Coupling electrokinetic remediation with ryegrass for the synergistic remediation of Cd and C14 alkane co-contaminated soil

Electrokinetic coupled with phytoremediation (EKPR) is an innovative technology to remediate heavy metals or petroleum hydrocarbons polluted soils. However, the feasibility and mechanism of EKPR remediation heavy metals and petroleum hydrocarbons co-contaminated soil are still unknown. This study evaluated the feasibility and potency of coupling EK remediation with Lolium perenne L. (ryegrass) (EKRG) in remediating the cadmium (Cd) and C14 alkane co-contaminated soil. The ryegrass biomass, Cd uptake amount, C14 alkane removal and soil bacterial community were determined for different soil sections of the EKRG treatment. Results indicated that the polarity reversal direct current electric field increased the total Cd uptake amount of ryegrass to 17.95 μg, most likely due to an increase of 41.7 % of the ryegrass shoot biomass. The ryegrass shoots, in the initial anode section of EKRG treatment, acquired an increment in biomass by 82.1 % and Cd uptake amount by 67.1 %, corresponding to 1.02 g and 7.76 μg, respectively. The EKRG treatment boosted the removal of C14 alkane in comparison with the mono-treatment of ryegrass or EK, i.e., increasing by 28.4 % and 36.5 %, respectively. Microbial community analysis suggested that the EKRG treatment promoted the relative abundances of hydrocarbons degrading bacteria, potentially responding to the enhanced removal of C14 alkane. Further, the correlation analysis showed that the removal of C14 alkane was positively correlated with the ryegrass biomass and Cd uptake amount in the EKRG treatment, which again validated that the addition of electric field benefited the remediation of Cd and the removal of C14 alkane. These results together indicated that the electric field assisted phytoremediation would be an effective approach for remediating the Cd and C14 alkane co-contaminated soils.