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Atrazine (ATR) continues being one of the most frequently detected pesticides in natural waters and soils. In this work, an electrokinetic-assisted phytoremediation pot test (EKPR) was performed for the remediation of an atrazine-spiked soil; a low electric voltage gradient (1 V cm−1) with two different electric field operation times (6 and 24 h per day) was used in combination with ryegrass (Lolium perenne L.). EKPR increased up to 27% and 7% the overall ATR removal from soil as compared to natural attenuation and phytoremediation treatments, respectively. ATR soil concentration vs time curves were fitted to a pseudofirst-order kinetic equation, obtaining ATR half-life values of 8.2, 7.1 and 5.4 days for the treatments corresponding, respectively, to 0, 6 and 24 h day−1 of electric current application. It clearly showed that the ATR removal from soils was enhanced by the electric field. ATR plant accumulation was significantly improved with respect to phytoremediation when the electric current was continuously applied throughout the experiment (24 h day−1); most of the ATR residues were accumulated in the shoot biomass of the ryegrass plants. Image 1 • Application of EKPR increased up to 27% and 7% as compared to natural attenuation and phytoremediation treatments. • 11–21% of the initial atrazine was accumulated in the ryegrass tissues. • Approximately 80% of the atrazine was removed in the first 4 days of treatment. [ABSTRACT FROM AUTHOR]

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]

Abstract An electrokinetic-assisted phytoremediation test using maize ( Zea mays L.) was conducted in order to assess the role of the electric field on the enhancement of plant uptake and degradation of the moderate polar pesticide atrazine in spiked soils. Twelve different treatments, including two different initial atrazine soil doses (5 and 10 mg kg−1) and two different values of the electric field applied (2 and 4 V cm−1), together with the corresponding control treatments without plants and/or without electric current, were tested. The application of an electric field during a period of 4 h a day and with periodical polarity inversion (each 2 h) did not caused significant changes in soil pH; moreover, maize plants increased the buffering capacity of the soil. The application of an electric field of 2 V cm−1 led to a slight decrease on maize biomass while the accumulation of atrazine and its main metabolites in plant tissues was significantly enhanced. On the overall, the yield of atrazine removal by electrokinetic-assisted phytoremediation with maize was increased up to 36.5% with respect to the phytoremediation process without electricity. On our knowledge, this work is the first one specifically focused on the removal of organic pollutants from soils by using the combination of phytoremediation and electrokinetic remediation. Graphical abstract Image 1 Highlights • Electric field application enhanced plant uptake and soil degradation of atrazine. • Soil pH did not changed using electricity 4 h a day and switching polarity each 2 h. • The application of an electric voltage of 2 V cm−1 increased the mobility of atrazine. [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]

Electrokinetic-assisted phytoremediation (EKPR) has been recently proposed for the removal of pesticides from polluted soils. In this work, we report the results from an EKPR experiment that was carried out in a mesocosm mock-up of 0.386 m3 using ryegrass (Lolium perenne L.) and a low permeability soil spiked with atrazine. Plants were initially grown for 35 days; then, the soil was spiked with atrazine at a dose of 2 mg kg−1 soil. A DC electrical field of 0.6 V cm−1 was applied 24 h every day, switching polarity daily. Another identical mock-up with the same experimental conditions but without plants was used for comparison purposes. The duration of the EKPR test was 19 days during which some operational parameters were registered (electric current intensity, soil pH and temperature) and soil porewater samples were taken and analysed. Plant tissues and soil samples from the different sections in which the mock-ups were divided, were also collected and analysed at the end of the experiment. 3-D profiles of soil pH, water content and atrazine residues concentration in plants and soil were obtained and discussed. The results of this experiment were compared with others previously reported by us from a similar EKPR pot test. In spite of the difficulties to get an adequate geometric and operational similarity between setups of different scale, the main output parameters of the EKPR process (electric current, specific current charge, overall atrazine removal, specific atrazine removal efficiency, root biomass:soil weight ratio) were discussed. It was shown that, although the processes carried out are essentially the same in both scales, their extent may be quite different; it highlights the limitations of small-scale experiments to predict the results at field conditions. Image 1 • The successfully EKPR of atrazine-polluted soils in a mesocosm scale has been demonstrated. •Electro-osmosis was the most relevant transport mechanism for atrazine in soils. •Atrazine overall removal efficiency was improved by ryegrass plants in approximately 44%. •The extent of biochemical and electrokinetic processes greatly varied with the setup scale. [ABSTRACT FROM AUTHOR]