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1.
《Oceanologica Acta》1998,21(4):543-550
Humic acids from sediments of different depositional environments have been studied by solid-state 13C NMR and the results compared with the traditional wet chemical analysis. Results obtained are well in agreement with the previous literature reports that the carboxyl content measured by NMR correlated better with the total acidity, as well as with the carboxyl content obtained by wet chemical analysis after correction for amino acid carboxyl is made (following hydrolysis of peptide bonds). There is a large discrepancy between the NMR and wet chemical measurements of phenolics. NMR spectra was also indicative of branched paraffinic structures in the humic acids from the Arabian Sea; the humic acids of sediments from estuarine and coastal areas of the Bay of Bengal being dominated by carbohydrates and aromatic structures and to a lesser extent by paraffinic structures. These differences are attributed to their different biogeochemical origin.  相似文献   

2.
The Bering Sea shelf and Chukchi Sea shelf are believed to hold enormous oil and gas reserves which have attracted a lot of geophysical surveys. For the interpretation of acoustic geophysical survey results, sediment sound velocity is one of the main parameters. On seven sediment cores collected from the Bering Sea and Chukchi Sea during the 5th Chinese National Arctic Research Expedition, sound velocity measurements were made at 35, 50, 100, 135, 150, 174, 200, and 250 k Hz using eight separate pairs of ultrasonic transducers. The measured sound velocities range from 1 425.1 m/s to 1 606.4 m/s and are dispersive with the degrees of dispersion from 2.2% to 4.0% over a frequency range of 35–250 k Hz. After the sound velocity measurements, the measurements of selected geotechnical properties and the Scanning Electron Microscopic observation of microstructure were also made on the sediment cores. The results show that the seafloor sediments are composed of silty sand, sandy silt, coarse silt, clayey silt, sand-silt-clay and silty clay. Aggregate and diatom debris is found in the seafloor sediments. Through comparative analysis of microphotographs and geotechnical properties, it is assumed that the large pore spaces between aggregates and the intraparticulate porosity of diatom debris increase the porosity of the seafloor sediments, and affect other geotechnical properties. The correlation analysis of sound velocity and geotechnical properties shows that the correlation of sound velocity with porosity and wet bulk density is extreme significant, while the correlation of sound velocity with clay content, mean grain size and organic content is not significant. The regression equations between porosity, wet bulk density and sound velocity based on best-fit polynomial are given.  相似文献   

3.
Matrix bound phosphine (MBP) is commonly considered an important phosphorus form in the natural environment. This paper presents an investigation of the spatial distribution of MBP and its relationship with the environmental factors in the Changjiang Estuary and its adjacent shelf areas (29.5–32°N, 122–124°E). A total of 32 surface sediment samples were collected from April 24 to 30, 2008. MBP was detected in all samples from the Changjiang Estuary and its adjacent shelf surface sediments (0.1–29.7 ng kg−1). The concentration of MBP decreased from the Changjiang Estuary to the East China Sea shelf. Environmental factors such as organic matter, type of sediments, and redox conditions were found to affect the concentration and distribution of MBP in the marine sediments. Although the MBP levels were low in the marine sediments, the marine biogeochemical cycles of MBP in sediments were established and the information presented here will contribute to the understanding of the biogeochemical cycle of phosphorus.  相似文献   

4.
Acoustics have the promise of being able to have a significant impact on our understanding of coastal sedimentary processes, which play such an important role in the dynamics of the coastal and shallow water environment. Due to this, the application of acoustics for remotely measuring suspended sediments, over ranges from metres to tens of metres, is gaining acceptance within the sediment community. This recognition of the use of acoustics to the area of sediment processes is based on advances which have been made decade in the understanding of the interaction of sound with marine suspended sediments, and also due to ongoing field observations which have shown the unique ability of the acoustic technique to measure suspended sediment profiles. In the present work acoustic measurements of suspended sediments have been conducted at 1, 2.5, 3, and 5 MHz in a number of different shallow water environments. The interpretation of the acoustic data to obtain suspended sediment concentration is presented, and some of the difficulties when inverting the acoustic information to obtain the suspended load are considered. Some discussion is also given to future uses of acoustics for studying sediment processes, and how one may utilize the application of underwater sound to manage our coastal environment more effectively  相似文献   

