is higher than measured. This may be due to, in the model, too strong an impact of partial nitrate assimilation in the Southern Ocean on the δ15N and δ18O of preformed nitrate and/or too little cycling of intermediate-depth nitrate through the low latitude photic zone. 相似文献
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南黄海表层不同粒级沉积物中氮的地球化学特征 总被引：18，自引：1，他引：17
南黄海不同粒级沉积物中可转化氮[离子交换态氮(IEF-N)、弱酸可浸取态氮(WAEF-N)、强碱可浸取态氮(SAEF-N)、强氧化剂可浸取氮(SOEF-N)]的地球化学特征各不相同,其中SOEF-N是3种粒级沉积物中含量最高的形态,IEF-N是可转化无机氮中的主要存在形态,也是最易参与循环的形态.当同一粒级沉积物中的可转化不同形态氮都能参与循环时,它们对氮循环的相对贡献从大至小依次为SOEF-N>IEF-N>SAEF-N>WAEF-N.对于不同粒级的沉积物来说,细粒级沉积物中的可转化不同形态氮的绝对含量最高,粗粒级沉积物中不同形态氮的绝对含量最低;如果沉积物中3种粒级组分所占的份额相同,那么细粒级沉积物中可转化氮的量占总可转化氮的60%,是中粒级中的2倍,粗粒级沉积物中可转化氮的近7倍,即细粒级沉积物对氮循环的可能贡献最大.随着沉积物粒级的由粗到细,沉积物中可转化有机氮的相对含量逐渐增加,而无机氮的相对含量逐渐降低. 相似文献
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《Ocean Modelling》2004,6(3-4):285-334
We have developed a general 1-D multi-component ecosystem model that incorporates a skillful upper ocean mixed layer model based on second moment closure of turbulence. The model is intended for eventual incorporation into coupled 3-D physical–biogeochemical ocean models with potential applications to modeling and studying primary productivity and carbon cycling in the global oceans as well as to promote the use of chlorophyll concentrations, in concert with satellite-sensed ocean color, as a diagnostic tool to delineate circulation features in numerical circulation models. The model is nitrogen-based and the design is deliberately general enough and modular to enable many of the existing ecosystem model formulations to be simulated and hence model-to-model comparisons rendered feasible. In its more general form (GEM10), the model solves for nitrate, ammonium, dissolved nitrogen, bacteria and two size categories of phytoplankton, zooplankton and detritus, in addition to solving for dissolved inorganic carbon and total alkalinity to enable estimation of the carbon dioxide flux at the air–sea interface. Dissolved oxygen is another prognostic variable enabling air–sea exchange of oxygen to be calculated. For potential applications to HNLC regions where productivity is constrained by the availability of a trace constituent such as iron, the model carries the trace constituent as an additional prognostic variable. Here we present 1-D model simulations for the Black Sea, Station PAPA and the BATS site. The Black Sea simulations assimilate seasonal monthly SST, SSS and surface chlorophyll, and the seasonal modulations compare favorably with earlier work. Station PAPA simulations for 1975–1977 with GEM5 assimilating observed SST and a plausible seasonal modulation of surface chlorophyll concentration also compare favorably with earlier work and with the limited observations on nitrate and pCO2 available. Finally, GEM5 simulations at BATS for 1985–1997 are consistent with the available time series. The simulations suggest that while it is generally desirable to employ a comprehensive ecosystem model with a large number of components when accurate depiction of the entire ecosystem is desirable, as is the prevailing practice, a simpler formulation such as GEM5 (N2PZD model) combined with assimilation of remotely sensed SST and chlorophyll concentrations may suffice for incorporation into 3-D prediction models of primary productivity, upper ocean optical clarity and carbon cycling. 相似文献
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The first objective of this introductory paper is to summarize our present understanding of the quantities of total organic carbon produced in the ocean by photosynthesis and non-biotic photochemical reactions, and the amount entering the ocean from rivers, the atmosphere, and the sediments. In this overview it will become apparent that our knowledge of the primary mechanisms and processes involved with the input of organic matter to the ocean via rivers, the atmosphere, sediments, and in situ photochemical reactions is fragmentary and often completely lacking. This becomes critical when we attempt to estimate the input of certain naturally occurring organic compounds and some synthetic organic compounds, since their primary input to the sea is generally via the atmosphere, rivers, and dumping. Thus the second objective of this paper is to emphasize our need to understand the mechanisms involved in these other input processes and the necessity of developing field programs and mathematical models to evaluate the input of specific organic compounds via these pathways. Polychlorinated biphenyls are used as examples of how necessary it is to understand these other input routes in order to evaluate the cycling of pollutant substances in the ocean. 相似文献