A preliminary study on fingerprinting approach in marine sediment dynamics with the rare earth elements

Locating the quantitized natural sediment fingerprints is an important work for marine sediment dynamics study.The total of 146 sediment samples were collected from the Shelf of the East China Sea and five rivers,including Huanghe (Yellow),Changjiang (Yangtze),Qiantang,Ou and Min River.The sediment grain size and the contents of rare earth elements (REEs) were measured with laser particle size analyzer and ICP-MS technology.The results show that absolute REE content (ΣREE) and the concentration ratio of light REEs to heavy REEs (L/HREE) are different in the sediments among those rivers.There are higher REE contents in being less than 2 m and 2–31 μm fractions in the Changjiang Estuary surface sediments.The REE contents of bulk sediment are dominated by the corresponding values of those leading size-fractions.REE of sediment is higher close to the estuaries and declines seaward on the inner shelf of the East China Sea (ECS).The L/HREE ratio has a tendency of increase southward from 28 ? N.Hydrodynamic conditions plays a predominate role on spacial distributions of the surficial sediment’s REE parameters.In some situations,the currents tend to remove the coarser light grains from initial populations,as well as the deposit of the finer heavy mineral grains.In other situations,the currents will change the ratio of sediment constituents,such as ratio between silts and clays in the sediments.As a result,the various values of REE or L/HREE ratio in different bulk sediments are more affected by the change of size-fractions than source location.Under the long-term stable hydrodynamic environment,i.e.,the East China Sea Shelf,new sediment transport model based on the size and density gradation concept may help to understand the spatial distribution patterns of REE parameters.     

稀土元素作为示踪标记在海洋沉积动力学中应用前景的初步探讨

根据对长江等5条河流和东海陆架区总计146个沉积物样品的稀土元素和粒度分析结果,借助统计学方法,讨论了河流和东海近岸沉积物稀土元素分布格局的形成因素及其对沉积动力作用的响应,结果表明,各河流沉积物在稀土元素总量和轻重稀土分异等参数上有差异;在长江口沉积物中稀土元素在小于2和2~31μm粒级中较富集,全岩稀土元素含量受物质组成占优的粒级控制;在东海陆架研究区稀土元素含量由岸向海有减小的趋势,在河口附近相对较高,轻重稀土分异自28°N向南有增大的趋势。     

削弱水分影响的潮滩表层沉积物遥感分类方法研究

潮滩沉积物中的水分掩盖了沉积物本身的光谱信息,不利于沉积物遥感分类。利用江苏大丰潮滩沉积物在不同含水量下的398条实测光谱曲线数据,基于线性光谱分解方法定量化分析了沉积物光谱对含水量变化的响应,建立削弱水分影响的潮滩表层沉积物组分(砂、粉砂、黏土)含量反演模型,应用于Hyperion高光谱遥感影像,获得沉积物组分的空间分布,并结合Shepard三角分类法实现了潮滩表层沉积物的自动分类。研究结果表明:(1)当沉积物含水量增加时,沉积物光谱中水分权重以含水量的2倍速率增加,含水量大于25%,则水分对光谱的影响占主导作用;(2)2 143 nm波段反射率对沉积物的含水量变化敏感,利用2 143 nm波段反射率进行潮滩沉积物的含水量反演,模型拟合度r2可达0.81;(3)983,1 134 nm波段反射率对沉积物组分含量反演敏感,将含水量与沉积物组分敏感波段一起建立多元线性回归方程,可有效削弱水分的影响,适用于高含水量潮滩区的沉积物组分含量反演;(4)将组分反演结果结合Shepard分类,可实现潮滩沉积物分类,得到潮滩沉积物类型的空间分布特征,分类精度为75.93%,Kappa系数为0.6。     

海洋沉积物重金属研究中的晶粒度与粒度效应

本文通过理论估算及实验数据验证，发现6/a（a为晶粒粒径）可以很好地表示晶粒的比表面积。结合吸附理论模式讨论发现参考元素Al、Li等的粒度效应和重金属的粒度效应有着本质上的区别；海洋自生矿物必须考虑到晶粒度效应，在陆源碎屑对重金属吸附的粒度效应校正中粒度可代替晶粒度；重金属含量随粒度变化的曲线为双曲线关系，在实际工作中应该重点分析粒度＜3μm的颗粒。     

悬浮泥沙含量与电导率关系及其影响因素的实验研究

为了寻求一种简单、快速、连续测定悬浮泥沙含量的方法,以高含沙量海区黄河口泥沙为研究对象,利用电导率仪测定了不同悬浮泥沙含量水体的电导率.前期实验结果已经证明悬浮泥沙含量与电导率之间有很好的线性关系.在此基础上扩大研究范围,并对影响悬浮泥沙含量与电导率关系的因素进行定量分析,结果表明,盐度、温度、颗粒粒径对电导率具有一定...     

