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1.
为初步评估海洋资源用作混凝土原材料的可行性，先通过数字图像技术求取海砂与河砂颗粒样本的椭圆率、圆度及坚固性参数，对两者颗粒形态特征做出综合评价，然后采用RCT法检测海拌混凝土游离氯离子含量，并测定混凝土不同龄期的抗压强度及碳化深度。结果表明，海砂与河砂颗粒细长程度、棱角及内凹曲面显著程度均非常接近，颗粒形态不存在本质差异；天然海水有助于混凝土早期强度的提升，对后期强度及碳化深度的影响则较为微弱；商品海砂会对混凝土力学性能产生轻微负面影响，并使抗碳化性能大幅下降。 相似文献
2.
采用X射线衍射技术,初步研究了网纹藤壶(Balanus reticulates Utinomi)壳板矿化结构特征,并采用钙黄绿素法、钙-羧酸指示剂法和铬黑T指示剂三种方法测量了来自不同海域藤壶壳板的碳酸钙含量。实验发现,网纹藤壶壳板中的矿化组织主要由方解石构成,碳酸钙微晶体排列有一定的取向,较为复杂。海口和陵水两地藤壶壳板中碳酸钙含量没有显著差异(P<0.05),最大值为93.87%,最小值90.77%。尽管三种碳酸钙含量测量法的结果没有显著性差异(P<0.05),但进一步综合分析发现钙黄绿素法测定结果最为稳定,且简单易操作,可作为首选方法。 相似文献
3.
目的：观察中医三步序贯法治疗急性脑出血的临床疗效。方法：将84例急性脑出血患者随机分为2组各42例，对照组采用西医常规治疗，治疗组采用中医三步序贯法治疗。结果：总有效率治疗组为95.24%，对照组为73.81%，2组比较，差异有统计学意义（P＜0.05）。治疗组治疗后FMA评分与ADL评分均明显高于对照组，差异有统计学意义（P<0.05）。结论：中医三步序贯法治疗急性脑出血的效果满意，可明显提升患者的运动功能与日常生活能力。 相似文献
4.
《海洋地质与第四纪地质》2010,(4)
黄河口潮间带沉积物团聚体的稳定性直接影响到海岸带的侵蚀过程。采用扫描电镜SEM、土壤物理和土壤化学领域的多种方法,对比分析影响黄土和黄河口沉积物团聚的主要物质基本理化性质,通过测定不同条件下碳酸钙和Ca2+对团聚度的影响,研究了碳酸钙和Ca2+的团聚作用和对黄河口沉积物水稳定性的影响。结果表明,碳酸钙是影响黄河口沉积物团聚的主要物质,其含量与黄土中的含量相当,为10.67%,而沉积物的平均粒径比黄土小,说明碳酸钙以微晶态形式胶结黏粒形成小粒径颗粒,被径流通过河道带到黄河三角洲沉积下来。碳酸钙的团聚呈现出粒级越大碳酸钙含量越高的趋势,对比碳酸钙与Ca2+对黄河口沉积物的团聚作用表明,碳酸钙对颗粒的团聚作用比Ca2+的团聚作用强。黄河口沉积物黏粒基本上不是分散存在的,而是被碳酸钙团聚成微团聚体存在的,在长期的往复潮流和波浪的作用下更加明显。 相似文献
5.
于1997年6月在青岛市沙子口海域采集文昌鱼样品，采用RT－PCR方法进行青岛文昌鱼LIM类同源框基因片段的扩增研究。结果表明，用一对引物一次PCR扩增的方法未能得到特异的PCR产物，用一对引物两次PCR扩增的方法也同样未果。在对套式PCR进行研究时发现，用普遍PCR方法进行的套式PCR结果不够理想，而用三步两段法和四步两段法套式PCR则可进行成功的扩增。用这两种方法扩增的PCR产物具有高度特异性。相比之下，用简并的引物对未知的基因片段进行PCR扩增时，三步两段法和四步两段法的套式PCR应是首选方法。 相似文献
6.
