Mineralogy, geochemistry and speciation of contaminants in urban sediments'

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Mineralogy, geochemistry and speciation of
contaminants in urban sediments.

• Kevin G. Taylor
• Environmental Sedimentology Research Group
• Manchester Metropolitan University, UK

Co-workers Judith Barrett, Fabienne Carraz
(MMU) Karen Hudson-Edwards
(Birkbeck)
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Urban Systems
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Urban Pollution Cascade
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What is road-deposited sediment?
Complex
Mobile
Location specific
Dynamic
Interactive
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1974
1980
1972
1974
1974
1974
1972
1974
1972
Significant source of water contaminants
(Sartor Boyd)
Health risk of Pb in RDS
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Spatial Compositional Variability (1)
Pb
Zn
1 km
Element concentration ranges Pb 25-645 ?g/g Zn
172-2183 ?g/g Cu 32-283 ?g/g
Cu
From Carraz et al., 2006
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Spatial Compositional Variability (2)
Chloride
Sulphate
Ammonium
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Temporal Compositional Variability
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Grain-size Heterogeneity
Mass distribution ()
Cu concentration (ug/g)
1-2 mm
lt38 um
1-2 mm
lt38 um
Cu loading ()
1-2 mm
lt38 um
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Metal-rich grains
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Metal-rich grains
Anthropogenic grains are major hosts for metals
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Powder X-ray diffractograms
63 -38µm
Quartz-dominated
1000-500 µm
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Cu-K edge for X-ray absorption near edge
spectroscopy (XANES)
Best Fit 43 Copper Acetate 32 Copper
Nitrate 16 Copper Metal 9 Copper
Chloride Chi 0.14 R 0.23
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Cu-K edge for X-ray absorption near edge
spectroscopy
Best Fit 43 Copper Acetate 32 Copper
Nitrate 16 Copper Metal 9 Copper
Chloride Chi 0.14 R 0.23
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Pb-LIII edge for X-ray absorption near edge
spectroscopy (XANES)
Best Fit 49 Lead Carbonate (Basic) 41 Lead
Chloride 11 Lead Chromate Chi 0.02 R
0.04
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Salford Quays
Manchester Ship Canal
River Irwell
Salford Quays
1 km
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Sediments Stored Pollution
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Anthropogenic material
Anthropogenic furnace-derived glass
grains abundant
From Taylor et al. (2003) Hydrological Processes.
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Sediment-Water Interactions
Early diagenesis results in contaminant release
into river basins.
For example, bacterial Fe(III) reduction, Mn(IV)
reduction, sulphate reduction and methanogenesis
release contaminants into porewaters.
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Glass Dissolution
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Diagenetic Minerals
Vivianite (FeII phosphate)
Pyrite
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Vivianite
?-EXAFS
?-XANES
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What are we now doing

• More EXAFS/XANES, FT-IR and Raman work on mineral
  and grains in both systems more information on
  the speciation of contaminants.
• Geomicrobiology on these systems (16s rRNA,
  experimental analysis). What role do bacteria
  play in likely contaminant cycling and what are
  these bacteria?
• Bacteria-mineral interactions?.