Sensitivity of plume dynamics to the parameterization of vertical mixing

A three‐dimensional primitive equation, baroclinic numerical model incorporating a range of turbulence closure schemes is used to investigate the effects of vertical diffusion of momentum and density upon the spread of a freshwater plume, with particular reference to the Ebro plume. Initial calculations show that there are some differences in the horizontal spread and vertical mixing of the plume when diffusion coefficients are computed from a two‐equation turbulence energy model compared with a one‐equation model. To understand results from the turbulence energy models, the sensitivity of the plume dynamics to variations in the coefficient of vertical eddy viscosity and diffusivity is also considered, with increases in these parameters having a significant effect upon the cross‐shore and along‐shore spread of the plume. Also, increasing these parameters changes the plume characteristics from supercritical to subcritical and reduces the occurrence of meandering and baroclinic instability along the plume's off‐shore edge. However, differences in the southerly spread (the direction of Kelvin wave propagation in the model) of the plume (although not its northerly spread) produced by changes in diffusion coefficients are small compared with the influence of changes in the bottom slope, upon the along‐shore southerly spread of the plume, which moves in the direction of Kelvin wave propagation in the near coastal region. Results from the series of calculations are used as a guide in experimental design, with reference to a planned experiment in the Ebro region involving a coastal HF Radar deployment, as well as off‐shore measurements. Calculations suggest that surface current measurements from a coastal HF Radar, together with a detailed survey of the density field associated with the plume, may be an appropriate, although indirect, means of determining suitable mixing coefficients to use in plume discharge problems. Detailed measurements of water depth variation will also be required. Copyright © 1999 John Wiley & Sons, Ltd.     

交汇、分流河道洪水演进模型及其应用

通过引入水深连接方程,耦合了干、支流河道的水流运动,给出了它们的流量分配关系,建立了交汇、分流河道洪水演进模型．对交汇河道中水流顶托作用随河道参数的变化规律进行了研究．分析了干、支流洪峰遭遇现象,指出干流和支流的洪峰遭遇是1998年长江大洪水干流高洪水位的重要原因之一．并定性解释长江干流荆江河段的裁弯取直和长江分流河道的淤积对河道水流的影响．     

钱塘江源头开化县生态建设探讨

钱塘江源头城市开化县复杂的地貌形态及多样的山地小气候孕育了丰富多样的生物资源。根据生态环境现状,提出了突出生物多样性保护、加强生态林业、生态工业、生态农业、生态城镇、生态旅游业等生态建设的思路。     

阳离子金黄锑染料的合成及其光谱研究

本文以阳离子金黄三氯化锑为原料,合成了阳离子金黄染料,并对该产物进行了锑含量的测定,测定了产物的可见光吸收光谱和红外光谱。     

阳离子金黄铋染料的合成及其光谱研究

本文以阳离子金黄和硝酸铋为原料合成了阳离子金黄铋染料,并对产物进行了铋含量的测定,测定了产物的可见光吸收光谱,红外光谱。     

Flood control and shrinkage in the Haihe River Mouth

Because of overusing water resources in the upper and middle reaches of the Haihe Basin, less and less water flows to the river mouth. The Haihe River flow is cut off in most time of the seasons, sediment deposited in the river mouth channel is rarely scoured away, and many of the river mouth channels have been shrinking quickly. The discharge capacity of the channel is consequently reduced greatly, which results in more and more serious flood hazard. Many tide gates have been built for storing fresh water and preventing the salty and turbid water. The channel downstream of the gate is silting up and people have to dredge the channel every year before the flood season. This paper studies the laws of the siltation and strategies controlling channel shrinkage. The strategies are digger dredging, trailer dredging, scouring with pumping water or storing tidal water, building double guiding dikes and building a new gate. Comparison of various strategies is performed, suggesting the most effective strategy con     

The change of characteristics of tidal wave in the Changjiang River mouth area since the post-glacial transgression maximum

During the period of the post-glacial transgression maximum (PGTM), there was a huge trumpet estuary in the modern Changjiang River Delta area. The location and the shape of the Paleo-Changjiang River Estuary (PCRE) were much different from those of the present Chang-Jiang River Estuary. The study on the change of characteristics of tidal wave in the Changjiang River mouth area since the PGTM can help to understand better the dynamic development of the Changjiang River Delta. The course curves of tidal level and tidal current velocity during a single tidal cycle for 35 points are calculated, and characteristics of tidal waves in the PCRE and its adjacent area are compared with those of tidal waves in the modern Changjiang River mouth area. The results show that the tidal waves within the PCRE and in its adjacent area during the period of the PGTM belonged to standing wave or a mixture of standing wave and progressive wave. Since then, the tidal wave in the Changjiang River mouth become gradually to be pr     

Estimation of dissolved inorganic nutrients fluxes from the Changjiang River into estuary

Because the estuary acts as either a trap or a source or both for nutrient elements and will modify greatly the riverine transport to the ocean, it is necessary to calculate the flux from river into estuary and that from estuary into sea, respectively. The present work aims to use a long-term record of nutrients concentrations and runoff discharges on H.e Datong section (625 km inland from the Changjiang River mouth) to identify the variability of nutrients concentrations and to estimate nutrients fluxes from the Changjiang River into the estuary.     

珠江三角洲蔬菜中的锰

珠江三角洲蔬菜中锰的含量范围为５．０１＊１０＾－６－３４６．８＊１０＾－６,平均６２．９１＊１０＾－６,大多数蔬菜中锰的含量为２０＊１０＾－６－７０＊１０＾－６,叶菜类锰的平均含量为６９．２０＊１０＾－６,头菜类平均为１９．８５＊１０＾－６,果蔬菜类,花菜类平均为３８．９０＊１０＾－６。蔬菜中锰的含量与蔬菜种类和土壤性质有密切关系。     

HR-ICP-MS研究丰水期黄河甘宁蒙段表层沉积物中重金属的形态分析与污染评价

为连续、系统地研究不同年份丰水期黄河甘宁蒙段表层沉积物中重金属的含量、污染状况和潜在生态风险,在前期工作的基础上,采用三级四步提取法(BCR)和高分辨电感耦合等离子体质谱(HR-ICP-MS)对2012年丰水期黄河甘宁蒙段包头浮桥(S2)、石嘴山陶乐镇(S6)和乌金峡(S9)等10个采样点水体表层沉积物中Cd,Pb,Cr,Ni,Cu,V,Co,Zn和Mn九种重金属元素进行含量测定和形态分析,并对重金属元素的污染作出评价。结果表明：各重金属元素在每个采样点分布趋势相同,平均含量顺序依次为：Mn＞V＞Zn＞Cr＞Cu＞Ni＞Pb＞Co＞Cd;表层沉积物中重金属主要以残渣态形式存在,表明重金属的生物有效性低,对环境影响较小;地积累指数法 (I_geo) 的评价结果显示Cd元素的I_geo值最高,对环境污染程度较高,其余元素对环境影响较小,其中Mn元素影响最小;富集因子法(EF)评价结果表明,Cd和Cu元素在某些采样点表现为显著富集,尤其是Cd在S5点处EF值高达4.69,表明该点处Cd受人类活动影响较为明显,其余元素均为非富集元素,这与I_geo评价结果吻合;潜在生态风险指数法(RI)表明,黄河甘宁蒙段S1,S2和S5点的RI值在150~300之间,为中等危害范畴,其余各采样点RI值均小于150,为轻微危害。研究结果为相关部门提供可信的实验数据和理论依据,也为建立该河段泥沙-污染物输移数学模型和系统研究持久性有毒污染物迁移转化规律及环境评价提供技术支撑。