对远场法、近场法和中场法这几种常用的二阶波浪力计算方法进行了总结,并结合算例对它们之间的差异进行了研究,重点分析了网格密度、浮体形状、水深等因素的影响。此外,还对全QTF法和Newman近似这两种不规则波中的二阶力计算方法进行了讨论,比较了不同水深条件下两种方法求得的二阶波浪力谱之间的差异。研究结果表明,远场和中场法给出的结果基本一致,且具有较好的数值稳定性;而近场法受网格密度、浮体形状等因素影响较大;Newman近似给出的结果在频率较低时与全QTF法接近,但在频率较高时存在一定的误差。 相似文献
7.
8.
以海水为溶剂,采用熔融法合成了纳米粉煤灰沸石。粉煤灰与NaOH的质量比为1:1.2,熔融温度550℃,熟料质量与海水固液的体积比为1:5(g/mL),晶化温度100℃,晶化时间6h。通过仪器分析和化学方法,对产物的结构、形貌、性能进行表征。同时,研究了产物的矿物组成、形貌、比表面积、阳离子交换量及化学组成。结果表明:产物为NaX型沸石和羟基方钠石的复合型沸石,海水晶化粉煤灰通过碱熔融法得到沸石质量优于传统水热法。合成沸石的性能和各项应用指标表明,所合成的沸石具有良好的实际应用价值。 相似文献
9.
海洋对CO2的吸收缓解了大气CO2浓度的持续上升,陆架海因其较高的初级生产而具有较强的固碳能力,在海洋碳循环中占据重要角色。然而由于陆架海过程时空变化剧烈,陆架海对人为CO2源/汇作用的动态格局还存在争议,陆架海碳循环的调控机制尚不清晰。IPCC AR4所采用的气候-碳循环耦合模型均未考虑陆架海碳循环,使其成为气候预测不确定性的主要来源之一。建立适宜的陆架海碳循环模型,可以探究陆架海不同区域CO2源/汇格局的长期变化,估算碳循环各关键过程的贡献,认识碳循环系统与生态系统的相互作用,评估陆架海碳循环在气候变化中的作用。基于陆架海碳循环模型研究现状,从物理过程、生物泵、碳化学系统等三个主要方面总结了陆架海碳循环模式在建模中应考虑的关键过程,提出了构建东中国陆架海碳循环模式的基本思路及拟解决的关键科学问题。 相似文献
10.
为了解南海北部末次间冰期以来的沉积环境演化,分析了西沙海槽83PC柱状沉积物的浮游有孔虫氧碳同位素、碳酸钙、有机碳和粒度组成。浮游有孔虫的δ18 O值具有冰期-间冰期旋回特征,记录了海平面的升降和古气候的变化,而海平面变化控制了沉积物的碳酸钙和有机碳含量。冰期,海平面下降,陆源物质输入增多,带来了大量的碎屑物质和陆源有机质,沉积物具有低碳酸钙含量和高有机碳含量;间冰期,海平面上升,陆源物质输入减少,碎屑物质的稀释作用减弱,沉积物具有高碳酸钙含量和低有机碳含量。南海北部83PC柱状沉积物记录了末次间冰期以来的多次海平面升降旋回,还记录了气候变冷事件以及低碳酸钙沉积事件,其中,150、510、660和740cm处的低碳酸钙含量和相对重δ18 O值记录了全球性气候变冷事件,而冰后期的低碳酸钙沉积事件,则主要反映了季风降雨的增强,出现了洪水高发期,陆源碎屑物质对碳酸钙沉积的稀释作用明显增强。 相似文献
11.
