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1.
大河影响下的边缘海沉积有机碳输运与埋藏及再矿化研究进展 总被引：4，自引：0，他引：4
大河影响下的边缘海是陆源输入物质的主要储库,也是有机碳埋藏和再矿化的主要场所,在全球碳的生物地球化学循环中有着重要作用。从有机碳的输运、埋藏和再矿化等方面综述了大河影响下的边缘海沉积有机碳生物地球化学研究的最新进展。研究表明,有机碳的来源、组成、粒径和密度分布等显著影响着有机碳的分布特征和归宿,大河影响下的边缘海中移动泥等特殊沉积环境在有机碳的输运、埋藏和再矿化分解等方面发挥了独特的作用;微生物分解作用则是边缘海沉积有机碳,特别是难降解陆源有机碳发生分解的重要因素。综合运用分子生物学、有机地球化学、生物地球化学等多学科研究手段,深入研究特定微生物、浮游生物功能类群等在大河影响下的边缘海沉积有机碳生物地球化学过程中的作用,将极大地丰富对河口和陆架边缘海生源要素生物地球化学循环的认识。 相似文献
2.
大河影响下的河口陆架区陆海相互作用活跃,是有机碳的主要沉积区,在全球碳的生物地球化学循环中发挥着重要作用。中国东部陆架海包括渤海、黄海和东海陆架,黄河和长江两条大河直接流入该区。从有机碳来源、输运和埋藏保存等方面总结介绍了近年来中国东部陆架海沉积有机碳源汇过程的研究进展。研究表明,土壤有机碳和海洋初级生产力是本区沉积有机碳的主要来源;有机分子标志物和多元统计分析模型的综合应用能更准确地评估近海沉积有机碳的源汇特征;陆架泥质区是长江和黄河陆源沉积有机碳的重要储库;河流输入、沉积再悬浮和远距离物质输运等沉积动力过程显著影响着本区不同来源、不同类型陆源沉积有机碳的输运和归宿;大河物质输入、海洋初级生产力以及陆架沉积作用共同支撑着该区较高的有机碳埋藏能力。本区的研究今后需要从海陆结合的地球系统科学的角度,从整体上研究沉积作用过程与有机碳迁移转化的影响机制和响应关系;结合我国东部陆架海特有的沉积物源汇体系特征,揭示从流域到近海物质输运体系中不同来源有机碳的年龄分布和归宿,并在气候变化和人类活动影响日益显著的背景下,探究不同时空尺度沉积有机碳的输运和埋藏保存及其对大气CO2和全球变化的影响和意义。 相似文献
3.
末次盛冰期以来冲绳海槽中部沉积物有机碳和磷的地球化学研究 总被引：1，自引：0，他引：1
利用元素及同位素地球化学方法研究了冲绳海槽中部沉积物岩芯中有机碳及磷的地球化学特征及影响因素。结果表明,冲绳海槽沉积速率（16.5~32.5 cm/ka）变化小,不是沉积物中有机碳埋藏的重要影响因素。相对于全新世氧化性底水环境,末次盛冰期/冰消期冲绳海槽缺氧底水环境提高了沉积物对有机碳的埋藏效率。冲绳海槽沉积物中各形态磷的相对含量与其他边缘海沉积物中的相似。交换态磷（Ex-P）含量低、变化小。末次盛冰期/冰消期缺氧底水环境下铁氧化物的还原溶解导致铁结合磷（Fe-P）释放以及自生磷矿物（Au-P）的形成。全新世氧化性底水条件有利于铁氧化物的有效再生及对磷的再吸附,但不利于Au-P的保存。总有机碳（TOC）和有机磷（Org-P）之间良好的相关性表明TOC埋藏对Org-P含量的重要控制作用。冲绳海槽沉积物中碎屑磷（De-P）含量低于长江口及东海陆架沉积物中的含量,这与陆源碎屑向外海传输减弱有关。在约9.3 ka BP（岩芯200 cm深度）,TOC、Fe-P、Org-P、De-P以及FeHR均出现的极小值可能由物质坡移造成。 相似文献
4.
