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Graphical abstract Highlights • The periodic polarity reversal of the DC field avoided marked changes in soil pH. • Plant growth was lesser in the electrode soil sections than in the interelectrode one. • Atrazine was transported through the soil by electromigration and electroosmotic flux. • Electrokinetic removal of atrazine was enhanced up to 30% by maize plants. Abstract 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 interelectrode 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. [ABSTRACT FROM AUTHOR]

• EKPR of atrazine-polluted soils is feasible at mesocosm scale. • Atrazine was transported in the soil by electro-osmosis and electromigration. • Final distribution of atrazine in soils agrees with its concentration in soil pore water. • Some limitations relative to the scaling up of EKPR processes have been detected. Phytoremediation, an ecological remediation technology based on the use of plants, can be combined with electrokinetic treatment for the removal of both inorganic and organic pollutants from soils. Electrokinetic-assisted phytoremediation (EKPR) of atrazine was tested in a mesocosm scale experiment using ryegrass (Lolium perenne L.). Two mock-ups with dimensions of 2.25 (L) × 0.49 (W) × 0.50 (H) m were initially filled with an unpolluted low plasticity clay soil and used to carry out an EKPR test and another electrokinetic remediation (EKR) one after spiking the soil with atrazine at a dose of 2 mg kg−1. Experiments were conducted for 19 days using a DC electrical field of 0.6 V cm−1 applied continuously without changing polarity. Samples of soil, plants and soil pore water corresponding to ten different soil sections of each mock-up were taken and analysed throughout the experiment. Soil pH followed an increasing profile from the anode to the cathode, although it kept moderate values in the range of 7.53–9.62. Electro-osmosis, gravity and plant roots (in the EKPR series) influenced the final distribution of water and atrazine in the soil. Additionally, the electromigration flux had a relevant role in the atrazine residues transport during the EKPR process. Concentration values of atrazine residues remaining in the different soil sections were in good agreement with those of the soil pore water, with most of the atrazine being accumulated in the cathode section. Atrazine was mainly removed from soils by biochemical degradation, which was greatly improved by ryegrass plants; the overall atrazine removal yield was increased from 40.20% (unplanted mock-up) to 61.01% (planted mock-up). [ABSTRACT FROM AUTHOR]