Heavy metal mobility in contaminated soils as affected by plants, amendments and biochar
(2013)
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- Authors
- Supervisors
- Sonnet, Philippe
- Abstract
- (en) The successful implementation of phytostabilization is conditioned by a sound understanding of all potential metal mobilizing and/or immobilizing mechanisms acting upon contaminated soils as well as the capacity to develop synergies with other environmental and economic priorities. With these objectives in mind, this PhD thesis aimed at gaining better insights on the impacts of plants, amendments and biochar on the mobility of heavy metals in soils and the consequent implications for phytostabilization. First, the effects of the presence of plants on the release of heavy metals from a single mineral (smithsonite, ZnCO3) and anthropogenic contaminated soils were studied using continuous flow experiments, leaching column tests and Zn stable isotope analysis. Results revealed that the presence of plants generally increases the release of Cd, Zn and Pb due to plant-induced acidification and the release of soluble organic compounds from both roots and long-term accumulated plant residues. The effects of cost-effective amendments on the immobilization of heavy metals were then tested by means of a pot experiment. Although some amendments, such as bone meal, showed contrasting effects, other amendments, such as CaCO3, were found to successfully reduce both the leaching and the phytoavailability of Cd, Zn and Pb. Finally, the efficacy of biochar as an amendment for phytostabilization was evaluated using biotests and both pot and incubation experiments. Biochar was found to induce the immobilization of Cd, Zn and Pb in soils to an extent which was proportional to its rate of application. The mechanisms responsible for the metal immobilization were identified as predominantly pH-dependent even though aging reactions may also occur. Compared to CaCO3 amendment, biochar applied at 10% (w/w) tripled the production of rapeseed biomass while it was equally efficient in reducing metal concentration in shoots. Thus, in addition to sequestering C, the application of biochar to contaminated soils can improve the phytostabilization of the site while providing economic and environmental benefits via the production of a valuable biomass. The thesis provides evidence that the optimization of the phytostabilization of contaminated sites requires the application of metal immobilizing soil amendments, among which biochar turns out to be full of promise.
- Affiliations
Citations
Houben, D. (2013). Heavy metal mobility in contaminated soils as affected by plants, amendments and biochar. https://hdl.handle.net/2078.5/162372