海底地震观测系统

基于OHP计划研制了几种类型的海底地震观测系统。本文将介绍这些观测系统，研制的关键是使这个宽频带系统能够长期使用，并且轻便、稳定和耐用。     

LONGITUDINAL DISPERSION IN SEDIMENT-LADEN OPEN CHANNEL FLOWS

Laboratory experiments on longitudinal dispersion in clear-water and sediment-laden open channel flows are reported. Data from these experiments and those available from previous studies indicate that the suspended sediment present in the flow affects the longitudinal dispersion process. The observed velocity distributions over the depth of sediment-laden flows indicate that the velocity deviates from the mean velocity more in sediment-laden flows than in clear-water flows. The velocity distributions over the cross section and secondary flow in the channel are also expected to be altereddue to the presence of suspended sediments in the flow. For these reasons, more dispersion is found in sediment-laden flows than in corresponding clear-water flows. A predictor for the dispersion coefficient in sediment-laden flows is proposed.     

GEOCHEMICAL RECOGNITION OF SPILLED SEDIMENTS USED IN NUMERICAL MODEL VALIDATION

A fixed link (tunnel and bridge, in total 16 km) was constructed between Sweden and Denmark during 1995-2000. As part of the work, approximately 16 million tonnes of seabed materials (limestone and clay till) were dredged, and about 0.6 million tonnes of these were spilled in the water. Modelling of the spreading and sedimentation of the spilled sediments took place as part of the environmental monitoring of the construction activities. In order to verify the results of the numerical modelling of sediment spreading and sedimentation, a new method with the purpose of distinguishing between the spilled sediments and the naturally occurring sediments was developed. Because the spilled sediments tend to accumulate at the seabed in areas with natural sediments of the same size, it is difficult to separate these based purely on the physical properties. The new method is based on the geo-chemical differences between the natural sediment in the area and the spill. The basic propertiesused are the higher content of calcium carbonate material in the spill as compared to the natural sediments and the higher Ca/Sr ratio in the spill compared to shell fragments dominating the natural calcium carbonate deposition in the area. The reason for these differences is that carbonate derived from recent shell debris can be discriminated from Danien limestone, which is the material in which the majority of the dredging took place, on the basis of the Ca/Sr ratio being 488 in Danien Limestone and 237 in shell debris. The geochemical recognition of the origin of the sediments proved useful in separating the spilled from the naturally occurring sediments. Without this separation, validation of the modelling of accumulation of spilled sediments would not have been possible. The method has general validity and can be used in many situations where the origin of a given sediment is sought.     

FLOW FIELD IN SCOURED ZONE OF CHANNEL CONTRACTIONS

Experiments were conducted in a laboratory flume to measure the two-dimensional turbulent flow field in the scoured zone of channel contractions under a clear-water scour condition. The Acoustic Doppler Velocimeter (ADV) was used to detect the flow field at different vertical lines along the centerline of uncontracted (main channel) and contracted zones of the channel. The distributions of time-averaged velocity components, turbulent intensity, turbulent kinetic energy, and Reynolds stresses are presented in nondimensional graphical form. The bed shear stresses are computed from the measured Reynolds stresses being in threshold condition within the zone of contraction where bed was scoured. The data presented in this paper would be useful to the investigators for the development of kinematic flow model and morphological model of scour at a channel or river contraction.     

Studies of a contaminated brackish marsh in the Hackensack Meadowlands of Northeastern New Jersey: benthic communities and metal contamination

Cores taken from 16 stations within Eight Day Swamp, a highly contaminated marsh in the Hackensack Meadowlands, were analyzed for metal concentrations and for benthic community structure. Metal levels were compared with the benchmark ERM values, and expressed in terms of toxic units. Mercury was the most important metal in all the samples in terms of its contribution to the total toxic units. The overall abundance and taxa richness in the benthic community were associated with the height of the location relative to the tidal cycle, but were generally not significantly correlated with metal concentrations at the sites. Ordination of the communities showed that the communities that were low-lying (on the mudflat) were most similar to one another, and those that were higher up on the marsh were most similar to one another. However, diversity indices (Shannon-Wiener H' and Simpson's) were significantly associated with concentrations of the metals (except As) and with the sum of the toxic units at a station.     

Comparison of the acid-base responses to CO2 and acidification in Japanese flounder (Paralichthys olivaceus)

To investigate whether the biological toxicity of aquatic hypercapnia is due to the direct effects of CO2 or to the effects of acidification of seawater by CO2, the Japanese flounder (Paralichthys olivaceus) was subjected to seawater equilibrated with a gas mixture of air containing 5% CO2 (pH 6.18) or seawater acidified to the same pH with 1 N H2SO4. All the fish died within 72 h in the CO2 exposure group, whereas no mortality occurred in the acid group. Acid-base parameters as well as plasma ion concentrations were severely perturbed in the CO2 exposure group, whereas they were minimally affected in the acid group. These results clearly demonstrate that the mortality in the CO2 group is a direct result of the elevated levels of dissolved CO2 and not to the effects of the reduced water pH.     

金在土壤中的存在形式及其预测意义

本文介绍了应用已知方法分离土壤（金含量由克拉克值水平到够矿石品位）中各种存在形式的金。查明金以自然金粒、矿物残留物和腐黑物的混入物、金富里酸和金胡敏酸络合物以及AuCI^-、Au(CIOH)^-、Au(OH)2^-类无机络合物等形式存在于土壤中，对隐伏金矿床来说，金在土壤中的各种存在形式呈带状分布，建议在为预测目的而解释弱地球化学异常时予以利用。     

在高温压下的循环溶液内矿物溶解作用化学动力学

<正> 作者重点分析在高温压的循环流动系统内,矿物溶解作用的化学动力学方面新实验结果。样品袋由金属网做成,内装矿物颗粒,悬在反应釜内。液体泵驱动水(或NaCl溶液)经过样袋与矿物发生反应,然后再经管道流出来。连续输入水,连续对输出溶液取样,并分析反应产物。流动系统可以近似地理理解为一个CSTR反应器——连续搅拌筒反应器。流动体系近似地划分为三部分:流体经过金属网部分——近似是一个柱塞流系统;但其上其下可近似于CSTR反应器,即平均停顿时间,近似看作空间时间。     

非均匀孔隙介质中的弥散作用——(2)层状二维空间间断系统的预报

第一部分(Plumb和whitaker,本期)提出的闭合法对层状系统和二维空间间断系统进行了求解,其中我们所说的w和η区形成了在空间分布的孔隙介质。闭合法问题的解使我们得到确定大范围弥散张量所需要的数据和解大范围弥散方程所需要的另外一些参数。层状系统的理论结果展示的纵向弥散系数与利用室内视均质孔隙介质根据传统关系式所得到的纵向弥散系数相比要增大几个数量级。对于这种情况的研究,混合时间—空间系数看来是重要的,而且能够引起弥散系数增大的条件该系数值也增大。二维空间间断系统的结果与实验观测是一致的,而且我们发现非均匀性的规模和两个区之间的水力传导系数的差别对大范围弥散张量具有重要影响。正如层状介质情况那样,时间—空间混合导数(不对称向量)的系数的预测值表明该项可能是非均质孔隙介质的物质运移预报的一个重要的因子。