5.
As a part of the environmental impact assessment studies, geotechnical properties of sediments were determined in the Central Indian Basin. The undrained shear strength and index properties of the siliceous sediments were determined on 20 box cores of uniform dimension collected from various locations in five preselected sites. The maximum core length encountered was 41 cm and most of the sediments were siliceous oozes consisting of radiolarian or diatomaceous tests. The shear strength measurements revealed that surface sediments deposited in recent times (0-10 cm) have a shear strength of 0-1 kPa; this value increases with depth, reaching 10 kPa at 40 cm deep. Older sediments have greater strength because of compaction. Water content varies in the wide range of 312-577% and decreases with depth. The clay minerals such as smectite and illite are dominant and show some control over water content. Wet density, specific gravity, and porosity do not indicate any notable variation with depth, thereby indicating a uniform, slow rate of sedimentation. The average porosity of sediments is 90.2%, specific gravity 2.18, and wet bulk density 1.12 g/cm 3 . Sediments exhibit medium to high plasticity characteristics, with the average plasticity index varying between 105% and 136%. Preliminary studies on postdisturbance samples showed an increase in natural water content and a decrease in undrained shear strength of sediments in the top 10- to 15-cm layer.  相似文献   

6.
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   

7.
Abstract

As a part of the environmental impact assessment studies, geotechnical properties of sediments were determined in the Central Indian Basin. The undrained shear strength and index properties of the siliceous sediments were determined on 20 box cores of uniform dimension collected from various locations in five preselected sites. The maximum core length encountered was 41 cm and most of the sediments were siliceous oozes consisting of radiolarian or diatomaceous tests. The shear strength measurements revealed that surface sediments deposited in recent times (0–10 cm) have a shear strength of 0–1 kPa; this value increases with depth, reaching 10 kPa at 40 cm deep. Older sediments have greater strength because of compaction. Water content varies in the wide range of 312–577% and decreases with depth. The clay minerals such as smectite and illite are dominant and show some control over water content. Wet density, specific gravity, and porosity do not indicate any notable variation with depth, thereby indicating a uniform, slow rate of sedimentation. The average porosity of sediments is 90.2%, specific gravity 2.18, and wet bulk density 1.12 g/cm3. Sediments exhibit medium to high plasticity characteristics, with the average plasticity index varying between 105% and 136%. Preliminary studies on postdisturbance samples showed an increase in natural water content and a decrease in undrained shear strength of sediments in the top 10- to 15-cm layer.  相似文献   

8.
利用大洋多金属结核矿区调查过程中4个航次所得的600多组表层沉积物物性测试资料,将矿区的沉积物分为5种类型,并分析了这些沉积物的物理性质,同时,运用回归分析方法,统计分析了不同类型沉积物的含水量、湿密度、孔隙比与埋藏深度的关系,以及各物性指标之间的相关关系。结果表明:(1)大洋多金属结核矿区表层沉积物均为粉质土,黄棕色粉质土是西部矿区的主要沉积物类型,棕黄色粉质土是东部矿区的主要沉积物类型;(2)除褐色粉质土外,其余4种类型土的含水量、孔隙比均随埋藏深度的增加而减少和降低,湿密度则随深度增加而增大;(3)各类土的物性指标与埋藏深度的相关性甚好,因而可以利用埋藏深度对矿区的沉积物进行物性指标预测;(4)含水量、孔隙比、湿密度等物性指标之间呈线性相关,其中含水量与孔隙比的相关性最为密切,呈明显线性关系。  相似文献   

