Impact of electrokinetic-assisted phytoremediation of heavy metal contaminated soil on its physicochemical properties, enzymatic and microbial activities

Electrokinetic-assisted phytoremediation is a potential technology for remediation of contaminated soils, but little is known about its impact on soil physicochemical and biological properties. This laboratory-scale study investigated changes of soil physicochemical properties, and enzymatic and microbial activities after electrokinetic-assisted phytoremediation of a heavy metal contaminated soil. After Indian mustard (Brassica juncea) had been grown for 35 d, three voltage gradients (1, 2, 4 V cm−1) of direct-current (DC) were applied for 8 h d−1 across the soil for 16 d. To allow comparison, two treatments were used as controls: the first with 2 V cm−1 of DC electric field only and the another with only Indian mustard. The results showed that the average contents of soil NO3−-N, NH4+-N, available-P and K were 0.90–3.49, 0.98–1.08, 1.08–1.55 and 1.07–1.11 times higher than the initial contents. The extractable soil Cd and Zn concentrations increased from the cathode to the anode, while the inverse was observed for Cu bioavailability. The soil urease, invertase and phosphatase activities were strongly inhibited, but the basal soil respiration and microbial biomass carbon near the anode and cathode were significantly increased. Bivariate correlation analysis and principal component analysis indicated that the DC electric field was the main factor affecting the soil properties, and plant growth partially counteracted the impact of electric field on soil properties.