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Soil, sludge and sediment
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LEACHING
In environmental studies, metals in sludge and sediment are usually determined after leaching the sample with semi-concentrated nitric acid in an autoclave (Swedish Standard 028183). During such acid leaching, loosely bound metals enter into solution while e.g. metals embedded in mineral particles remain in the granules. Only a very small amount of solid material is dissolved. The residue is separated from the test solution before analysis. As a result, part of the metal in the sample evades analysis, and the analysis is consequently not total.
The differential between total and leachable concentrations varies by element and sample material. In some cases it is negligible (e.g. zinc). For elements occurring in poorly soluble minerals (e.g. chromium), the differential can exceed 30%. The leachable fraction can be expected more accurately to reflect the portion of the metal content accessible to organisms in the environment.
In environmental protection, the ability to compare different investigations is also very important. M-1a, M-1b and M-2 have therefore been designed to provide results that are comparable in terms of the Swedish standard.
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FUSION
The total sample content of many elements can be determined after dissolution by a fusion method (lithium metaborate fusion). This also yields the concentration of main elements (silicon, calcium, iron etc.). In e.g. sediment, this makes it possible to relate heavy metal concentrations to natural geochemical processes and relationships. Many metals are, for instance, concentrated in precipitates of iron and manganese.
Certain elements (e.g. Cd, Hg, Pb) are lost if the fusion method is used. The MG-1 package has been designed to offer a broad range of substances by combining the leaching and fusion methods.
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EXTRACTION
For organic compounds it is especially important to note that different analytical methods, including sample preparation, may yield different analytical results. Extraction of solid samples does not generally produce a 100% yield of the extracted substances and the yield may also vary between extraction methods. For analytical results to be comparable, it is essential to ensure that they are obtained by comparable methods.
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LEACHING TESTS
In some cases, it is important to know to what extent pollutants in waste or soil are leached to the environment. Leaching here refers to the release of organic or inorganic compounds from a material as a response to static or dynamic contact with water. To be able to estimate the mobility of various pollutants, tests have been developed, simulating leaching under controlled laboratory conditions. Leaching tests for building materials, solid waste and soil are described in Dutch (NEN) and European (CEN) standards. The leachates are usually tested for metals (package V-3a.)
For collect samples - contact the laboratory.
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