共查询到18条相似文献，搜索用时 78 毫秒
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水质数学模拟扩散系数大亚湾现场求取实验，采用示踪剂扩散实验法，示踪剂扩散实验的目的，在于了解水流运动的稀释扩散能力，根据示踪剂运动轨迹和浓度分布，求出水平纵向扩散系数和横向扩散系数，供水质数学模拟应用。 相似文献
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水质扩散系数在伶仃洋水域水体交换中的影响分析 总被引：1，自引：0，他引：1
选取珠江河口伶仃洋水域为例,建立了贴体曲线坐标系下的二维珠江河口水流数学模型,并采用纯隐格式的混合有限分析法对数学模型进行了离散和求解。在对模型验证的基础上,针对珠江河口伶仃洋水域中的水质扩散系数选取问题进行了分析和探讨。研究表明,主潮汐通道水体的置换率基本不受扩散系数取值的影响,扩散系数的影响主要体现在远离伶仃洋主潮汐通道和示踪剂浓度分界线的水域,并初步推荐了该水域示踪剂扩散系数的取值范围。 相似文献
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象山港水交换数值研究──Ⅰ.对流-扩散型的水交换模式 总被引：9，自引：2，他引：7
以溶解态的保守性物质作为湾内水的示踪剂,建立了对流－扩散型的海湾水交换数值模型。数值模型使用参数化的方法把重力环流和潮振荡的垂向剪切作用的水平混合效应包纳在水平二维的示踪剂对流－扩散方程中。在空间网距较小时,模型的稳定性和守恒性均可满足海湾水交换研究的需要。 相似文献
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《海洋湖沼通报》2015,(3)
近年来,由于人类各种活动的增加,使得湿地中陆源性溶解有机质(DOM)的含量在湿地总DOM中所占的比重不断增加,日益引起人们的关注。木质素为陆地维管束植物细胞壁的特有组分,也是湿地陆源性DOM的特有组分,在湿地环境中具有较高的化学稳定性和抗微生物降解能力,因此成为湿地中一种良好的陆源性示踪剂。利用木质素的这种独特性和稳定性,对湿地中陆源性DOM进行辨识已经成为现代研究的一个方向。本文主要对木质素作为陆源性DOM示踪剂的指示原理以及木质素在湿地陆源性DOM辨识中的具体应用进行了综述。总结提出了木质素作为陆源性DOM的示踪剂在湿地陆源性DOM识别研究中存在的问题,并对其研究前景进行了展望,为木质素在湿地中陆源性DOM的辨识提供理论参考。 相似文献
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为研究感潮河口的水力特征及溶质扩散规律，通过布放仪器监测水文参数，分析研究区的水力特征；采用荧光染色剂罗丹明B作为示踪剂开展现场示踪实验，研究示踪剂的扩散规律；基于Delft 3D模型的水动力模块与示踪模块相耦合，对研究区的动力场和示踪结果进行模拟，获取了小清河口的水平湍流扩散系数。结果表明：调查期间（非汛期）小清河口的水力条件主要受潮汐控制，潮汐对河口下游的作用更明显。由于河流径流量较小，在潮汐作用下，示踪剂从小清河口向海传输的速度较慢，导致示踪剂在河口长时间滞留。相关性分析（R2）和均方根误差（RMSE）结果表明示踪剂迁移模拟结果的可靠性高。基于本研究得到小清河口的水平湍流扩散系数（Dξ，η）为6t0.12 m2/s。本研究可为小清河口以及同类河口中水平湍流扩散系数的估值提供参考，对于评价污染物在同类河口中的传输行为具有指导意义。 相似文献
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海洋放射化学是研究放射性核素(或元素)在海洋中变化规律的一门学科。它的主要内容是研究天然和人工放射性核素(或元素)及放射性示踪剂(也称示踪原子或示踪剂等)在海洋学中的应用。它的研究首先是从1908年发现海底沉积物中含有镭开始的。而海洋中人工放射性核素的研究,则开始于二十世纪四十年代。五十年代后,由于美、苏等国不断进行各 相似文献
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本文报道了示踪剂罗丹明B在青岛外海近岸海域中瞬时点源扩散试验情况;描述了罗丹明B在海洋表层的平面分布及其在深层的垂直分布特征;认为青岛外海近岸海域扩散能力较强。 相似文献
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为了研究含油多孔介质的二维水动力弥散特性,控制砂土中柴油和机油含油率为0、1%、2%,作为供试的含油多孔介质,采用自己设计的二维水动力弥散试验装置测定示踪剂(氯化钙)的穿透曲线,并定量确定了含油砂土的有效孔隙度、纵向弥散度、横向弥散度以及砂土中孔隙水的流速。试验结果表明,有效孔隙度随石油含量的增加而减小,而且含柴油砂土的有效孔隙度减小比含机油砂土更加显著;在纵向上,示踪剂浓度峰值的到达时间和峰值浓度的大小主要取决于孔隙水流速的大小,孔隙水流速越大,示踪剂达到浓度峰值的时间越短,且峰值浓度越大;含机油砂土的纵向弥散度小于清洁砂土,而含柴油砂土的纵向弥散度大于清洁砂土;不同含油率砂土的纵向弥散度变化范围为0.133～0.370cm,横向弥散度变化范围为9.83×10-3～4.64×10-2 cm,纵向弥散度均大于其横向弥散度。 相似文献
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本文研究了硫氰酸汞铵沉淀海水中。~(60)Co的条件,并以放射性。~(60)Co及罗丹明B为示踪剂、硫氰酸汞铵沉淀、低本底仪测量~(60)Co β放射性的方法,对青岛某海区海水稀释因子作了测定。 相似文献
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Zeng’an Deng Jiye Jin Fengying Ji Feng Zhang Xiaoyi Jiang Wei Wang 《Marine Geodesy》2013,36(1):109-122
Tracer diffusion is an important issue in ocean modeling, and isoneutral slope is key to parameterization of tracer diffusion in the ocean interior when using the isoneutral/dianeutral scheme. In this study, multiyear mean temperature, salinity, and pressure-gridded products that cover the upper 2000 m of the global ocean are created by employing all the Argo float observations up to date. Comparison with WOA09 data indicates that Argo temperature and salinity depict the reality well. Based on the reliable Argo gridded products, the in situ density fields are calculated. Then isoneutral slope in the ocean interior deep to 2000 m was determined by using the Argo-derived density. Taking advantage of isoneutral slope, therefore, diffusion tensor as well as isoneutral tracer diffusion flux can be obtained in combination of the tracer diffusion coefficient. The aim of this work is to propose a procedure to estimate the isoneutral slope using Argo observations and to offer new isoneutral slope-gridded products in the hope of further facilitating the parameterization of isoneutral tracer diffusion in geopotential (Z-coordinate) ocean models. 相似文献
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《Ocean Modelling》1999,1(1):1-15
