SREL Reprint #2940




Assessment of contaminant retention in constructed wetland sediments

A. S. Knox1, D. Dunn1, M. Paller1, E. A. Nelson1, W. L. Specht1, and J. C. Seaman2

1Savannah River National Laboratory, Environmental Sciences & Technology Department,
Bldg. 773-42A, Aiken, South Carolina 29803, USA
2The University of Georgia, Savannah River Ecology Laboratory, Aiken, South Carolina 29802, USA

Abstract: The A-01 wetland treatment system (WTS) was designed to remove metals from an industrial effluent at the Savannah River Site, Aiken, SC. Sequential extraction data were used to evaluate remobilization and retention of Cu, Pb, Zn, Mn, and Fe in the wetland sediment. Remobilization of metals was determined by the Potentially Mobile Fraction (PMF) and metal retention by the Recalcitrant Factor (RF). The PMF, which includes water soluble, exchangeable, and amorphous oxides fractions, is the contaminant fraction that has the potential to enter into the mobile aqueous phase under fluctuating environmental conditions. PMF values were low for Cu, Zn, and Pb (13-27%) and high for Fe and Mn (62-70%). The RF, which includes crystalline oxides, sulfides or silicates and aluminosilicates, is the ratio of strongly bound fractions to the total concentration of elements in sediment. RF values ranged from 73-87% for Cu, Zn, and Pb, indicating high retention in the sediment and from 30-38% for Fe and Mn, indicating low retention. Contaminant retention, which is determined by solid phase metal speciation, determines the potential mobility and bioavailability of captured metals in wetland sediments; hence, their likelihood of being released if chemical, physical, or biological conditions within the wetland change.

Keywords: Contamination • Heavy metals • Sediments • Water treatment

SREL Reprint #2940

Knox, A. S., D. L. Dunn, M. H. Paller, E. A. Nelson, W. L. Specht, and J. C. Seaman. 2006. Assessment of contaminant retention in constructed wetland sediments. Engineering in Life Sciences 6:31-36.

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