Efficacy of EDTA and Olive Mill Wastewater to Enhance As, Pb, and Zn Phytoextraction by Pteris vittata L. from a Soil Heavily Polluted by Mining Activities

A pot experiment was conducted to evaluate the effect of Na 2 -EDTA 0.01 M (E) and olive mill wastewater 15% (OMW) on As, Pb, and Zn uptake by Pteris vittata L. grown in a soil highly contaminated by mining activities. A two-factor experimental design was followed; 3 treatments (E, OMW, and E + OMW) × 2 batches (single or double dose). Six weeks after the P. vittata transplanting, all pots received the selected dose of each treatment (Batch I). At 8 weeks, in half of the pots, a second dose of the same treatments was added (Batch II). Plants were harvested after 10 weeks and As, Pb, and Zn concentrations were determined in fronds and roots. Depending on the element, both treatment and batch effects were significant. In Batch II, EDTA application resulted in a 55% increase of As and 9- and 4-fold of Pb and Zn concentrations in the fronds, while OMW treatment substantially reinforced plant uptake when combined with EDTA. Roots to fronds translocation of the metal(loid)s highly increased in Batch II. After harvest, composite soil samples of all treatment–batch combinations were subjected to sequential extraction, but no significant differentiations of As, Pb, and Zn partitioning in soil phases were detected.