In regions of sloping isopycnals, isopycnal mixing acting in conjunction with biological cycling can produce patterns in the nutrient field which have negative values of tracer in light water and unrealistically large values of tracer in dense water. Under certain circumstances, these patterns can start to grow unstably. This paper discusses why such behavior occurs. Using a simple four-box model, it demonstrates that the instability appears when the isopycnal slopes exceed the grid aspect ratio (Δz/Δx). In contrast to other well known instabilities of the CFL type, this instability does not depend on the time step or time-stepping scheme. Instead it arises from a fundamental incompatibility between two requirements for isopycnal mixing schemes, namely that they should produce no net flux of passive tracer across an isopycnal and everywhere reduce tracer extrema. In order to guarantee no net flux of tracer across an isopycnal, some upgradient fluxes across certain parts of an isopycnal are required to balance downgradient fluxes across other parts of the isopycnal. However, these upgradient fluxes can cause local maxima in the nutrient field to become self-reinforcing. Although this is less of a problem in larger domains, there is still a strong tendency for isopycnal mixing to overconcentrate tracer in the dense water. The introduction of eddy-induced advection is shown to be capable of counteracting the upgradient fluxes of nutrient which cause problems, stabilizing the solution. The issue is not simply a numerical curiosity. When used in a GCM, different parameterizations of eddy mixing result in noticeably different distributions of nutrient and large differences in biological production. While much of this is attributable to differences in convection and circulation, the numerical errors described here may also play an important role in runs with isopycnal mixing alone. 相似文献
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The response time of the large-scale oceanic circulation due to freshwater perturbations is investigated with models of different complexity. A three-dimensional ocean general circulation model (OGCM) and a zonally averaged ocean model are employed. In order to distinguish advection and diffusion from fast baroclinic processes (e.g. waves in the OGCM) a color tracer is injected at the same time and location as the freshwater discharges. In spite of the inability of the zonally averaged model to represent wave processes in a realistic way similarities with the OGCM are found for the propagation patterns of density anomalies and of color tracer. In the OGCM as well as in the zonally averaged model, density anomalies propagate faster than anomalies of a passive color tracer in the case of vertical density stratification. The progression of density anomalies leads to changes of the oceanic circulation, and both oceanic models exhibit circulation changes in areas distant from the discharge places long before the passively entrained color tracer has reached these regions. The fact that a zonally averaged model simulates baroclinic processes faster than advection even if internal gravity waves are not represented due to neglected acceleration terms, is clarified with a conceptual box model. 相似文献
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The aim of this study was to identify a method for determining the number of tracer particles required to define the mean longshore transport distance of indigenous littoral shingle with a particular level of precision. A method is presented which can be applied to existing tracer data to determine both the precision of the measurements collected and the number of tracers required to achieve a particular level of precision. The method, which utilises well established statistical relationships, is demonstrated by applying it to archive tracer data. The study demonstrates the sensitivity of the number of tracers to the variance of the transport distances of indigenous particles at the site and the precision with which the investigator wishes to define the mean. It is anticipated that application of the method by other practitioners, in the future, will allow a dataset to develop which can be used alongside the method presented here to allow the number of tracers required for a study to be estimated prior to entering the field. Results are presented to initiate the development of this dataset and a “look-up chart” derived using the method is given to aid its application. 相似文献
