Sediment Analysis

Abstract: Chemical analysis of sediments provides an efficient tool for water-quality management. A basic sequence of measurements comprises three steps: sampling and sample preparation; grain size as a characteristic sediment feature; and, analytical procedures based on standardized extraction schemes and reference materials. These can be considered as an unbroken chain of comparisons. Further steps are split with regard to specific purposes: sediment-quality assessment, including biological effects; coupling of sediment-quality data with erosion-risk evaluation; chemical changes following resuspension of anoxic sediments; and, modeling of chemical sediment data. In the light of the economic value of these further steps for developing and executing far-reaching management plans, coordinated efforts should be made to improve their traceability (e.g., by organized dissemination of results from on-going research (ageing effects), official documentation of techniques and instruments in a relative new field (erosion effects), extension of standardized extraction schemes (anoxic sediments, capacity-controlling properties), and development of new reference materials (pore water)).

Abstract: Single or sequential extraction procedures are often used for soil and sediment studies to determine forms or phases of elements (e.g. `bioavailable' forms of elements). The significance of the analytical results is highly dependent on the extraction procedures used, owing to the `operationally defined' character of these schemes which requires the adoption of standardized protocols. The first part of the present review discusses the aspects of standardization of leaching and extraction schemes as applied to environmental analysis. This second part focuses on the validation aspects of such procedures and describes the preparation and certification of soil and sediment reference materials certified for their extractable trace element contents, following standardized single and sequential extraction procedures.

Abstract: Santos-Sao Vicente Estuarine System is a highly populated coastal zone in Brazil and where it is located the major port of Latin America. Historically, port activities, industrial and domestic effluents discharges have constituted the main sources of contaminants to estuarine system. This study aimed to assess the recent status of sediment quality from 5 zones of Port of Santos by applying a lines-of-evidence approach through integrating results of: (1) acute toxicity of whole sediment and chronic toxicity of liquid phases; (2) grain size, organic matter, organic carbon, nitrogen, phosphorus, trace metals, polycyclic aromatic hydrocarbons, linear alkylbenzenes and butyltins; (3) benthic community descriptors. Results revealed a gradient of increasing contamination for metals and organic compounds, alongside with their geochemical carriers. Sediment liquid phases were more toxic compared to whole sediment. Low number of species and individuals indicated the impoverishment of benthic community. The use of site-specific sediment quality guidelines was more appropriate to predict sediment toxicity. The integration of results through Sediment Quality Triad approach and principal component analysis allowed observing the effects of natural stressors and dredging on sediment quality and benthic distribution. Even with recent governmental efforts to control, pollution is still relevant in Port of Santos and a threat to local ecosystems.

Abstract: Chemical analyses of sediment are used for assessing the ability of sediment to support a healthy benthos (sediment quality) and for determining contaminant source and dispersion in aquatic systems. Total sediment analysis is used for sediment quality assessment, whereas source identification and dispersion requires normalised contaminant data. Normalized contaminant data are obtained by physical fractionation (size-normalization) of the sediment and analyses of a constant size fraction (usually the 62.5 μm fraction), whereas elemental normalization uses the total sediment analysis normalized to a conservative element. Elemental normalization is preferable, as it is cheaper and less time consuming than size-normalization techniques. In addition, some contaminants associated with oxides and oxyhydroxides in the coarse fraction are excluded in fine fraction analyses. Five techniques used to normalize sedimentary contaminant data were tested in the current study, including a new post-extraction normalization method where total sediment data are normalized to the residue after digestion, on the assumption that this fraction acts as a diluent only. Results of the tests indicated that simple normalization to the mud fraction provides useful dispersion information, but that the post-extraction normalization method produced a superior indication of source. Limited source and dispersion information was gleamed from the elemental-normalization (Al, Fe) approach, whereas the size-normalization technique provided the clearest indication of source and dispersion. Simple mud normalization and post-extraction normaliaation methods should be considered because only one analysis provides sediment quality, as well as source and dispersion information. However, for detailed information on source and dispersion, size normalization is recommended.