研究表明,海洋沉积物中有超过20%的有机碳是通过与铁结合而被稳定地保存下来,阐明铁对有机碳的保护作用能深入理解碳封存机制。本文1)从与铁结合的有机碳的含量、碳同位素和二者的结合机制等方面梳理了铁在促进有机碳埋藏中所发挥的作用;2)阐述海洋环境(包括水动力和氧化还原条件)和有机碳来源等因素可能控制着铁与有机碳之间的相互耦合,并影响着与铁结合的有机碳的分布、组成和年龄特征;3)分析铁与有机碳之间吸附和共沉淀的结合机制,讨论了影响二者结合方式的因素;4)探讨铁循环与碳循环之间的密切生物地球化学联系在海洋碳封存中的作用。综合梳理了沉积物中“生锈的碳汇”(rusty sink)的研究进展,对当前应对碳中和-全球气候变化具有重要意义。 相似文献
5.
作为长期碳汇,海洋沉积物中埋藏的大量有机碳对全球碳循环和气候变化有重要影响。有机碳从海洋输出到沉积物中后,在沉积物中还要经历有氧降解和无氧降解。有机物降解是一个十分复杂的过程,影响这一过程的因素有很多,包括有机物本身的分子结构和组成种类;氧化还原状态;有机物所附着的基质;温度、压力、盐度等物理环境因素以及生物因素。研究沉积有机碳的含量及埋藏量变化首先需要校正降解对沉积有机碳含量的影响。降解模式是定量估算降解对沉积有机碳的影响的一个主要手段。在前人的研究基础上,讨论了影响沉积有机碳降解的因素,对降解模式的研究进展和应用进行了综述,提出了未来降解模式的发展中存在的问题。 相似文献
6.
《中国海洋大学学报(自然科学版)》2017,(9)
中国边缘海(本文特指渤海、黄海和东海,不包括南海)是陆源和海源有机质的重要碳汇。总有机质指标和生物标志物的结果显示,表层沉积物中陆源有机质高值集中在近岸尤其是河口附近;海源有机质在陆架海盆处有高值,受控于海洋生产力和沉积环境。利用多参数指标对表层沉积物中不同来源和不同年龄有机质的贡献比例估算的结果显示,我国边缘海的有机碳埋藏量约13 Mt/a,占全球边缘海沉积物有机碳埋藏量(~138 Mt/a)的~10%,其中陆源有机质的碳埋藏量(3.9 Mt/a)占全球边缘海沉积物陆源有机质埋藏量的~7%。若假定陈化土壤有机质和古老有机质主要是陆源物质,则非现代有机质的碳埋藏量为~6Mt/a,占我国边缘海总有机质碳埋藏量的~46%,与全球边缘海沉积物中陆源有机质的平均比例(44%)相当。这些结果表明我国边缘海在全球海洋碳循环中具有重要地位。本文利用已发表的文献数据,总结和归纳了中国边缘海沉积有机质来源及其碳汇意义。 相似文献
7.
桑沟湾和胶州湾沉积物耗氧率研究 总被引：2，自引：0，他引：2
为评价浅海海域底层在碳元素生物地化循环中的作用,采用现场取样培养法测定了黄海桑沟湾和胶州湾的沉积物耗氧率。桑沟湾5月和8月的沉积物耗氧率分别为15和24 mmol.m-2.d-1;胶州湾8月的沉积物耗氧率为18 mmol.m-2.d-1。回归分析表明,2个湾的沉积物耗氧率分别与沉积物表层的有机碳和总氮含量正相关。取呼吸商为0.8,得到桑沟湾底层对有机碳的矿化率占水层初级生产力的102%(5月)和67%(8月),胶州湾底层对有机碳的矿化率占水层初级生产力的28%(8月)。取桑沟湾颗粒有机碳的生物沉积速率为236 mg.m-2.d-1,得到底层对有机碳的埋置效率为40%(5月)和3%(8月),埋置的有机碳占水层初级生产力的69%(5月)和2%(8月);胶州湾颗粒有机碳的自然沉积速率为251 mg.m-2.d-1,底层对有机碳的埋置效率为32%(8月),埋置的有机碳占水层初级生产力的13%(8月)。 相似文献
8.
