Normalization of heavy-metal data from estuarine and coastal sediments

Normalization is the attempt to compensate for the natural variability of trace metals in sediments so that any anthropogenic metal contributions may be detected and quantified. Grain size and provenance are the two most significant parameters which must be compensated for by any normalization procedure. The various granulometric and geochemical approaches used for the normalization of heavy-metal data from estuarine and coastal sediments are reviewed in this paper. Overall, geochemical normalization appears to be superior to granulometric methods because it compensates for the mineralogical as well as the natural granular variability of trace-metal concentrations in sediments. Detailed examination of heavy metal, aluminium (Al), and lithium (Li) concentrations indicates that Li is superior to Al for the normalization of the metal data from sediments derived mainly from glacial erosion of crystalline rocks. Lithium is of equal merit, or superior to Al, for the normalization of metal data from most other silicate sediments. Lithium normalization provides an alternative procedure to those used previously for the identification and estimation of relative anthropogenic trace-metal contributions to estuarine and coastal sediments.