AbstractSporosarcina pasteurii (ATCC 11859) is a nitrogen-circulating bacterium capable of precipitating calcium carbonate given a calcium source and urea. This microbially induced carbonate precipitation (MICP) is able to infill inter-granular porosity and act as a biological clogging agent, thus having a wide potential application in strengthening coastal foundations, preventing erosion by seas and rivers and in reducing sand liquefaction potential in coastal areas. A successful MICP application requires the understanding of the primary parameters that influence the microbially mediated process to achieve its engineering goals, such as injection scheme, chemical concentrations, retention times, and injection rates. However, the granular morphology has generally been oversimplified to ideal shape without enough consideration in previous studies. The following explores the critical micro-scale influence of particle morphology on mechanisms of microbially induced clogging. Spherical, non-spherical and angular particles were used as granular aggregates in permeating column experiments with the resulting permeability and calcium carbonate content of the treated aggregates examined. Microscopic examination (SEM) defines the features of the distribution of microbially precipitated calcium carbonate and the forms of clogging. The results show: (1) given a fixed duration of treatment, the calcium carbonate content for the spherical particle aggregate is significantly higher than that for near-spherical and angular particle aggregates; (2) for identical durations of treatment, the maximum permeability reduction occurs for angular particles (rather than for spherical particles with the highest carbonate content). This suggests that the microscopic distribution of calcium carbonate is significantly influenced by particle morphology, exerting a critical control in the effectiveness of clogging. SEM images indicate that the microbial calcium carbonate precipitates encapsulate the spherical particles as a near-uniform shell and occlude the pore space only by increasing the shell thickness. In contrast, the near-spherical and angular particles are only partially coated by a calcium carbonate film with scattered crystals of vaterite and calcite further clogging the void space. The polyhedral nature of the non-spherical particles tends to result in a slot-shaped pore structure which critically defines the hydraulic conductivity of the ensemble medium. As the microbial vaterite and calcite continue to accumulate on the particle surface, these slot-shaped pore structures become increasingly more tortuous – resulting in a noticeable reduction of permeability at a lower calcium carbonate content. 相似文献
12.
The most important feature of the distribution of the alkalinity and calcium in the Sea of Japan—the increase in the potential
alkalinity with depth under the conditions when the waters are supersaturated in relation to calcium carbonate—is considered.
It is demonstrated that this fact cannot be accounted for by the reaction of the formation-dissolution of calcium carbonate.
A new concept explaining the alkalinity distribution in the sea is proposed. According to it, the biological pump is the basic
process responsible for the alkalinity transport from the euphotic layer into the interior of the sea. Photosynthesis is the
driving force for this process. The role of the active element transporting the alkalinity is not calcium carbonate, as has
been claimed elsewhere, but extracellular polysaccharides (EPSs) produced by phytoplankton. EPSs bind to calcium and other
cations to form transparent exopolymer particles (TEPs). The proposed conception makes it possible to explain the following:
(a) the vertical flux of calcium carbonate that is independent of the super-saturation—undersaturation state of the ambient
water regarding calcium carbonate; (b) the existence of the calcium carbonate flux regardless of the nature of the plankton
skeletons; (c) the nonstoichiometric ratio between the alkalinity and calcium fluxes. 相似文献
13.
Jürgen Alheit 《Estuarine, Coastal and Shelf Science》1983,17(5):547-554
Harrington Sound, Bermuda, is a shallow subtropical lagoon with carbonate sediments. The most important fishes in this lagoon, in terms of biomass, are grunts (Haemulon aurolineatum, H. flavolineatum, H. sciurus) and a sea-bream (Diplodus bermudensis). These undertake diel feeding migrations from the shallow rocky zone towards the deeper sand and mud zones. When feeding on zoobenthos they cannot avoid swallowing carbonate sediment particles. These sediment particles pass through the alimentary canal of the fishes and are deposited again, after digestion of the food, as faeces in the shallow zones. Thus, the fishes transport the sediment in an unusual direction, from the deep to the shallow zones, in effect against the force of gravity. By recording the fish stock densities, digestion rates, and calcium carbonate content of fish stomach and guts, it was possible to estimate the amount of sediment transported by the fishes. In Harrington Sound, this amounts annually to 4530 kg calcium carbonate, 40% of which is deposited in the very shallow areas. The pH-values measured in fish stomachs seem to be acidic enough for the dissolution of carbonate sediment particles when transported by fishes. 相似文献
14.
《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(10):1653-1669
We find a diverse but increasing amount of evidence to suggest considerable dissolution of calcium carbonate, perhaps as much as 60–80%, in the upper 500–1000 m of the ocean, well above the chemical lysocline. The same biological processes that promote the rapid settling of carbonate particles (i.e. ingestion, digestion and egestion by zooplankton) as well as biologically mediated processes within flocculates and aggregates may be responsible – directly or indirectly – for much of this dissolution. The significance of shallow-water dissolution of carbonate particles necessitates further research into both its validity and, if true, specific causal mechanisms. 相似文献
15.
