Fractionation of phosphorus in the sediments of a tropical estuary

Fractionation of phosphorus in the sediments of the Cochin estuary situated along the southwest coast of India was studied by applying sequential chemical extraction. The different forms of phosphorus were estimated seasonally (premonsoon, monsoon, and postmonsoon) under eight different schemes. The major forms of phosphorus analyzed were exchangeable P, anion exchangeable P, carbonate-bound P, labile and resistant organic P, Fe and Al P, calcium-bound P, and hydrolyzable surplus P. Quantitatively, the above fractions in isolation or in combination vary in content due to chemoestuarine variability and seasonal fluctuations. Changes in speciation have been noted in association with salinity variations in the waterway, especially following enhanced river runoff during the monsoon. The chemical forms of the sediment-bound phosphorus in the northern parts of this estuary have been shown to be modified by nonpoint sources. Sediment P fractionation defines the role of chemical speciation of phosphates (as nutrients) and is indicative of the processes controlling the pathways of P into the coastal waters. The changes in the exchangeable P, together with marked regional variations in calcium-bound P, exemplify the complex estuarine variability of phosphorus. Enhanced amounts of exchangeable P mark its appearence in high saline waters, signifying the presence of biologically available nutrient phosphorus. The calcium-bound P and hydrolyzable surplus P show significant relation with sediment organic carbon and Fe whereas other forms do not exhibit any marked covariation. The Ca and Na NTA extraction scheme is very specific in its selectivity.     

长江口南支沉积物元素地球化学分区与环境指示意义

对采自长江口南支的130个表层底质沉积物样品采用X射线荧光光谱法进行了20种常、微量元素的地球化学分析。在此基础上,应用系统聚类法对该区域进行了元素地球化学分区。研究结果表明,研究区主要可以分为两大地球化学分区:Ⅰ区以相对富集SiO2,Sr,Zr元素为典型特征,主要涵盖5 m等深线以浅的长江三角洲前缘区;Ⅱ区以相对富集Al2O3,TFe2O3(全铁),MgO,Pb元素为典型特征,涵盖了前三角洲的广大区域。从地球化学分区的空间分布来分析,这两个分区元素之间的差异反映的是沉积水动力条件与沉积介质物化性质这两个环境要素空间分布的差异性,即在研究区内,表层沉积物元素地球化学空间分布的差异性实质上反映了沉积环境空间分布的差异性。     

Vertical distribution of the macrobenthic community and its relationships to trace metals and natural sediment characteristics in the lower Douro estuary, Portugal

Vertical distribution (0–15 cm) of the macrobenthic community and its relationships to natural sediment characteristics and trace metal contents and bioavailability were studied at five locations in the lower Douro estuary, Portugal. An analysis of vertical metal distribution, for the interpretation of anthropogenic impact on the estuarine sediments, was also investigated. Sediment characterisation included organic matter, grain size, metals (Al, Fe, Cu, Pb, Cr, Ni, Cd, Zn and Mn), acid volatile sulphide (AVS) and simultaneously extracted metals (SEM). The macrobenthic community had low diversity (14 species), was dominated by small size opportunists and seemed to be controlled mainly by natural factors such as grain size distribution, Al and Fe contents and sediment depth. The vertically heterogeneous distribution of macrobenthic community appears to affect redox status of the sediments and consequently metal bioavailability. Despite anthropogenic contamination in terms of Zn, Cu, Pb, Cr and Ni having already been detected in the north bank, the analysis of vertical distribution was essential for the identification of current anthropogenic contamination in terms of Zn, Pb and Cd in the south bank.     

Seasonally Hypersaline Estuaries in Mediterranean-climate Regions

Data collected in three Californian estuaries indicate that hypersaline conditions exist during the dry summers typical of a Mediterranean climate. The generalised seasonal and longitudinal hydrographic structures are described and explained. It is argued that this seasonal hypersalinity is common and that it represents a major class of estuaries. The observed accumulation of salt indicates surprisingly long residence times in small basins which have free exchange with the ocean. This semi-isolation of the inner basin leads to a large build-up or severe depletion of nutrients, pollutants and plankton in these systems. Of concern are the trends to increase pollutant loading in the same systems that are experiencing an increase in residence times owing to freshwater extraction in the watershed.     

黄河入海径流量与河口沉积物的侵蚀关系

河口地区海水环境变化复杂,岸滩侵蚀严重,入海径流对侵蚀的影响不可忽视。从入海径流量与河口盐度变化的关系入手,主要阐述了海水盐度变化对河口泥沙沉降及泥沙沉降后固结的影响,进而讨论盐度变化对河口沉积物侵蚀的影响,其中,着重对黄河口地区入海径流量与河口沉积物侵蚀的关系进行了探讨;并且概述了黄河口沉积物侵蚀相关的研究情况,指出在黄河三角洲等河口岸滩侵蚀的研究中,可以以盐度等为媒介,把入海径流与沉积物本身联系起来,综合考虑分析岸滩侵蚀机理。     