悬浮泥沙含量与电导率关系及其影响因素的实验研究

为了寻求一种简单、快速、连续测定悬浮泥沙含量的方法,以高含沙量海区黄河口泥沙为研究对象,利用电导率仪测定了不同悬浮泥沙含量水体的电导率。前期实验结果已经证明悬浮泥沙含量与电导率之间有很好的线性关系。在此基础上扩大研究范围,并对影响悬浮泥沙含量与电导率关系的因素进行定量分析,结果表明,盐度、温度、颗粒粒径对电导率具有一定的影响,其中盐度的影响最大,颗粒粒径的影响最小,几乎可以忽略。在此基础上通过大量的实验数据初步建立起在盐度、温度较大变化范围内电导率与泥沙含量的一般函数关系,为实现海水悬浮泥沙含量的现场电导率原位监测系统提供可靠的数据支持。     

南黄海海底沉积物声学特性及其影响因素试验研究

利用自南黄海中西部海底取回的沉积物样品,对其声学特性及其影响因素进行了试验研究,结果显示,研究区海底沉积物的压缩波速为1.359 ~1.695 km/s,剪切波速为12.5 ~70.9 m/s;颗粒较细的沉积物与较低的压缩波速、剪切波速对应,主要集中在研究区东侧水深较深处;沉积物的物理力学性质对其压缩波速、剪切波速的影响较显著,沉积物的温度和换能器的频率对上述声学两参数也具有一定的影响,而沉积物的包含物及薄夹层等影响声波传播的理论计算结果。给出了研究区海底沉积物物理力学各参数与压缩波速、剪切波速之间的回归方程,以期为国防、工程提供基础资料。     

长江口及邻近海域沉积物再悬浮对水体磷酸盐的影响的模拟研究

以长江口及邻近海域为研究区域,采用改进后的SEDEX法对沉积物中各形态磷的含量进行了分析,并通过模拟实验探讨了沉积物再悬浮对上覆水体磷酸盐浓度的影响。结果表明:碎屑磷（De-P）是沉积物磷的主要赋存形态,占总磷（TP）的50%以上;其次是可提取态有机磷（Or-P）和非活性有机磷（Re-P）;生物可利用磷（BAP）占总磷的比例约为21%,可提取态有机磷（Or-P）是生物可利用磷（BAP）的主要存在形态。沉积物再悬浮时,水体磷酸盐的浓度显著升高,说明沉积物再悬浮会引起沉积物中磷的释放;水体磷酸盐浓度升高主要源于沉积物中磷的释放,而间隙水的贡献较低。沉积物发生再悬浮时,厌氧条件相对于好氧条件,更有利于沉积物磷的释放。     

Experimental study on strength characteristics and microscopic mechanism of marine soft clays

Abstract

The effect of microstructure on shear strength of saturated marine clays was investigated by conducting a series of consolidated-drained (CD), consolidated-undrained (CU) triaxial shear tests and mercury intrusion porosimetry (MIP) tests on undisturbed and reconstitute specimens. The valuable findings from the experimental study are follows: (1) The shear strength of undisturbed specimens is lower than that of corresponding reconstituted specimens due to larger void ratio at the same confining pressure. However, undisturbed specimens have higher strength than reconstituted specimens when their void ratios are the same. (2) The main reason for the lower shear strength of reconstituted specimens with the same void ratio as undisturbed specimens is that more volume of inter-aggregate pores exists in the reconstituted specimens according to the MIP test results. And the difference in shear strength between undisturbed and reconstituted specimens is mainly caused by the difference in soil fabric. (3) The shear test results dealt with a reference void ratio, as a fabric index, show that there is a unique linear relation between strength and void ratio at failure to the reference void ratio. Moreover, the linear relation is suitable for other marine clays from the literature. Therefore, the reference void ratio can be used as a soil fabric index to normalize the strength characteristics of marine soft clays.     

Experimental study on suspended sediment concentration and its vertical distribution under spilling breaking wave actions in silty coast

In this paper,flume experiments are focused on sediment transport inside and outside the surf zone.According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissipation of spilling breaking wave and hydraulic jump,formulas are proposed to predict time averaged suspended sediment concentration under both non-breaking and breaking waves.Assuming that the sediment diffusion coefficient,which is related with energy dissipation,is proportional to water depth,formulas are proposed to predict close-to-bed suspended sediment concentration and vertical distribution of suspended sediment under spilling breaking waves,and the prediction shows a good agreement with the measurement.