Science, Technology and Engineering

School of Life Sciences

Department of Environmental Management & Ecology

	Dr Ewen Silvester
	Lecturer
	PO Box 821, Wodonga VIC 3689
	Tel: (02) 6024 9878
	Fax: (02) 6024 9888
	Email: e.silvester@latrobe.edu.au

Dr Ewen Silvester

Ewen Silvester's research interests are in the chemical processes occurring in natural systems, both pristine and those impacted by human activities. In a broad sense this research aims to understand nutrient, trace metal and organic compound regulatory mechanisms at the atomic level, and to understand the role of mineral surfaces in these processes.

Research Areas

Specific research areas include:

Geochemistry of Iron(II)

This work aims to determine the role of iron(II) in controlling redox conditions in soils and sediments. Our interest in this topic forms part of a collaborative effort with Prof Laurent Charlet (University of Grenoble, France) directed towards understanding the reactivity of iron(II) adsorbed on to oxide and clay substrates (publications 9 and 15).

Variation of the redox potential of soils with depth and mineralogy is relevant to the mobility of nutrients and aquatic pollutants (pesticides and herbicides), and the greater understanding of the role of iron(II) can lead to improved land management practices. It is likely that the outcomes of this research will be particularly relevant to the use of reclaimed (high oxygen demand) water wastewater in agriculture.

The current phase of this work is the measurement of electron transfer rates between adsorbed iron(II) and simple outer-sphere one-electron oxidants, as a method of determining the redox level of adsorbed iron(II).

Alpine peat bog function and rehabilitation

  Alpine peat bogs play a vital role in regulating the chemical composition and flow regime of upland streams. During snow melt and rainfall events alpine peat bogs act as water retention zones, decreasing the direct surface run-off, and minimizing the potential for downstream erosion events and flooding. This critically important water regulation function is potentially compromised by cattle grazing activities due to the compaction of the bog area, reducing the infiltration of rain and melt-water, and increasing direct surface run-off.

Water that passes through peat bogs will experience conditions that are predominantly reducing, with high microbial activity and long retention times, whereas run-off water will have a shorter retention times, and encounter conditions that are predominantly oxidizing. It is reasonable to expect that water originating from the peat bog mass will have compositional characteristics that reflect the reducing conditions of the peat bog. Such characteristics may include nutrient levels, natural organic matter (NOM) content and type, as well as bio-degradable organic carbon levels. Through the trophic relationships within these systems, these chemical characteristics will ultimately determine the form of the biological community associated with the peat bog.

This research project will examine and compare pristine and impacted alpine peat bogs, from both the chemical and biological perspectives, with the aim of understanding how these systems differ in terms of their trophic relationships. Through this work we aim to develop and propose rehabilitation strategies for impacted alpine peat bog systems.

Peer Reviewed Publications

1. Synthesis and characterization of optically transparent colloidal chalcopyrite (CuFeS 2 ); E.J. Silvester , T.W. Healy, F. Grieser, B. A. Sexton Langmuir, 1991, 7 , 19.

2. Spectroscopic studies on copper sulfide sols; E.J. Silvester , F. Grieser, B. A. Sexton, T. W. Healy Langmuir , 1991, 7 , 2917.

3. Oxidation kinetics of ultra-small colloidal chalcopyrite with one electron oxidants; E.J. Silvester , F. Grieser, D. Meisel, T. W. Healy, J.C. Sullivan J. Phys. Chem. 1992, 96 , 4382.

4. Thermodynamics and kinetics of interaction of copper(II) and iron(III) with ultra-small colloidal chalcopyrite (CuFeS 2 ) at low and neutral pH; E. J. Silvester , F. Grieser, D. Meisel, T. W. Healy, J. C. Sullivan J. Chem. Soc. Faraday Trans. 1994, 90 , 3301.

5. The mechanism of chromium(III) oxidation by sodium buserite. E.J. Silvester ; L. Charlet; A. Manceau J. Phys. Chem . 1995, 99 , 16662.

6. The structure of synthetic monoclinic Na-rich birnessite and hexagonal birnessite. I. Results from X-ray diffraction and selected area electron diffraction. V.A. Drits; E.J. Silvester ; A.I. Gorshkov; A. Manceau American Mineralogist 1997, 82 , 946.

7. The structure of synthetic monoclinic Na-rich birnessite and hexagonal birnessite. II. Results from chemical studies and EXAFS spectroscopy . E.J. Silvester ; A. Manceau; V.A. Drits American Mineralogist 1997, 82 , 962.

8. Structural Mechanism of Co 2+ oxidation by the phyllomanganate buserite. A. Manceau; V.A. Drits; E.J. Silvester ; C. Bartoli; B. Lanson American Mineralogist 1997, 82 , 1150.

[Nominated for best paper in American Mineralogist 1997].

9. N-compound reduction and actinide immobilisation in surficial fluids by Fe(II): the surface º Fe III OFe II OH o species, as major reductant. L. Charlet; E.J. Silvester ; E. Liger. Chemical Geology 1998, 151 , 85.

10. Steady-state radiolysis study of the reductive dissolution of ultrasmall colloidal CuS. K. M. Drummond; F. Grieser; T. W. Healy; E. J. Silvester ; M. Giersig. Langmuir , 1999, 15 , 6637.

11. Structure of H-exchanged hexagonal birnessite and it mechanism of formation from Na-rich monoclinic buserite at low pH: New data from X-ray diffraction. B. Lanson; V.A. Drits; E.J. Silvester ; A. Manceau American Mineralogist 2000, 85 , 826.

12. Spectroscopic characterisation of ethyl xanthate oxidation products and analysis by ion-interaction chromatography . F-P. Hao; E. J. Silvester ; G. D. Senior. Analytical Chemistry 2000, 72 , 4836.

13. The oxidation of ethyl xanthate and ethyl thiocarbonate by hydrogen peroxide. E. J. Silvester ; D. Trucccolo; F-P. Hao Journal of the Chemical Society Perkin Trans. 2 2002, 1562.

14. The structure of heavy-metal sorbed birnessite: Part 1. results from X-ray diffraction. B. Lanson; V. A. Drits; A.-C. Gaillot; E. J. Silvester ; A. Manceau; A Plançon American Mineralogist 2002, 87 , 1631.

15. Redox Potential Measurements and M ö ssbauer Spectrometry of Fe II Adsorbed onto Fe III (Oxyhydr)oxides . E. Silvester ; L. Charlet; C. Tournassat; A. G é hin; J.-M. Greneche; E. Liger ( Geochimica Cosmochimica Acta , Accepted)

16. Structural and spectroscopic properties of O -ethyl dithiocarbonate S -oxide. E. J. Silvester ; P. Persson; L. Lövgren (in prep).

17. The adsorption of ethyl perxanthate onto goethite ( a -FeOOH). E. J. Silvester ; L. Lövgren; P. Persson; A. Shchukarev (in prep).