9.
对中国北方莱州湾南岸钻孔上部54m海陆交互相沉积物的亮度进行研究,探讨其作为海陆交互相沉积物的环境指标的可行性,同时通过对比不同样品处理方式所得的亮度值探讨影响亮度的几个因素。测量分2次进行,分别使用Minolta CM-2002分光光度计针对柱状原样及Minolta CR400/410色差计针对风干研磨后的散样进行。研究结果表明,海陆交互相沉积物的亮度,尤其是经过风干处理后样品的亮度值,与碳酸钙含量及粒度两个古气候代用指标均具有显著相关关系,可以将其作为碳酸钙含量的替代指标应用于海陆交互相沉积物的环境演化研究。而亮度值与碳酸钙含量不一致性,可归因于沉积物中非碳酸钙组分的性质及含量。粒度与亮度的相关性显示,钻孔砂质沉积中含有的大量深色的有机质使得钻孔中粒度0～31μm的部分比例越高,亮度会越大,而粒度>31μm的部分比例越高,亮度会越小。2次亮度值的对比表明,水分、氧化作用及研磨是沉积物2次测量所得亮度值存在差异的主要原因。  相似文献   

10.
The behavior of radon in the sea-floor region provides a useful test of theories which describe mass transport in sediments. We have made measurements of Rn-222 and Ra-226 in near-bottom waters and near-surface sediments at the same location. The distribution of radon in sediments can be described by a simplified diagenetic equation when advection, adsorption, and bioturbation are ignored. Sediment measurements show a radon deficit relative to radium emanation. A reasonable balance is found between integrated radon deficit in sediment and radon surplus in the overlying water.In most cores radium increased with depth in the top 10 cm of sediment. This implies that bioturbation and other mixing processes do not homogenize the radium concentration in the zone of diffusive radon loss, and that radium is diffusing out of the sediments.Radon leakage is less than that predicted by previous authors. Radon leakage depends upon the physical distribution of radium in marine sediments. We present a model that predicts leakage of 30–40% for normal deep-sea sediments, in agreement with measured values.Radon surplus in near-bottom waters depends upon the radium distribution, radon leakage, and effective diffusion coefficients. These in turn depend on the properties of the sediment, such as composition, accumulation rate, and porosity. As we learn how these factors interact we may be able to infer sedimentary features from measurements of radon in overlying waters.  相似文献   

11.
Proliferation of fast-growing ephemeral macroalgae in shallow-water embayments constitutes a large-scale environmental change of coastal marine ecosystems. Since inorganic nutrients essential for the initiation and maintenance of macroalgal growth may be supplied from the underlying sediment, we investigated the coupling between benthic inorganic nutrient (mainly N and P) fluxes and sediment properties in 6 bays representing a wide gradient of sediment characteristics (grain size, organic matter content, solid phase C and N). The initial characterization of bays was made in June and also included measurements of oxygen flux and microphytobenthic and macrofaunal biomass. In September, still within the growth season of the macroalgae, complementary experiments with sediment-water incubations for benthic flux measurements of oxygen and nutrients focused on trophic status (balance between auto- and heterotrophy) as a controlling factor for rates of measured benthic nutrient fluxes. Generally, sediments rendered autotrophic by microphytobenthic photosynthesis removed nutrients from the overlying water, while heterotrophic sediments supplied nutrients to the overlying bottom water. Estimations of the green-algal nutrient demand suggested that late in the growth season, net heterotrophic sediments could cover 20% of the N-demand and 70% of the P demand. As the benthic trophic status is a functional variable more closely coupled to nutrient fluxes than the comparably conservative structural parameter organic matter content, we suggest that the trophic status is a more viable parameter to classify sediments and predict benthic nutrient fluxes in shallow-water environments.  相似文献   

12.
Pore water, sediment and microbiological samples were collected from two areas in the Gulf of Maine. The Jeffreys Basin sediments had low organic carbon and low reduced sulfur values; the quality of their pore water indicated that nitrification and subsequent denitrification were major biogeochemical processes occurring in the upper 115 cm. Sediments from the Wilkinson Basin had higher values of organic carbon and higher reduced sulfur and total plate-count bacteria. These data indicate that the major biogeochemical processes occurring in these sediments are denitrification followed by sulfate reduction. The differences in the rates of these microbially mediated processes can be related to differences in sedimentation rates at the two sites.  相似文献   