John Hedley 《Geo-Marine Letters》2012,32(2):173-182
The optical scattering properties of non-spherical calcium carbonate particles were modelled using the finite difference time
domain (FDTD) method. This algorithm is computationally expensive but an implementation running on a standard computer’s graphics
processing unit (GPU) provided up to 40 times speed increase and made feasible several thousand model runs for particles up
to size parameter 33 (4 μm for a wavelength of 376 nm in water). The model evaluates all coefficients of the single-particle
Mueller matrix and, when applied to spheres in this size range, compares closely to Mie theory. The modelled unpolarised and
polarised angular irradiance scattering from elongate calcium carbonate spicules displayed many differences from that of spheres
of equivalent volume. Scattering features were observed that are not immediately obvious consequences of spicule geometry.
The extinction efficiency of these particles is also less than that of spheres of equivalent volume. These results suggest
both potential consequences of the non-sphericity of particles on instrument calibration and radiative transfer modelling,
and opportunities for information extraction by polarimetry. 相似文献
16.
When biogenic particles of calcium carbonate and organic matter are formed or decomposed in sea water, calcium concentration, alkalinity and nitrate concentration are changed according to the following equation: ΔCa=0.5 ΔTA+0.63 ΔNO 3, where ΔCa, ΔTA and ΔNO 3 are the differences in calcium, alkalinity and nitrate concentration, respectively, between two waters. This relationship was pointed out in a previous paper of ours, and it holds well for data obtained from the North Pacific and the Japan Sea. Furthermore, in sea water containing little or no nutrients, the variations in calcium concentration and alkalinity are consistent with the variations expected from the formation and dissolution of calcium carbonate alone. 相似文献
17.
Sediment deposition and production in SE-Asia seagrass meadows 总被引：1，自引：0，他引：1
E. Gacia C. M. Duarte N. Marb J. Terrados H. Kennedy M. D. Fortes N. H. Tri 《Estuarine, Coastal and Shelf Science》2003,56(5-6):909-919
Seagrass meadows play an important role in the trapping and binding of particles in coastal sediments. Yet seagrass may also contribute to sediment production directly, through the deposition of detritus and also the deposition of the associated mineral particles. This study aims at estimating the contribution of different seagrass species growing across an extensive range of deposition to inorganic (carbonate and non-carbonate) and organic sediment production. Total daily deposition measured with sediment traps varied from 18.8 (±2.0) g DW m−2 d−1 in Silaqui (Philippines) to 681.1 (±102) g DW m−2 d−1 in Bay Tien (Vietnam). These measurements correspond to a single sampling event and represent sedimentation conditions during the dry season in SE-Asia coastal areas. Enhalus acoroides was the most common species in the seagrass meadows visited and, together with Thalassia hemprichii, was present at sites from low to very high deposition. Halodule uninervis and Cymodocea species were present in sites from low to medium deposition. The mineral load in seagrass leaves increased with age, and was high in E. acoroides because it had the largest and long-lived leaves (up to 417 mg calcium carbonate per leaf and 507 mg non-carbonate minerals per leaf) and low in H. uninervis with short-lived leaves (4 mg calcium carbonate per leaf and 2 mg non-carbonate minerals per leaf). In SE-Asia seagrass meadows non-carbonate minerals accumulate at slower rates than the production of calcium carbonate by the epiphytic community, consequently the final loads supported by fully grown leaves were, as average, lower than calcium carbonate loads. Our results show that organic and inorganic production of the seagrasses in SE-Asia represents a small contribution (maximum of 15%) of the materials sedimented on a daily base by the water column during the sampling period. The contribution of the carbonate fraction can be locally significant (i.e. 34% in Silaqui) in areas where the depositional flux is low, but is minor (<1%) in sites were siltation is significant (i.e. Umalagan and all the visited sites in Vietnam). 相似文献
18.
