『Abstract
The re-vegetation of soils contaminated by potentially harmful
metals is generally considered a suitable option to reduce the
metal dispersion in surrounding environments. A continuous flow
experiment was conducted to quantitatively assess the effect of
Italian ryegrass (Lolium multiflorum Lam,) root the weathering
of smithsonite (ZnCO3), a common Zn mineral.
At the end of the experiment (10 days), the total amount of Zn
released by smithsonite was increased by a factor of 2.25 in the
presence of plants. This increase was due not only to plant uptake
but also to the enhancement of the Zn release into leachates.
The rate of Zn release from smithsonite to leachates was 2.9×10-4μg
g-1 s-1 and 1.5×10-4μg g-1
s-1 in the presence and the absence of plants, respectively.
The strong correlation (r = 0.95; p<0.001) between concentrations
of Zn and dissolved organic C (DOC) produced by the rhizosphere
activity in leachates indicated that organic root exudates and
secretions were closely involved in smithsonite weathering. Although
the results are derived from laboratory study, and further in
situ investigations over the long term are needed, they clearly
highlighted that plants can enhance metal release into the environment
by accelerating mineral weathering. Therefore, it is suggested
that the ability of plants to alter metal phases in soils should
be further taken into account when re-vegetation strategies are
proposed for the rehabilitation of metal-polluted soils.』
1. Introduction
2. Materials and methods
2.1. Smithsonite
2.2. Nutrient solution
2.3. Experimental set-up
2.4. Leachate analysis
2.5. Plant analysis
3. Results and discussion
3.1. Plant roots influence on pH and dissolved organic carbon
(DOC)
3.2. Kinetics of Zn release into leachates
3.3. Mass balance of released Zn
3.4. Possible mechanisms for plant-induced weathering of smithsonite
4. Conclusions and implications
Acknowledgements
References