Abstract:

The chemical fractions of manganese, iron, copper, lead, zinc and cadmium in the natural surface coating samples(NSCSs), which were collected in the Songhuajiang River, were investigated by using the modified sequential extraction procedure in order to identify the relative roles of Fe/Mn oxides and organic materials in the NSCSs in controlling heavy metals adsorption.  The results show that trace metals were mostly present as solid oxides/hydroxides with 62.9%, 58.3%, 53.8% and 326% for Cu, Zn, Pb and Cd, and little were bound to organic material with 1.1%, 0.6%, 9.9% and 1.8% for Cu, Zn, Pb and Cd, respectively.  It indicates that Fe/Mn oxides contributed the most to trace metals adsorption with less roles of  organic materials in trace metals adsorption.  These percent distributions of the trace metals in the NSCSs were also in excellent agreement with those obtained through direct experiments and reported in independent investigations from the natural surface coatings(NSCs) developed in natural waters.  Meanwhile, the results obtained in this paper could be confirmed through the selective extraction technique on the NSCS regardless of Fe oxides bound to residual. 

Key words: Natural surface coatings sample; Fe/Mn oxide; Copper, zinc, lead and cadmium; Sequential extraction