An investigation has been made of available data on the saturation state of seawater with respect to calcium carbonate and its possible significance for scale formation on Ocean Thermal Energy Conversion (OTEC) heat exchangers. Pertinent oceanographic data is lacking at or near potential OTEC sites for the calculation of the degree of saturation of seawater with respect to calcium carbonate. Consequently, only “extrapolated” saturation values can be used. These indicate that near surface seawater is probably supersaturated, with respect to the calcium carbonate phases calcite and aragonite, at all potential OTEC sites. The deep seawater that would be brought to the surface at the potential Atlantic Ocean sites is also likely to be supersaturated with respect to calcium carbonate. The deep seawater at the potential Pacific Ocean sites may be slightly undersaturated.The fact that OTEC heat exchangers will be operating in seawater, which is supersaturated with respect to calcium carbonate, means that if nucleation of calcite or aragonite occurs on the heat exchanger surfaces, significant growth rates of calcium carbonate scale may be expected. The potential for calcium carbonate nucleation is highest at cathodic metal surface locations, which are produced as the result of aluminum corrosion in seawater. Consequently, corrosion and scale formation may be closely related. What the possible effects of biofouling may be on this process are not known. 相似文献
19.
In this study, we test various parameters in deep-sea sediments (bulk sediment parameters and changes in microfossil abundances and preservation character) which are generally accepted as indicators of calcium carbonate dissolution. We investigate sediment material from station GeoB 1710-3 in the northern Cape Basin (eastern South Atlantic), 280 km away from the Namibian coast, well outside today’s coastal upwelling. As northern Benguela upwelling cells were displaced westward and periodically preceded the core location during the past 245 kyr (Volbers et al., submitted), GeoB 1710-3 sediments reflect these changes in upwelling productivity. Results of the most commonly used calcium carbonate dissolution proxies do not only monitor dissolution within these calcareous sediments but also reflect changes in upwelling intensity. Accordingly, these conventional proxy parameters misrepresent, to some extent, the extent of calcium carbonate dissolution. These results were verified by an independent dissolution proxy, the Globigerina bulloides dissolution index (BDX′) (Volbers and Henrich, submitted). The BDX′ is based on scanning electronic microscope ultrastructural investigation of planktonic foraminiferal tests and indicates persistent good carbonate preservation throughout the past 245 kyr, with the exception of one pronounced dissolution event at early oxygen isotopic stage (OIS) 6.
The early OIS 6 is characterized by calcium carbonate contents, sand contents, and planktonic foraminiferal concentrations all at their lowest levels for the last 245 kyr. At the same time, the ratio of radiolarian to planktonic foraminiferal abundances and the ratio of benthic to planktonic foraminiferal tests are strongly increased, as are the rain ratio, the fragmentation index, and the BDX′. The sedimentary calcite lysocline rose above the core position and GeoB 1710-3 sediments were heavily altered, as attested to by the unusual accumulation of pellets, aggregates, sponge spicules, radiolaria, benthic foraminifera, and planktonic foraminiferal assemblages.
Solely the early OIS 6 dissolution event altered the coarse fraction intensely, and is therefore reflected by all conventional calcium carbonate preservation proxies and the BDX′. We attribute the more than 1000 m rise of the sedimentary calcite lysocline to the combination of two processes: (a) a prominent change in the deep-water mass distribution within the South Atlantic and (b) intense degradation of organic material within the sediment (preserved as maximum total organic carbon content) creating microenvironments favorable for calcium carbonate dissolution. 相似文献
20.
前处理步骤与方法对风成红粘土粒度测量的影响 总被引：37，自引：1，他引：37
中国北方晚第三纪红粘土堆积为研究古气候与古环境提供了很好的地质记录,其粒度测量作为一个重要的代用指标被广泛应用。粒度测量结果受到前处理方法的影响,但是,现在各个实验室的前处理方法还不一致,这就为粒度数据分析和古气候古环境解释带来了困难。在黄土高原从北到南选择了3个具有代表性的红粘土剖面,对每个剖面从下向上取10块样品总计得到30块样品,对每个样品用不同的前处理方法与步骤（包括化学分离石英的方法）处理后用激光粒度仪进行颗粒测量。结果表明,前处理方法与步骤可以使同一个样品粒度参数发生几倍甚至于二十几倍的变化。综合理论和经验分析,推荐了一种较好的进行风尘堆积粒度测量的前处理方法（正文中方法C）。化学分离的纯石英的粒度分布比本文推荐的方法处理同一个样品的粒度结果偏粗,表明在提纯石英的过程中较细的不稳定矿物已经被剔除。 相似文献