EDTA assisted phytoextraction of metals using Erica andevalensis

Phytoremediation techniques applying chelating agents are frequently used to increase the bioavailability of heavy metals. These procedures may increase plant metal uptake and enhance soil-cleaning processes. Such techniques are particularly useful in cases of widespread pollution limited to the surface soil layer, as it occurs in abandoned mine sites. Our study was designed to explore the use of Erica andevalensis jointly with EDTA application to enhance phytoextraction of metals in soils of an abandoned mine area (Riotinto, Spain). Such soils are acidic (pH 3), poor in plant essential elements and have Cd and Pb contents above the toxicity threshold. Plants were grown in soil irrigated with EDTA solutions at different concentrations (1, 3 and 5 mM) or in EDTA-extracted soil solutions during three weeks. The metal concentrations in plants cultivated in soil+EDTA were similar to those in control conditions (without EDTA) indicating that EDTA was not able to promote metal uptake in Erica plants. In addition, EDTA caused significant reduction in plant biomass suggesting phytotoxic effects, however, no visible damages were observed on plants. On the other hand, plants grown in EDTA-extracted soil solutions showed severe toxicity symptoms. These results indicate that the strategy of EDTA-assisted phytoextraction does not work with Erica andevalensis. However, for its capability to colonize mine tailings, this species is good candidate for phytostabilization in mining districts.