Effects of biochar-immobilized bacteria on phytoremediation of cadmium-polluted soil.

This work is the first report of the ability of biochar-immobilized cadmium-resistant bacteria (CRB) on promoting the efficiency of cadmium phytoextraction by Chlorophytum laxum R.Br. The survival of CRB immobilized on biochar in cadmium-contaminated soil at a concentration of 75.45 mg kg-1 was studied. The results found that both CRB, namely Arthrobacter sp. TM6 and Micrococcus sp. MU1, can survive and grow in cadmium-contaminated soil. To study phytoextraction in the pot experiments, 2-month-old C. laxum was individually planted in cadmium-contaminated soil and divided into four treatments, including (i) untreated control, (ii) biochar, (iii) biochar-immobilized (BC) Arthrobacter sp., and (iv) BC-Micrococcus sp. The results found that biochar-immobilized CRB did not cause any effect to the root lengths and shoot heights of plants compared to the untreated control. Interestingly, inoculation of biochar-immobilized CRB significantly increased cadmium accumulation in the shoots and roots compared to the untreated control. In addition, the highest cadmium content in a whole plant, best phytoextraction performance, and greatest bioaccumulation factor was found in plant inoculated with BC-Micrococcus sp., followed by BC-Arthrobacter sp. In conclusion, inoculation of biochar-immobilized CRB enhanced cadmium accumulation and translocation of cadmium from the roots to shoots, suggesting further applying biochar-immobilized CRB in cadmium-polluted soil for promoting cadmium phytoextraction efficiency of ornamental plants. Graphical abstract.