长江口枯季水动力悬沙特征与再悬浮研究

2004年2月13~22日枯季大小潮期间在长江口北港、口门及口外进行了水动力、悬沙浓度和盐度的全潮观测,并对数据进行分析,同时对研究区域的再悬浮/沉降通量进行计算,进而讨论长江口枯季水动力和再悬浮特征.结果表明,长江口外以潮流作用为主,但流速、悬沙浓度和盐度的分布和变化仍与径流作用有关,观测期间再悬浮现象不显著.北港内及口门处,径流作用较强,盐度较低,落潮流速大于涨潮流速,当流速较大时,底部再悬浮作用显著.计算结果表明,再悬浮通量的数量级为10-3~10-6kg m-2s-1,沉降通量为10-9~10-10kg m-2s-1.     

悬浮絮凝体特征及其影响因子的综合作用——以长江口内河槽和口门最大浑浊带为例

絮凝对河口细颗粒悬沙运动起着极其重要的作用.为深入探讨长江口悬浮絮凝体的特征及其主要影响因子的综合作用,于2014年10月19—23日(长江口径流量、潮差、风浪均接近多年平均值)利用多种仪器在人类活动干扰较小的南支-北港-口外海滨水域进行了综合现场观测和取样,获得了四个潮流特征时刻(涨急、涨憩、落急、落憩)的悬浮絮凝体粒径、分散粒径(即分散悬沙的原始粒径)、悬沙浓度、体积浓度、流速流向、盐度等数据.利用灰色关联度分析方法分析五大影响因子(悬沙浓度、体积浓度、流速、盐度和分散粒径)对絮凝体粒径和有效密度影响程度.结果表明,在相同体积水体中,口门最大浑浊带测点的絮凝体相对口内河槽测点数量多、粒径小,絮凝体内粘土颗粒少、空隙大、自由水多.在口内河槽,絮凝体粒径主要受悬沙浓度、分散粒径和体积浓度控制,有效密度主要受到分散粒径、悬沙浓度和流速控制;在口门最大浑浊带,絮凝体粒径的主控因子是流速,有效密度主要受到盐度、悬沙浓度控制.     

长江口南支分流分沙比观测与分析

2007年2月在长江口南支进行沉积动力学参数的全潮观测,以获取枯季期间南北槽、南北港的分流分沙特征．结果表明,多数站位涨潮流速大于落潮流速,涨潮历时小于落潮历时,涨潮悬沙浓度大于落潮悬沙浓度,这种涨落潮不对称效应主要与径流作用和潮波变形有关．悬沙浓度与流速也有一定的相关关系,表明再悬浮作用较为显著．从净泄水量看,北港大于南港,南槽大于北槽,形成由陆向海输运的格局．输沙量则为由海向陆,尤以南槽和南港为最大,加之河流上游亦有来沙,最终在南支拦门沙附近海域形成较为显著的淤积状态．     

长江口悬沙输运观测中ADCP的应用

在近些年的声学流速测量仪器当中,ADCP（声学多普勒流速剖面仪）是应用非常广泛的仪器之一。该仪器在获得悬沙浓度数值方面,其工作方式主要构建现场取得水样与回声强度的回归关系式,并利用该关系式来计算悬沙浓度数值。通过ADCP（声学多普勒流速剖面仪）在长江口悬沙输运观测中实际应用,结果显示,在长江南槽与南港的全部悬沙输送的过程中,平均流输运作用发挥着非常重要乃至主导的作用,同时,影响潮平均悬沙输运的各种因素中,斯托克斯漂移效应（Storks-drift）导致的输运作用是非常关键的。在本文中,笔者主要探讨了ADCP（声学多普勒流速剖面仪）在长江口悬沙输运观测中实际应用情况。     

长江口启海港枯季悬沙浓度的特征分析

分析2012年枯季启海港海域的实测水文泥沙数据,得到如下结论：该港区海域的悬沙浓度与流速成正相关关系;悬沙浓度的峰值一般出现涨、落急后。港区海域悬沙浓度在垂向上分布为：斜线型、准直线型和混合型,近岸水域的泥沙在中上层运动紊乱,离岸水域的泥沙紊乱则集中在下层。盐度对泥沙的再悬浮作用起一定作用,在流速较大时,底部悬沙浓度变化幅度很小,最大含沙量出现在中层。     