在早期成岩作用理想稳定状态的观点中,沉积物沉淀包含了多个仅能发生某些氧化还原反应的剧变的限定带。实际上由于孔隙水成分可能受到有机碳输入、底层水温度和化学成分变化及沉积速率变化的影响,带与带之间的界线多少有点模糊。这些变化能造成沉积物中氧化—缺氧边界位... 相似文献
9.
海洋碳汇作用是大洋生态系统的重要生态系统服务功能,不仅影响着海洋生态系统的能量流动,也是元素循环的重要驱动力。本文以中国大洋48航次采集自西北太平洋典型海山区海盆的沉积物样品和资料为基础,对西北太平洋山间盆地沉积物有机碳质量累积速率(Forgc)特征及影响因素展开初步研究。结果表明,西北太平洋山间盆地有机碳质量累积速率变化范围为1.41～1.73 g/(m2·ka),均值为1.60 g/(m2·ka),以中部偏西海区的有机碳质量累积速率最高;全区平均净初级生产力转移效率约为0.003 1%。西北太平洋山间盆地有机碳质量累积速率和净初级生产力转移效率均低于东太平洋海区和赤道太平洋海区。本区有机碳质量累积速率受水层和沉积层的生物地球化学循环驱动因素,如海洋净初级生产力、沉积物质量累积速率、有机碳含量、氧化还原电位等的综合影响,同时也受距海山距离、水深等地形因子的影响。 相似文献
10.
边缘海初级生产力普遍较高,有机碳在沉积物中的埋藏高达全球的80%。黄渤海是位于我国东部的一个半封闭的温带陆架边缘海,在近20年中,黄渤海经历的台风事件频率不断增大,对碳循环关键过程发生多重影响。文章利用多组卫星及再分析资料,围绕2003~2020年期间夏季台风过境对黄渤海关键环境变量的影响,分析生物和非生物过程对不同海域水体中颗粒有机碳的贡献。结果表明,夏季台风过境一次、两次对黄渤海叶绿素的影响没有明显差异,叶绿素浓度增加主要在渤海西南部和南黄海约50%的海域。总体上看,台风过境对渤海、北黄海大部分海域水体中颗粒有机碳影响不大,但两次台风过境引起了南黄海约80%的离岸海域颗粒有机碳浓度的显著增加。南黄海中部海域水体中颗粒有机碳与叶绿素的比值在台风过后明显降低,表明该海域颗粒有机碳浓度的提高主要是由生物固碳过程的增强引起。台风过境加剧了黄海与渤海、近岸与离岸的水流交换,此过程增强了高营养盐和有机物水向南黄海尤其是中部海域的输送,因而提高了南黄海大部分海域颗粒有机碳浓度。除了光合作用等生物过程及水流交换对颗粒有机碳有影响外,黄渤海水体中颗粒有机碳浓度还受到沉积物再悬浮、陆源有机碳输入等过程的影响。台风过境可以加剧沉积物再悬浮和陆源有机物的输入,进一步提高黄渤海近岸及离岸海域颗粒有机碳的浓度。 相似文献
11.
