Study On Bacillus Mucilaginosus And Citric Acid Enhanced Phytolacca Acinosa Remediation Of Cadmium Contamined Soil

Bio-availability of Cadmium (Cd) in soil is one of the main factors which greatly restrict phytoremediation efficiency. Ameliorants can greatly enhance heavy metal mobility in soil. In the thesis, the effects of Bacillus mucilaginosus (Bm) and Citric acid (CA) on growth, physiological characters, Cd absorption coefficient and transformation coefficient of Phytolacca acinosa under Cd stress were investigated. The results are as follows:(1) Treated for 60 days, height growth of P. acinosa was stimulated at low concentration (10 mg/Kg and 25 mg/Kg) Cd, while inhibited at concentration higher than 50 mg/Kg. And the leaves became smaller and etiolated or appeared purple spots at high Cd concentration. However no seedlings died, which demonstrated that P. acinosa had high resistance to Cd stress. The Cd combined with Bacillus mucilaginosus (Cd+Bm) or Cd combined with Citric acid (Cd+CA) treated P. acinosa seedlings had the similar growth performance, but had mild damage symptoms.(2) The chlorophyll content of P. acinosa increased at low Cd concentration (10 mg/Kg and 25 mg/Kg), and decreased at 50mg/Kg Cd and higher concentration. The soluble sugar, soluble protein, CAT activity, POD activity and SOD activity also had similar trends. But the relative conductivity of leaves increased with Cd concentration rising. Applying B. mucilaginosus into soil could promote CAT and POD activity and increase proline content. While applying citric acid into soil could enhance SOD activity and raise water content of leaves.(3) Cd content in the leaves of P. acinosa was highest, and then in stem, lowest in root, which was the same trend in Cd+Bm and Cd+CA treatment. Applying B. mucilaginosus into soil increased Cd content both of aerial part and root of P. acinosa seedlings. Citric acid increased Cd content of aerial part, but decreased Cd content of root. So, applying B. mucilaginosus and citric acid could improve transformation coefficient of P. acinosa under Cd stress, and citric acid was more effective.In conlusion, P. acinosa had high Cd tolerance and Cd accumulation ability. B. mucilaginosus and citric acid can promote remediation efficiency of Cd contaminated soil.