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Characterisation of Constructed Wetland Substrates by Chemical Sequential Extraction and X-Ray Diffraction Analyses

Characterisation of Constructed Wetland Substrates by Chemical Sequential Extraction and X-Ray... Substrates from four-and-a-half year old constructed wetlands built to treat wastewater from an active metal mine were analysed for elevated metal and sulphur concentrations by chemical sequential extractions and X-ray diffraction analyses. Amounts of Fe, Pb, Zn and S were quantified in substrates from the first cells of multi-celled (in-series) treatment wetland systems at three different depths. The analyses showed that the majority of metals removed from the wastewater were retained in residual immobile forms in the upper 0–5cm of the waterlogged anaerobic substrates. Although substantial concentrations of metals and sulphur were retained in the substrates, the amounts were generally not sufficient to allow accurate mineralogical identification by X-ray diffraction. Classification of the sediments using X-ray techniques was further confounded by the highly organic nature of the wetland substrates. These results suggest that chemical analyses of wetland substrates may still provide a clearer interpretation of metal accumulation over time, especially in wastewaters characterised by relatively low metal concentrations flowing through organically rich substrates. While X-ray diffraction can provide useful interpretation of sediment crystallography and mineralogy, there are limitations in using this technology to characterise young wetland substrates. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Biology and Environment: Proceedings of the Royal Irish Academy Royal Irish Academy

Characterisation of Constructed Wetland Substrates by Chemical Sequential Extraction and X-Ray Diffraction Analyses

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Publisher
Royal Irish Academy
Copyright
Copyright © 2005 RIA
ISSN
0791-7945
eISSN
2009-003X
DOI
10.3318/BIOE.2005.105.2.87
Publisher site
See Article on Publisher Site

Abstract

Substrates from four-and-a-half year old constructed wetlands built to treat wastewater from an active metal mine were analysed for elevated metal and sulphur concentrations by chemical sequential extractions and X-ray diffraction analyses. Amounts of Fe, Pb, Zn and S were quantified in substrates from the first cells of multi-celled (in-series) treatment wetland systems at three different depths. The analyses showed that the majority of metals removed from the wastewater were retained in residual immobile forms in the upper 0–5cm of the waterlogged anaerobic substrates. Although substantial concentrations of metals and sulphur were retained in the substrates, the amounts were generally not sufficient to allow accurate mineralogical identification by X-ray diffraction. Classification of the sediments using X-ray techniques was further confounded by the highly organic nature of the wetland substrates. These results suggest that chemical analyses of wetland substrates may still provide a clearer interpretation of metal accumulation over time, especially in wastewaters characterised by relatively low metal concentrations flowing through organically rich substrates. While X-ray diffraction can provide useful interpretation of sediment crystallography and mineralogy, there are limitations in using this technology to characterise young wetland substrates.

Journal

Biology and Environment: Proceedings of the Royal Irish AcademyRoyal Irish Academy

Published: May 1, 2005

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