渤海表层沉积物中有机碳的分布和来源 总被引：3，自引：0，他引：3
大河影响下的陆架边缘海沉积有机碳的分布和来源是全球碳循环研究的重要内容。本研究于2012年5月采集了渤海海域的29个表层沉积物样品,分析了粒度组成、总有机碳(TOC)、总氮(TN)、木质素含量和稳定碳同位素丰度(δ13C)等参数,结合基于蒙特卡洛模拟的三端元混合模型,定量研究了沉积物中有机碳的分布和来源情况,并讨论了其影响因素。结果表明,研究区域表层沉积物中TOC含量为0.19%~0.81%,渤海中部泥质区站位(大于0.65%)明显高于其周围砂质区域站位(小于0.40%);TOC与黏土含量也有显著的正相关性,说明细颗粒沉积物容易富集有机碳。沉积有机碳的δ13C范围为-23.7‰~-21.8‰,显示沉积有机碳是海源和陆源有机碳的混合输入。木质素参数,如C/V、S/V和LPVI的数值范围显示研究区域表层沉积物中木质素主要来源于被子植物草本组织与木本组织的混合,同时有少量裸子植物的贡献。基于蒙特卡洛模拟的三端元混合模型显示研究区域沉积物中有机碳主要来源于海洋浮游植物,平均为64%,陆源有机碳中来自土壤的贡献最高(平均为27%),C3维管植物的贡献较少(平均为9%)。海洋浮游植物有机碳主要分布在渤海中部泥质区及离岸较远的区域,而土壤有机碳和C3维管植物有机碳则主要沉积在河口附近及近岸区,并可以离岸输运到较远的地方。 相似文献
12.
《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(8):1405-1428
Benthic fluxes of O2, titration alkalinity (TA), total inorganic carbon (TIC), Ca2+, NO3−, NH4+, PO43−, and Si(OH)4 were measured by in situ benthic flux chamber incubations at 13 locations on the North Carolina continental slope. The majority of measurements were made at water depths of approximately 700–850 m, in the previously identified upper slope depocenter. This region is characterized by extremely high organic matter deposition rates and near saturation bottom water oxygen concentrations. Measured benthic fluxes of TA are reasonably correlated with O2 benthic fluxes. Because bottom waters are supersaturated with respect to calcite and aragonite at these shallow water depths, these results demonstrate the importance of metabolically driven dissolution in this region. Subtraction of the calcium carbonate dissolution contributions from the TIC benthic fluxes suggests rates of organic matter remineralization ranging from 0.97 to 3.9 mol C m−2 yr−1 at the depocenter sites, a factor of 3–10 greater than estimated for the adjacent continental rise and upper slope areas. Because biological primary production in the overlying waters does not follow this pattern, these extremely high values are most likely supported by lateral inputs of highly reactive organic matter. Mass balance calculations indicate that despite the oxygenated bottom water conditions, 68% of the organic nitrogen released during organic matter remineralization processes is ultimately denitrified. The release of PO43− from the depocenter sediments is equivalent to or larger than that predicted from the remineralization of Redfield organic matter. This implies either that PO43− is preferentially released in this setting and that the accumulating sediments must be depleted in PO43− relative to organic carbon or that another, non-organic, phase is contributing PO43− to the system. The molar ratio of the Si benthic flux and organic carbon remineralization rate ranges from 0.30 to 0.86. This is significantly greater than the ratio reported for most pelagic diatoms. Possible reasons for this high ratio include the deposition of benthic diatoms that may have a larger Si : C ratio than pelagic diatoms, the near-bottom lateral input of partially reworked organic matter that may have an elevated Si : C ratio relative to fresh diatoms, preferential loss of carbon in sinking particulates or the release of Si from non-opaline materials. 相似文献
13.
To examine the source and preservation of organic matter in the shelf sediments of the East China Sea (ECS), we measured bulk
C/N and isotopes, organic biomarkers (n-alkanes and fatty acids) and compound-specific (fatty acids) stable carbon isotope ratios in three sediment cores collected
from two sites near the Changjiang Estuary and one in the ECS shelf. Contrasting chemical and isotopic compositions of organic
matter were observed between the estuarine and shelf sediments. The concentrations of total n-alkanes and fatty acids in the shelf surface sediments (0–2 cm) were 5–10 times higher than those in estuarine surface sediments
but they all decreased rapidly to comparable levels below the surface layer. The compositions of n-alkanes in the estuarine sediments were dominated by C26-C33 long-chain n-alkanes with a strong odd-to-even carbon number predominance. In contrast, the composition of n-alkanes in the shelf sediment was dominated by nC15 to nC22 compounds. Long-chain (>C20) fatty acids (terrestrial biomarkers) accounted for a significantly higher fraction in the estuarine sediments compared to
that in the shelf sediment, while short-chain (<C20) saturated and unsaturated fatty acids were more abundant in the shelf surface sediments than in the estuarine sediments.
