Innovative assisted phytoremediation of multi-elements contaminated soil by ryegrass: an electro-bio-chemical approach

Purpose The present study was conducted to evaluate the effectiveness of an innovative electro-bio-chemical approach, in the phytoremediation of multi-elements polluted soil. Methods A 3×4 factorial greenhouse trial was conducted with four levels of amendments (without amendment, chemical amendment, nitrilotriacetic acid (NTA), biological amendment ( Thiobacillus ), and both) and three levels of electrical current (0, 1, and 2 V cm −1 ). Ryegrass seeds were sown in a soil polluted with Pb, Cd, Zn, and Ni. Two months after planting, roots and shoots were harvested. Dry matter yield was measured in harvested parts, and the contents of metals in different parts of ryegrass were determined. Results Application of electric current (1 V cm −1 ) increased mean root and shoot dry weights of ryegrass and consequently increased Ni, Zn, Pb, and Cd uptake in ryegrass root and shoot. Application of 2 V cm −1 electric current increased Pb shoot uptake but decreased root dry weight, Cd and Zn root and shoot uptake, and also Pb root uptake. Although the addition of NTA and/or inoculation of Thiobacillus enhanced metal uptakes, co-application of these two treatments caused higher enhancement in metal uptakes by ryegrass. Plant position (anode vs cathode) had no considerable effect on most parameters measured. Mean Ni and Cd uptakes were higher in plants grown in anode position. Overall, the highest root and shoot dry weight, metal uptake, phytoextraction efficiency, uptake efficiency, and translocation factor especially for Pb were observed following the triple usage of 1 V cm −1 electric current along with application of chemical and biological treatments. Conclusion The main conclusion derived from these observations is that the proposed electro-bio-chemical approach is highly influential in the phytoremediation of multi-elements polluted soil.