A mesocosm study of electrokinetic-assisted phytoremediation of atrazine-polluted soils

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) x 0.49 (W) x 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).