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991.
The relationship between seagrass (Posidonia oceanica) decline and sulfide porewater concentration in carbonate sediments 总被引:2,自引:0,他引:2
Maria Ll. Calleja Núria Marb Carlos M. Duarte 《Estuarine, Coastal and Shelf Science》2007,73(3-4):583-588
In this study we test the hypothesized negative relationship between seagrass status and porewater hydrogen sulfide (H2S) levels, through a comparative analysis within a range of seven Posidonia oceanica meadows growing over carbonate sediments in the NW Mediterranean Sea around Mallorca Island. The studied meadows range from meadows growing on sediments with very low sulfide porewater concentrations (4.6 μM) to those growing over higher sulfide conditions (33.5 μM). Organic matter content, sulfate reduction rates and sulfide porewater concentrations in the sediments were determined concurrently with the assessment of demographic plant dynamics (specific mortality and net population growth rates). Sulfide porewater concentration increased with increasing organic matter content in the sediment, while net population growth decreased significantly with low increases of sulfide concentrations. Our results confirm the previously suspected vulnerability of seagrass meadows growing on carbonate sediments to increased sulfide levels. An excess of 10 μmols H2S L−1 porewater is identified to already conduce P. oceanica meadows to decline, which this study identifies, particularly, as strongly sensitive to sulfides. The results reported here suggest that even moderate increases in organic carbon inputs may lead to enhancement of dissolved sulfides and may be an important factor for seagrass status in these iron-depleted carbonate sediments from the Mediterranean Sea. 相似文献
992.
M. Snoek 《Marine Geophysical Researches》2005,26(2-4):275-286
The last few years has seen a surge in research activities directed towards investigating properties and dynamics of young
marine, limnic and fluvial sediments. It is by now a well established fact that the sequence of sediments ranging from concentrated
benthic suspension over fluid mud to un-consolidated material summarized as liquid sediments (LS), act as carriers for a wide
range of pollutants discharged or migrated into waterways. Knowledge of the transport and fate of LS allows determining the
transport and fate of adsorbed constituents (e.g., heavy metals, pesticides, PCBs, PAHs). To assess the environmental impact
of LS, efforts have to be made to better understand the processes in relation to hydrodynamics and the chemical and physical
properties of the layers. Since physical laws limit the resolution and detection power of conventional seismo-acoustic systems
in respect of LS, alternative measurement, data analysis and processing approaches have to be found. Adapted acoustic procedures
initially developed for shallow water marine environments to extreme shallow water regimes using matched field inversion techniques
can reveal geoacoustic parameters including density, compressional wave speed and attenuation as a function of depth and time.
The paper outlines the effects of sediment mobility upon the environment followed by a short overview of techniques commonly
used to investigate sediments and other freshwater/marine events. The problems faced and limitations of existing systems are
briefly outlined. Results obtained with recently developed and refined geoacoustic inversion methods are presented highlighting
their potential for long-term study of physical properties and dynamics of LS. 相似文献
993.
利用放射性示踪沙定量观测长江口北槽航道抛泥区底沙运动 总被引:3,自引:0,他引:3
1991年6月在国际原子能机构的合作下,在长江口北槽航道上抛泥区进行了一次大规模的放射性示踪沙试验。示踪核素为钪-46,总活度为17.95×10~(10)Bq(4.85Ci),示踪沙投放总量为495g。本试验目的是通过定量观测底沙运移的方向、路线、速度和输沙率,以期为北槽航道上抛泥区今后能否继续作为抛泥区使用提供直观可靠论据。本次试验观测资料表明,在北槽航道上抛泥区,在中小讯期间,无论是涨潮时投放的示踪沙还是落潮时投放的示踪沙都受落潮流控制,并向北槽航道中段输移。据测量资料分析,在上口抛泥区投放的示踪沙最终沿着110°的运动方向以758m/d的运动速度,在269~#航标附近进入挖槽,单宽输沙率为47.8m~3/md。 相似文献
994.
黄河口及渤海中南部沉积特征变化及其环境动力分析 总被引:3,自引:0,他引:3
渤海中南部沉积类型及其分布受海底地形、水动力条件和物质来源影响 ,具有明显的分区多样性。而黄河巨大的输沙量进入渤海南部 ,其运移和扩散对这一地区沉积物的分布产生很大的影响。本文通过对不同时期底质情况的对比 ,说明研究区海底沉积的分布格局受到黄河河口不断向海延伸的影响在最近十几年中发生了很大的变化。而河口区的底质分布还受到最近几年黄河断流 ,水沙来量减少的深刻影响。 相似文献
995.