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A modelling study of residence time in a macro-tidal estuary 总被引：2，自引：0，他引：2
This paper outlines a numerical modelling study to predict the average residence time of a conservative tracer in a macro-tidal estuary, namely the Mersey Estuary, UK. An integrated hydrodynamic-dispersion model was used to predict the average residence time in the estuary for various tidal level and freshwater discharge conditions. The numerical model was verified against six sets of field measured hydrodynamic data, with the model-predicted water elevations and salinity levels generally agreeing well with the field measurements. The numerical model results show that in the Mersey Estuary both the tidal level and river discharge affect significantly the predicted average residence time. The value of the average residence time is also shown to be closely linked to the intensity of the residual tidal current. This is due to the fact that a large proportion of the Upper and Inner Estuary dries out during low tides, thus a significant amount of the tracer material is transported through the deep channels. An increase in the freshwater discharge causes a considerable increase in the intensity of the residual current along the main channels and thus a reduction in the average residence time. The predicted overall tracer residence time for the whole estuary is relatively short for a relatively large estuary, ranging from less than 1 day to 4 days for various tidal level and freshwater flow combinations. When the tidal range and freshwater discharge are both small, then the local tracer residence time in the upper part of the estuary can be significantly longer than the values predicted for the middle and lower reaches of the estuary. 相似文献
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In situ 《Estuarine, Coastal and Shelf Science》1999,49(6):813
Laboratory and in situ experiments were performed to assess the use of bromide as a tracer forin situ studies of benthic solute exchange. Bromide was used in the benthic chamber lander ‘ Elinor ’ for flux measurements in coastal sediments of the German Bight, Kiel Bight and Skagerrak (28–700 m water depth). Tracer and total oxygen uptake were monitored simultaneously in the same chamber incubation. Concurrently, in situ oxygen micro-profiles were recorded at the same locations by the profiling lander ‘ Profilur ’. Deployment in an anoxic silt (Kiel Bight) confirmed that in the absence of bioturbation and advection, tracer transport into the sediment was driven solely by molecular diffusion. This flux could be well described by a simple box model accounting for molecular diffusion only. In oxic sediments (German Bight and Skagerrak) enhanced exchange of bromide tracer due to bioirrigation parallelled enhanced oxygen uptake equivalent to a 4-fold molecular diffusive flux. Our experiments showed that incubations can be short. Depending on irrigation activity of the fauna, however, incubation length should exceed 3 h in order to provide a useful data base for flux calculations. The method demonstrating caveats is discussed and indicate possible improvements. The results show how the bromide tracer addition can be used as a tool for determining solute fluxes exceeding diffusive flux in benthic chamber incubations. 相似文献
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P.R. Jackson J.R. Ledwell A.M. Thurnherr 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(1):37-52
