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Use of citric and tartaric acid to enhance phytoextraction of metals from degraded mine

Research Areas
  • Agriculture

Mining activities are important sources of metal contamination, which can cause land degradation and ground cover losses. A promising strategy to remediate these sites is phytoextraction, but the slow desorption of metals in soils has been a major limitation for the success of this technique. Low molecular weight organic acids, such as citric and tartaric acid, play an important role in metal mobility and its subsequent accumulation in plants. In this study, the effects of citric and tartaric acids on metal mobilisation were assessed through a one-step extraction procedure and a soil column experiment in order to facilitate the phytoextraction of metals by plants. Different extracting solutions were prepared with a background electrolyte (KNO3 0.01 M) and different concentrations of organic acids: control without organic acids, citric 0.5 mM, tartaric 0.5 mM, citric 10 mM, tartaric 10 mM and citric 5 mM + tartaric 5 mM. A Visual Minteq speciation modeling of the soil solution and the metal fractionation of soils at the beginning and at the end of the column experiment was performed to elucidate the main chemical processes that affect metal desorption by organic acids. Results of the one-step extraction procedure showed that metal desorption was correlated to the type of organic acid and its concentration. Higher concentrations of organic acids significantly increased metal desorption and citric acid was more effective than tartaric acid. Metal desorption was mainly determined by the decreasing pH and the dissolution of Fe and Mn oxides, and not so by the formation of soluble metal-organic complexes as it was predicted by the speciation modeling. The results of the soil column study reported that low concentrations of organic acids (0-0.5 mM) did not significantly increase metal mobilisation and higher doses were not also able to mobilise important amounts of Zn. Citric acid at 5-10 mM remarkably promoted Cu mobilisation (from 1 mg kg-1 in control and with organic acids at 0.5 mM to 42 mg kg-1 with citric acid at 10 mM) and reduced the exchangeable (from 21 to 3 mg kg-1) and bound to Fe and Mn oxides (from 443 to 277 mg kg-1) fractions of this metal. Citric acid could improve metal phytoextraction by plants without environmental risk in order to reclaim degraded lands
3rd International Conference on Soil Bio- and Eco-Engineering
Vancouver, Canada
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ABSTRACT BOOK 3rd International Conference on Soil Bio- and Eco-Engineering

Research Group, Departaments and Institutes related
  • Creador: Grupo de Investigación: Calidad de Suelos y Aplicaciones medioambientales