Phytomanagement of heavy metals contaminated soils: mobilization or immobilization of pollutants?

Lambrechts, Thomas;Gustot, Quentin;Couder, Eléonore;Houben, David;Lutts, Stanley;et.al.
(2011) The 6th International Conférence on Soils of Urban, Industrial, Traffic, Mining and Military Areas — Location: Marrakech (Marocco) (3.October.2011)

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  • Lambrechts, ThomasUCLouvain
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  • Gustot, QuentinUCLouvain
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  • Couder, EléonoreUCLouvain
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  • Houben, DavidUCLouvain
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  • Iserentant, AnneUCLouvain
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  • Lutts, StanleyUCLouvain
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Abstract
Phytoremediation is a promising and cost-effective strategy to manage heavy metal polluted sites. In this experiment, we compare phytoextraction and phytostabilisation technologies on a soil contaminated by Cd and Zn fallouts from a former Zn smelter. Lolium perenne plants were cultivated for 2 months under controlled conditions in a 27.6dm³-pot experiment filled with the contaminated soil. A leachate tank below the soil compartment allowed the collect of leachates. The heavy metals phytoextraction was promoted by adding Na-EDTA (0.5 g.kg-1) in watering solution 4 days after germination. Phytostabilisation was assessed by mixing soil with steel shots (1%) before Lolium perenne sowing. Plants, soils and leachates were regularly monitored during 2 months for plant growth, leachate volume, elemental concentrations (Ca, Cd, Fe, K, Mg, Na and Zn), pH and electrical conductivity. Shoot biomass was low, because of high heavy metal toxicity. Presence of plants exacerbated heavy metal leaching, by improving soil hydraulic conductivity. Use of EDTA for phytoextraction increased heavy metal mobility in soil, leading to higher concentration of heavy metal in shoots. Moreover, biomass production was also increased despite higher Cd and Zn concentration in shoots, because EDTA was able to reduce metal toxicity in plant tissues. However, this higher heavy metal extraction was insufficient to significantly reduce the heavy metal content in soil, and did not justify the important leaching induced by EDTA. On the other hand, addition of steel shots decreased efficiently both CaCl2 (0.01M) extraction of Cd and Zn, and therefore heavy metal mobility in soil, and their leaching. This input improved also shoot biomass production. However, improvement of growth conditions by steel shots led to higher heavy metal mass in shoot tissues. Therefore, soil heavy metal mobility and plant uptake are not always linked, as reduction of metal mobility enhanced plant metal uptake in our experiment.
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Lambrechts, T., Gustot, Q., Couder, E., Houben, D., Iserentant, A., & Lutts, S. (2011). Phytomanagement of heavy metals contaminated soils: mobilization or immobilization of pollutants? The 6th International Conférence on Soils of Urban, Industrial, Traffic, Mining and Military Areas, Marrakech (Marocco). https://hdl.handle.net/2078.5/220694