Stable carbon isotopic ratios of individual fatty acids showed a general positive shift from estuarine to shelf sediments,
consistent with the variations in bulk δ
13CTOCTOC. These contrasts between the estuarine and shelf sediments indicate that terrestrial organic matter was mainly deposited
within the Changjiang Estuary and inner shelf of ECS. Post-depositional diagenetic processes in the surface sediments rapidly
altered the chemical compositions and control the preservation of organic matter in the region. 相似文献
14.
《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(5):807-830
The presence of a strongly developed oxygen minimum zone (OMZ; [O2]<2 μM) in the northeastern Arabian Sea affords the opportunity to investigate whether oxygen deficiency in bottom waters enhances the preservation of organic matter in the underlying sediments. We explored if the observed patterns of organic matter accumulation could be explained by differences in productivity, sedimentation rate, water depth, and mineral texture. The differences in the burial rates of organic matter in sediments deposited within or below the OMZ could not be explained on the basis of these factors. All collected evidence points to a coupling of low oxygen concentrations and enhanced organic matter preservation. Under more oxygenated conditions bioturbation as well as the presence of labile manganese and iron oxides are probably important factors for a more efficient microbially mediated degradation of organic matter. Pore water profiles of dissolved Mn2+ and Fe2+ show that reduction of manganese and iron oxides plays a minor role in sediments lying within the OMZ and a larger role in sediments lying below the OMZ. 相似文献
15.
《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(2):185-204
Remineralization ratios (–O2:P, Corg.:P, N:P) in the ocean are estimated from ocean tracer data using a new approach, which takes into account the effects of local exchange across neutral surfaces. This approach is applied to temperature, salinity, phosphate, nitrate, dissolved oxygen, alkalinity, and dissolved inorganic carbon data from the low- and mid-latitude Pacific, Indian, and South Atlantic Oceans. The consideration of local exchange effects tends to reduce the –O2:P and Corg.:P remineralization estimates above 1500 m compared to earlier estimates. Below 1500 m, exchange effects can be neglected (except in the South Atlantic) and earlier estimates appear robust. In the deep South Atlantic, the consideration of these effects leads to increased –O2:P and Corg.:P remineralization ratio estimates, bringing them more in line with the robust deep ocean estimates. For reasonable, open ocean mixing coefficient values and several choices for phosphate remineralization rate profiles, –O2:P (Corg.:P) remineralization ratios in the ocean increase from about 140 (100) at 750 m depth to about 170 (130) at 1500 m and remain so deeper down. Such an increase down through the upper ocean thermocline implies significant fractionation during remineralization of organic matter—nutrients are released higher in the water column than inorganic carbon. These results also argue for a –O2:P (Corg.:P) uptake ratio in new production of about 140–150 (100–110). N:P remineralization ratios decrease from about 15 at 750 m to about 12 at 1500–2000 m. This may reflect a “true” N:P remineralization (and uptake) ratio of about 16, modified by denitrification.These results imply that applications of derived, quasi-conservative tracers, based on the assumption of constant remineralization ratios, may be subject to significant error for depths less than 1500 m. In addition, present Ocean General Circulation Models of the natural carbon cycle in the ocean–atmosphere system assume remineralization to occur without fractionation but have problems simulating observed, pre-industrial levels of atmospheric pCO2, given observed ocean inventories of alkalinity and dissolved inorganic carbon. Implementation of uptake and (depth-dependent) remineralization ratios estimated here would likely reduce this problem considerably. Furthermore, calculations with a simple global carbon cycle model show that fractionation in the modern ocean, as estimated in the present work, has reduced atmospheric pCO2 by more than 20 ppm below the level it would have had without fractionation. 相似文献
16.
