Report, the editors replaced the term "speciation" wherever it occurred by "identification and quantification," or "description of abundance," or "reactivity," or "transformation" of a chemical species, according to whichever one of the four meanings the author had evidently meant to convey. In line with the Dahlem Workshop Model, this Report comprises the background papers written in advance of the meeting on the current status of problems in environmental research and on advanced analytical tech niques for the identification and quantification of chemical species, as well as the group reports summarizing the results of the discussions held during the meeting. Each group report was prepared during the meeting by one "rapporteur" with the help of members of that group and finalized by the rapporteur (listed as the first author of the group report) after the meeting, taking into account both verbal comments made during the presentation of the reports in the plenary session at the end of the workshop and written comments received afterwards.

Inhalt
Why Speciation?.- Importance and Determination of Chemical Species in Biological Systems Group Report.- Approaches to the Determination of Chemical Species in Biological Materials.- The Dependence of Toxic Reactions on the Chemical Species of Elements.- The Influence of Chemical Species on the Absorption and Physiological Utilization of Trace Elements from the Diet or Environment.- The Interaction of Inorganic Species with Biomembranes.- Does the Coordination Environment Determine the Reactivity of Metals in Enzymes?.- Chemical Species in Freshwater and Terrestrial Systems Group Report.- Analytical Aspects of Organometallic Species Determination in Freshwater Systems.- Heavy Metal Species, Mobility and Availability in Soils.- Chemical Species and Metal Transport in Lakes.- Interactions between Natural Organic Polymers and Metals in Soil and Freshwater Systems: Equilibria.- Adsorption and Transformation of Trace Element Species at Sediment/Water Interfaces.- Transformation of Sulfur Species by Phototrophic and Chemotrophic Microbes.- Chemical Species in Marine and Estuarine Systems Group Report.- Chemical Species in Seawater and Marine Particulates.- Equilibrium Models in Seawater: Applications and Limitations.- Formation and Transformation of Element Species in Estuaries.- Importance of Chemical Species in Uptake, Loss, and Toxicity of Elements for Marine Organisms.- Chemical Species in Systems under Stress Group Report.- Chemical Species in Industrial Discharges and Effluents.- Chemical Forms and Environmental Effects of Critical Elements in Solid-Waste Materials: Combustion Residues.- Microbial Intervention in Trace Element-containing Industrial Process Streams and Waste Products.- Microbial Interactions with Toxic Elements in the Environment.- ElectrochemicalMethods and Their Limitations for the Determination of Metal Species in Natural Waters.- Multinuclear NMR Methods for the in situ Characterization of Chemical Species.- Analysis of Inorganic Species by Ion Chromatography and Liquid Chromatography.- Mass Spectrometers as Detectors for Liquid Chromatography.- Mass Spectrometry of Biomolecules.- Surface Characterization Techniques Applied to Environmental Problems.- Liquid Chromatography Element-specific Detection Systems for Analysis of Molecular Species.- The Basis for Quality Assurance of Chemical Measurements and Standards.- Ad hoc Analytical Report Group Report.- List of Participants with Fields of Research.- Author Index.