自组织数据地图在大辽河河口水质分析中的应用

自组织数据地图(SOM,Self-organizing Map)具有强大的数据压缩和提炼功能,应用它可以对水质监测数据进行处理,找到水质分析的新方法。本文以大辽河河口水质监测数据为例,应用MATLAB中SOM工具箱,采用批处理SOM算法,利用MATLAB语言编写出水质分析程序。该程序通过SOM的训练对数据特征进行分析和显示,并进一步分析SOM训练结果,将监测数据分成4类,最后实现数据跟踪及新的监测数据的自动归类。该方法可以将水质监测数据的特征可视化,便于直观、深入地分析水质状况,为识别水质特征、跟踪水质变化和应对措施提供决策支持。     

珠江口沉积物酸挥发性硫化物与重金属生物毒性的研究

研究了2003年10月采于珠江口5个站位的沉积物剖面酸挥发性硫化物(AVS)和同时提取的重金属(SEM:Pb,Zn,Cu,Cd,Ni)。其中,站位1、2位于中滩,其沉积物的AVS含量变化范围较小,为0.25—4.06μmol.g-1;站位3、4位于西滩,其沉积物的AVS含量变化范围较大,为0—26.09μmol.g-1。中滩和西滩沉积物的AVS含量均随深度增加。西滩表层沉积物的AVS含量接近于零,这可能与该水域较强的底层流和沉积物的再悬浮作用有关。站位5位于珠江口外侧,其表层沉积物的AVS含量相对较高,且垂向变化较小,可能是还原性沉积物间歇性再悬浮后重新沉积的结果。站位1、2和5沉积物中同时提取的重金属含量大体在0.95±0.2μmol.g-1范围内,随深度增加略呈下降趋势;而西滩沉积物重金属含量相对较高,为1.43—2.42μmol.g-1,且在一定深度范围内随深度增加呈明显下降的趋势,表明珠江口西滩沉积物中的重金属污染有加重的趋势。对AVS/SEM摩尔比值和单个金属的毒性效应研究显示,珠江口内尤其是西滩的表层沉积物存在重金属污染,对其中生活的底栖生物具有潜在的毒性效应。     

潮致泥沙全沙净输运解析模式

泥沙运动作为水流和底床相互作用的纽带,是河流、河口及海岸工程研究的重要内容。在潮波作用明显的河口、海岸地区,周期性的动力作用下的泥沙运动具有往复和可逆的特征,因此研究这类水域的泥沙的净输运更具有实际的意义。基于泥沙输运和流速呈指数关系假设,建立潮流环境下的泥沙全沙净输运的解析解公式,并对该公式的计算结果和数值计算以及数学模型的结果进行了检验和验证,结果表明本研究提出的公式能较好地反应潮流环境下的泥沙净输运。由此,基于本公式采用潮流分潮调和常数可计算得到全沙净输运,并可以分析各分潮流及其相互作用与泥沙净输运的关系。研究结果显示,在受径流影响较大的半日潮河口,S2、MS4、M2三潮相互作用对全沙净输运的贡献显著高于通常的潮流不对称作用,即M2、M4的相互作用。此外,河口区域径流导致的余流对泥沙净输运的贡献不可忽略,特别是在洪季,大径流量条件下往往导致余流较大,其对泥沙净输运的贡献所占比例较大。     

鸭绿江口与邻近西海岸沉积记录的耦合

通过对采自鸭绿江口主汊道的5个柱状样的210Pb和137Cs测年以及粒度参数的分析,并与前期合作研究的西汊道及西岸潮滩的4个柱状样沉积物的测年和粒度研究成果进行比对,探讨了流域来水来沙、河口沉积与海岸发育之间的耦合效应及鸭绿江河口地貌演化的新证据。结果表明:鸭绿江口主汊道存在河流和潮流两种沉积作用,不同时期动力作用不同;以潮流作用为主的沉积时段,其沉积特征与西汊道及西岸潮滩的一致;主汊道沉积物的物质来源与西汊道和西岸潮滩的物质来源存在差异。鸭绿江口的主汊道、西汊道及邻近海岸的沉积记录对环境变化、人类活动、流域大洪水等事件均存在响应,响应的时间基本同步,具有耦合效应。沉积记录中存在5个明显的“事件信号”,其中1960年最为重要,是鸭绿江河口地貌发生巨变的时间。     

近50 a来杭州湾冲淤变化规律与机制研究

使用杭州湾1959-2010年的水下地形图, 结合过去数十年来长江入海水沙量和钱塘江河口段冲淤变化状况, 分析了近50 a来杭州湾在长江入海泥沙量锐减和治江围涂等人类活动作用下的冲淤变化规律及其物理机理。结果表明, 乍浦以上区域近50 a来处于较显著的淤积状态, 且有自上向下发展的趋势, 这种淤积主要是由于钱塘江河口治江缩窄工程所引起的;湾内地形发生了局部调整, 部分小型潮流槽脊系统趋于消亡, 地形趋于平坦化, 湾口北部2003年以后有转淤为冲的趋势, 这与长江入海泥沙量锐减和该区域围垦工程等因素有关;1959-2003和2003-2010年两个时段, 湾内泥沙淤积的年平均值分别为0.91×108和1.66×108 m3。对于整个钱塘江河口系统而言, 即自杭州湾湾口至钱塘江河口段的闸口断面, 长江入海泥沙量减少所产生的影响尚不明显, 2003年以后泥沙淤积速率甚至有所上升。杭州湾近50 a的冲淤变化是人为强烈干预下的大流域-河口系统响应与中小流域-河口系统响应的调整结果。