《Marine Chemistry》2005,93(1):53-73
The provenance of organic matter in sediments from the Mackenzie River and Beaufort Shelf was investigated using the stable carbon and radiocarbon isotopic compositions of bulk organic matter and the stable carbon isotopic compositions of individual organic compounds, including lignin-derived phenols and lipid-derived fatty acids. Most river suspended sediments and shelf surface sediments contained organic carbon characterized by highly depleted Δ14C values that were consistent with average radiocarbon ages exceeding 7000 years. The stable carbon isotopic signatures of lignin phenols were uniformly depleted (−25≥δ13C≥−32‰), indicating the predominant contributions of C3 vascular plant sources. The isotopic compositions of C14 and C16 fatty acids exhibited important contrasts between the river (−36‰ to −40‰) and shelf (−25‰ to −29‰) sediments that were consistent with contributions from freshwater algae and/or vascular plants in the former and marine phytoplankton in the latter. Using 14C isotopic mass balance, the abundances of modern and ancient organic matter were quantitatively constrained. The fate of organic matter in the Beaufort Shelf was explored by normalizing these abundances to the specific surface area of sediments. Ancient organic carbon, which may include old pre-aged soil material as well as fossil bitumen or kerogen, accounted for the majority (∼70%) of the particulate organic matter exported by the Mackenzie River and deposited in surface sediments of the Beaufort Shelf. Modern organic carbon accounted for ∼30% in both river and shelf sediments, with significant contributions from vascular plant-derived materials in both river and shelf samples and from marine algae in the shelf sediments. Respiration (and/or leaching) of particle-bound marine organic matter dominates the carbon metabolism in the Mackenzie Delta/Beaufort Shelf region. However, land-derived pools, including modern carbon derived from vascular plants as well as ancient carbon also appeared to undergo a degree of post-depositional degradation prior to burial in the shelf. These novel source apportionments are reflected in an updated carbon budget for the study area. 相似文献
17.
A sequential leaching technique has been used to characterize the solid state speciation of total copper (∑Cu) among a number of operationally defined host fractions in surface seawater particulates from the Atlantic Ocean, a diagenetically active hemipelagic sediment core from the eastern Mediterranean, a turbidite - rich sediment core from the Madeira Abyssal Plain and a series of 79 Atlantic Ocean surface or near surface sediments. Around 50% of the ∑Cu in the surface water particulates is held in organic associations. When the material is deposited at the sediment surface, following its entry into the down-column carbon flux, the ∑Cu undergoes phase transformations as the organic carriers are destroyed. However, some of the organically associated copper (Cu5) is preserved in the sediments, the amount depending on the diagenetic environment of deposition. The relationship between ∑Cu and organic carbon in an oceanic sediment may be masked, but the partitioning speciation data has shown that good correlations can be found between organic carbon and Cu5. The concentration of Cu5 in Atlantic Ocean surface sediments is highest in hemipelagic (diagenetically active) sediments deposited in the marginal regions, and lowest in open-ocean (less diagenetically active) sediments of the Mid-Atlantic Ridge and ridge flanks. The marginal sediments contain an average of 20% of their total Cu in an organic association, with the result that these sediments can act as traps for seawater-derived Cu that would normally be regarded as being ‘reactive’ in the marine environment. To a first approximation, the preservation of Cu5 in the sediments mimics that of primary production in the overlying waters, and so ‘fingerprints’ the operation of the global ocean carbon flux in oceanic deposits. However, the relationship can be perturbed by the off-shelf transport of organic-rich, Cu5-containing, turbidites which can result in the transfer and burial of organic copper host fractions in open-ocean oxic environments. 相似文献
18.
