Electrokinetic-assisted phytoremediation of atrazine: Differences between electrode and interelectrode soil sections

Electrokinetic-assisted phytoremediation (EKPR) has been recently proposed by us to remediate soils contaminated by atrazine, a common pesticide in agrarian areas. The goal of this work was to study the differences of electrochemical and biological processes occurred in the different soil sections (anode, cathode and inter electrode section) of the pots used in an EKPR test carried out with maize and a low permeability soil spiked with atrazine. An initial atrazine soil concentration of 5 mg kg(-1) was used; the electric current (with voltage gradients of 2 and 4 V cm(-1)) was applied during 14 days, 4 h a day and changing the polarity of the electrodes each 2 h. This operation mode avoided the extreme soil pH values, although it tended to increase throughout the EKPR test causing soil alkalinisation, especially in the cathode. As a result, maize growth was poorer in the electrode soil sections. Atrazine and its metabolites, deethylatrazine and deisopropylatrazine, were taken up and accumulated in the maize tissues in a different extent depending on the soil section considered, showing the mobilization of atrazine by the electric current. The best results were found for the 2 V cm(-1) treatment, for which the presence of maize increased 20-30% the overall atrazine removal in the cathode and middle sections of the planted pots as compared to the unplanted pots, showing the ability of EKPR to improve the efficiency of the electrokinetic remediation. Electromigration and electroosmotic flux contributed to transport atrazine and its metabolites throughout the soil.