A COMPARISON OF SEQUENTIAL EXTRACTION METHODS USED FOR BIOAVAILABILITY ASSESSMENT OF POTENTIAL TOXIC ELEMENT

Abstract

ABSTRACT Understanding potentially toxic element (PTE) bioavailability has eluded the research community for decades. Here we compare three PTE extraction methods that are widely used in foraminiferal pollution studies. Evident discrepancies between methods were observed when diversity indices and relative abundances were influenced differently by the same and, in some cases, by different PTEs depending on the method. This was reflected in the canonical correspondence analysis (CCA), where Cr-Ni (Method B) and Zn-Pb-Cu (Method C) had a respective positive and negative influence over the foraminiferal relative abundances while no positive correlations were observed for Method A. These discrepancies stem from each method extracting different concentration levels of the same PTE from the same sediment samples. We recommend bioavailable PTEs to be extracted from the following fractions: (1) mud-bound from Method A (F1- exchangeable); (2) organic-bound from Method B (F3- oxidizable); and (3) completely avoid using Method C.