Optimal voltage and treatment time of electric field with assistant Solanum nigrum L. cadmium hyperaccumulation in soil

Abstract

We have attempted to obtain optimal conditions of direct current electrical field with switching polarity to increase Cd accumulation of the hyperaccumulator Solanum nigrum L. from soil. The effects of different voltages and treatment times on S. nigrum accumulating Cd were determined. The results showed that Cd concentration in S. nigrum under all electrical field conditions were significantly higher (p < 0.05) than that of the CK. The Cd concentration in shoot and root of treatment T3 (3 V cm−1) were higher than the equal results of treatment T2 (2 V cm−1) and T1 (1 V cm−1) under the same condition of 6 h d−1 treatment time. In different treatments concerning time of T1 (6 h d−1), T4 (10 h d−1) and T5 (14 h d−1) under same voltage of 1 V cm−1, the S. nigrum Cd concentration were with similar trend to the different voltage treatments (T5 with the highest Cd concentration). These results might be caused by positive change trends of pH, EC and extractable Cd concentration in soil. However, the S. nigrum biomasses of T3 were the lowest and the highest biomass happened in treatment of T4. Finally, the highest Cd accumulation in S. nigrm (μg pot−1) was the T4 with the condition of 1 V cm−1 and 10 h d−1, which was also the optimal voltage and treatment time of the electric field. The optimal conditions were important references in the practice of combined use of electrokinetic remediation and phytoremediation.