海洋沉积粘土矿物与全球变化研究的探讨 总被引:6,自引:0,他引:6
本文对我国粘土矿物的科研成果进行了初步综述,概述了海洋沉积粘土矿物在全球变化研究中的作用,探讨了海洋沉积粘土矿物的古环境,古气候指示意义。 相似文献
996.
通过对海洋沉积物声速及其物理-力学参数相关性的初步分析和研究,可以找到估算沉积物压缩波速Vp和切变波速Vs的经验式,最终为海底沉积物的性质进行声学遥测、为发展海底参数声遥感服务。本文给出了7个较为理想的回归方程。沉积物的物理参数与Vp有密切的关系;力学参数对Vs的预报有较大的作用。若增加物理参数作为修正项,其效果更佳。 相似文献
997.
利用黄河利津站的精密水文泥沙测量结果对一些常用水流泥沙输沙率公式进行验证表明,Van Rijn公式最适合于黄河泥沙输沙率的预测,对公式做部分校正则可以大大提高其预测能力。 相似文献
998.
J.A. Borg M.J. Attrill A.A. Rowden P.J. Schembri M.B. Jones 《Estuarine, Coastal and Shelf Science》2005,62(4):667-678
Seagrass beds occur in various morphological forms, ranging from small patches to continuous meadows. The endemic Mediterranean seagrass Posidonia oceanica forms dense and extensive stands that occur in several different morphotypes, including reticulate (seagrass interspersed with a different habitat type, such as bare sand) and continuous beds. This study, undertaken in the Maltese Islands, examined whether reticulate and continuous P. oceanica beds, located adjacent to each other and at similar depths, had different within-bed architectural characteristics. Five commonly used architectural measures (shoot density, number of leaves per shoot, mean leaf length, mean leaf width and shoot biomass) were measured from P. oceanica shoots collected from the two bed types at three different spatial scales: (1) tens of metres (‘small’ scale); (2) hundreds of metres (‘medium’ scale); and (3) kilometres (‘large’ scale). Results of 2-factor ANOVA (factor 1=bed type; factor 2=sampling locality) carried out at the three spatial scales indicated significant differences between the two bed types in shoot density (P<0.01) and leaf length (P<0.05) at the small scale, and in leaf number (P<0.05) at the large scale. Significant interactions were also apparent for shoot density (at the large scale) and for shoot biomass (at the medium scale). However, the results obtained did not indicate consistent architectural differences between the two P. oceanica bed types over the spatial scales considered. Spatial variations in within-bed architectural characteristics observed were therefore thought to be attributable mainly to the influence of local environmental factors. The findings are discussed with reference to the conservation and management of P. oceanica habitat. 相似文献
999.
本文对黄海中南部10个沉积物样品和东海北部24个沉积物样品用等离子光谱做了Ba、Be、Co、Cr、Ga、Li、Mn、Nb、Ni、P、Pb、Sr、V、Zn、Y和Yb的分析,并对该区沉积物中元素的丰度和不同类型沉积物中微量元素的分布规律做了研究。通过对区内微量元素与主要元素的相关图解分析表明,大多数微量元素与主要元素Al、Mg、K呈正相关,其高值区与粘土沉积物相一致,低值区与粉砂质沉积物相吻合;Be、Sr、Mn的高含量与粘土沉积物无关 相似文献
1000.
太平洋东部深海沉积物稀土元素地球化学 总被引:9,自引:0,他引:9
刘季花 《海洋地质与第四纪地质》1992,12(2):33-42
通过对太平洋东部CC区深海沉积物的稀土元素研究发现:该区沉积物的REE含量较高,普遍具有较小的Eu正异常和较大的Ce负异常;不同类型沉积物中的稀土含量、比值和分布模式存在着差异,这种差异主要取决于沉积物组分的不同;沉积物的来源有自生源、火山源、生物源和陆源,稀土元素主要是通过自生组分富集的,区域上,Ce异常值低处,Eh值高,为强氧化环境区,也是南极底层流的流经路径,是多金属结核富集的有利地区。 相似文献