Phytotoxicity and metal leaching in EDDS-assisted phytoextraction from pyrite wastes with Ethiopian mustard and fodder radish.

This study examines the influence of a low-persistent chelator (S,S-EDDS) on the growth of Ethiopian mustard ( Brassica carinata A. Braun) and fodder radish (Raphanus sativus L. var. oleiformis) and on metal leaching in As-Co-Pb-Zn contaminated pyrites wastes. Shoot biomass, leaf area and root biomass being more affected than lenght and electrical capacitance. EEDS generally improved shoot concentration of Cu, Co, Zn and Pb but repeated treatments caused significant metal leaching (mainly of Cu), explained by a multivariate relationship (R2= 0.52) including the integral over time of both leaf area (R2= 0.43) and root electrical capacitance (R2= 0.09). We conclude that roots play a secondary role in preventing metal leaching, because of the prevailing effect of leaf transpirationin cotrolling percolation. The best metal phytoextraction was achived with EDDS applied at harvest-a safe metal leaching strategy, expeciallyat the low dose of 2,5 mmol per kg of soil.