I would like to know the possible reasons behind the high concentration of trace metals like Pb, Cu, Ni etc in deep sea sediments, especially in the so-called residual fraction (in case of sequential extraction) which is generally considered to be alumino-silicates. Can there be any significant contribution of dust laden trace metals in the deeper parts of the ocean (Indian Ocean)?
Simontini
The residue if it contains just the aluminosilicate material cannot have high concentrations of the metals you mentioned. The residue values for these metals should be closer to the upper crustal values. If they are higher than that, there is a chance of presence of small quantity of sulfidic minerals. In any case, one should ensure a proper removal of oxide bound fraction during the initial stages of extraction. You may read Mascarenhas-Pereira and Nath (2010) in Marine Chemistry for a leaching experiment study carried out on Indian Ocean pelagic clay. Good luck!
Higher concentration of metals in residual phase obtained by BCR-SEP signifies lithogenic origin of metals. However, if the metal concentration is higher in other forms (other than residual), anthropogenic sources could be the principal cause. You may refer various literature on the same like Metals in Hydrocycle by Salomons and Forstner and research paper by V Subramanian. You may also refer to Pandey et al. 2014 (Risk assessment of metal species in sediments of the river Ganga) published in Catena. However, this study is on river bed sediments.
Yes Mayank, I am aware of that but thank you anyway for the valuable inputs. My samples are, however, deep sea sediments. So both land rocks and ridge rocks could be the source for residual fraction I guess.
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