动水条件下泥沙絮凝体粒径变化分析实验研究

絮凝体广泛存在于自然界水体中,而在河口海岸动水环境下的黏性细颗粒泥沙的絮凝变化过程是一个重要且有待完善的研究课题。利用长江口北槽现场悬沙样本开展了系统的室内絮凝实验。采用粒径分布与有效粒径两种分析方法,研究了在水流紊动、盐度和悬沙浓度等不同絮凝因子条件作用下对长江口北槽泥沙絮凝体粒径变化的影响。实验结果表明:紊动剪切率对絮凝体粒径作用为先促进后减小,临界值出现在23. 09 s~(-1),此时最大有效粒径为50. 26μm;而悬沙浓度会抑制絮凝体生长;同时长江口北槽悬沙的絮凝饱和盐度要大于高岭土,约为14. 4 ppt。     

长江口深水航道北槽口外悬沙浓度垂向分布

在长江口深长航道北槽，利用“声学悬潲观测系统”观测得到了大潮不同潮时近瞬时高时空分辩率细颗粒悬沙浓度垂直向分布，此外，还观测了流速和和盐度地垂线分布，在涨潮初期，悬沙浓度的垂向分布均均匀，在接近涨憩时，悬沙浓度的梯度小，在落潮时，悬沙浓度随水深水面到水底按指数递增，可视为恒定均匀流中悬潲处于平衡条件的分布，泥沙垂向扩散系数εｓ可用泥沙颗粒沉降速度ωｓ的两倍来近似，在接近落憩时，悬沙浓度的垂向梯度适     

长江口北槽下游河道悬沙浓度垂向分布特征研究

根据2013年10月26日至11月9日在长江口北槽下游河道从小潮到大潮连续14 d的现场定点水沙观测数据,对北槽下游河道悬沙浓度的垂向分布特征进行了研究,并探讨了盐度梯度和流速大小潮变化对悬沙浓度分布的影响.结果表明,北槽下游河道的水动力条件存在显著的大小潮差异,小潮具有流速弱、悬沙浓度低、盐度梯度大、盐度分层显著的特点,而大潮则具有流速强、悬沙浓度高、盐淡水混合程度高、盐度分层弱的动力特点.受较大盐度梯度和弱流速的影响,小潮期间的悬沙浓度分布主要为阶梯型和L型,强盐度密度分层使悬沙难以扩散到水体表层,高浓度悬沙仅出现在水体中下部.在强流速和弱盐度分层的影响下,大潮期间的悬沙浓度分布主要为线性分布,悬沙能够扩散到水体表层,盐度密度分层对悬沙浓度分布的影响显著削弱,在落潮后期悬沙浓度分布表现为典型的垂线型分布,悬沙在水体中充分混合.研究表明,小潮和大潮的悬沙浓度分布基本偏离Rouse分布,仅在小潮落憩时刻符合.在大潮期间,实测的线性分布都很好地符合Soulsby公式,利用该公式能够很准确地预测这些浓度分布.     

长江口及其邻近海域洪季悬沙分布特征分析

基于近几年大量的实测资料,对长江口及其邻近海域洪季期间悬沙浓度的时空分布特征进行了分析.结果表明,悬沙浓度空间上以杭州湾测点最高,其次是长江口内、长江口外,舟山海域最低;悬沙平面分布总体态势为近岸高而外海低;长江口纵向上自口内经口门向口外悬沙浓度大致呈“低-高-低”分布,沿杭州湾测点则由西向东逐渐降低;横向比较长江口外海滨四个测点发现其悬沙浓度自北向南顺次升高;悬沙浓度一般由表及底逐渐增大,但在不同水域其主要呈现的垂线结构类型则有所不同.时间上由于潮流的大小潮和潮周期变化,悬沙浓度还存在大小潮和涨落潮周期变化.另外,对长江口及其邻近海域悬沙浓度时空分布特征的原因进行了初步分析.     

