Growing Metals

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Growing Metals
Using metal-accumulating plants to remediate
contaminated sites
Chris Anderson Soil and Earth Sciences,
Institute of Natural Resources, Massey
University, Palmerston North, New
Zealand Phytomine Environmental Ltd., Wellington,
New Zealand
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Phytoremediation

• Environmental solutions are needed for
  contaminated sites
• Conventional solutions chemical or physical
  methods at high cost
• Phytoremediation a softer solution that uses
  plants to uptake or degrade contaminants
• Intelligent synergy of botany, geochemistry and
  microbiology
• SOLAR DRIVEN BIOPUMPS

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• Phytoextraction plant removal of
• water
• nitrates, phosphates
• heavy-metals
• some organic nasties

• Phytodegradation and stabilisation enhanced by
• soil aeration
• plant exudates
• soil microbiota stimulated by plant exudates

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Phytoextraction

• Natural hyperaccumulation
• Some plant species have evolved to accumulate
  very high metal concentrations
• Sb, As, Cd, Co, Cu, Ni, Se, Tl, Mn, Zn
• Induced hyperaccumulation
• Forcing plants to accumulate other metals by
  making these soluble in soil solution
• Au, Pb, Hg, Pd, Pt

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Natural hyperaccumulation
Data from Reeves, 1992a
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The phytoextraction operation
Chemicals added
Biopump grown
Plant material harvested and burnt to produce
bio-ore
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Ni
Cu
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Pd
Au
Bio-ore smelted
Bio-ore landfilled
Phytomining
Phytoremediation
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Phytoextraction in action
The location a base-metal smelter, South Africa
The problem Ni contamination over 5ha due to Ni
salt storage and spillage
The solution phytoextraction using a native
nickel-accumulating species
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Phytoextraction for gold

• Thio-ligands can induce the solubility and uptake
  of gold from waste, low-grade rock
• Discovery made in New Zealand
• Proof of concept achieved and the technology is
  being field tested
• Aim is a crop of 10 t/ha biomass with 100 mg/kg
  gold concentration dry weight
• This will yield 1000 g of gold per hectare as
  well as other metals made soluble
• Current focus is on mercury (Hg) removal at the
  same time as gold

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An intelligent system

• Importance of botany and geochemistry is clear,
  but microbiology is also important
• Bugs for contaminant assessment
• Bugs as inoculum to increase plant growth and
  metal uptake
• The choice to use phytoremediation is facilitated
  by a decision support system
• System developed and used by Phytomine
  Environmental Ltd.

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Fosterville gold mine, Victoria, Australia
6th May 2002
3rd July 2002
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17th September 2002
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17th September 2002
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29th April
Tui base-metal mine, Coromandel, NZ
22nd May
21st September
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1st July 2002
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1st July 2002
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When to use phyto a DSS

• Phytoremediation, will only be used for land
  clean-up and management IF the technology will
  deliver the most economically favourable outcome
• Consider
• alternatives conventional or inaction
• revenue from the plants metals and energy
  generation through biomass burning (gasification)
• proposed end use for the land
• legislative incentive and public perception
• The suitability of phytoremediation is thus
  dependant upon economics

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• Research tools
• Greenhouse experiments to study metal uptake
• Hydroponic and soil systems
• Geochemical modeling through simple laboratory
  extractions
• Atomic absorption and ICP analysis for cations
• IC for anions
• These tools support field trials

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Hg volatilisation studies
Air Outlets
Air Tight Plastic Chamber (4.25 L Volume)
B. juncea plantlet grown in hydroponics solution
Air Inlets
KMnO4 H2SO4 Traps
Air Pump
Air Tight Plastic Pot (100 mL Volume)
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Conclusions

• Phytoremediation is land-management technology
• Where suitable, phytoremediation is a low-cost,
  sustainable solution for contaminated land and
  waste-streams
• Making the technology work relies on the
  intelligent synergy of botany, microbiology and
  geochemistry
• Revegetation, land stabilisation and
  phytoextraction are all working scenarios of
  phytoremediation

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Conclusions (contd.)

• Phytoremediation is suitable for
• Acid, artisanal, laterite and ultrabasic tailings
• Heap-leach pads
• Contaminated water (metals and non-metals)
• Municipal sewage wastes
• Soil contamination through industrial/mining
  activity
• Geogenic sources of metals (e.g. As in
  Bangladesh)
• A plant-based management system can be designed
  for nearly all contaminating waste-streams and
  for many contaminated sites
• Implementation depends upon suitable assessment
  and design