A test of normalization methods for marine sediment, including a new post-extraction normalization (PEN) technique

摘要

Chemical analyses of sediment are used or 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 normalized 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 mum 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.