ADCP在琼州海峡悬沙观测中的应用

根据琼州海峡西口一测站4个季节的声学多普勒流速剖面仪(简称ADCP)回波强度数据以及现场采集的水样反演了悬沙浓度(SSC).结果显示,春季悬沙浓度为0.017～0.05 kg/m3,平均0.025 kg/m3,夏季悬沙浓度为0.012～0.026 kg/m3,平均0.017 kg/m3,秋季悬沙浓度为0.012～0.074 kg/m3,平均0.028 kg/m3,冬季悬沙浓度为0.012～0.1 kg/m3,平均0.028 kg/m3,悬沙的沉积和再悬浮跟潮流密切相关,各季节流速的不同导致夏季悬沙浓度明显的小于其他季节,大小潮流速的差别导致大潮期间的悬沙浓度大于小潮期间的悬沙浓度.观测点海水和悬沙由表到底都是全年向西输送,春季净输沙量为-7.5×104 kg,夏季净输沙量为-1.3×104 kg,秋季净输沙量为-3.03×105 kg,冬季净输沙量为-1.05×105 kg.     

黄岛金沙滩现代波痕沉积特征与水动力关系

 黄岛金沙滩为典型的无障壁高能海岸,后滨发育有风成波痕,前滨滩槽和近滨上部可见大量浪成波痕。本文通过对上述3种环境下波痕的形态、沉积物粒度特征及前滨波痕形成水动力条件进行分析研究发现：1）后滨风成波痕波长、波高、迎流面及背流面相对浪成波痕较小,但波痕指数较大,而前滨滩槽、近滨上部波痕由陆向海波长、迎流面、背流面变小。2）风成波痕沉积物粒度波峰较粗,而浪成波痕沉积物粒度波谷较粗,从前滨到后滨沉积物粗组分减少,细组分增多;风成波痕、前滨滩槽波痕粒度频率分布曲线呈“双峰”特征,而近滨上部波痕粒度频率分布曲线主体呈“单峰”特征,风成波痕、滩槽波痕沉积物缺少悬浮组分;波痕沉积物分选-峰度图、分选-偏度图可以较好地判别沉积环境。3）平均粒径与流速、水深、弗劳德数Fr有很好的线性关系,前滨退潮时形成波痕的水动力条件具有水体浅、流速小和水动力弱的特点,可能与退潮时水速、水深变化较快有关。4）对前滨波痕沉积特征与相应流速、水深分别进行逐步回归分析,获得了形成环境的流速、水深的回归关系式。     

长江口粘性细颗粒泥沙絮凝试验研究

长江口航道淤积的主要成因是河流从上游带来的大量粘性细颗粒泥沙，在河口盐、淡水交汇处遇强电解质海水，产生絮凝形成絮团而加速沉降形成的。用长江口粘性泥沙在不同盐度的人工海水中做了大量的试验，研究结果表明，影响絮凝的主要因素为含盐度、颗粒大小、含沙量、泥沙矿物成分、有机质含量等、这些因素和絮团形成的大小有密切关系。     

Remobilization of heavy metals during the resuspension of Liangshui River sediments using an annular flume

The release and transport of heavy metals(Ni,Cr,Cu and Pb) from Liangshui River sediments into the overlying water column during the resuspension event were determined using an annular flume with a velocity ranging from 0.15 to 0.35 m/s.It is shown that the suspended particulate matters(SPM) increased as much as nearly 25 times from 165 to 4220 mg/L as the velocity increased.Heavy metals showed an increase in dissolved phase as the velocity increased due to their desorption from the SPM.Acid-soluble heavy metals increased as the velocity increased,indicating that part of the heavy metals transformed from stable phase to labile phase during resuspension.Heavy metal concentrations in the SPM on volume normalization increased by approximately 2-6 times.However,on the mass weighted basis they decreased,approaching the bulk-sediment contents at high velocity,due to the "particle concentration effect".The distribution coefficients(K D) of heavy metals were higher at slower velocity during the sediment resuspension,which could be attributed to the decrease of fine particles(silt/clay fraction) during resuspension.     