On 12 November 2006, 3 kg of sulfur hexafluoride were released in a 1.2 km long streak in the axial summit trough of the East Pacific Rise at 9°30′N to study how circulation and mixing affect larval dispersion. The first half of a tracer survey performed approximately 40 days after the injection found a small percentage of the tracer on the ridge axis between 9°30′N and 10°10′N, with the main concentration near 9°50′N, a site of many active hydrothermal vents. These observations provide evidence of larval connectivity between vent sites on the ridge. The latter half of the survey detected the primary patch of tracer west of the ridge and just south of the Lamont Seamounts, as a majority of the tracer had been transported off the ridge. However, by the end of the survey, the eastern edge of this patch was transported back to within 10 km of the ridge crest at 9°50′N by a reversal in the subinertial flow, suggesting another pathway for larvae between points along the ridge. Both the horizontal and vertical distributions of the tracer were complex and were likely heavily influenced by topography and vents in the area. Elevated tracer concentrations within the axial summit trough and an adjacent depression on the upper ridge flank suggest that tracers may be detained in such depressions. Correlated tracer/turbidity profiles provide direct evidence of entrainment of the tracer into vent plumes from 9°30′N to 10°N. A comparison of the vertical tracer inventory with neutral density vent-plume observations suggests that on the order of 10% of the tracer injected was entrained into vent plumes near the injection site. The results imply that effluent from diffuse hydrothermal sources and larvae of hydrothermal vent fauna can be entrained in significant quantities into plumes from discrete sources and dispersed in the neutrally buoyant plumes. 相似文献
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Longshore drift estimation using fluorescent tracers: New insights from an experiment at Comporta Beach, Portugal 总被引：1，自引：0，他引：1
Ana Silva Rui Taborda Aurora Rodrigues Joo Duarte Joo Cascalho 《Marine Geology》2007,240(1-4):137-150
A fluorescent sand-tracer experiment was performed at Comporta Beach (Portugal) with the aim of acquiring longshore sediment transport data on a reflective beach, the optimization of field and laboratory tracer procedures and the improvement of the conceptual model used to support tracer data interpretation.
The field experiment was performed on a mesotidal reflective beach face in low energetic conditions (significant wave height between 0.4 and 0.5 m). Two different colour tracers (orange and blue) were injected at low tide and sampled in the two subsequent low tides using a high resolution 3D grid extending 450 m alongshore and 30 m cross-shore. Marked sand was detected using an automatic digital image processing system developed in the scope of the present experiment.
Results for the two colour tracers show a remarkable coherence, with high recovery rates attesting data validity. Sand tracer displayed a high advection velocity, but with distinct vertical distribution patterns in the two tides: in the first tide there was a clear decrease in tracer advection velocity with depth while in the second tide, the tracer exhibited an almost uniform vertical velocity distribution. This differing behaviour suggests that, in the first tide, the tracer had not reached equilibrium within the transport system, pointing to a considerable time lag between injection and complete mixing. This issue has important implications for the interpretation of tracer data, indicating that short term tracer experiments tend to overestimate transport rates. In this work, therefore, longshore estimates were based on tracer results obtained during the second tide.
The estimated total longshore transport rate at Comporta Beach was 2 × 10− 3 m3/s, more than four times larger than predicted using standard empirical longshore formulas. This discrepancy, which results from the unusually large active moving layer observed during the experiment, confirms the idea that most common longshore transport equations under-estimate total sediment transport in plunging/surging waves. 相似文献