13.
Hydrothermal venting has a profound effect on the chemical and biological properties of local and distal seawater and sediments. In this study, lipid biomarkers were analyzed to examine the potential influence of hydrothermal activity on the fate of organic matter(OM) in surface sediments around Tianxiu Hydrothermal Field in the Carlsberg Ridge(CR), Northwest Indian Ocean. By comparing the biomarker distributions of the samples with that of other typical hydrothermal sediments in the mid ocean ridge, it is shown that the location of the samples is not affected by the hydrothermal activity. The relatively low abundances of terrestrial n-alkyl lipids and riverine1,15-C32 diol suggested a minor contribution of terrigenous OM to the study area. The bacteria contributed predominantly to sedimentary marine OM; however, other marine source organisms, e.g., eukaryotes(i.e.,phytoplankton and fungi) could not be completely neglected. The marine-originated biomarkers showed significantly variable distributions between the two sediments, suggesting different dynamic physical and biogeochemical processes controlling the fate of marine OM. This study identified various diagnostic biomarkers(5,5-diethyl alkanes, diols and β-OH FAs), which may have significant environmental implications for future works in this region.  相似文献   

14.
海湾是海洋和陆地相互作用和人类活动最强烈的区域,沉积物中重金属的含量和分布都受到人类活动的影响。为了探究钦州湾沉积物中重金属的含量水平、污染程度和可能来源,本研究分析了钦州湾表层沉积物中Cu、Pb、Zn、Cd、Cr、Hg和As的含量及空间分布,采用地质累计指数（Igeo）和潜在生态风险指数（PERI）定量分析了重金属的污染程度和生态风险,并利用自组织映射(SOM)和正定矩阵因子分解法(PMF)模型评估了重金属的可能来源。结果表明：钦州湾表层沉积物重金属中Zn的平均含量最高,Hg平均含量最低;除个别站位的Pb含量符合海洋沉积物质量第二类标准外,其他重金属含量均符合海洋沉积物质量第一类标准;Igeo结果表明钦州湾表层沉积物主要的污染元素为Pb、Hg和Cu;PERI结果表明Hg是钦州湾表层沉积物主要的生态风险元素。SOM和PMF模型结果表明钦州湾表层沉积物重金属主要受自然来源、农业活动、工业生产活动的共同影响,各来源的相对贡献率分别为39.65%、29.15%和31.20%。  相似文献   

15.
The aim of this paper was to test how benthic fauna and biogeochemical properties of sediment will vary in response to similar levels of organic enrichment (induced by fish farming) as a function of bottom-habitat type (i.e., mud versus seagrass/coarse sediments), distance from the enrichment source and depth. Our results showed that samples from silty sediments in the vicinity of fish farms have higher TOC and TON values, higher oxygen consumption, higher PO4 release and lower benthic diversity. In this context muddy sites are more likely to be identified as impacted/critical, than coarse sediment ones.  相似文献   

16.
浙闽近岸与南黄海中部沉积物物理力学性质的差异性分析   总被引：1，自引：0，他引：1  
本文对浙闽近岸和南黄海中部泥质区沉积物的物理力学性质,分别从基本物理性质、水理性质及力学性质进行对比分析,发现两个区域沉积物均以淤泥为主,含水率与密度、压缩系数与压缩模量均呈良好的幂函数负相关性,液限与塑限呈良好的幂函数正相关性,含水率与孔隙比呈较好的线性正相关,十字板剪切强度与微型贯入阻力呈较好的多项式函数关系。总体来说,南黄海中部泥质区沉积物相对于浙闽近岸泥质区沉积物具有含水率高、孔隙比大、密度小、塑性高,压缩性大,抗剪强度低等特征。从地形特征、物质来源、水动力条件、沉积速率和物质组成等方面进行两个区域沉积物物理力学性质差异性的成因分析。结果显示,与浙闽近岸相比,南黄海中部离陆较远、地势低洼、水动力条件较弱,能够扩散至此的物质较少并以极细的粘粒物质为主,沉积物中的蒙脱石和有机质含量高。这些因素使得南黄海中部沉积物的含水率高,塑性大,密度低,强度低。  相似文献   

