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Two
heavy metal-contaminated soils are being employed to study the
effects of natural chelates on phytoextraction potential and
biomass production of metal hyperaccumulator plants. One soil
is contaminated with zinc, which is leached from the galvanised
coating of electrical transmission towers. The other soil, a
nickel laterite, has been enriched geologically.
The
organic amendments used in this study, Colac Peat and Organic
Humate (Australian brown coal), are natural plant products that
have been obtained locally. The effects of these potential complexing
agents on metal uptake and sequestration, as well as biomass
production, are currently being tested using the hyperaccumulators
Alyssum murale (Ni) and Thlaspi caerulescens (Zn) as well as
two 'control' non-accumulating crop plants, Brassica napus (canola)
and Lolium perenne (ryegrass).
During
this study, Induced Polarisation [IP] - an electrical geophysical
technique - has been employed to detect the extent (concentration
and area affected) of zinc contamination at the transmission
towers sites. Data collected have already shown that this method
is a very plausible, non-invasive technique for identifying
areas of elevated soil zinc concentrations, in the field. The
next phase will be to use the IP instrumentation in a glasshouse
trial. It is hypothesised that changes in the actual soil concentrations
of zinc will be quantifiable by changes in the soil chargeability.
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