Trace Metals in the Westerschelde Estuary: A Case-Study of a Polluted, Partially Anoxic Estuary


Book Description

Oceans and lakes are characterized by large residence times and can thus be considered as being in an equilibrium or quasi-equilibrium state. In contrast, estuaries, which constitute the interface between the fresh water and marine ecosystems, are biogeochemically and physically very dynamic. Strong gradients in physical and chemical variables such as temperature, pH, salinity, dissolved oxygen, nutrients, amount and composition of particulates result from the mixing of fresh water and saline end members. These gradients provoke increased biogeochemical processes, generally resulting in a geochemical filter (the area of high turbidity, showing enhanced adsorption-desorption processes) and a biological filter (the area of high plankton activity showing, besides a high uptake of nutrients, a high accumulation of trace metals). Both filters disturb the conservative mixing pattern of the trace metals in an estuary. In addition, four aspects make the Scheldt estuary very unusual and different from other estuaries: the Scheldt is a tide-governed estuary which means larger residence times; the upper estuary receives large inputs of biodegradable organic matter which leads to oxygen depletion in winter and to anoxic conditions in summer; inputs of toxic pollutants occur in the upper estuary by the industrial park of Antwerp; the anoxic zone, the zone of pollutant input and the zone of the turbidity maximum coincide geographically. The Scheldt estuary is thus an ideal field laboratory for the study of biogeochemical processes which do not occur elsewhere, or only partially, to a very low extent or in a specific compartment, i.e. the sediments. More specifically, redox processes involving trace metals, the formation of non-labile metal complexes, and the methylation of mercury occur as a result of anoxic conditions and the high load of organic matter. Several models describing in detail the transport, the sedimentation and the speciation of the trace metals in this well-mixed estuary (all major estuaries in EC countries adjacent to the North Sea or the Atlantic Ocean are well-mixed) are presented in this book. A comparison of the metal concentrations over a 15-year period shows a net reduction of the pollution level.













Complexation of trace metals in natural waters


Book Description

It is presently well recognized that total concentrations of trace elements in any environmental compartment supply insufficient information to understand important phenomena. The distinction and separate analysis of specific chemical species are essential for understanding cycles in the aquatic environment, involving identification and quantification of sources, transport pathways, distributions and sinks, or, in the area of interactions between trace elements and organisms to understand uptake, distribution, excretion mechanisms and effects. In the past, various ways have been developed to determine the nature and extent of complexation of trace elements in natural systems. Approaches have been followed along very different lines. These have not always been fully appreciated by specialists working in even related fields of complexation research. The first International Symposium on the Complexation of Trace metals in Natural Waters was held at the Netherlands Institute for Sea Research (NIOZ, Texel, the Netherlands from 2-6 May 1983. The scientific programme was planned by the chief organizers Drs. C.J.M. Kramer and J.C. Duinker (NIOZ) together with Prof. Dr. H.W. Nurnberg (Kernforschungsanlage, Julich, Federal Republic of Germany) and Dr. M. Branica (Rudjer Boskovic Institute, Zagreb, Yugoslavia).







Treatise on Estuarine and Coastal Science


Book Description

The study of estuaries and coasts has seen enormous growth in recent years, since changes in these areas have a large effect on the food chain, as well as on the physics and chemistry of the ocean. As the coasts and river banks around the world become more densely populated, the pressure on these ecosystems intensifies, putting a new focus on environmental, socio-economic and policy issues. Written by a team of international expert scientists, under the guidance of Chief Editors Eric Wolanski and Donald McClusky, the Treatise on Estuarine and Coastal Science, Ten Volume Set examines topics in depth, and aims to provide a comprehensive scientific resource for all professionals and students in the area of estuarine and coastal science Most up-to-date reference for system-based coastal and estuarine science and management, from the inland watershed to the ocean shelf Chief editors have assembled a world-class team of volume editors and contributing authors Approach focuses on the physical, biological, chemistry, ecosystem, human, ecological and economics processes, to show how to best use multidisciplinary science to ensure earth's sustainability Provides a comprehensive scientific resource for all professionals and students in the area of estuarine and coastal science Features up-to-date chapters covering a full range of topics




Marine Geochemistry


Book Description

The first edition of Marine Geochemistry received strongcritical acclaim, and the reviews included the comments that it'provides a benchmark in the field' and 'is clearly recognizable asa standard text for years to come'. Marine Geochemistry offers a fully comprehensive andintegrated treatment of the chemistry of the oceans, theirsediments and biota. It addresses the fundamental question 'How dothe oceans work as a chemical system?' by capitalizing on thesignificant advances in understanding oceanic processes made overthe past three decades. These advances have been facilitated byimproved sampling and analytical techniques, a better understandingof theoretical concepts and the instigation of large-sizedinternational oceanographic programs. Designed for use as a text, the book treats the oceans as a'unified system' in which material stored in the sea water, thesediment and the rock reservoirs interacts to control thecomposition of sea water itself. Part I covers the transport ofmaterial to the oceans via rivers, the atmosphere and hydrothermalsystems, and discusses their relative flux magnitudes. Part IIconsiders the oceans as a reservoir, introducing water-columnparameters before discussing water-column fluxes and the benthicboundary layer. Part III is devoted to the sediment reservoir. Thetopics covered include diagenesis, the major components of thesediments, and the processes controlling the geochemistry ofoceanic deposit, which are discussed in terms of sediment-formingsignals. Part IV offers an overview and synthesis of the integratedmarine geochemical system. Since the publication of the first edition, there have beenfurther significant advances in several areas of the subject. Therevised text of this edition accommodates these advances, whilestill retaining the emphasis on identifying key processes operatingwithin a 'unified ocean.' Special attention has been paid tofundamental conceptual changes, such as those related to tracemetal speciation in sea water, hydrothermal activity, carbondioxide and the importance of the oceans in world climate change,the transport of particulate material to the interior of the ocean,primary production and iron limitation, colloids, and thepreservation/destruction of organic matter in marine sediments. Intermediate and advanced students with interests in chemicaloceanography, marine geochemistry, marine biology and environmentalchemistry will welcome this revised comprehensive text. Otherstudents in the broader field of earth sciences will find it to bean essential reference source dealing with the interaction betweenthe atmosphere, the ocean and the solid earth. Incorporates all significant recent advances in thefield. 'Unified system' approach to ocean chemistry. Emphasises geological contexts, e.g. sediment diagenesis.