Resistant Strain Enhanced Effects On The Phytoremediation Of Soils Contaminated With Pb And Cd By Vetiveria Zizanioides

Resistant strain were selected from heavy metal contaminated soil in a mining area by selected culture medium, and study its properties, to provide the idea strain for bioremediation of heavy metal pollution. And then reinforced Vetiveria zizanioides, that is a heavy metal enrichment plant, by resistant bacteria effects on the phytoremediation of soils contaminated with Lead and Cadmium. The main result are as follows:The resistant bacteria J3was Gram-positive monococcus, Ochrobactrum haematophilum by molecular biological identification. It can grow in beef extract peptone medium containing1000mg-L"1Pb2+, or30mg-L-1Cd2+. Its phenotype was stable by subculturing. And it grew well in the condition of pH value of5.0-11.0and NaCl concentration of1.5%-3.5%, and had different sensitivities in kinds of given antibiotics. To some extant, J3is a good strain with strong adaptability for the remediation of heavy metal pollution.Adding resistant strain would increase the number of microorganism in the rhizosphere soil. In single Pb-contaminated soil, when the concentration of Pbup to2500mg·kg-1, the number of resistant strain in the rhizosphere soil was29.81×105CFU·g-1, and was4.94-fold than CK. In single Cd-contaminated soil, the number of resistant strain in the rhizosphere soil was between0.72-2.98fold than CK when the concentration of Cd up to80mg·kg-1is most. In mining soil, the number of resistant strain in the rhizosphere soil was5.67×105CFU·g-1, and2.53-fold than CK with the treatment under highest adding strain level. Resistant bacteria strengthen Vetiver repair system would reduce soil pH, especially reduce the rhizosphere soil pH. In single Pb-contaminated soil, the pH in rhizosphere soil under adding strain was less0.25-0.81unit than non-added bacteria, and the concentration up to3500mg·kg-1was the lest. In single Cd-contaminated soil, the pH in Vetiver rhizosphere soil under adding strain treatment was less0.05-0.25unit than without added bacteria, and the Cd concentration up to55mg·kg-1was the lest. In Pb-Cd contaminated soil, the pH value was less0.34unit than CK with the treatment under highest adding strain level.Added resistant bacteria to phytoremediation system would change the proportion of heavy metal forms. In single contaminated soil, when the Pb concentration up to3500mg·kg-1or the Cd concentration up to55mg·kg-1, in Vetiver rhizosphere soil, the proportion of weak acid soluble form of heavy metal was9.16%or15.67%. In Pb-Cd contaminated soil, the proportion of weak acid soluble form of Pb and Cd were higher13.99%and11.91%than CK, with the treatment under highest adding strain level.The pot experiments that resistant strain strengthen the ability of Vetiveria zizanioides restore soil pollution suggest that resistant strains can promote the growth of Vetiver grass and enhance the absorb of heavy metal. In single Pb-contaminated soil, the dry weight of Vetiver was higher5.1%-46.2%and the extra of Pb in over-ground part was higher16.1%-104.9%than non-added strain, and the Pb concentration up to5500mg·kg-1was the most. In single Cd-contaminated soil, the dry weight of Vetiver was higher5.7%-46.3%, and the extra of Cd in over-ground part was higher30.12%-96.47%than non-added strain. And the Cd concentration up to80mg·kg-1was the most. In mining soil, the treatment under highest adding strain level was the best, the dry weight was84.6g, it was2.07-fold than CK, and the amount of Pb and Cd of over-ground part was42.15mg and3.49mg, was2.75-fold and6.00fold than CK.