Richard A. Feely Christopher L. Sabine Reiner Schlitzer John L. Bullister Sabine Mecking Dana Greeley 《Journal of Oceanography》2004,60(1):45-52
As a part of the JGOFS synthesis and modeling project, researchers have been working to synthesize the WOCE/JGOFS/DOE/NOAA
global CO2 survey data to better understand carbon cycling processes in the oceans. Working with international investigators we have
compiled a Pacific Ocean data set with over 35,000 unique samples analyzed for at least two carbon species, oxygen, nutrients,
chlorofluorocarbon (CFC) tracers, and hydrographic parameters. We use these data here to estimate in-situ oxygen utilization
rates (OUR) and organic carbon remineralization rates within the upper water column of the Pacific Ocean. OURs are derived
from the observed apparent oxygen utilization (AOU) and the water age estimates based on CFCs in the upper water and natural
radiocarbon in deep waters. The rates are generally highest just below the euphotic zone and decrease with depth to values
that are much lower and nearly constant in water deeper than 1200 m. OURs ranged from about 0.02–10 μmol kg−1yr−1 in the upper water masses from about 100–1000 m, and averaged = 0.10 μmol kg−1yr−1 in deep waters below 1200 m. The OUR data can be used to directly estimate organic carbon remineralization rates using the
C:O Redfield ratio given in Anderson and Sarmiento (1994). When these rates are integrated we obtain an estimate of 5.3 ±
1 Pg C yr−1 for the remineralization of organic carbon in the upper water column of the Pacific Ocean.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
《Marine Geology》1999,153(1-4):319-335
Sediments from a boxcore in the previously anoxic brine-filled Poseidon Basin, eastern Mediterranean, have been studied and compared to sediments deposited in a `normal' eastern Mediterranean environment. The boxcore can be divided into three main sedimentary intervals based on AMS-radiocarbon ages, foraminiferal and geochemical zonations. From the base of the core upwards these are: (1) 12.3–31.2 cm, organic-rich sediments redeposited from within the brine; (2) 6.6–12.3 cm, sediment containing a `cold' foraminifera fauna redeposited from above the brine into the basin while the brine was still present; (3) 0–6.6 cm, oxic pelagic sediment accumulated since the reoxygenation of Poseidon Basin which occurred ∼1800 yrs BP. Near the base of the latter unit, a Mn-oxide peak has formed and it marks the present boundary between oxic and suboxic environments. A progressive downward oxidation front, which is usually found in `normal' sapropel S1 sediments, has never formed in Poseidon Basin sediments. This has resulted in the preservation of the relationship between organic carbon and organic-related trace elements, e.g. Se, in the organic-rich sediments of Poseidon Basin, whereas such a relationship has been obliterated in `normal' sapropel S1 sediments. On the basis of the carbonate content as well as the Sr/Ca ratio, preservation of carbonates appears to be better in the brine sapropel sediments of BC15 than it is in `normal' sapropel S1 sediments. The high opal content of BC15 shows that biogenic opal is also much better preserved. The overall lower Corg/Ba ratio in BC15 suggests a better preservation of barite relative to that of organic carbon in shallow brine sediments, but is as yet inconclusive for the organic carbon preservation potential of brine relative to `normal' unoxidised sediments. 相似文献
20.
O. G. Ignat’eva E. I. Ovsyanyi A. S. Romanov S. K. Konovalov N. A. Orekhova 《Physical Oceanography》2008,18(2):96-105
On the basis of the experimental data accumulated in 1998–2005, we analyzed the space and time variations of the carbonate
system of waters and the content of organic carbon in bottom sediments of the Sevastopol Bay. The intensity of gas exchange
through the water-atmosphere interface was quantitatively estimated. It was shown that the partial pressure of carbon dioxide
pCO2 in waters of the bay became much higher for the period of observations. The maximum changes were observed in summer. They
were especially pronounced for the bottom layer of waters. For the entire period of observations, the invasion of carbon dioxide
CO2 was predominant in the major part of the bay, and the content of organic carbon in the bottom sediments increased. The ability
of waters in the bay to absorb CO2 is explained by the synthesis of organic substances, which becomes possible due to the presence of the equivalent load of
nutrients.
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Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 57–67, March–April, 2008. 相似文献