Impact of Redox Cycles on Manganese, Iron, Cobalt, and Lead in Nodules
- S. Cornu *ab,
- J. A. Cattleac,
- A. Samouëliana,
- C. Laveufa,
- L. R. G. Guilhermeade and
- P. Albéricf
- a INRA, UR0272 Science du sol, F-45166 Olivet, France
b INRA, UR1119 Géochimie des Sols et des Eaux, Europôle de l'Arbois, BP 80, F-13545 Aix en Provence, CEDEX 4, France
c Ecotoxicology and Environmental, Contaminants Section, Dep. of Environment and Climate Change, PO Box A290, Sydney South, NSW 1232, Australia
d le STUDIUM Institute for Advanced Studies, 3D avenue de la Recherche scientifique, 45071 Orléans CEDEX 2, France
e Federal Univ. of Lavras, Soil Science Dep., CP 3037, 37200-000 Lavras (MG), Brazil
f ISTO UMR 6113- CNRS/Université d'Orléans, 1A, rue de la Férollerie, 45071 Orléans CEDEX 2, France
Redox processes are responsible for Fe and Mn segregation as Fe–Mn oxide coatings or nodules. These nodules are also trace element scavengers in soils. Redox processes are of particular importance in seasonally saturated soil containing naturally high concentrations of trace metals. We investigated the dynamics of Fe–Mn nodules and two associated trace elements, Co and Pb, under controlled redox conditions in a column experiment, including five columns fed with mimicked topsoil solution that was elevated in Fe and Mn. The results show that the redox conditions reached 100 mV, which was sufficient to dissolve Mn oxides and release the associated Co, while Pb was readsorbed onto nodule surfaces. The amounts of Mn and Co released into the water were small compared with the quantities stored in the nodules (<0.1% of the initial stock stored in the nodules). The redox conditions were insufficient, however, to allow Fe oxide dissolution. On the contrary, 70 to 90% of the Fe entering the column was fixed onto the nodules. In terms of an environmental threat, these results showed that Pb would not be released from soil during nodule dissolution, whereas Co, which is less toxic, would be released.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2009.