Normalization of heavy-metal data from estuarine and coastal sediments

TLDR

Normalization compensates for natural variability of trace metals in sediments, especially grain size and provenance, to detect anthropogenic contributions. This paper reviews granulometric and geochemical approaches for normalizing heavy‑metal data from estuarine and coastal sediments. The authors evaluate various granulometric and geochemical normalization techniques. Geochemical normalization outperforms granulometric methods, with lithium proving superior or equal to aluminum for normalizing metals from glacial‑derived and other silicate sediments, providing an alternative for estimating anthropogenic trace‑metal contributions.

Abstract

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.