黄河泥沙含量对磷迁移过程的影响研究

磷是我国河流主要污染物质之一,泥沙含量对磷的迁移过程具有重要影响,但针对磷在沉积物-水界面的迁移机制理解尚不完全．黄河作为典型的高含沙量和高磷负荷河流,对于磷在河流介质的迁移过程具有重要研究意义．在2019 年10 月份选取黄河沿程18 个水样采集点位和2 个沉积柱采集点位,对水样含沙量、总磷含量（TP）和沉积物样磷形态含量（Ca-P、Fe/Al-P、OP）进行测量,结合2000—2019 年黄河主要水文站实测输沙量、含沙量、泥沙粒径数据进行分析．从时空尺度上,尽管中游河段输沙量近20 年呈显著下降趋势,但下游输沙量仍保持稳定,下游前段水体含沙量呈上升趋势．将水体含沙量与TP 含量进行协同分析,下游河段水体含沙量同TP 含量呈相反变化规律．对泥沙粒径进行分析,冲刷作用导致较大粒径沉积物再悬浮,这一过程对磷的迁移具有重要影响．对沉积物磷形态进行分析,IP 为黄河流域沉积物磷主要赋存形态,Ca-P 是IP 的主要赋存形态．研究认为,当流速慢时,水体泥沙含量低,沉积物再悬浮作用弱,Fe/Al-P 在沉积物-水界面迁移. 当流速快时,水体泥沙含量高,沉积物再悬浮作用强,下游地区沉积物和悬浮颗粒物成为磷汇．      

Spatial and temporal distribution of trace elements in Yangtze Estuary, China: Significance of diluted setting

The present study is to examine the spatial and temporal distribution of eight trace elements (Sr, Ba, B, Ga, Ni, V, Cu, and F) in various Holocene marine subfacies in the Yangtze Estuary, including its subaqueous delta by sediment borehole and vibrocore. Results demonstrate that grain size is the determinant factor in controlling the concentration of most trace elements discussed. Prodelta mud that occurs usually below the normal wave base can serve as a depository sink for trapping trace elements over the long-term time period. For example, copper concentration is 5-6 times higher than those found in the estuarine sediment. Boron, which is used to be a salinity indicator, shows a strong negative correlation with paleosalinity (using sediment phosphate method), implying desalinized water setting in the Yangtze Estuary, into which a large quantity of the Yangtze freshwater (924 × 10⁹ m³/a) has discharged. Trace element concentrations of the study area were compared with those collected from the middle and lower Yangtze River reaches, and from the east China continental shelf, including the Okinawa Trough. Result tends to show a terrigenous derivation of most geochemical components of the study area. Concentrations of strontium and barium are correlated with an increase in distance away from the estuary, rather than affected by grain size. Variation of trace elements in downcore Holocene sediment sections are fairly consistent with concentrations revealed by the modern vibrocore transect that extends from nearshore delta front, to offshore prodelta and to the delta-shelf transit zone. The overall distribution of geochemical elements discussed is capable of environmental implication to characterize the Yangtze estuarine transit between land and sea.     

High-resolution data collection for analysis of sediment dynamic processes associated with combined current-wave action over intertidal flats

Intertidal flat systems represent an important coastal geomorphological unit, providing habitat for wild life, land resource for reclamation and protection for the coast against extreme storm events. In addition, the tidal flats covered with flourishing h…     

Characteristics of hydrocarbon sources and controlling factors of their formation in Pingliang Formation,West Ordos Basin

According to organic geochemistry and organic petrology, the hydrocarbon sources in Pingliang Formation, W. Ordos basin, are systematically evaluated. The organic abundance of hydrocarbon source in this research is higher in the upper part of profiles than in the low, and more in mudstone than in carbonate. Most of organic matters become sapropelic, and few are humic-sapropelic in the regions of Shibangou and Zhuzisan. According to stable isotopes of carbon and oxygen in carbonate rock, boron index and ratios of elements, palaeo-salinity and sedimentary velocity are calculated. The two factors of paleao-salinity and sediment velocity, which control the distribution of organic matters, are discussed. Good relationship is found between water salinity and abundance of organic matter; in contrast, poor correlation is observed between salinity and types of organic matters. The relative sediment velocity in the research regions is also related with organic abundance and types. A low sediment velocity would lead to high abundance and good type of organic matters, and vice versa.