17.
Keeling plots of dissolved organic carbon (DOC) concentration and Δ14C depth profiles imply rapid, diapycnal transport of DOC to the meso- and bathypelagic zones, but do not constrain the mechanism of redistribution. We review the 2-component Keeling plot model, and present an alternative formulation explicitly based on homogenization of water parcels. Applying this new model to DOC and dissolved inorganic carbon (DIC) depth profiles suggests that the dominant controls on DOC redistribution differ throughout the water column. DOC concentration and Δ14C gradients were consistent with biogeochemical processing in the epipelagic and advection in the mesopelagic. Vertical gradients in DOC concentration and Δ14C were insufficient for further interpretation in the bathypelagic. Ultimately, additional concurrent measurements of DOC and DIC concentrations and Δ14C values throughout the water column at more locations are needed to constrain the applicability of two-component mixing models to marine DOC.  相似文献   

18.
Gravity measurements in the South Atlantic Ocean over Burdwood Bank show a large negative gravity anomaly extending along its northern edge. An interpretation of the gravity data has been made based on the seismic refraction measurements of Ludwig et al. (1968) and shows that the negative gravity anomaly can be largely attributed to a basin containing low density sediments about 8 km thick. The crustal sections constructed also indicate that the crust increases in thickness from about 20 km under Burdwood Bank to about 30 km under the Falkland Islands platform.  相似文献   

19.
《Marine Chemistry》2002,79(1):37-47
Profiles of dissolved organic carbon (DOC) were measured in the pore water of sediments from 1000, 2000 and 3500 m water depth in the eastern North Atlantic. A net DOC accumulation in the pore waters was observed, which followed closely the zonation of microbial respiration in these sediments. The concentration of pore water DOC in the zone of oxic respiration was elevated relative to that in the bottom ocean water. The resulting upward gradient across the sediment–water interface indicated a steady state diffusive benthic flux, FDOC, of 0.25–0.44 mmol m−2 day−1 from these sediments. Subsequent increase in the concentration of DOC in the pore water occurred only in the sediments from 1000 and 2000 m water depth that supported anoxic respiration, leading to a deep concentration maximum. By contrast, in the sediments from 3500 m water depth, a deep concentration minimum was measured, coincident with minimal postoxic respiration in this near-abyssal setting. The gradient-based FDOC represented approximately 14% of the total remineralized organic carbon (TCR=sum of FDOC and depth-integrated organic carbon oxidation rate) in the sediments from 1000 and 2000 m water depth, while it was 36% of the TCR in the sediments from 3500 m water depth. A covariance of particulate organic carbon (POC) and pore water DOC with depth in the sediments was evident, more consistently at the deepest site. While the covariance can be related to biotic processes in these sediments, an alternative interpretation suggests a possible contribution of sorption to the biotic control on sedimentary organic carbon cycling. The steady state diagenetic conditions in which this may occur can be conceivable for some organic-poor deep-sea locations, but direct evidence is clearly required to validate them.  相似文献   

20.
The capacity of turbidity currents to carry sand and coarser sediment from shallow to deep regions in the submarine environment has attracted the attention of researchers from different disciplines. Yet not only are field measurements of oceanic turbidity currents a rare achievement, but also the data that have been collected consist mostly of velocity records with very limited or no suspended sediment concentration or grain size distribution data. This work focuses on two turbidity currents measured in Monterey Canyon in 2002 with emphasis on suspended sediment from unique samples collected within the body of these currents. It is shown that concentration and grain size of the suspended material, primarily controlled by the source of the gravity flows and their interaction with bed material, play a significant role in shaping the characteristics of the turbidity currents as they travel down the canyon. Before the flows reach their normal or quasi-steady state, which is defined by bed slope, bed roughness, and suspended grain size, they might pass through a preliminary adjustment stage where they are subject to capacity-driven deposition, and release heavy material in excess. Flows composed of fine (silt/clay) sediments tend to be thicker than those with sands. The measured velocity and concentration data confirm that flow patterns differ between the front and body of turbidity currents and that, even after reaching normal state, the flow regime can be radically disrupted by abrupt changes in canyon morphology.  相似文献   

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